diff --git a/src/compiler/commandLineParser.ts b/src/compiler/commandLineParser.ts
index 59482af12e14e..bd9373e2d3f3f 100644
--- a/src/compiler/commandLineParser.ts
+++ b/src/compiler/commandLineParser.ts
@@ -317,9 +317,32 @@ namespace ts {
             }
         },
         {
-            name: "traceModuleResolution",
+            name: "typesSearchPaths",
+            type: "list",
+            isTSConfigOnly: true,
+            element: {
+                name: "typesSearchPaths",
+                type: "string",
+                isFilePath: true
+            }
+        },
+        {
+            name: "typesRoot",
+            type: "string"
+        },
+        {
+            name: "types",
+            type: "list",
+            element: {
+                name: "types",
+                type: "string"
+            },
+            description: Diagnostics.Type_declaration_files_to_be_included_in_compilation
+        },
+        {
+            name: "traceResolution",
             type: "boolean",
-            description: Diagnostics.Enable_tracing_of_the_module_resolution_process
+            description: Diagnostics.Enable_tracing_of_the_name_resolution_process
         },
         {
             name: "allowJs",
@@ -641,6 +664,7 @@ namespace ts {
         const compilerOptions: CompilerOptions = convertCompilerOptionsFromJsonWorker(json["compilerOptions"], basePath, errors, configFileName);
         const options = extend(existingOptions, compilerOptions);
         const typingOptions: TypingOptions = convertTypingOptionsFromJsonWorker(json["typingOptions"], basePath, errors, configFileName);
+        options.configFilePath = configFileName;
 
         const fileNames = getFileNames(errors);
 
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 505442eb99384..793118d008b8d 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -1903,10 +1903,10 @@
         "category": "Error",
         "code": 2684
     },
-    "The 'this' types of each signature are incompatible.": {
-        "category": "Error",
-        "code": 2685
-    },
+    "The 'this' types of each signature are incompatible.": {
+        "category": "Error",
+        "code": 2685
+    },
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",
         "code": 4000
@@ -2187,6 +2187,11 @@
         "category": "Error",
         "code": 4082
     },
+    "Conflicting library definitions for '{0}' found at '{1}' and '{2}'. Copy the correct file to the 'typings' folder to resolve this conflict.": {
+        "category": "Message",
+        "code": 4090
+    },
+
     "The current host does not support the '{0}' option.": {
         "category": "Error",
         "code": 5001
@@ -2540,7 +2545,7 @@
         "category": "Message",
         "code": 6084
     },
-    "Enable tracing of the module resolution process.": {
+    "Enable tracing of the name resolution process.": {
         "category": "Message",
         "code": 6085
     },
@@ -2588,7 +2593,7 @@
         "category": "Message",
         "code": 6096
     },
-    "File '{0}' exist - use it as a module resolution result.": {
+    "File '{0}' exist - use it as a name resolution result.": {
         "category": "Message",
         "code": 6097
     },
@@ -2600,11 +2605,11 @@
         "category": "Message",
         "code": 6099
     },
-    "'package.json' does not have 'typings' field.": {
+    "'package.json' does not have 'types' field.": {
         "category": "Message",
         "code": 6100
     },
-    "'package.json' has 'typings' field '{0}' that references '{1}'.": {
+    "'package.json' has '{0}' field '{1}' that references '{2}'.": {
         "category": "Message",
         "code": 6101
     },
@@ -2620,7 +2625,7 @@
         "category": "Message",
         "code": 6104
     },
-    "Expected type of 'typings' field in 'package.json' to be 'string', got '{0}'.": {
+    "Expected type of '{0}' field in 'package.json' to be 'string', got '{1}'.": {
         "category": "Message",
         "code": 6105
     },
@@ -2662,8 +2667,60 @@
     },
     "Raise error on 'this' expressions with an implied 'any' type.": {
         "category": "Message",
-        "code": 6115
-    },
+        "code": 6115
+    },
+    "======== Resolving type reference directive '{0}', containing file '{1}', root directory '{2}'. ========": {
+        "category": "Message",
+        "code": 6116
+    },
+    "Resolving using primary search paths...": {
+        "category": "Message",
+        "code": 6117
+    },
+    "Resolving from node_modules folder...": {
+        "category": "Message",
+        "code": 6118
+    },
+    "======== Type reference directive '{0}' was successfully resolved to '{1}', primary: {2}. ========": {
+        "category": "Message",
+        "code": 6119
+    },
+    "======== Type reference directive '{0}' was not resolved. ========": {
+        "category": "Message",
+        "code": 6120
+    },
+    "Resolving with primary search path '{0}'": {
+        "category": "Message",
+        "code": 6121
+    },
+    "Root directory cannot be determined, skipping primary search paths.": {
+        "category": "Message",
+        "code": 6122
+    },
+    "======== Resolving type reference directive '{0}', containing file '{1}', root directory not set. ========": {
+        "category": "Message",
+        "code": 6123
+    },
+    "Type declaration files to be included in compilation.": {
+        "category": "Message",
+        "code": 6124
+    },
+    "Looking up in 'node_modules' folder, initial location '{0}'": {
+        "category": "Message",
+        "code": 6125
+    },
+    "Containing file is not specified and root directory cannot be determined, skipping lookup in 'node_modules' folder.": {
+        "category": "Message",
+        "code": 6126
+    },
+    "======== Resolving type reference directive '{0}', containing file not set, root directory '{1}'. ========": {
+        "category": "Message",
+        "code": 6127
+    },
+    "======== Resolving type reference directive '{0}', containing file not set, root directory not set. ========": {
+        "category": "Message",
+        "code": 6128
+    },
     "Variable '{0}' implicitly has an '{1}' type.": {
         "category": "Error",
         "code": 7005
diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index 5119358d8d049..38a341eaa5af7 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -5509,6 +5509,7 @@ namespace ts {
         function processReferenceComments(sourceFile: SourceFile): void {
             const triviaScanner = createScanner(sourceFile.languageVersion, /*skipTrivia*/false, LanguageVariant.Standard, sourceText);
             const referencedFiles: FileReference[] = [];
+            const typeReferenceDirectives: FileReference[] = [];
             const amdDependencies: { path: string; name: string }[] = [];
             let amdModuleName: string;
 
@@ -5535,7 +5536,12 @@ namespace ts {
                     sourceFile.hasNoDefaultLib = referencePathMatchResult.isNoDefaultLib;
                     const diagnosticMessage = referencePathMatchResult.diagnosticMessage;
                     if (fileReference) {
-                        referencedFiles.push(fileReference);
+                        if (referencePathMatchResult.isTypeReferenceDirective) {
+                            typeReferenceDirectives.push(fileReference);
+                        }
+                        else {
+                            referencedFiles.push(fileReference);
+                        }
                     }
                     if (diagnosticMessage) {
                         parseDiagnostics.push(createFileDiagnostic(sourceFile, range.pos, range.end - range.pos, diagnosticMessage));
@@ -5567,6 +5573,7 @@ namespace ts {
             }
 
             sourceFile.referencedFiles = referencedFiles;
+            sourceFile.typeReferenceDirectives = typeReferenceDirectives;
             sourceFile.amdDependencies = amdDependencies;
             sourceFile.moduleName = amdModuleName;
         }
diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index 0c4d6bc8ffbbb..58ae0e3faf963 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -12,6 +12,12 @@ namespace ts {
 
     const emptyArray: any[] = [];
 
+    const defaultLibrarySearchPaths = [
+        "types/",
+        "node_modules/",
+        "node_modules/@types/",
+    ];
+
     export const version = "1.9.0";
 
     export function findConfigFile(searchPath: string, fileExists: (fileName: string) => boolean): string {
@@ -35,13 +41,58 @@ namespace ts {
         return normalizePath(referencedFileName);
     }
 
+    /* @internal */
+    export function computeCommonSourceDirectoryOfFilenames(fileNames: string[], currentDirectory: string, getCanonicalFileName: (fileName: string) => string): string {
+        let commonPathComponents: string[];
+        const failed = forEach(fileNames, sourceFile => {
+            // Each file contributes into common source file path
+            const sourcePathComponents = getNormalizedPathComponents(sourceFile, currentDirectory);
+            sourcePathComponents.pop(); // The base file name is not part of the common directory path
+
+            if (!commonPathComponents) {
+                // first file
+                commonPathComponents = sourcePathComponents;
+                return;
+            }
+
+            for (let i = 0, n = Math.min(commonPathComponents.length, sourcePathComponents.length); i < n; i++) {
+                if (getCanonicalFileName(commonPathComponents[i]) !== getCanonicalFileName(sourcePathComponents[i])) {
+                    if (i === 0) {
+                        // Failed to find any common path component
+                        return true;
+                    }
+
+                    // New common path found that is 0 -> i-1
+                    commonPathComponents.length = i;
+                    break;
+                }
+            }
+
+            // If the sourcePathComponents was shorter than the commonPathComponents, truncate to the sourcePathComponents
+            if (sourcePathComponents.length < commonPathComponents.length) {
+                commonPathComponents.length = sourcePathComponents.length;
+            }
+        });
+
+        // A common path can not be found when paths span multiple drives on windows, for example
+        if (failed) {
+            return "";
+        }
+
+        if (!commonPathComponents) { // Can happen when all input files are .d.ts files
+            return currentDirectory;
+        }
+
+        return getNormalizedPathFromPathComponents(commonPathComponents);
+    }
+
     function trace(host: ModuleResolutionHost, message: DiagnosticMessage, ...args: any[]): void;
     function trace(host: ModuleResolutionHost, message: DiagnosticMessage): void {
         host.trace(formatMessage.apply(undefined, arguments));
     }
 
     function isTraceEnabled(compilerOptions: CompilerOptions, host: ModuleResolutionHost): boolean {
-        return compilerOptions.traceModuleResolution && host.trace !== undefined;
+        return compilerOptions.traceResolution && host.trace !== undefined;
     }
 
     function hasZeroOrOneAsteriskCharacter(str: string): boolean {
@@ -82,6 +133,160 @@ namespace ts {
         skipTsx: boolean;
     }
 
+    function tryReadTypesSection(packageJsonPath: string, baseDirectory: string, state: ModuleResolutionState): string {
+        let jsonContent: { typings?: string, types?: string };
+        try {
+            const jsonText = state.host.readFile(packageJsonPath);
+            jsonContent = jsonText ? <{ typings?: string, types?: string }>JSON.parse(jsonText) : {};
+        }
+        catch (e) {
+            // gracefully handle if readFile fails or returns not JSON
+            jsonContent = {};
+        }
+
+        let typesFile: string;
+        let fieldName: string;
+        // first try to read content of 'typings' section (backward compatibility)
+        if (jsonContent.typings) {
+            if (typeof jsonContent.typings === "string") {
+                fieldName = "typings";
+                typesFile = jsonContent.typings;
+            }
+            else {
+                if (state.traceEnabled) {
+                    trace(state.host, Diagnostics.Expected_type_of_0_field_in_package_json_to_be_string_got_1, "typings", typeof jsonContent.typings);
+                }
+            }
+        }
+        // then read 'types'
+        if (!typesFile && jsonContent.types) {
+            if (typeof jsonContent.types === "string") {
+                fieldName = "types";
+                typesFile = jsonContent.types;
+            }
+            else {
+                if (state.traceEnabled) {
+                    trace(state.host, Diagnostics.Expected_type_of_0_field_in_package_json_to_be_string_got_1, "types", typeof jsonContent.types);
+                }
+            }
+        }
+        if (typesFile) {
+            const typesFilePath = normalizePath(combinePaths(baseDirectory, typesFile));
+            if (state.traceEnabled) {
+                trace(state.host, Diagnostics.package_json_has_0_field_1_that_references_2, fieldName, typesFile, typesFilePath);
+            }
+            return typesFilePath;
+        }
+        return undefined;
+    }
+
+    const typeReferenceExtensions = [".d.ts"];
+
+    /**
+     * @param {string | undefined} containingFile - file that contains type reference directive, can be undefined if containing file is unknown.
+     * This is possible in case if resolution is performed for directives specified via 'types' parameter. In this case initial path for secondary lookups
+     * is assumed to be the same as root directory of the project.
+     */
+    export function resolveTypeReferenceDirective(typeReferenceDirectiveName: string, containingFile: string, options: CompilerOptions, host: ModuleResolutionHost): ResolvedTypeReferenceDirectiveWithFailedLookupLocations {
+        const traceEnabled = isTraceEnabled(options, host);
+        const moduleResolutionState: ModuleResolutionState = {
+            compilerOptions: options,
+            host: host,
+            skipTsx: true,
+            traceEnabled
+        };
+
+        // use typesRoot and fallback to directory that contains tsconfig if typesRoot is not set
+        const rootDir = options.typesRoot || (options.configFilePath ? getDirectoryPath(options.configFilePath) : undefined);
+
+        if (traceEnabled) {
+            if (containingFile === undefined) {
+                if (rootDir === undefined) {
+                    trace(host, Diagnostics.Resolving_type_reference_directive_0_containing_file_not_set_root_directory_not_set, typeReferenceDirectiveName);
+                }
+                else {
+                    trace(host, Diagnostics.Resolving_type_reference_directive_0_containing_file_not_set_root_directory_1, typeReferenceDirectiveName, rootDir);
+                }
+            }
+            else {
+                if (rootDir === undefined) {
+                    trace(host, Diagnostics.Resolving_type_reference_directive_0_containing_file_1_root_directory_not_set, typeReferenceDirectiveName, containingFile);
+                }
+                else {
+                    trace(host, Diagnostics.Resolving_type_reference_directive_0_containing_file_1_root_directory_2, typeReferenceDirectiveName, containingFile, rootDir);
+                }
+            }
+        }
+
+        const failedLookupLocations: string[] = [];
+
+        // Check primary library paths
+        if (rootDir !== undefined) {
+            const effectivePrimarySearchPaths = options.typesSearchPaths || defaultLibrarySearchPaths;
+            for (const searchPath of effectivePrimarySearchPaths) {
+                const primaryPath = combinePaths(rootDir, searchPath);
+                if (traceEnabled) {
+                    trace(host, Diagnostics.Resolving_with_primary_search_path_0, primaryPath);
+                }
+                const candidate = combinePaths(primaryPath, typeReferenceDirectiveName);
+                const candidateDirectory = getDirectoryPath(candidate);
+                const resolvedFile = loadNodeModuleFromDirectory(typeReferenceExtensions, candidate, failedLookupLocations,
+                    !directoryProbablyExists(candidateDirectory, host), moduleResolutionState);
+
+                if (resolvedFile) {
+                    if (traceEnabled) {
+                        trace(host, Diagnostics.Type_reference_directive_0_was_successfully_resolved_to_1_primary_Colon_2, typeReferenceDirectiveName, resolvedFile, true);
+                    }
+                    return {
+                        resolvedTypeReferenceDirective: { primary: true, resolvedFileName: resolvedFile },
+                        failedLookupLocations
+                    };
+                }
+            }
+        }
+        else {
+            if (traceEnabled) {
+                trace(host, Diagnostics.Root_directory_cannot_be_determined_skipping_primary_search_paths);
+            }
+        }
+
+        let resolvedFile: string;
+        let initialLocationForSecondaryLookup: string;
+        if (containingFile) {
+            initialLocationForSecondaryLookup = getDirectoryPath(containingFile);
+        }
+        else {
+            initialLocationForSecondaryLookup = rootDir;
+        }
+
+        if (initialLocationForSecondaryLookup !== undefined) {
+            // check secondary locations
+            if (traceEnabled) {
+                trace(host, Diagnostics.Looking_up_in_node_modules_folder_initial_location_0, initialLocationForSecondaryLookup);
+            }
+            resolvedFile = loadModuleFromNodeModules(typeReferenceDirectiveName, initialLocationForSecondaryLookup, failedLookupLocations, moduleResolutionState);
+            if (traceEnabled) {
+                if (resolvedFile) {
+                    trace(host, Diagnostics.Type_reference_directive_0_was_successfully_resolved_to_1_primary_Colon_2, typeReferenceDirectiveName, resolvedFile, false);
+                }
+                else {
+                    trace(host, Diagnostics.Type_reference_directive_0_was_not_resolved, typeReferenceDirectiveName);
+                }
+            }
+        }
+        else {
+            if (traceEnabled) {
+                trace(host, Diagnostics.Containing_file_is_not_specified_and_root_directory_cannot_be_determined_skipping_lookup_in_node_modules_folder);
+            }
+        }
+        return {
+            resolvedTypeReferenceDirective: resolvedFile
+                ? { primary: false, resolvedFileName: resolvedFile }
+                : undefined,
+            failedLookupLocations
+        };
+    }
+
     export function resolveModuleName(moduleName: string, containingFile: string, compilerOptions: CompilerOptions, host: ModuleResolutionHost): ResolvedModuleWithFailedLookupLocations {
         const traceEnabled = isTraceEnabled(compilerOptions, host);
         if (traceEnabled) {
@@ -361,7 +566,7 @@ namespace ts {
         const traceEnabled = isTraceEnabled(compilerOptions, host);
 
         const failedLookupLocations: string[] = [];
-        const state = {compilerOptions, host, traceEnabled, skipTsx: false};
+        const state = { compilerOptions, host, traceEnabled, skipTsx: false };
         let resolvedFileName = tryLoadModuleUsingOptionalResolutionSettings(moduleName, containingDirectory, nodeLoadModuleByRelativeName,
             failedLookupLocations, supportedExtensions, state);
 
@@ -397,7 +602,7 @@ namespace ts {
     }
 
     /* @internal */
-    export function directoryProbablyExists(directoryName: string, host: { directoryExists?: (directoryName: string) => boolean } ): boolean {
+    export function directoryProbablyExists(directoryName: string, host: { directoryExists?: (directoryName: string) => boolean }): boolean {
         // if host does not support 'directoryExists' assume that directory will exist
         return !host.directoryExists || host.directoryExists(directoryName);
     }
@@ -407,6 +612,13 @@ namespace ts {
      * in cases when we know upfront that all load attempts will fail (because containing folder does not exists) however we still need to record all failed lookup locations.
      */
     function loadModuleFromFile(candidate: string, extensions: string[], failedLookupLocation: string[], onlyRecordFailures: boolean, state: ModuleResolutionState): string {
+        if (!onlyRecordFailures) {
+            // check if containig folder exists - if it doesn't then just record failures for all supported extensions without disk probing
+            const directory = getDirectoryPath(candidate);
+            if (directory) {
+                onlyRecordFailures = !directoryProbablyExists(directory, state.host);
+            }
+        }
         return forEach(extensions, tryLoad);
 
         function tryLoad(ext: string): string {
@@ -416,7 +628,7 @@ namespace ts {
             const fileName = fileExtensionIs(candidate, ext) ? candidate : candidate + ext;
             if (!onlyRecordFailures && state.host.fileExists(fileName)) {
                 if (state.traceEnabled) {
-                    trace(state.host, Diagnostics.File_0_exist_use_it_as_a_module_resolution_result, fileName);
+                    trace(state.host, Diagnostics.File_0_exist_use_it_as_a_name_resolution_result, fileName);
                 }
                 return fileName;
             }
@@ -437,36 +649,16 @@ namespace ts {
             if (state.traceEnabled) {
                 trace(state.host, Diagnostics.Found_package_json_at_0, packageJsonPath);
             }
-
-            let jsonContent: { typings?: string };
-
-            try {
-                const jsonText = state.host.readFile(packageJsonPath);
-                jsonContent = jsonText ? <{ typings?: string }>JSON.parse(jsonText) : { typings: undefined };
-            }
-            catch (e) {
-                // gracefully handle if readFile fails or returns not JSON
-                jsonContent = { typings: undefined };
-            }
-
-            if (jsonContent.typings) {
-                if (typeof jsonContent.typings === "string") {
-                    const typingsFile = normalizePath(combinePaths(candidate, jsonContent.typings));
-                    if (state.traceEnabled) {
-                        trace(state.host, Diagnostics.package_json_has_typings_field_0_that_references_1, jsonContent.typings, typingsFile);
-                    }
-                    const result = loadModuleFromFile(typingsFile, extensions, failedLookupLocation, !directoryProbablyExists(getDirectoryPath(typingsFile), state.host), state);
-                    if (result) {
-                        return result;
-                    }
-                }
-                else if (state.traceEnabled) {
-                    trace(state.host, Diagnostics.Expected_type_of_typings_field_in_package_json_to_be_string_got_0, typeof jsonContent.typings);
+            const typesFile = tryReadTypesSection(packageJsonPath, candidate, state);
+            if (typesFile) {
+                const result = loadModuleFromFile(typesFile, extensions, failedLookupLocation, !directoryProbablyExists(getDirectoryPath(typesFile), state.host), state);
+                if (result) {
+                    return result;
                 }
             }
             else {
                 if (state.traceEnabled) {
-                    trace(state.host, Diagnostics.package_json_does_not_have_typings_field);
+                    trace(state.host, Diagnostics.package_json_does_not_have_types_field);
                 }
             }
         }
@@ -481,20 +673,31 @@ namespace ts {
         return loadModuleFromFile(combinePaths(candidate, "index"), extensions, failedLookupLocation, !directoryExists, state);
     }
 
+    function loadModuleFromNodeModulesFolder(moduleName: string, directory: string, failedLookupLocations: string[], state: ModuleResolutionState): string {
+        const nodeModulesFolder = combinePaths(directory, "node_modules");
+        const nodeModulesFolderExists = directoryProbablyExists(nodeModulesFolder, state.host);
+        const candidate = normalizePath(combinePaths(nodeModulesFolder, moduleName));
+        // Load only typescript files irrespective of allowJs option if loading from node modules
+        let result = loadModuleFromFile(candidate, supportedTypeScriptExtensions, failedLookupLocations, !nodeModulesFolderExists, state);
+        if (result) {
+            return result;
+        }
+        result = loadNodeModuleFromDirectory(supportedTypeScriptExtensions, candidate, failedLookupLocations, !nodeModulesFolderExists, state);
+        if (result) {
+            return result;
+        }
+    }
+
     function loadModuleFromNodeModules(moduleName: string, directory: string, failedLookupLocations: string[], state: ModuleResolutionState): string {
         directory = normalizeSlashes(directory);
         while (true) {
             const baseName = getBaseFileName(directory);
             if (baseName !== "node_modules") {
-                const nodeModulesFolder = combinePaths(directory, "node_modules");
-                const nodeModulesFolderExists = directoryProbablyExists(nodeModulesFolder, state.host);
-                const candidate = normalizePath(combinePaths(nodeModulesFolder, moduleName));
-                // Load only typescript files irrespective of allowJs option if loading from node modules
-                let result = loadModuleFromFile(candidate, supportedTypeScriptExtensions, failedLookupLocations, !nodeModulesFolderExists, state);
-                if (result) {
-                    return result;
-                }
-                result = loadNodeModuleFromDirectory(supportedTypeScriptExtensions, candidate, failedLookupLocations, !nodeModulesFolderExists, state);
+                const result =
+                    // first: try to load module as-is
+                    loadModuleFromNodeModulesFolder(moduleName, directory, failedLookupLocations, state) ||
+                    // second: try to load module from the scope '@types'
+                    loadModuleFromNodeModulesFolder(combinePaths("@types", moduleName), directory, failedLookupLocations, state);
                 if (result) {
                     return result;
                 }
@@ -544,7 +747,7 @@ namespace ts {
 
 
         return referencedSourceFile
-            ? { resolvedModule: { resolvedFileName: referencedSourceFile  }, failedLookupLocations }
+            ? { resolvedModule: { resolvedFileName: referencedSourceFile }, failedLookupLocations }
             : { resolvedModule: undefined, failedLookupLocations };
     }
 
@@ -689,9 +892,9 @@ namespace ts {
 
     export function getPreEmitDiagnostics(program: Program, sourceFile?: SourceFile, cancellationToken?: CancellationToken): Diagnostic[] {
         let diagnostics = program.getOptionsDiagnostics(cancellationToken).concat(
-                          program.getSyntacticDiagnostics(sourceFile, cancellationToken),
-                          program.getGlobalDiagnostics(cancellationToken),
-                          program.getSemanticDiagnostics(sourceFile, cancellationToken));
+            program.getSyntacticDiagnostics(sourceFile, cancellationToken),
+            program.getGlobalDiagnostics(cancellationToken),
+            program.getSemanticDiagnostics(sourceFile, cancellationToken));
 
         if (program.getCompilerOptions().declaration) {
             diagnostics = diagnostics.concat(program.getDeclarationDiagnostics(sourceFile, cancellationToken));
@@ -726,68 +929,80 @@ namespace ts {
         }
     }
 
+    function loadWithLocalCache<T>(names: string[], containingFile: string, loader: (name: string, containingFile: string) => T): T[] {
+        if (names.length === 0) {
+            return [];
+        }
+        const resolutions: T[] = [];
+        const cache: Map<T> = {};
+        for (const name of names) {
+            let result: T;
+            if (hasProperty(cache, name)) {
+                result = cache[name];
+            }
+            else {
+                result = loader(name, containingFile);
+                cache[name] = result;
+            }
+            resolutions.push(result);
+        }
+        return resolutions;
+    }
+
     export function createProgram(rootNames: string[], options: CompilerOptions, host?: CompilerHost, oldProgram?: Program): Program {
         let program: Program;
         let files: SourceFile[] = [];
-        let fileProcessingDiagnostics = createDiagnosticCollection();
-        const programDiagnostics = createDiagnosticCollection();
-
         let commonSourceDirectory: string;
         let diagnosticsProducingTypeChecker: TypeChecker;
         let noDiagnosticsTypeChecker: TypeChecker;
         let classifiableNames: Map<string>;
 
+        let resolvedTypeReferenceDirectives: Map<ResolvedTypeReferenceDirective> = {};
+        let fileProcessingDiagnostics = createDiagnosticCollection();
         let skipDefaultLib = options.noLib;
+        const programDiagnostics = createDiagnosticCollection();
+        const currentDirectory = host.getCurrentDirectory();
         const supportedExtensions = getSupportedExtensions(options);
 
         const start = new Date().getTime();
 
         host = host || createCompilerHost(options);
+
         // Map storing if there is emit blocking diagnostics for given input
         const hasEmitBlockingDiagnostics = createFileMap<boolean>(getCanonicalFileName);
 
-        const currentDirectory = host.getCurrentDirectory();
-        const resolveModuleNamesWorker = host.resolveModuleNames
-            ? ((moduleNames: string[], containingFile: string) => host.resolveModuleNames(moduleNames, containingFile))
-            : ((moduleNames: string[], containingFile: string) => {
-                const resolvedModuleNames: ResolvedModule[] = [];
-                // resolveModuleName does not store any results between calls.
-                // lookup is a local cache to avoid resolving the same module name several times
-                const lookup: Map<ResolvedModule> = {};
-                for (const moduleName of moduleNames) {
-                    let resolvedName: ResolvedModule;
-                    if (hasProperty(lookup, moduleName)) {
-                        resolvedName = lookup[moduleName];
-                    }
-                    else {
-                        resolvedName = resolveModuleName(moduleName, containingFile, options, host).resolvedModule;
-                        lookup[moduleName] = resolvedName;
-                    }
-                    resolvedModuleNames.push(resolvedName);
-                }
-                return resolvedModuleNames;
-            });
+        let resolveModuleNamesWorker: (moduleNames: string[], containingFile: string) => ResolvedModule[];
+        if (host.resolveModuleNames) {
+            resolveModuleNamesWorker = (moduleNames, containingFile) => host.resolveModuleNames(moduleNames, containingFile);
+        }
+        else {
+            const loader = (moduleName: string, containingFile: string) => resolveModuleName(moduleName, containingFile, options, host).resolvedModule;
+            resolveModuleNamesWorker = (moduleNames, containingFile) => loadWithLocalCache(moduleNames, containingFile, loader);
+        }
+
+        let resolveTypeReferenceDirectiveNamesWorker: (typeDirectiveNames: string[], containingFile: string) => ResolvedTypeReferenceDirective[];
+        if (host.resolveTypeReferenceDirectives) {
+            resolveTypeReferenceDirectiveNamesWorker = (typeDirectiveNames, containingFile) => host.resolveTypeReferenceDirectives(typeDirectiveNames, containingFile);
+        }
+        else {
+            const loader = (typesRef: string, containingFile: string) => resolveTypeReferenceDirective(typesRef, containingFile, options, host).resolvedTypeReferenceDirective;
+            resolveTypeReferenceDirectiveNamesWorker = (typeReferenceDirectiveNames, containingFile) => loadWithLocalCache(typeReferenceDirectiveNames, containingFile, loader);
+        }
 
         const filesByName = createFileMap<SourceFile>();
         // stores 'filename -> file association' ignoring case
         // used to track cases when two file names differ only in casing
         const filesByNameIgnoreCase = host.useCaseSensitiveFileNames() ? createFileMap<SourceFile>(fileName => fileName.toLowerCase()) : undefined;
 
-        if (oldProgram) {
-            // check properties that can affect structure of the program or module resolution strategy
-            // if any of these properties has changed - structure cannot be reused
-            const oldOptions = oldProgram.getCompilerOptions();
-            if ((oldOptions.module !== options.module) ||
-                (oldOptions.noResolve !== options.noResolve) ||
-                (oldOptions.target !== options.target) ||
-                (oldOptions.noLib !== options.noLib) ||
-                (oldOptions.jsx !== options.jsx) ||
-                (oldOptions.allowJs !== options.allowJs)) {
-                oldProgram = undefined;
+        if (!tryReuseStructureFromOldProgram()) {
+            // load type declarations specified via 'types' argument
+            if (options.types && options.types.length) {
+                const resolutions = resolveTypeReferenceDirectiveNamesWorker(options.types, /*containingFile*/ undefined);
+                for (let i = 0; i < options.types.length; i++) {
+                    processTypeReferenceDirective(options.types[i], resolutions[i]);
+                }
             }
-        }
 
-        if (!tryReuseStructureFromOldProgram()) {
             forEach(rootNames, name => processRootFile(name, /*isDefaultLib*/ false));
             // Do not process the default library if:
             //  - The '--noLib' flag is used.
@@ -831,7 +1046,8 @@ namespace ts {
             getIdentifierCount: () => getDiagnosticsProducingTypeChecker().getIdentifierCount(),
             getSymbolCount: () => getDiagnosticsProducingTypeChecker().getSymbolCount(),
             getTypeCount: () => getDiagnosticsProducingTypeChecker().getTypeCount(),
-            getFileProcessingDiagnostics: () => fileProcessingDiagnostics
+            getFileProcessingDiagnostics: () => fileProcessingDiagnostics,
+            resolvedTypeReferenceDirectives
         };
 
         verifyCompilerOptions();
@@ -878,6 +1094,21 @@ namespace ts {
                 return false;
             }
 
+            // check properties that can affect structure of the program or module resolution strategy
+            // if any of these properties has changed - structure cannot be reused
+            const oldOptions = oldProgram.getCompilerOptions();
+            if ((oldOptions.module !== options.module) ||
+                (oldOptions.noResolve !== options.noResolve) ||
+                (oldOptions.target !== options.target) ||
+                (oldOptions.noLib !== options.noLib) ||
+                (oldOptions.jsx !== options.jsx) ||
+                (oldOptions.allowJs !== options.allowJs) ||
+                (oldOptions.rootDir !== options.rootDir) ||
+                (oldOptions.typesSearchPaths !== options.typesSearchPaths) ||
+                (oldOptions.configFilePath !== options.configFilePath)) {
+                return false;
+            }
+
             Debug.assert(!oldProgram.structureIsReused);
 
             // there is an old program, check if we can reuse its structure
@@ -886,6 +1117,10 @@ namespace ts {
                 return false;
             }
 
+            if (!arrayIsEqualTo(options.types, oldOptions.types)) {
+                return false;
+            }
+
             // check if program source files has changed in the way that can affect structure of the program
             const newSourceFiles: SourceFile[] = [];
             const filePaths: Path[] = [];
@@ -924,26 +1159,33 @@ namespace ts {
                         return false;
                     }
 
+                    if (!arrayIsEqualTo(oldSourceFile.typeReferenceDirectives, newSourceFile.typeReferenceDirectives, fileReferenceIsEqualTo)) {
+                        // 'types' references has changed
+                        return false;
+                    }
+
+                    const newSourceFilePath = getNormalizedAbsolutePath(newSourceFile.fileName, currentDirectory);
                     if (resolveModuleNamesWorker) {
                         const moduleNames = map(concatenate(newSourceFile.imports, newSourceFile.moduleAugmentations), getTextOfLiteral);
-                        const resolutions = resolveModuleNamesWorker(moduleNames, getNormalizedAbsolutePath(newSourceFile.fileName, currentDirectory));
+                        const resolutions = resolveModuleNamesWorker(moduleNames, newSourceFilePath);
                         // ensure that module resolution results are still correct
-                        for (let i = 0; i < moduleNames.length; i++) {
-                            const newResolution = resolutions[i];
-                            const oldResolution = getResolvedModule(oldSourceFile, moduleNames[i]);
-                            const resolutionChanged = oldResolution
-                                ? !newResolution ||
-                                  oldResolution.resolvedFileName !== newResolution.resolvedFileName ||
-                                  !!oldResolution.isExternalLibraryImport !== !!newResolution.isExternalLibraryImport
-                                : newResolution;
-
-                            if (resolutionChanged) {
-                                return false;
-                            }
+                        const resolutionsChanged = hasChangesInResolutions(moduleNames, resolutions, oldSourceFile.resolvedModules, moduleResolutionIsEqualTo);
+                        if (resolutionsChanged) {
+                            return false;
                         }
                     }
-                    // pass the cache of module resolutions from the old source file
+                    if (resolveTypeReferenceDirectiveNamesWorker) {
+                        const typesReferenceDirectives = map(newSourceFile.typeReferenceDirectives, x => x.fileName);
+                        const resolutions = resolveTypeReferenceDirectiveNamesWorker(typesReferenceDirectives, newSourceFilePath);
+                        // ensure that types resolutions are still correct
+                        const resolutionsChanged = hasChangesInResolutions(typesReferenceDirectives, resolutions, oldSourceFile.resolvedTypeReferenceDirectiveNames, typeDirectiveIsEqualTo);
+                        if (resolutionsChanged) {
+                            return false;
+                        }
+                    }
+                    // pass the cache of module/types resolutions from the old source file
                     newSourceFile.resolvedModules = oldSourceFile.resolvedModules;
+                    newSourceFile.resolvedTypeReferenceDirectiveNames = oldSourceFile.resolvedTypeReferenceDirectiveNames;
                     modifiedSourceFiles.push(newSourceFile);
                 }
                 else {
@@ -966,6 +1208,7 @@ namespace ts {
             for (const modifiedFile of modifiedSourceFiles) {
                 fileProcessingDiagnostics.reattachFileDiagnostics(modifiedFile);
             }
+            resolvedTypeReferenceDirectives = oldProgram.resolvedTypeReferenceDirectives;
             oldProgram.structureIsReused = true;
 
             return true;
@@ -1058,9 +1301,9 @@ namespace ts {
         }
 
         function getDiagnosticsHelper(
-                sourceFile: SourceFile,
-                getDiagnostics: (sourceFile: SourceFile, cancellationToken: CancellationToken) => Diagnostic[],
-                cancellationToken: CancellationToken): Diagnostic[] {
+            sourceFile: SourceFile,
+            getDiagnostics: (sourceFile: SourceFile, cancellationToken: CancellationToken) => Diagnostic[],
+            cancellationToken: CancellationToken): Diagnostic[] {
             if (sourceFile) {
                 return getDiagnostics(sourceFile, cancellationToken);
             }
@@ -1534,7 +1777,8 @@ namespace ts {
 
                 const basePath = getDirectoryPath(fileName);
                 if (!options.noResolve) {
-                    processReferencedFiles(file, basePath, /*isDefaultLib*/ isDefaultLib);
+                    processReferencedFiles(file, basePath, isDefaultLib);
+                    processTypeReferenceDirectives(file);
                 }
 
                 // always process imported modules to record module name resolutions
@@ -1558,6 +1802,73 @@ namespace ts {
             });
         }
 
+        function processTypeReferenceDirectives(file: SourceFile) {
+            const typeDirectives = map(file.typeReferenceDirectives, l => l.fileName);
+            const resolutions = resolveTypeReferenceDirectiveNamesWorker(typeDirectives, file.fileName);
+
+            for (let i = 0; i < typeDirectives.length; i++) {
+                const ref = file.typeReferenceDirectives[i];
+                const resolvedTypeReferenceDirective = resolutions[i];
+                // store resolved type directive on the file
+                setResolvedTypeReferenceDirective(file, ref.fileName, resolvedTypeReferenceDirective);
+                processTypeReferenceDirective(ref.fileName, resolvedTypeReferenceDirective, file, ref.pos, ref.end);
+            }
+        }
+
+        function processTypeReferenceDirective(typeReferenceDirective: string, resolvedTypeReferenceDirective: ResolvedTypeReferenceDirective,
+            refFile?: SourceFile, refPos?: number, refEnd?: number): void {
+
+            // If we already found this library as a primary reference - nothing to do
+            const previousResolution = resolvedTypeReferenceDirectives[typeReferenceDirective];
+            if (previousResolution && previousResolution.primary) {
+                return;
+            }
+            let saveResolution = true;
+            if (resolvedTypeReferenceDirective) {
+                if (resolvedTypeReferenceDirective.primary) {
+                    // resolved from the primary path
+                    processSourceFile(resolvedTypeReferenceDirective.resolvedFileName, /*isDefaultLib*/ false, /*isReference*/ true, refFile, refPos, refEnd);
+                }
+                else {
+                    // If we already resolved to this file, it must have been a secondary reference. Check file contents
+                    // for sameness and possibly issue an error
+                    if (previousResolution) {
+                        const otherFileText = host.readFile(resolvedTypeReferenceDirective.resolvedFileName);
+                        if (otherFileText !== getSourceFile(previousResolution.resolvedFileName).text) {
+                            fileProcessingDiagnostics.add(createDiagnostic(refFile, refPos, refEnd,
+                                Diagnostics.Conflicting_library_definitions_for_0_found_at_1_and_2_Copy_the_correct_file_to_the_typings_folder_to_resolve_this_conflict,
+                                typeReferenceDirective,
+                                resolvedTypeReferenceDirective.resolvedFileName,
+                                previousResolution.resolvedFileName
+                            ));
+                        }
+                        // don't overwrite previous resolution result
+                        saveResolution = false;
+                    }
+                    else {
+                        // First resolution of this library
+                        processSourceFile(resolvedTypeReferenceDirective.resolvedFileName, /*isDefaultLib*/ false, /*isReference*/ true, refFile, refPos, refEnd);
+                    }
+                }
+            }
+            else {
+                fileProcessingDiagnostics.add(createDiagnostic(refFile, refPos, refEnd, Diagnostics.Cannot_find_name_0, typeReferenceDirective));
+            }
+
+            if (saveResolution) {
+                resolvedTypeReferenceDirectives[typeReferenceDirective] = resolvedTypeReferenceDirective;
+            }
+        }
+
+        function createDiagnostic(refFile: SourceFile, refPos: number, refEnd: number, message: DiagnosticMessage, ...args: any[]): Diagnostic {
+            if (refFile === undefined || refPos === undefined || refEnd === undefined) {
+                return createCompilerDiagnostic(message, ...args);
+            }
+            else {
+                return createFileDiagnostic(refFile, refPos, refEnd - refPos, message, ...args);
+            }
+        }
+
         function getCanonicalFileName(fileName: string): string {
             return host.getCanonicalFileName(fileName);
         }
@@ -1605,51 +1916,13 @@ namespace ts {
         }
 
         function computeCommonSourceDirectory(sourceFiles: SourceFile[]): string {
-            let commonPathComponents: string[];
-            const failed = forEach(files, sourceFile => {
-                // Each file contributes into common source file path
-                if (isDeclarationFile(sourceFile)) {
-                    return;
+            const fileNames: string[] = [];
+            for (const file of sourceFiles) {
+                if (!file.isDeclarationFile) {
+                    fileNames.push(file.fileName);
                 }
-
-                const sourcePathComponents = getNormalizedPathComponents(sourceFile.fileName, currentDirectory);
-                sourcePathComponents.pop(); // The base file name is not part of the common directory path
-
-                if (!commonPathComponents) {
-                    // first file
-                    commonPathComponents = sourcePathComponents;
-                    return;
-                }
-
-                for (let i = 0, n = Math.min(commonPathComponents.length, sourcePathComponents.length); i < n; i++) {
-                    if (getCanonicalFileName(commonPathComponents[i]) !== getCanonicalFileName(sourcePathComponents[i])) {
-                        if (i === 0) {
-                            // Failed to find any common path component
-                            return true;
-                        }
-
-                        // New common path found that is 0 -> i-1
-                        commonPathComponents.length = i;
-                        break;
-                    }
-                }
-
-                // If the sourcePathComponents was shorter than the commonPathComponents, truncate to the sourcePathComponents
-                if (sourcePathComponents.length < commonPathComponents.length) {
-                    commonPathComponents.length = sourcePathComponents.length;
-                }
-            });
-
-            // A common path can not be found when paths span multiple drives on windows, for example
-            if (failed) {
-                return "";
             }
-
-            if (!commonPathComponents) { // Can happen when all input files are .d.ts files
-                return currentDirectory;
-            }
-
-            return getNormalizedPathFromPathComponents(commonPathComponents);
+            return computeCommonSourceDirectoryOfFilenames(fileNames, currentDirectory, getCanonicalFileName);
         }
 
         function checkSourceFilesBelongToPath(sourceFiles: SourceFile[], rootDirectory: string): boolean {
@@ -1797,7 +2070,7 @@ namespace ts {
 
                 // If we failed to find a good common directory, but outDir is specified and at least one of our files is on a windows drive/URL/other resource, add a failure
                 if (options.outDir && dir === "" && forEach(files, file => getRootLength(file.fileName) > 1)) {
-                        programDiagnostics.add(createCompilerDiagnostic(Diagnostics.Cannot_find_the_common_subdirectory_path_for_the_input_files));
+                    programDiagnostics.add(createCompilerDiagnostic(Diagnostics.Cannot_find_the_common_subdirectory_path_for_the_input_files));
                 }
             }
 
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 4968766c2d021..75255ff2f6d2d 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -1537,6 +1537,7 @@ namespace ts {
         amdDependencies: AmdDependency[];
         moduleName: string;
         referencedFiles: FileReference[];
+        typeReferenceDirectives: FileReference[];
         languageVariant: LanguageVariant;
         isDeclarationFile: boolean;
 
@@ -1584,6 +1585,7 @@ namespace ts {
         // It is used to resolve module names in the checker.
         // Content of this field should never be used directly - use getResolvedModuleFileName/setResolvedModuleFileName functions instead
         /* @internal */ resolvedModules: Map<ResolvedModule>;
+        /* @internal */ resolvedTypeReferenceDirectiveNames: Map<ResolvedTypeReferenceDirective>;
         /* @internal */ imports: LiteralExpression[];
         /* @internal */ moduleAugmentations: LiteralExpression[];
     }
@@ -1660,6 +1662,7 @@ namespace ts {
         /* @internal */ getTypeCount(): number;
 
         /* @internal */ getFileProcessingDiagnostics(): DiagnosticCollection;
+        /* @internal */ resolvedTypeReferenceDirectives: Map<ResolvedTypeReferenceDirective>;
         // For testing purposes only.
         /* @internal */ structureIsReused?: boolean;
     }
@@ -2418,6 +2421,7 @@ namespace ts {
         jsx?: JsxEmit;
         reactNamespace?: string;
         listFiles?: boolean;
+        typesSearchPaths?: string[];
         locale?: string;
         mapRoot?: string;
         module?: ModuleKind;
@@ -2457,7 +2461,7 @@ namespace ts {
         baseUrl?: string;
         paths?: PathSubstitutions;
         rootDirs?: RootPaths;
-        traceModuleResolution?: boolean;
+        traceResolution?: boolean;
         allowSyntheticDefaultImports?: boolean;
         allowJs?: boolean;
         noImplicitUseStrict?: boolean;
@@ -2471,8 +2475,15 @@ namespace ts {
         // Do not perform validation of output file name in transpile scenarios
         /* @internal */ suppressOutputPathCheck?: boolean;
 
-        list?: string[];
+        /* @internal */
+        // When options come from a config file, its path is recorded here
+        configFilePath?: string;
+        /* @internal */
+        // Path used to used to compute primary search locations 
+        typesRoot?: string;
+        types?: string[];
 
+        list?: string[];
         [option: string]: CompilerOptionsValue;
     }
 
@@ -2753,6 +2764,18 @@ namespace ts {
         failedLookupLocations: string[];
     }
 
+    export interface ResolvedTypeReferenceDirective {
+        // True if the type declaration file was found in a primary lookup location
+        primary: boolean;
+        // The location of the .d.ts file we located, or undefined if resolution failed
+        resolvedFileName?: string;
+    }
+
+    export interface ResolvedTypeReferenceDirectiveWithFailedLookupLocations {
+        resolvedTypeReferenceDirective: ResolvedTypeReferenceDirective;
+        failedLookupLocations: string[];
+    }
+
     export interface CompilerHost extends ModuleResolutionHost {
         getSourceFile(fileName: string, languageVersion: ScriptTarget, onError?: (message: string) => void): SourceFile;
         getCancellationToken?(): CancellationToken;
@@ -2772,6 +2795,10 @@ namespace ts {
          * 'throw new Error("NotImplemented")'
          */
         resolveModuleNames?(moduleNames: string[], containingFile: string): ResolvedModule[];
+        /**
+         * This method is a companion for 'resolveModuleNames' and is used to resolve 'types' references to actual type declaration files 
+         */
+        resolveTypeReferenceDirectives?(typeReferenceDirectiveNames: string[], containingFile: string): ResolvedTypeReferenceDirective[];
     }
 
     export interface TextSpan {
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index 780a6d615efd6..660f12b99e089 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -6,6 +6,7 @@ namespace ts {
         fileReference?: FileReference;
         diagnosticMessage?: DiagnosticMessage;
         isNoDefaultLib?: boolean;
+        isTypeReferenceDirective?: boolean;
     }
 
     export interface SynthesizedNode extends Node {
@@ -118,6 +119,43 @@ namespace ts {
         sourceFile.resolvedModules[moduleNameText] = resolvedModule;
     }
 
+    export function setResolvedTypeReferenceDirective(sourceFile: SourceFile, typeReferenceDirectiveName: string, resolvedTypeReferenceDirective: ResolvedTypeReferenceDirective): void {
+        if (!sourceFile.resolvedTypeReferenceDirectiveNames) {
+            sourceFile.resolvedTypeReferenceDirectiveNames = {};
+        }
+
+        sourceFile.resolvedTypeReferenceDirectiveNames[typeReferenceDirectiveName] = resolvedTypeReferenceDirective;
+    }
+
+    /* @internal */
+    export function moduleResolutionIsEqualTo(oldResolution: ResolvedModule, newResolution: ResolvedModule): boolean {
+        return oldResolution.resolvedFileName === newResolution.resolvedFileName && oldResolution.isExternalLibraryImport === newResolution.isExternalLibraryImport;
+    }
+
+    /* @internal */
+    export function typeDirectiveIsEqualTo(oldResolution: ResolvedTypeReferenceDirective, newResolution: ResolvedTypeReferenceDirective): boolean {
+        return oldResolution.resolvedFileName === newResolution.resolvedFileName && oldResolution.primary === newResolution.primary;
+    }
+
+    /* @internal */
+    export function hasChangesInResolutions<T>(names: string[], newResolutions: T[], oldResolutions: Map<T>, comparer: (oldResolution: T, newResolution: T) => boolean): boolean {
+        if (names.length !== newResolutions.length) {
+            return false;
+        }
+        for (let i = 0; i < names.length; i++) {
+            const newResolution = newResolutions[i];
+            const oldResolution = oldResolutions && hasProperty(oldResolutions, names[i]) ? oldResolutions[names[i]] : undefined;
+            const changed =
+                oldResolution
+                    ? !newResolution || !comparer(oldResolution, newResolution)
+                    : newResolution;
+            if (changed) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     // Returns true if this node contains a parse error anywhere underneath it.
     export function containsParseError(node: Node): boolean {
         aggregateChildData(node);
@@ -541,6 +579,7 @@ namespace ts {
     }
 
     export let fullTripleSlashReferencePathRegEx = /^(\/\/\/\s*<reference\s+path\s*=\s*)('|")(.+?)\2.*?\/>/;
+    export let fullTripleSlashReferenceTypeReferenceDirectiveRegEx = /^(\/\/\/\s*<reference\s+types\s*=\s*)('|")(.+?)\2.*?\/>/;
     export let fullTripleSlashAMDReferencePathRegEx = /^(\/\/\/\s*<amd-dependency\s+path\s*=\s*)('|")(.+?)\2.*?\/>/;
 
     export function isTypeNode(node: Node): boolean {
@@ -1591,25 +1630,26 @@ namespace ts {
                 };
             }
             else {
-                const matchResult = fullTripleSlashReferencePathRegEx.exec(comment);
-                if (matchResult) {
+                const refMatchResult = fullTripleSlashReferencePathRegEx.exec(comment);
+                const refLibResult = !refMatchResult && fullTripleSlashReferenceTypeReferenceDirectiveRegEx.exec(comment);
+                if (refMatchResult || refLibResult) {
                     const start = commentRange.pos;
                     const end = commentRange.end;
                     return {
                         fileReference: {
                             pos: start,
                             end: end,
-                            fileName: matchResult[3]
+                            fileName: (refMatchResult || refLibResult)[3]
                         },
-                        isNoDefaultLib: false
-                    };
-                }
-                else {
-                    return {
-                        diagnosticMessage: Diagnostics.Invalid_reference_directive_syntax,
-                        isNoDefaultLib: false
+                        isNoDefaultLib: false,
+                        isTypeReferenceDirective: !!refLibResult
                     };
                 }
+
+                return {
+                    diagnosticMessage: Diagnostics.Invalid_reference_directive_syntax,
+                    isNoDefaultLib: false
+                };
             }
         }
 
diff --git a/src/harness/compilerRunner.ts b/src/harness/compilerRunner.ts
index 3362cb1d375be..ea0877c42b204 100644
--- a/src/harness/compilerRunner.ts
+++ b/src/harness/compilerRunner.ts
@@ -102,6 +102,10 @@ class CompilerBaselineRunner extends RunnerBase {
                     });
                 }
 
+                if (tsConfigOptions && tsConfigOptions.configFilePath !== undefined) {
+                    tsConfigOptions.configFilePath = ts.combinePaths(rootDir, tsConfigOptions.configFilePath);
+                }
+
                 const output = Harness.Compiler.compileFiles(
                     toBeCompiled, otherFiles, harnessSettings, /*options*/ tsConfigOptions, /*currentDirectory*/ undefined);
 
@@ -140,7 +144,7 @@ class CompilerBaselineRunner extends RunnerBase {
             });
 
             it (`Correct module resolution tracing for ${fileName}`, () => {
-                if (options.traceModuleResolution) {
+                if (options.traceResolution) {
                     Harness.Baseline.runBaseline("Correct sourcemap content for " + fileName, justName.replace(/\.tsx?$/, ".trace.json"), () => {
                         return JSON.stringify(result.traceResults || [], undefined, 4);
                     });
diff --git a/src/harness/fourslash.ts b/src/harness/fourslash.ts
index 44057cad3276d..f7039fb1fe929 100644
--- a/src/harness/fourslash.ts
+++ b/src/harness/fourslash.ts
@@ -222,7 +222,7 @@ namespace FourSlash {
             function tryAdd(path: string) {
                 const inputFile = inputFiles[path];
                 if (inputFile && !Harness.isDefaultLibraryFile(path)) {
-                    languageServiceAdapterHost.addScript(path, inputFile);
+                    languageServiceAdapterHost.addScript(path, inputFile, /*isRootFile*/ true);
                     return true;
                 }
             }
@@ -247,6 +247,10 @@ namespace FourSlash {
             // Create a new Services Adapter
             this.cancellationToken = new TestCancellationToken();
             const compilationOptions = convertGlobalOptionsToCompilerOptions(this.testData.globalOptions);
+            if (compilationOptions.typesRoot) {
+                compilationOptions.typesRoot = ts.getNormalizedAbsolutePath(compilationOptions.typesRoot, this.basePath);
+            }
+
             const languageServiceAdapter = this.getLanguageServiceAdapter(testType, this.cancellationToken, compilationOptions);
             this.languageServiceAdapterHost = languageServiceAdapter.getHost();
             this.languageService = languageServiceAdapter.getLanguageService();
@@ -268,7 +272,7 @@ namespace FourSlash {
 
             if (startResolveFileRef) {
                 // Add the entry-point file itself into the languageServiceShimHost
-                this.languageServiceAdapterHost.addScript(startResolveFileRef.fileName, startResolveFileRef.content);
+                this.languageServiceAdapterHost.addScript(startResolveFileRef.fileName, startResolveFileRef.content, /*isRootFile*/ true);
 
                 const resolvedResult = languageServiceAdapter.getPreProcessedFileInfo(startResolveFileRef.fileName, startResolveFileRef.content);
                 const referencedFiles: ts.FileReference[] = resolvedResult.referencedFiles;
@@ -292,18 +296,18 @@ namespace FourSlash {
                 // Check if no-default-lib flag is false and if so add default library
                 if (!resolvedResult.isLibFile) {
                     this.languageServiceAdapterHost.addScript(Harness.Compiler.defaultLibFileName,
-                        Harness.Compiler.getDefaultLibrarySourceFile().text);
+                        Harness.Compiler.getDefaultLibrarySourceFile().text, /*isRootFile*/ false);
                 }
             }
             else {
                 // resolveReference file-option is not specified then do not resolve any files and include all inputFiles
                 ts.forEachKey(this.inputFiles, fileName => {
                     if (!Harness.isDefaultLibraryFile(fileName)) {
-                        this.languageServiceAdapterHost.addScript(fileName, this.inputFiles[fileName]);
+                        this.languageServiceAdapterHost.addScript(fileName, this.inputFiles[fileName], /*isRootFile*/ true);
                     }
                 });
                 this.languageServiceAdapterHost.addScript(Harness.Compiler.defaultLibFileName,
-                    Harness.Compiler.getDefaultLibrarySourceFile().text);
+                    Harness.Compiler.getDefaultLibrarySourceFile().text, /*isRootFile*/ false);
             }
 
             this.formatCodeOptions = {
diff --git a/src/harness/harness.ts b/src/harness/harness.ts
index d519156641329..7c6ff20302ade 100644
--- a/src/harness/harness.ts
+++ b/src/harness/harness.ts
@@ -65,6 +65,11 @@ namespace Utils {
         return Buffer ? (new Buffer(s)).toString("utf8") : s;
     }
 
+    export function byteLength(s: string, encoding?: string): number {
+        // stub implementation if Buffer is not available (in-browser case)
+        return Buffer ? Buffer.byteLength(s, encoding) : s.length;
+    }
+
     export function evalFile(fileContents: string, fileName: string, nodeContext?: any) {
         const environment = getExecutionEnvironment();
         switch (environment) {
@@ -835,7 +840,7 @@ namespace Harness {
         export let fourslashSourceFile: ts.SourceFile;
 
         export function getCanonicalFileName(fileName: string): string {
-            return Harness.IO.useCaseSensitiveFileNames() ? fileName : fileName.toLowerCase();
+            return fileName;
         }
 
         export function createCompilerHost(
@@ -883,6 +888,7 @@ namespace Harness {
                     newLineKind === ts.NewLineKind.LineFeed ? lineFeed :
                         Harness.IO.newLine();
 
+
             return {
                 getCurrentDirectory: () => currentDirectory,
                 getSourceFile,
@@ -891,8 +897,12 @@ namespace Harness {
                 getCanonicalFileName,
                 useCaseSensitiveFileNames: () => useCaseSensitiveFileNames,
                 getNewLine: () => newLine,
-                fileExists: fileName => getSourceFile(fileName, ts.ScriptTarget.ES5) !== undefined,
-                readFile: (fileName: string): string => { return Harness.IO.readFile(fileName); }
+                fileExists: fileName => {
+                    return fileMap.contains(ts.toPath(fileName, currentDirectory, getCanonicalFileName));
+                },
+                readFile: (fileName: string): string => {
+                    return fileMap.get(ts.toPath(fileName, currentDirectory, getCanonicalFileName)).getText();
+                }
             };
         }
 
@@ -1033,7 +1043,7 @@ namespace Harness {
                 options.newLine);
 
             let traceResults: string[];
-            if (options.traceModuleResolution) {
+            if (options.traceResolution) {
                 traceResults = [];
                 compilerHost.trace = text => traceResults.push(text);
             }
@@ -1479,6 +1489,7 @@ namespace Harness {
                         baseDir = ts.getNormalizedAbsolutePath(baseDir, rootDir);
                     }
                     tsConfig = ts.parseJsonConfigFileContent(configJson.config, parseConfigHost, baseDir);
+                    tsConfig.options.configFilePath = data.name;
 
                     // delete entry from the list
                     testUnitData.splice(i, 1);
diff --git a/src/harness/harnessLanguageService.ts b/src/harness/harnessLanguageService.ts
index 12bb6a470e4f7..b27d746390b9b 100644
--- a/src/harness/harnessLanguageService.ts
+++ b/src/harness/harnessLanguageService.ts
@@ -9,7 +9,7 @@ namespace Harness.LanguageService {
         public editRanges: { length: number; textChangeRange: ts.TextChangeRange; }[] = [];
         private lineMap: number[] = undefined;
 
-        constructor(public fileName: string, public content: string) {
+        constructor(public fileName: string, public content: string, public isRootFile: boolean) {
             this.setContent(content);
         }
 
@@ -135,7 +135,13 @@ namespace Harness.LanguageService {
 
         public getFilenames(): string[] {
             const fileNames: string[] = [];
-            ts.forEachKey(this.fileNameToScript, (fileName) => { fileNames.push(fileName); });
+            ts.forEachValue(this.fileNameToScript, (scriptInfo) => {
+                if (scriptInfo.isRootFile) {
+                    // only include root files here
+                    // usually it means that we won't include lib.d.ts in the list of root files so it won't mess the computation of compilation root dir.
+                    fileNames.push(scriptInfo.fileName);
+                }
+            });
             return fileNames;
         }
 
@@ -143,8 +149,8 @@ namespace Harness.LanguageService {
             return ts.lookUp(this.fileNameToScript, fileName);
         }
 
-        public addScript(fileName: string, content: string): void {
-            this.fileNameToScript[fileName] = new ScriptInfo(fileName, content);
+        public addScript(fileName: string, content: string, isRootFile: boolean): void {
+            this.fileNameToScript[fileName] = new ScriptInfo(fileName, content, isRootFile);
         }
 
         public editScript(fileName: string, start: number, end: number, newText: string) {
@@ -177,7 +183,7 @@ namespace Harness.LanguageService {
         getCompilationSettings() { return this.settings; }
         getCancellationToken() { return this.cancellationToken; }
         getCurrentDirectory(): string { return ""; }
-        getDefaultLibFileName(): string { return ""; }
+        getDefaultLibFileName(): string { return Harness.Compiler.defaultLibFileName; }
         getScriptFileNames(): string[] { return this.getFilenames(); }
         getScriptSnapshot(fileName: string): ts.IScriptSnapshot {
             const script = this.getScriptInfo(fileName);
@@ -210,6 +216,7 @@ namespace Harness.LanguageService {
         private nativeHost: NativeLanguageServiceHost;
 
         public getModuleResolutionsForFile: (fileName: string) => string;
+        public getTypeReferenceDirectiveResolutionsForFile: (fileName: string) => string;
 
         constructor(preprocessToResolve: boolean, cancellationToken?: ts.HostCancellationToken, options?: ts.CompilerOptions) {
             super(cancellationToken, options);
@@ -236,12 +243,25 @@ namespace Harness.LanguageService {
                     }
                     return JSON.stringify(imports);
                 };
+                this.getTypeReferenceDirectiveResolutionsForFile = (fileName) => {
+                    const scriptInfo = this.getScriptInfo(fileName);
+                    const preprocessInfo = ts.preProcessFile(scriptInfo.content, /*readImportFiles*/ false);
+                    const resolutions: ts.Map<ts.ResolvedTypeReferenceDirective> = {};
+                    const settings = this.nativeHost.getCompilationSettings();
+                    for (const typeReferenceDirective of preprocessInfo.typeReferenceDirectives) {
+                        const resolutionInfo = ts.resolveTypeReferenceDirective(typeReferenceDirective.fileName, fileName, settings, moduleResolutionHost);
+                        if (resolutionInfo.resolvedTypeReferenceDirective.resolvedFileName) {
+                            resolutions[typeReferenceDirective.fileName] = resolutionInfo.resolvedTypeReferenceDirective;
+                        }
+                    }
+                    return JSON.stringify(resolutions);
+                };
             }
         }
 
         getFilenames(): string[] { return this.nativeHost.getFilenames(); }
         getScriptInfo(fileName: string): ScriptInfo { return this.nativeHost.getScriptInfo(fileName); }
-        addScript(fileName: string, content: string): void { this.nativeHost.addScript(fileName, content); }
+        addScript(fileName: string, content: string, isRootFile: boolean): void { this.nativeHost.addScript(fileName, content, isRootFile); }
         editScript(fileName: string, start: number, end: number, newText: string): void { this.nativeHost.editScript(fileName, start, end, newText); }
         positionToLineAndCharacter(fileName: string, position: number): ts.LineAndCharacter { return this.nativeHost.positionToLineAndCharacter(fileName, position); }
 
@@ -442,6 +462,7 @@ namespace Harness.LanguageService {
         getPreProcessedFileInfo(fileName: string, fileContents: string): ts.PreProcessedFileInfo {
             let shimResult: {
                 referencedFiles: ts.IFileReference[];
+                typeReferenceDirectives: ts.IFileReference[];
                 importedFiles: ts.IFileReference[];
                 isLibFile: boolean;
             };
@@ -453,7 +474,8 @@ namespace Harness.LanguageService {
                 referencedFiles: [],
                 importedFiles: [],
                 ambientExternalModules: [],
-                isLibFile: shimResult.isLibFile
+                isLibFile: shimResult.isLibFile,
+                typeReferenceDirectives: []
             };
 
             ts.forEach(shimResult.referencedFiles, refFile => {
@@ -472,6 +494,13 @@ namespace Harness.LanguageService {
                 });
             });
 
+            ts.forEach(shimResult.typeReferenceDirectives, typeRefDirective => {
+                convertResult.importedFiles.push({
+                    fileName: typeRefDirective.path,
+                    pos: typeRefDirective.position,
+                    end: typeRefDirective.position + typeRefDirective.length
+                });
+            });
             return convertResult;
         }
     }
diff --git a/src/server/editorServices.ts b/src/server/editorServices.ts
index 4b9f17798c8e6..4c054664a1838 100644
--- a/src/server/editorServices.ts
+++ b/src/server/editorServices.ts
@@ -81,8 +81,14 @@ namespace ts.server {
         }
     }
 
-    interface TimestampedResolvedModule extends ResolvedModuleWithFailedLookupLocations {
-        lastCheckTime: number;
+    interface Timestamped {
+        lastCheckTime?: number;
+    }
+
+    interface TimestampedResolvedModule extends ResolvedModuleWithFailedLookupLocations, Timestamped {
+    }
+
+    interface TimestampedResolvedTypeReferenceDirective extends ResolvedTypeReferenceDirectiveWithFailedLookupLocations, Timestamped {
     }
 
     export class LSHost implements ts.LanguageServiceHost {
@@ -90,13 +96,16 @@ namespace ts.server {
         compilationSettings: ts.CompilerOptions;
         filenameToScript: ts.FileMap<ScriptInfo>;
         roots: ScriptInfo[] = [];
+
         private resolvedModuleNames: ts.FileMap<Map<TimestampedResolvedModule>>;
+        private resolvedTypeReferenceDirectives: ts.FileMap<Map<TimestampedResolvedTypeReferenceDirective>>;
         private moduleResolutionHost: ts.ModuleResolutionHost;
         private getCanonicalFileName: (fileName: string) => string;
 
         constructor(public host: ServerHost, public project: Project) {
             this.getCanonicalFileName = createGetCanonicalFileName(host.useCaseSensitiveFileNames);
             this.resolvedModuleNames = createFileMap<Map<TimestampedResolvedModule>>();
+            this.resolvedTypeReferenceDirectives = createFileMap<Map<TimestampedResolvedTypeReferenceDirective>>();
             this.filenameToScript = createFileMap<ScriptInfo>();
             this.moduleResolutionHost = {
                 fileExists: fileName => this.fileExists(fileName),
@@ -105,46 +114,51 @@ namespace ts.server {
             };
         }
 
-        resolveModuleNames(moduleNames: string[], containingFile: string): ResolvedModule[] {
-            const path = toPath(containingFile, this.host.getCurrentDirectory(), this.getCanonicalFileName);
-            const currentResolutionsInFile = this.resolvedModuleNames.get(path);
+        private resolveNamesWithLocalCache<T extends Timestamped & { failedLookupLocations: string[] }, R>(
+            names: string[],
+            containingFile: string,
+            cache: ts.FileMap<Map<T>>,
+            loader: (name: string, containingFile: string, options: CompilerOptions, host: ModuleResolutionHost) => T,
+            getResult: (s: T) => R): R[] {
 
-            const newResolutions: Map<TimestampedResolvedModule> = {};
-            const resolvedModules: ResolvedModule[] = [];
+            const path = toPath(containingFile, this.host.getCurrentDirectory(), this.getCanonicalFileName);
+            const currentResolutionsInFile = cache.get(path);
 
+            const newResolutions: Map<T> = {};
+            const resolvedModules: R[] = [];
             const compilerOptions = this.getCompilationSettings();
 
-            for (const moduleName of moduleNames) {
+            for (const name of names) {
                 // check if this is a duplicate entry in the list
-                let resolution = lookUp(newResolutions, moduleName);
+                let resolution = lookUp(newResolutions, name);
                 if (!resolution) {
-                    const existingResolution = currentResolutionsInFile && ts.lookUp(currentResolutionsInFile, moduleName);
+                    const existingResolution = currentResolutionsInFile && ts.lookUp(currentResolutionsInFile, name);
                     if (moduleResolutionIsValid(existingResolution)) {
-                        // ok, it is safe to use existing module resolution results
+                        // ok, it is safe to use existing name resolution results
                         resolution = existingResolution;
                     }
                     else {
-                        resolution = <TimestampedResolvedModule>resolveModuleName(moduleName, containingFile, compilerOptions, this.moduleResolutionHost);
+                        resolution = loader(name, containingFile, compilerOptions, this.moduleResolutionHost);
                         resolution.lastCheckTime = Date.now();
-                        newResolutions[moduleName] = resolution;
+                        newResolutions[name] = resolution;
                     }
                 }
 
                 ts.Debug.assert(resolution !== undefined);
 
-                resolvedModules.push(resolution.resolvedModule);
+                resolvedModules.push(getResult(resolution));
             }
 
             // replace old results with a new one
-            this.resolvedModuleNames.set(path, newResolutions);
+            cache.set(path, newResolutions);
             return resolvedModules;
 
-            function moduleResolutionIsValid(resolution: TimestampedResolvedModule): boolean {
+            function moduleResolutionIsValid(resolution: T): boolean {
                 if (!resolution) {
                     return false;
                 }
 
-                if (resolution.resolvedModule) {
+                if (getResult(resolution)) {
                     // TODO: consider checking failedLookupLocations
                     // TODO: use lastCheckTime to track expiration for module name resolution
                     return true;
@@ -156,6 +170,14 @@ namespace ts.server {
             }
         }
 
+        resolveTypeReferenceDirectives(typeDirectiveNames: string[], containingFile: string): ResolvedTypeReferenceDirective[] {
+            return this.resolveNamesWithLocalCache(typeDirectiveNames, containingFile, this.resolvedTypeReferenceDirectives, resolveTypeReferenceDirective, m => m.resolvedTypeReferenceDirective);
+        }
+
+        resolveModuleNames(moduleNames: string[], containingFile: string): ResolvedModule[] {
+            return this.resolveNamesWithLocalCache(moduleNames, containingFile, this.resolvedModuleNames, resolveModuleName, m => m.resolvedModule);
+        }
+
         getDefaultLibFileName() {
             const nodeModuleBinDir = ts.getDirectoryPath(ts.normalizePath(this.host.getExecutingFilePath()));
             return ts.combinePaths(nodeModuleBinDir, ts.getDefaultLibFileName(this.compilationSettings));
@@ -172,6 +194,7 @@ namespace ts.server {
             this.compilationSettings = opt;
             // conservatively assume that changing compiler options might affect module resolution strategy
             this.resolvedModuleNames.clear();
+            this.resolvedTypeReferenceDirectives.clear();
         }
 
         lineAffectsRefs(filename: string, line: number) {
@@ -212,6 +235,7 @@ namespace ts.server {
             if (!info.isOpen) {
                 this.filenameToScript.remove(info.path);
                 this.resolvedModuleNames.remove(info.path);
+                this.resolvedTypeReferenceDirectives.remove(info.path);
             }
         }
 
@@ -239,6 +263,7 @@ namespace ts.server {
                 this.filenameToScript.remove(info.path);
                 this.roots = copyListRemovingItem(info, this.roots);
                 this.resolvedModuleNames.remove(info.path);
+                this.resolvedTypeReferenceDirectives.remove(info.path);
             }
         }
 
diff --git a/src/services/services.ts b/src/services/services.ts
index 3aa07fe4e410a..37339037c75c5 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -125,6 +125,7 @@ namespace ts {
     }
     export interface PreProcessedFileInfo {
         referencedFiles: FileReference[];
+        typeReferenceDirectives: FileReference[];
         importedFiles: FileReference[];
         ambientExternalModules: string[];
         isLibFile: boolean;
@@ -793,6 +794,7 @@ namespace ts {
         public amdDependencies: { name: string; path: string }[];
         public moduleName: string;
         public referencedFiles: FileReference[];
+        public typeReferenceDirectives: FileReference[];
 
         public syntacticDiagnostics: Diagnostic[];
         public referenceDiagnostics: Diagnostic[];
@@ -814,6 +816,7 @@ namespace ts {
         public identifiers: Map<string>;
         public nameTable: Map<number>;
         public resolvedModules: Map<ResolvedModule>;
+        public resolvedTypeReferenceDirectiveNames: Map<ResolvedTypeReferenceDirective>;
         public imports: LiteralExpression[];
         public moduleAugmentations: LiteralExpression[];
         private namedDeclarations: Map<Declaration[]>;
@@ -1040,6 +1043,7 @@ namespace ts {
          * host specific questions using 'getScriptSnapshot'.
          */
         resolveModuleNames?(moduleNames: string[], containingFile: string): ResolvedModule[];
+        resolveTypeReferenceDirectives?(typeDirectiveNames: string[], containingFile: string): ResolvedTypeReferenceDirective[];
         directoryExists?(directoryName: string): boolean;
     }
 
@@ -2147,6 +2151,7 @@ namespace ts {
 
     export function preProcessFile(sourceText: string, readImportFiles = true, detectJavaScriptImports = false): PreProcessedFileInfo {
         const referencedFiles: FileReference[] = [];
+        const typeReferenceDirectives: FileReference[] = [];
         const importedFiles: FileReference[] = [];
         let ambientExternalModules: { ref: FileReference, depth: number }[];
         let isNoDefaultLib = false;
@@ -2175,7 +2180,11 @@ namespace ts {
                     isNoDefaultLib = referencePathMatchResult.isNoDefaultLib;
                     const fileReference = referencePathMatchResult.fileReference;
                     if (fileReference) {
-                        referencedFiles.push(fileReference);
+                        const collection = referencePathMatchResult.isTypeReferenceDirective
+                            ? typeReferenceDirectives
+                            : referencedFiles;
+
+                        collection.push(fileReference);
                     }
                 }
             });
@@ -2476,7 +2485,7 @@ namespace ts {
                     importedFiles.push(decl.ref);
                 }
             }
-            return { referencedFiles, importedFiles, isLibFile: isNoDefaultLib, ambientExternalModules: undefined };
+            return { referencedFiles, typeReferenceDirectives, importedFiles, isLibFile: isNoDefaultLib, ambientExternalModules: undefined };
         }
         else {
             // for global scripts ambient modules still can have augmentations - look for ambient modules with depth > 0
@@ -2494,7 +2503,7 @@ namespace ts {
                     }
                 }
             }
-            return { referencedFiles, importedFiles, isLibFile: isNoDefaultLib, ambientExternalModules: ambientModuleNames };
+            return { referencedFiles, typeReferenceDirectives, importedFiles, isLibFile: isNoDefaultLib, ambientExternalModules: ambientModuleNames };
         }
     }
 
@@ -2831,7 +2840,7 @@ namespace ts {
                 getCurrentDirectory: () => currentDirectory,
                 fileExists: (fileName): boolean => {
                     // stub missing host functionality
-                    Debug.assert(!host.resolveModuleNames);
+                    Debug.assert(!host.resolveModuleNames || !host.resolveTypeReferenceDirectives);
                     return hostCache.getOrCreateEntry(fileName) !== undefined;
                 },
                 readFile: (fileName): string => {
@@ -2840,7 +2849,7 @@ namespace ts {
                     return entry && entry.scriptSnapshot.getText(0, entry.scriptSnapshot.getLength());
                 },
                 directoryExists: directoryName => {
-                    Debug.assert(!host.resolveModuleNames);
+                    Debug.assert(!host.resolveModuleNames || !host.resolveTypeReferenceDirectives);
                     return directoryProbablyExists(directoryName, host);
                 }
             };
@@ -2851,6 +2860,11 @@ namespace ts {
             if (host.resolveModuleNames) {
                 compilerHost.resolveModuleNames = (moduleNames, containingFile) => host.resolveModuleNames(moduleNames, containingFile);
             }
+            if (host.resolveTypeReferenceDirectives) {
+                compilerHost.resolveTypeReferenceDirectives = (typeReferenceDirectiveNames, containingFile) => {
+                    return host.resolveTypeReferenceDirectives(typeReferenceDirectiveNames, containingFile);
+                };
+            }
 
             const newProgram = createProgram(hostCache.getRootFileNames(), newSettings, compilerHost, program);
 
@@ -4683,6 +4697,26 @@ namespace ts {
             }
         }
 
+        function findReferenceInPosition(refs: FileReference[], pos: number): FileReference {
+            for (const ref of refs) {
+                if (ref.pos <= pos && pos < ref.end) {
+                    return ref;
+                }
+            }
+            return undefined;
+        }
+
+        function getDefinitionInfoForFileReference(name: string, targetFileName: string): DefinitionInfo {
+            return {
+                fileName: targetFileName,
+                textSpan: createTextSpanFromBounds(0, 0),
+                kind: ScriptElementKind.scriptElement,
+                name: name,
+                containerName: undefined,
+                containerKind: undefined
+            };
+        }
+
         /// Goto definition
         function getDefinitionAtPosition(fileName: string, position: number): DefinitionInfo[] {
             synchronizeHostData();
@@ -4702,18 +4736,20 @@ namespace ts {
             }
 
             /// Triple slash reference comments
-            const comment = forEach(sourceFile.referencedFiles, r => (r.pos <= position && position < r.end) ? r : undefined);
+            const comment = findReferenceInPosition(sourceFile.referencedFiles, position);
             if (comment) {
                 const referenceFile = tryResolveScriptReference(program, sourceFile, comment);
                 if (referenceFile) {
-                    return [{
-                        fileName: referenceFile.fileName,
-                        textSpan: createTextSpanFromBounds(0, 0),
-                        kind: ScriptElementKind.scriptElement,
-                        name: comment.fileName,
-                        containerName: undefined,
-                        containerKind: undefined
-                    }];
+                    return [getDefinitionInfoForFileReference(comment.fileName, referenceFile.fileName)];
+                }
+                return undefined;
+            }
+            // Type reference directives
+            const typeReferenceDirective = findReferenceInPosition(sourceFile.typeReferenceDirectives, position);
+            if (typeReferenceDirective) {
+                const referenceFile = lookUp(program.resolvedTypeReferenceDirectives, typeReferenceDirective.fileName);
+                if (referenceFile && referenceFile.resolvedFileName) {
+                    return [getDefinitionInfoForFileReference(typeReferenceDirective.fileName, referenceFile.resolvedFileName)];
                 }
                 return undefined;
             }
diff --git a/src/services/shims.ts b/src/services/shims.ts
index ecfcd6f84dab4..9155c057ef2f2 100644
--- a/src/services/shims.ts
+++ b/src/services/shims.ts
@@ -67,6 +67,7 @@ namespace ts {
         useCaseSensitiveFileNames?(): boolean;
 
         getModuleResolutionsForFile?(fileName: string): string;
+        getTypeReferenceDirectiveResolutionsForFile?(fileName: string): string;
         directoryExists(directoryName: string): boolean;
     }
 
@@ -281,6 +282,7 @@ namespace ts {
         private tracingEnabled = false;
 
         public resolveModuleNames: (moduleName: string[], containingFile: string) => ResolvedModule[];
+        public resolveTypeReferenceDirectives: (typeDirectiveNames: string[], containingFile: string) => ResolvedTypeReferenceDirective[];
         public directoryExists: (directoryName: string) => boolean;
 
         constructor(private shimHost: LanguageServiceShimHost) {
@@ -298,6 +300,12 @@ namespace ts {
             if ("directoryExists" in this.shimHost) {
                 this.directoryExists = directoryName => this.shimHost.directoryExists(directoryName);
             }
+            if ("getTypeReferenceDirectiveResolutionsForFile" in this.shimHost) {
+                this.resolveTypeReferenceDirectives = (typeDirectiveNames: string[], containingFile: string) => {
+                    const typeDirectivesForFile = <Map<ResolvedTypeReferenceDirective>>JSON.parse(this.shimHost.getTypeReferenceDirectiveResolutionsForFile(containingFile));
+                    return map(typeDirectiveNames, name => lookUp(typeDirectivesForFile, name));
+                };
+            }
         }
 
         public log(s: string): void {
@@ -919,36 +927,47 @@ namespace ts {
             });
         }
 
+        public resolveTypeReferenceDirective(fileName: string, typeReferenceDirective: string, compilerOptionsJson: string): string {
+            return this.forwardJSONCall(`resolveTypeReferenceDirective(${fileName})`, () => {
+                const compilerOptions = <CompilerOptions>JSON.parse(compilerOptionsJson);
+                const result = resolveTypeReferenceDirective(typeReferenceDirective, normalizeSlashes(fileName), compilerOptions, this.host);
+                return {
+                    resolvedFileName: result.resolvedTypeReferenceDirective ? result.resolvedTypeReferenceDirective.resolvedFileName : undefined,
+                    primary: result.resolvedTypeReferenceDirective ? result.resolvedTypeReferenceDirective.primary : true,
+                    failedLookupLocations: result.failedLookupLocations
+                };
+            });
+        }
+
         public getPreProcessedFileInfo(fileName: string, sourceTextSnapshot: IScriptSnapshot): string {
             return this.forwardJSONCall(
                 "getPreProcessedFileInfo('" + fileName + "')",
                 () => {
                     // for now treat files as JavaScript 
                     const result = preProcessFile(sourceTextSnapshot.getText(0, sourceTextSnapshot.getLength()), /* readImportFiles */ true, /* detectJavaScriptImports */ true);
-                    const convertResult = {
-                        referencedFiles: <IFileReference[]>[],
-                        importedFiles: <IFileReference[]>[],
+                    return {
+                        referencedFiles: this.convertFileReferences(result.referencedFiles),
+                        importedFiles: this.convertFileReferences(result.importedFiles),
                         ambientExternalModules: result.ambientExternalModules,
-                        isLibFile: result.isLibFile
+                        isLibFile: result.isLibFile,
+                        typeReferenceDirectives: this.convertFileReferences(result.typeReferenceDirectives)
                     };
+                });
+        }
 
-                    forEach(result.referencedFiles, refFile => {
-                        convertResult.referencedFiles.push({
-                            path: normalizePath(refFile.fileName),
-                            position: refFile.pos,
-                            length: refFile.end - refFile.pos
-                        });
-                    });
-
-                    forEach(result.importedFiles, importedFile => {
-                        convertResult.importedFiles.push({
-                            path: normalizeSlashes(importedFile.fileName),
-                            position: importedFile.pos,
-                            length: importedFile.end - importedFile.pos
-                        });
-                    });
-                    return convertResult;
+        private convertFileReferences(refs: FileReference[]): IFileReference[] {
+            if (!refs) {
+                return undefined;
+            }
+            const result: IFileReference[] = [];
+            for (const ref of refs) {
+                result.push({
+                    path: normalizeSlashes(ref.fileName),
+                    position: ref.pos,
+                    length: ref.end - ref.pos
                 });
+            }
+            return result;
         }
 
         public getTSConfigFileInfo(fileName: string, sourceTextSnapshot: IScriptSnapshot): string {
diff --git a/tests/baselines/reference/library-reference-1.js b/tests/baselines/reference/library-reference-1.js
new file mode 100644
index 0000000000000..e709db72deabf
--- /dev/null
+++ b/tests/baselines/reference/library-reference-1.js
@@ -0,0 +1,17 @@
+//// [tests/cases/conformance/references/library-reference-1.ts] ////
+
+//// [index.d.ts]
+
+// We can find typings in the ./types folder
+
+declare var $: { foo(): void };
+
+
+//// [consumer.ts]
+/// <reference types="jquery" />
+$.foo();
+
+
+//// [consumer.js]
+/// <reference types="jquery" />
+$.foo();
diff --git a/tests/baselines/reference/library-reference-1.symbols b/tests/baselines/reference/library-reference-1.symbols
new file mode 100644
index 0000000000000..0e848c626c541
--- /dev/null
+++ b/tests/baselines/reference/library-reference-1.symbols
@@ -0,0 +1,16 @@
+=== /consumer.ts ===
+/// <reference types="jquery" />
+$.foo();
+>$.foo : Symbol(foo, Decl(index.d.ts, 3, 16))
+>$ : Symbol($, Decl(index.d.ts, 3, 11))
+>foo : Symbol(foo, Decl(index.d.ts, 3, 16))
+
+=== /types/jquery/index.d.ts ===
+
+// We can find typings in the ./types folder
+
+declare var $: { foo(): void };
+>$ : Symbol($, Decl(index.d.ts, 3, 11))
+>foo : Symbol(foo, Decl(index.d.ts, 3, 16))
+
+
diff --git a/tests/baselines/reference/library-reference-1.trace.json b/tests/baselines/reference/library-reference-1.trace.json
new file mode 100644
index 0000000000000..1b8c237dff15a
--- /dev/null
+++ b/tests/baselines/reference/library-reference-1.trace.json
@@ -0,0 +1,7 @@
+[
+    "======== Resolving type reference directive 'jquery', containing file '/consumer.ts', root directory '/'. ========",
+    "Resolving with primary search path '/types/'",
+    "File '/types/jquery/package.json' does not exist.",
+    "File '/types/jquery/index.d.ts' exist - use it as a name resolution result.",
+    "======== Type reference directive 'jquery' was successfully resolved to '/types/jquery/index.d.ts', primary: true. ========"
+]
\ No newline at end of file
diff --git a/tests/baselines/reference/library-reference-1.types b/tests/baselines/reference/library-reference-1.types
new file mode 100644
index 0000000000000..99133f2f8df9a
--- /dev/null
+++ b/tests/baselines/reference/library-reference-1.types
@@ -0,0 +1,17 @@
+=== /consumer.ts ===
+/// <reference types="jquery" />
+$.foo();
+>$.foo() : void
+>$.foo : () => void
+>$ : { foo(): void; }
+>foo : () => void
+
+=== /types/jquery/index.d.ts ===
+
+// We can find typings in the ./types folder
+
+declare var $: { foo(): void };
+>$ : { foo(): void; }
+>foo : () => void
+
+
diff --git a/tests/baselines/reference/library-reference-10.js b/tests/baselines/reference/library-reference-10.js
new file mode 100644
index 0000000000000..a6dbdfce6106e
--- /dev/null
+++ b/tests/baselines/reference/library-reference-10.js
@@ -0,0 +1,22 @@
+//// [tests/cases/conformance/references/library-reference-10.ts] ////
+
+//// [package.json]
+
+// package.json in a primary reference can refer to another file
+
+{
+    "typings": "jquery.d.ts"
+}
+
+//// [jquery.d.ts]
+declare var $: { foo(): void };
+
+
+//// [consumer.ts]
+/// <reference types="jquery" />
+$.foo();
+
+
+//// [consumer.js]
+/// <reference types="jquery" />
+$.foo();
diff --git a/tests/baselines/reference/library-reference-10.symbols b/tests/baselines/reference/library-reference-10.symbols
new file mode 100644
index 0000000000000..9d0f7e4781e35
--- /dev/null
+++ b/tests/baselines/reference/library-reference-10.symbols
@@ -0,0 +1,13 @@
+=== /consumer.ts ===
+/// <reference types="jquery" />
+$.foo();
+>$.foo : Symbol(foo, Decl(jquery.d.ts, 0, 16))
+>$ : Symbol($, Decl(jquery.d.ts, 0, 11))
+>foo : Symbol(foo, Decl(jquery.d.ts, 0, 16))
+
+=== /types/jquery/jquery.d.ts ===
+declare var $: { foo(): void };
+>$ : Symbol($, Decl(jquery.d.ts, 0, 11))
+>foo : Symbol(foo, Decl(jquery.d.ts, 0, 16))
+
+
diff --git a/tests/baselines/reference/library-reference-10.trace.json b/tests/baselines/reference/library-reference-10.trace.json
new file mode 100644
index 0000000000000..e6a1918a44653
--- /dev/null
+++ b/tests/baselines/reference/library-reference-10.trace.json
@@ -0,0 +1,8 @@
+[
+    "======== Resolving type reference directive 'jquery', containing file '/consumer.ts', root directory '/'. ========",
+    "Resolving with primary search path '/types/'",
+    "Found 'package.json' at '/types/jquery/package.json'.",
+    "'package.json' has 'typings' field 'jquery.d.ts' that references '/types/jquery/jquery.d.ts'.",
+    "File '/types/jquery/jquery.d.ts' exist - use it as a name resolution result.",
+    "======== Type reference directive 'jquery' was successfully resolved to '/types/jquery/jquery.d.ts', primary: true. ========"
+]
\ No newline at end of file
diff --git a/tests/baselines/reference/library-reference-10.types b/tests/baselines/reference/library-reference-10.types
new file mode 100644
index 0000000000000..42d78f72865c3
--- /dev/null
+++ b/tests/baselines/reference/library-reference-10.types
@@ -0,0 +1,14 @@
+=== /consumer.ts ===
+/// <reference types="jquery" />
+$.foo();
+>$.foo() : void
+>$.foo : () => void
+>$ : { foo(): void; }
+>foo : () => void
+
+=== /types/jquery/jquery.d.ts ===
+declare var $: { foo(): void };
+>$ : { foo(): void; }
+>foo : () => void
+
+
diff --git a/tests/baselines/reference/library-reference-11.js b/tests/baselines/reference/library-reference-11.js
new file mode 100644
index 0000000000000..773fe5a890a89
--- /dev/null
+++ b/tests/baselines/reference/library-reference-11.js
@@ -0,0 +1,22 @@
+//// [tests/cases/conformance/references/library-reference-11.ts] ////
+
+//// [package.json]
+
+// package.json in a secondary reference can refer to another file
+
+{
+    "typings": "jquery.d.ts"
+}
+
+//// [jquery.d.ts]
+declare var $: { foo(): void };
+
+
+//// [consumer.ts]
+/// <reference types="jquery" />
+$.foo();
+
+
+//// [consumer.js]
+/// <reference types="jquery" />
+$.foo();
diff --git a/tests/baselines/reference/library-reference-11.symbols b/tests/baselines/reference/library-reference-11.symbols
new file mode 100644
index 0000000000000..22b8bdf1b449c
--- /dev/null
+++ b/tests/baselines/reference/library-reference-11.symbols
@@ -0,0 +1,13 @@
+=== /a/b/consumer.ts ===
+/// <reference types="jquery" />
+$.foo();
+>$.foo : Symbol(foo, Decl(jquery.d.ts, 0, 16))
+>$ : Symbol($, Decl(jquery.d.ts, 0, 11))
+>foo : Symbol(foo, Decl(jquery.d.ts, 0, 16))
+
+=== /a/node_modules/jquery/jquery.d.ts ===
+declare var $: { foo(): void };
+>$ : Symbol($, Decl(jquery.d.ts, 0, 11))
+>foo : Symbol(foo, Decl(jquery.d.ts, 0, 16))
+
+
diff --git a/tests/baselines/reference/library-reference-11.trace.json b/tests/baselines/reference/library-reference-11.trace.json
new file mode 100644
index 0000000000000..e0af1e39c5ac8
--- /dev/null
+++ b/tests/baselines/reference/library-reference-11.trace.json
@@ -0,0 +1,21 @@
+[
+    "======== Resolving type reference directive 'jquery', containing file '/a/b/consumer.ts', root directory not set. ========",
+    "Root directory cannot be determined, skipping primary search paths.",
+    "Looking up in 'node_modules' folder, initial location '/a/b'",
+    "File '/a/b/node_modules/jquery.ts' does not exist.",
+    "File '/a/b/node_modules/jquery.d.ts' does not exist.",
+    "File '/a/b/node_modules/jquery/package.json' does not exist.",
+    "File '/a/b/node_modules/jquery/index.ts' does not exist.",
+    "File '/a/b/node_modules/jquery/index.d.ts' does not exist.",
+    "File '/a/b/node_modules/@types/jquery.ts' does not exist.",
+    "File '/a/b/node_modules/@types/jquery.d.ts' does not exist.",
+    "File '/a/b/node_modules/@types/jquery/package.json' does not exist.",
+    "File '/a/b/node_modules/@types/jquery/index.ts' does not exist.",
+    "File '/a/b/node_modules/@types/jquery/index.d.ts' does not exist.",
+    "File '/a/node_modules/jquery.ts' does not exist.",
+    "File '/a/node_modules/jquery.d.ts' does not exist.",
+    "Found 'package.json' at '/a/node_modules/jquery/package.json'.",
+    "'package.json' has 'typings' field 'jquery.d.ts' that references '/a/node_modules/jquery/jquery.d.ts'.",
+    "File '/a/node_modules/jquery/jquery.d.ts' exist - use it as a name resolution result.",
+    "======== Type reference directive 'jquery' was successfully resolved to '/a/node_modules/jquery/jquery.d.ts', primary: false. ========"
+]
\ No newline at end of file
diff --git a/tests/baselines/reference/library-reference-11.types b/tests/baselines/reference/library-reference-11.types
new file mode 100644
index 0000000000000..267ee08e6d6e8
--- /dev/null
+++ b/tests/baselines/reference/library-reference-11.types
@@ -0,0 +1,14 @@
+=== /a/b/consumer.ts ===
+/// <reference types="jquery" />
+$.foo();
+>$.foo() : void
+>$.foo : () => void
+>$ : { foo(): void; }
+>foo : () => void
+
+=== /a/node_modules/jquery/jquery.d.ts ===
+declare var $: { foo(): void };
+>$ : { foo(): void; }
+>foo : () => void
+
+
diff --git a/tests/baselines/reference/library-reference-12.js b/tests/baselines/reference/library-reference-12.js
new file mode 100644
index 0000000000000..42d0f650b50d1
--- /dev/null
+++ b/tests/baselines/reference/library-reference-12.js
@@ -0,0 +1,22 @@
+//// [tests/cases/conformance/references/library-reference-12.ts] ////
+
+//// [package.json]
+
+// package.json in a secondary reference can refer to another file
+
+{
+    "types": "dist/jquery.d.ts"
+}
+
+//// [jquery.d.ts]
+declare var $: { foo(): void };
+
+
+//// [consumer.ts]
+/// <reference types="jquery" />
+$.foo();
+
+
+//// [consumer.js]
+/// <reference types="jquery" />
+$.foo();
diff --git a/tests/baselines/reference/library-reference-12.symbols b/tests/baselines/reference/library-reference-12.symbols
new file mode 100644
index 0000000000000..2e25588bf77f6
--- /dev/null
+++ b/tests/baselines/reference/library-reference-12.symbols
@@ -0,0 +1,13 @@
+=== /a/b/consumer.ts ===
+/// <reference types="jquery" />
+$.foo();
+>$.foo : Symbol(foo, Decl(jquery.d.ts, 0, 16))
+>$ : Symbol($, Decl(jquery.d.ts, 0, 11))
+>foo : Symbol(foo, Decl(jquery.d.ts, 0, 16))
+
+=== /a/node_modules/jquery/dist/jquery.d.ts ===
+declare var $: { foo(): void };
+>$ : Symbol($, Decl(jquery.d.ts, 0, 11))
+>foo : Symbol(foo, Decl(jquery.d.ts, 0, 16))
+
+
diff --git a/tests/baselines/reference/library-reference-12.trace.json b/tests/baselines/reference/library-reference-12.trace.json
new file mode 100644
index 0000000000000..2cdf1f5f20ace
--- /dev/null
+++ b/tests/baselines/reference/library-reference-12.trace.json
@@ -0,0 +1,21 @@
+[
+    "======== Resolving type reference directive 'jquery', containing file '/a/b/consumer.ts', root directory not set. ========",
+    "Root directory cannot be determined, skipping primary search paths.",
+    "Looking up in 'node_modules' folder, initial location '/a/b'",
+    "File '/a/b/node_modules/jquery.ts' does not exist.",
+    "File '/a/b/node_modules/jquery.d.ts' does not exist.",
+    "File '/a/b/node_modules/jquery/package.json' does not exist.",
+    "File '/a/b/node_modules/jquery/index.ts' does not exist.",
+    "File '/a/b/node_modules/jquery/index.d.ts' does not exist.",
+    "File '/a/b/node_modules/@types/jquery.ts' does not exist.",
+    "File '/a/b/node_modules/@types/jquery.d.ts' does not exist.",
+    "File '/a/b/node_modules/@types/jquery/package.json' does not exist.",
+    "File '/a/b/node_modules/@types/jquery/index.ts' does not exist.",
+    "File '/a/b/node_modules/@types/jquery/index.d.ts' does not exist.",
+    "File '/a/node_modules/jquery.ts' does not exist.",
+    "File '/a/node_modules/jquery.d.ts' does not exist.",
+    "Found 'package.json' at '/a/node_modules/jquery/package.json'.",
+    "'package.json' has 'types' field 'dist/jquery.d.ts' that references '/a/node_modules/jquery/dist/jquery.d.ts'.",
+    "File '/a/node_modules/jquery/dist/jquery.d.ts' exist - use it as a name resolution result.",
+    "======== Type reference directive 'jquery' was successfully resolved to '/a/node_modules/jquery/dist/jquery.d.ts', primary: false. ========"
+]
\ No newline at end of file
diff --git a/tests/baselines/reference/library-reference-12.types b/tests/baselines/reference/library-reference-12.types
new file mode 100644
index 0000000000000..2ab9fb8ba95e8
--- /dev/null
+++ b/tests/baselines/reference/library-reference-12.types
@@ -0,0 +1,14 @@
+=== /a/b/consumer.ts ===
+/// <reference types="jquery" />
+$.foo();
+>$.foo() : void
+>$.foo : () => void
+>$ : { foo(): void; }
+>foo : () => void
+
+=== /a/node_modules/jquery/dist/jquery.d.ts ===
+declare var $: { foo(): void };
+>$ : { foo(): void; }
+>foo : () => void
+
+
diff --git a/tests/baselines/reference/library-reference-13.js b/tests/baselines/reference/library-reference-13.js
new file mode 100644
index 0000000000000..be52aba1a39c7
--- /dev/null
+++ b/tests/baselines/reference/library-reference-13.js
@@ -0,0 +1,12 @@
+//// [tests/cases/conformance/references/library-reference-13.ts] ////
+
+//// [index.d.ts]
+declare var $: { foo(): void };
+
+
+//// [consumer.ts]
+$.foo();
+
+
+//// [consumer.js]
+$.foo();
diff --git a/tests/baselines/reference/library-reference-13.symbols b/tests/baselines/reference/library-reference-13.symbols
new file mode 100644
index 0000000000000..04d50373caae0
--- /dev/null
+++ b/tests/baselines/reference/library-reference-13.symbols
@@ -0,0 +1,12 @@
+=== /a/b/consumer.ts ===
+$.foo();
+>$.foo : Symbol(foo, Decl(index.d.ts, 0, 16))
+>$ : Symbol($, Decl(index.d.ts, 0, 11))
+>foo : Symbol(foo, Decl(index.d.ts, 0, 16))
+
+=== /a/types/jquery/index.d.ts ===
+declare var $: { foo(): void };
+>$ : Symbol($, Decl(index.d.ts, 0, 11))
+>foo : Symbol(foo, Decl(index.d.ts, 0, 16))
+
+
diff --git a/tests/baselines/reference/library-reference-13.trace.json b/tests/baselines/reference/library-reference-13.trace.json
new file mode 100644
index 0000000000000..2133414f41424
--- /dev/null
+++ b/tests/baselines/reference/library-reference-13.trace.json
@@ -0,0 +1,7 @@
+[
+    "======== Resolving type reference directive 'jquery', containing file not set, root directory '/a'. ========",
+    "Resolving with primary search path '/a/types/'",
+    "File '/a/types/jquery/package.json' does not exist.",
+    "File '/a/types/jquery/index.d.ts' exist - use it as a name resolution result.",
+    "======== Type reference directive 'jquery' was successfully resolved to '/a/types/jquery/index.d.ts', primary: true. ========"
+]
\ No newline at end of file
diff --git a/tests/baselines/reference/library-reference-13.types b/tests/baselines/reference/library-reference-13.types
new file mode 100644
index 0000000000000..b00d778c5b2a2
--- /dev/null
+++ b/tests/baselines/reference/library-reference-13.types
@@ -0,0 +1,13 @@
+=== /a/b/consumer.ts ===
+$.foo();
+>$.foo() : void
+>$.foo : () => void
+>$ : { foo(): void; }
+>foo : () => void
+
+=== /a/types/jquery/index.d.ts ===
+declare var $: { foo(): void };
+>$ : { foo(): void; }
+>foo : () => void
+
+
diff --git a/tests/baselines/reference/library-reference-14.js b/tests/baselines/reference/library-reference-14.js
new file mode 100644
index 0000000000000..0fb5ff04fb9be
--- /dev/null
+++ b/tests/baselines/reference/library-reference-14.js
@@ -0,0 +1,13 @@
+//// [tests/cases/conformance/references/library-reference-14.ts] ////
+
+//// [index.d.ts]
+
+declare var $: { foo(): void };
+
+
+//// [consumer.ts]
+$.foo();
+
+
+//// [consumer.js]
+$.foo();
diff --git a/tests/baselines/reference/library-reference-14.symbols b/tests/baselines/reference/library-reference-14.symbols
new file mode 100644
index 0000000000000..162afc50ca785
--- /dev/null
+++ b/tests/baselines/reference/library-reference-14.symbols
@@ -0,0 +1,13 @@
+=== /a/b/consumer.ts ===
+$.foo();
+>$.foo : Symbol(foo, Decl(index.d.ts, 1, 16))
+>$ : Symbol($, Decl(index.d.ts, 1, 11))
+>foo : Symbol(foo, Decl(index.d.ts, 1, 16))
+
+=== /a/types/jquery/index.d.ts ===
+
+declare var $: { foo(): void };
+>$ : Symbol($, Decl(index.d.ts, 1, 11))
+>foo : Symbol(foo, Decl(index.d.ts, 1, 16))
+
+
diff --git a/tests/baselines/reference/library-reference-14.trace.json b/tests/baselines/reference/library-reference-14.trace.json
new file mode 100644
index 0000000000000..2133414f41424
--- /dev/null
+++ b/tests/baselines/reference/library-reference-14.trace.json
@@ -0,0 +1,7 @@
+[
+    "======== Resolving type reference directive 'jquery', containing file not set, root directory '/a'. ========",
+    "Resolving with primary search path '/a/types/'",
+    "File '/a/types/jquery/package.json' does not exist.",
+    "File '/a/types/jquery/index.d.ts' exist - use it as a name resolution result.",
+    "======== Type reference directive 'jquery' was successfully resolved to '/a/types/jquery/index.d.ts', primary: true. ========"
+]
\ No newline at end of file
diff --git a/tests/baselines/reference/library-reference-14.types b/tests/baselines/reference/library-reference-14.types
new file mode 100644
index 0000000000000..f4196e10744e2
--- /dev/null
+++ b/tests/baselines/reference/library-reference-14.types
@@ -0,0 +1,14 @@
+=== /a/b/consumer.ts ===
+$.foo();
+>$.foo() : void
+>$.foo : () => void
+>$ : { foo(): void; }
+>foo : () => void
+
+=== /a/types/jquery/index.d.ts ===
+
+declare var $: { foo(): void };
+>$ : { foo(): void; }
+>foo : () => void
+
+
diff --git a/tests/baselines/reference/library-reference-15.errors.txt b/tests/baselines/reference/library-reference-15.errors.txt
new file mode 100644
index 0000000000000..a311633ca76d5
--- /dev/null
+++ b/tests/baselines/reference/library-reference-15.errors.txt
@@ -0,0 +1,15 @@
+error TS2304: Cannot find name 'jquery'.
+/a/b/consumer.ts(1,1): error TS2304: Cannot find name '$'.
+
+
+!!! error TS2304: Cannot find name 'jquery'.
+==== /a/b/consumer.ts (1 errors) ====
+    $.foo();
+    ~
+!!! error TS2304: Cannot find name '$'.
+    
+==== /a/types/jquery/index.d.ts (0 errors) ====
+    
+    declare var $: { foo(): void };
+    
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/library-reference-15.js b/tests/baselines/reference/library-reference-15.js
new file mode 100644
index 0000000000000..f9aa7038d539d
--- /dev/null
+++ b/tests/baselines/reference/library-reference-15.js
@@ -0,0 +1,13 @@
+//// [tests/cases/conformance/references/library-reference-15.ts] ////
+
+//// [index.d.ts]
+
+declare var $: { foo(): void };
+
+
+//// [consumer.ts]
+$.foo();
+
+
+//// [consumer.js]
+$.foo();
diff --git a/tests/baselines/reference/library-reference-15.trace.json b/tests/baselines/reference/library-reference-15.trace.json
new file mode 100644
index 0000000000000..9a19d75ffacb1
--- /dev/null
+++ b/tests/baselines/reference/library-reference-15.trace.json
@@ -0,0 +1,5 @@
+[
+    "======== Resolving type reference directive 'jquery', containing file not set, root directory not set. ========",
+    "Root directory cannot be determined, skipping primary search paths.",
+    "Containing file is not specified and root directory cannot be determined, skipping lookup in 'node_modules' folder."
+]
\ No newline at end of file
diff --git a/tests/baselines/reference/library-reference-2.js b/tests/baselines/reference/library-reference-2.js
new file mode 100644
index 0000000000000..20729db6c6032
--- /dev/null
+++ b/tests/baselines/reference/library-reference-2.js
@@ -0,0 +1,22 @@
+//// [tests/cases/conformance/references/library-reference-2.ts] ////
+
+//// [package.json]
+
+// package.json in a primary reference can refer to another file
+
+{
+    "types": "jquery.d.ts"
+}
+
+//// [jquery.d.ts]
+declare var $: { foo(): void };
+
+
+//// [consumer.ts]
+/// <reference types="jquery" />
+$.foo();
+
+
+//// [consumer.js]
+/// <reference types="jquery" />
+$.foo();
diff --git a/tests/baselines/reference/library-reference-2.symbols b/tests/baselines/reference/library-reference-2.symbols
new file mode 100644
index 0000000000000..9d0f7e4781e35
--- /dev/null
+++ b/tests/baselines/reference/library-reference-2.symbols
@@ -0,0 +1,13 @@
+=== /consumer.ts ===
+/// <reference types="jquery" />
+$.foo();
+>$.foo : Symbol(foo, Decl(jquery.d.ts, 0, 16))
+>$ : Symbol($, Decl(jquery.d.ts, 0, 11))
+>foo : Symbol(foo, Decl(jquery.d.ts, 0, 16))
+
+=== /types/jquery/jquery.d.ts ===
+declare var $: { foo(): void };
+>$ : Symbol($, Decl(jquery.d.ts, 0, 11))
+>foo : Symbol(foo, Decl(jquery.d.ts, 0, 16))
+
+
diff --git a/tests/baselines/reference/library-reference-2.trace.json b/tests/baselines/reference/library-reference-2.trace.json
new file mode 100644
index 0000000000000..b5ef5f3e2089a
--- /dev/null
+++ b/tests/baselines/reference/library-reference-2.trace.json
@@ -0,0 +1,8 @@
+[
+    "======== Resolving type reference directive 'jquery', containing file '/consumer.ts', root directory '/'. ========",
+    "Resolving with primary search path '/types/'",
+    "Found 'package.json' at '/types/jquery/package.json'.",
+    "'package.json' has 'types' field 'jquery.d.ts' that references '/types/jquery/jquery.d.ts'.",
+    "File '/types/jquery/jquery.d.ts' exist - use it as a name resolution result.",
+    "======== Type reference directive 'jquery' was successfully resolved to '/types/jquery/jquery.d.ts', primary: true. ========"
+]
\ No newline at end of file
diff --git a/tests/baselines/reference/library-reference-2.types b/tests/baselines/reference/library-reference-2.types
new file mode 100644
index 0000000000000..42d78f72865c3
--- /dev/null
+++ b/tests/baselines/reference/library-reference-2.types
@@ -0,0 +1,14 @@
+=== /consumer.ts ===
+/// <reference types="jquery" />
+$.foo();
+>$.foo() : void
+>$.foo : () => void
+>$ : { foo(): void; }
+>foo : () => void
+
+=== /types/jquery/jquery.d.ts ===
+declare var $: { foo(): void };
+>$ : { foo(): void; }
+>foo : () => void
+
+
diff --git a/tests/baselines/reference/library-reference-3.js b/tests/baselines/reference/library-reference-3.js
new file mode 100644
index 0000000000000..6f9ad2d43d2cb
--- /dev/null
+++ b/tests/baselines/reference/library-reference-3.js
@@ -0,0 +1,16 @@
+//// [tests/cases/conformance/references/library-reference-3.ts] ////
+
+//// [index.d.ts]
+
+// Secondary references are possible
+
+declare var $: { foo(): void };
+
+//// [consumer.ts]
+/// <reference types="jquery" />
+$.foo();
+
+
+//// [consumer.js]
+/// <reference types="jquery" />
+$.foo();
diff --git a/tests/baselines/reference/library-reference-3.symbols b/tests/baselines/reference/library-reference-3.symbols
new file mode 100644
index 0000000000000..a1785fd77c9a5
--- /dev/null
+++ b/tests/baselines/reference/library-reference-3.symbols
@@ -0,0 +1,15 @@
+=== /src/consumer.ts ===
+/// <reference types="jquery" />
+$.foo();
+>$.foo : Symbol(foo, Decl(index.d.ts, 3, 16))
+>$ : Symbol($, Decl(index.d.ts, 3, 11))
+>foo : Symbol(foo, Decl(index.d.ts, 3, 16))
+
+=== /src/node_modules/jquery/index.d.ts ===
+
+// Secondary references are possible
+
+declare var $: { foo(): void };
+>$ : Symbol($, Decl(index.d.ts, 3, 11))
+>foo : Symbol(foo, Decl(index.d.ts, 3, 16))
+
diff --git a/tests/baselines/reference/library-reference-3.trace.json b/tests/baselines/reference/library-reference-3.trace.json
new file mode 100644
index 0000000000000..30dbbc3fca4d2
--- /dev/null
+++ b/tests/baselines/reference/library-reference-3.trace.json
@@ -0,0 +1,10 @@
+[
+    "======== Resolving type reference directive 'jquery', containing file '/src/consumer.ts', root directory '/src'. ========",
+    "Resolving with primary search path '/src/types/'",
+    "File '/src/types/jquery/package.json' does not exist.",
+    "File '/src/types/jquery/index.d.ts' does not exist.",
+    "Resolving with primary search path '/src/node_modules/'",
+    "File '/src/node_modules/jquery/package.json' does not exist.",
+    "File '/src/node_modules/jquery/index.d.ts' exist - use it as a name resolution result.",
+    "======== Type reference directive 'jquery' was successfully resolved to '/src/node_modules/jquery/index.d.ts', primary: true. ========"
+]
\ No newline at end of file
diff --git a/tests/baselines/reference/library-reference-3.types b/tests/baselines/reference/library-reference-3.types
new file mode 100644
index 0000000000000..ed7da59525f32
--- /dev/null
+++ b/tests/baselines/reference/library-reference-3.types
@@ -0,0 +1,16 @@
+=== /src/consumer.ts ===
+/// <reference types="jquery" />
+$.foo();
+>$.foo() : void
+>$.foo : () => void
+>$ : { foo(): void; }
+>foo : () => void
+
+=== /src/node_modules/jquery/index.d.ts ===
+
+// Secondary references are possible
+
+declare var $: { foo(): void };
+>$ : { foo(): void; }
+>foo : () => void
+
diff --git a/tests/baselines/reference/library-reference-4.js b/tests/baselines/reference/library-reference-4.js
new file mode 100644
index 0000000000000..39e4b1d73a57a
--- /dev/null
+++ b/tests/baselines/reference/library-reference-4.js
@@ -0,0 +1,27 @@
+//// [tests/cases/conformance/references/library-reference-4.ts] ////
+
+//// [index.d.ts]
+
+// Secondary references may be duplicated if they agree in content
+
+/// <reference types="alpha" />
+declare var foo: any;
+
+//// [index.d.ts]
+declare var alpha: any;
+
+//// [index.d.ts]
+/// <reference types="alpha" />
+declare var bar: any;
+
+//// [index.d.ts]
+declare var alpha: any;
+
+//// [root.ts]
+/// <reference types="foo" />
+/// <reference types="bar" />
+
+
+//// [root.js]
+/// <reference types="foo" />
+/// <reference types="bar" />
diff --git a/tests/baselines/reference/library-reference-4.symbols b/tests/baselines/reference/library-reference-4.symbols
new file mode 100644
index 0000000000000..f7c082a946d1a
--- /dev/null
+++ b/tests/baselines/reference/library-reference-4.symbols
@@ -0,0 +1,21 @@
+=== /src/root.ts ===
+/// <reference types="foo" />
+No type information for this code./// <reference types="bar" />
+No type information for this code.
+No type information for this code.=== /node_modules/foo/index.d.ts ===
+
+// Secondary references may be duplicated if they agree in content
+
+/// <reference types="alpha" />
+declare var foo: any;
+>foo : Symbol(foo, Decl(index.d.ts, 4, 11))
+
+=== /node_modules/foo/node_modules/alpha/index.d.ts ===
+declare var alpha: any;
+>alpha : Symbol(alpha, Decl(index.d.ts, 0, 11))
+
+=== /node_modules/bar/index.d.ts ===
+/// <reference types="alpha" />
+declare var bar: any;
+>bar : Symbol(bar, Decl(index.d.ts, 1, 11))
+
diff --git a/tests/baselines/reference/library-reference-4.trace.json b/tests/baselines/reference/library-reference-4.trace.json
new file mode 100644
index 0000000000000..90b6eb7b01d74
--- /dev/null
+++ b/tests/baselines/reference/library-reference-4.trace.json
@@ -0,0 +1,90 @@
+[
+    "======== Resolving type reference directive 'foo', containing file '/src/root.ts', root directory '/src'. ========",
+    "Resolving with primary search path '/src/types/'",
+    "File '/src/types/foo/package.json' does not exist.",
+    "File '/src/types/foo/index.d.ts' does not exist.",
+    "Resolving with primary search path '/src/node_modules/'",
+    "File '/src/node_modules/foo/package.json' does not exist.",
+    "File '/src/node_modules/foo/index.d.ts' does not exist.",
+    "Resolving with primary search path '/src/node_modules/@types/'",
+    "File '/src/node_modules/@types/foo/package.json' does not exist.",
+    "File '/src/node_modules/@types/foo/index.d.ts' does not exist.",
+    "Looking up in 'node_modules' folder, initial location '/src'",
+    "File '/src/node_modules/foo.ts' does not exist.",
+    "File '/src/node_modules/foo.d.ts' does not exist.",
+    "File '/src/node_modules/foo/package.json' does not exist.",
+    "File '/src/node_modules/foo/index.ts' does not exist.",
+    "File '/src/node_modules/foo/index.d.ts' does not exist.",
+    "File '/src/node_modules/@types/foo.ts' does not exist.",
+    "File '/src/node_modules/@types/foo.d.ts' does not exist.",
+    "File '/src/node_modules/@types/foo/package.json' does not exist.",
+    "File '/src/node_modules/@types/foo/index.ts' does not exist.",
+    "File '/src/node_modules/@types/foo/index.d.ts' does not exist.",
+    "File '/node_modules/foo.ts' does not exist.",
+    "File '/node_modules/foo.d.ts' does not exist.",
+    "File '/node_modules/foo/package.json' does not exist.",
+    "File '/node_modules/foo/index.ts' does not exist.",
+    "File '/node_modules/foo/index.d.ts' exist - use it as a name resolution result.",
+    "======== Type reference directive 'foo' was successfully resolved to '/node_modules/foo/index.d.ts', primary: false. ========",
+    "======== Resolving type reference directive 'bar', containing file '/src/root.ts', root directory '/src'. ========",
+    "Resolving with primary search path '/src/types/'",
+    "File '/src/types/bar/package.json' does not exist.",
+    "File '/src/types/bar/index.d.ts' does not exist.",
+    "Resolving with primary search path '/src/node_modules/'",
+    "File '/src/node_modules/bar/package.json' does not exist.",
+    "File '/src/node_modules/bar/index.d.ts' does not exist.",
+    "Resolving with primary search path '/src/node_modules/@types/'",
+    "File '/src/node_modules/@types/bar/package.json' does not exist.",
+    "File '/src/node_modules/@types/bar/index.d.ts' does not exist.",
+    "Looking up in 'node_modules' folder, initial location '/src'",
+    "File '/src/node_modules/bar.ts' does not exist.",
+    "File '/src/node_modules/bar.d.ts' does not exist.",
+    "File '/src/node_modules/bar/package.json' does not exist.",
+    "File '/src/node_modules/bar/index.ts' does not exist.",
+    "File '/src/node_modules/bar/index.d.ts' does not exist.",
+    "File '/src/node_modules/@types/bar.ts' does not exist.",
+    "File '/src/node_modules/@types/bar.d.ts' does not exist.",
+    "File '/src/node_modules/@types/bar/package.json' does not exist.",
+    "File '/src/node_modules/@types/bar/index.ts' does not exist.",
+    "File '/src/node_modules/@types/bar/index.d.ts' does not exist.",
+    "File '/node_modules/bar.ts' does not exist.",
+    "File '/node_modules/bar.d.ts' does not exist.",
+    "File '/node_modules/bar/package.json' does not exist.",
+    "File '/node_modules/bar/index.ts' does not exist.",
+    "File '/node_modules/bar/index.d.ts' exist - use it as a name resolution result.",
+    "======== Type reference directive 'bar' was successfully resolved to '/node_modules/bar/index.d.ts', primary: false. ========",
+    "======== Resolving type reference directive 'alpha', containing file '/node_modules/foo/index.d.ts', root directory '/src'. ========",
+    "Resolving with primary search path '/src/types/'",
+    "File '/src/types/alpha/package.json' does not exist.",
+    "File '/src/types/alpha/index.d.ts' does not exist.",
+    "Resolving with primary search path '/src/node_modules/'",
+    "File '/src/node_modules/alpha/package.json' does not exist.",
+    "File '/src/node_modules/alpha/index.d.ts' does not exist.",
+    "Resolving with primary search path '/src/node_modules/@types/'",
+    "File '/src/node_modules/@types/alpha/package.json' does not exist.",
+    "File '/src/node_modules/@types/alpha/index.d.ts' does not exist.",
+    "Looking up in 'node_modules' folder, initial location '/node_modules/foo'",
+    "File '/node_modules/foo/node_modules/alpha.ts' does not exist.",
+    "File '/node_modules/foo/node_modules/alpha.d.ts' does not exist.",
+    "File '/node_modules/foo/node_modules/alpha/package.json' does not exist.",
+    "File '/node_modules/foo/node_modules/alpha/index.ts' does not exist.",
+    "File '/node_modules/foo/node_modules/alpha/index.d.ts' exist - use it as a name resolution result.",
+    "======== Type reference directive 'alpha' was successfully resolved to '/node_modules/foo/node_modules/alpha/index.d.ts', primary: false. ========",
+    "======== Resolving type reference directive 'alpha', containing file '/node_modules/bar/index.d.ts', root directory '/src'. ========",
+    "Resolving with primary search path '/src/types/'",
+    "File '/src/types/alpha/package.json' does not exist.",
+    "File '/src/types/alpha/index.d.ts' does not exist.",
+    "Resolving with primary search path '/src/node_modules/'",
+    "File '/src/node_modules/alpha/package.json' does not exist.",
+    "File '/src/node_modules/alpha/index.d.ts' does not exist.",
+    "Resolving with primary search path '/src/node_modules/@types/'",
+    "File '/src/node_modules/@types/alpha/package.json' does not exist.",
+    "File '/src/node_modules/@types/alpha/index.d.ts' does not exist.",
+    "Looking up in 'node_modules' folder, initial location '/node_modules/bar'",
+    "File '/node_modules/bar/node_modules/alpha.ts' does not exist.",
+    "File '/node_modules/bar/node_modules/alpha.d.ts' does not exist.",
+    "File '/node_modules/bar/node_modules/alpha/package.json' does not exist.",
+    "File '/node_modules/bar/node_modules/alpha/index.ts' does not exist.",
+    "File '/node_modules/bar/node_modules/alpha/index.d.ts' exist - use it as a name resolution result.",
+    "======== Type reference directive 'alpha' was successfully resolved to '/node_modules/bar/node_modules/alpha/index.d.ts', primary: false. ========"
+]
\ No newline at end of file
diff --git a/tests/baselines/reference/library-reference-4.types b/tests/baselines/reference/library-reference-4.types
new file mode 100644
index 0000000000000..a0a7d370b4cdf
--- /dev/null
+++ b/tests/baselines/reference/library-reference-4.types
@@ -0,0 +1,21 @@
+=== /src/root.ts ===
+/// <reference types="foo" />
+No type information for this code./// <reference types="bar" />
+No type information for this code.
+No type information for this code.=== /node_modules/foo/index.d.ts ===
+
+// Secondary references may be duplicated if they agree in content
+
+/// <reference types="alpha" />
+declare var foo: any;
+>foo : any
+
+=== /node_modules/foo/node_modules/alpha/index.d.ts ===
+declare var alpha: any;
+>alpha : any
+
+=== /node_modules/bar/index.d.ts ===
+/// <reference types="alpha" />
+declare var bar: any;
+>bar : any
+
diff --git a/tests/baselines/reference/library-reference-5.errors.txt b/tests/baselines/reference/library-reference-5.errors.txt
new file mode 100644
index 0000000000000..ea571cad1a3c5
--- /dev/null
+++ b/tests/baselines/reference/library-reference-5.errors.txt
@@ -0,0 +1,26 @@
+/node_modules/bar/index.d.ts(1,1): message TS4090: Conflicting library definitions for 'alpha' found at '/node_modules/bar/node_modules/alpha/index.d.ts' and '/node_modules/foo/node_modules/alpha/index.d.ts'. Copy the correct file to the 'typings' folder to resolve this conflict.
+
+
+==== /src/root.ts (0 errors) ====
+    /// <reference types="foo" />
+    /// <reference types="bar" />
+    
+==== /node_modules/foo/index.d.ts (0 errors) ====
+    
+    // Secondary references may not be duplicated if they disagree in content
+    
+    /// <reference types="alpha" />
+    declare var foo: any;
+    
+==== /node_modules/foo/node_modules/alpha/index.d.ts (0 errors) ====
+    declare var alpha: any;
+    
+==== /node_modules/bar/index.d.ts (1 errors) ====
+    /// <reference types="alpha" />
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! message TS4090: Conflicting library definitions for 'alpha' found at 'index.d.ts' and 'index.d.ts'. Copy the correct file to the 'typings' folder to resolve this conflict.
+    declare var bar: any;
+    
+==== /node_modules/bar/node_modules/alpha/index.d.ts (0 errors) ====
+    declare var alpha: {};
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/library-reference-5.js b/tests/baselines/reference/library-reference-5.js
new file mode 100644
index 0000000000000..40d2131920e3a
--- /dev/null
+++ b/tests/baselines/reference/library-reference-5.js
@@ -0,0 +1,27 @@
+//// [tests/cases/conformance/references/library-reference-5.ts] ////
+
+//// [index.d.ts]
+
+// Secondary references may not be duplicated if they disagree in content
+
+/// <reference types="alpha" />
+declare var foo: any;
+
+//// [index.d.ts]
+declare var alpha: any;
+
+//// [index.d.ts]
+/// <reference types="alpha" />
+declare var bar: any;
+
+//// [index.d.ts]
+declare var alpha: {};
+
+//// [root.ts]
+/// <reference types="foo" />
+/// <reference types="bar" />
+
+
+//// [root.js]
+/// <reference types="foo" />
+/// <reference types="bar" />
diff --git a/tests/baselines/reference/library-reference-5.trace.json b/tests/baselines/reference/library-reference-5.trace.json
new file mode 100644
index 0000000000000..272009782b5ce
--- /dev/null
+++ b/tests/baselines/reference/library-reference-5.trace.json
@@ -0,0 +1,58 @@
+[
+    "======== Resolving type reference directive 'foo', containing file '/src/root.ts', root directory not set. ========",
+    "Root directory cannot be determined, skipping primary search paths.",
+    "Looking up in 'node_modules' folder, initial location '/src'",
+    "File '/src/node_modules/foo.ts' does not exist.",
+    "File '/src/node_modules/foo.d.ts' does not exist.",
+    "File '/src/node_modules/foo/package.json' does not exist.",
+    "File '/src/node_modules/foo/index.ts' does not exist.",
+    "File '/src/node_modules/foo/index.d.ts' does not exist.",
+    "File '/src/node_modules/@types/foo.ts' does not exist.",
+    "File '/src/node_modules/@types/foo.d.ts' does not exist.",
+    "File '/src/node_modules/@types/foo/package.json' does not exist.",
+    "File '/src/node_modules/@types/foo/index.ts' does not exist.",
+    "File '/src/node_modules/@types/foo/index.d.ts' does not exist.",
+    "File '/node_modules/foo.ts' does not exist.",
+    "File '/node_modules/foo.d.ts' does not exist.",
+    "File '/node_modules/foo/package.json' does not exist.",
+    "File '/node_modules/foo/index.ts' does not exist.",
+    "File '/node_modules/foo/index.d.ts' exist - use it as a name resolution result.",
+    "======== Type reference directive 'foo' was successfully resolved to '/node_modules/foo/index.d.ts', primary: false. ========",
+    "======== Resolving type reference directive 'bar', containing file '/src/root.ts', root directory not set. ========",
+    "Root directory cannot be determined, skipping primary search paths.",
+    "Looking up in 'node_modules' folder, initial location '/src'",
+    "File '/src/node_modules/bar.ts' does not exist.",
+    "File '/src/node_modules/bar.d.ts' does not exist.",
+    "File '/src/node_modules/bar/package.json' does not exist.",
+    "File '/src/node_modules/bar/index.ts' does not exist.",
+    "File '/src/node_modules/bar/index.d.ts' does not exist.",
+    "File '/src/node_modules/@types/bar.ts' does not exist.",
+    "File '/src/node_modules/@types/bar.d.ts' does not exist.",
+    "File '/src/node_modules/@types/bar/package.json' does not exist.",
+    "File '/src/node_modules/@types/bar/index.ts' does not exist.",
+    "File '/src/node_modules/@types/bar/index.d.ts' does not exist.",
+    "File '/node_modules/bar.ts' does not exist.",
+    "File '/node_modules/bar.d.ts' does not exist.",
+    "File '/node_modules/bar/package.json' does not exist.",
+    "File '/node_modules/bar/index.ts' does not exist.",
+    "File '/node_modules/bar/index.d.ts' exist - use it as a name resolution result.",
+    "======== Type reference directive 'bar' was successfully resolved to '/node_modules/bar/index.d.ts', primary: false. ========",
+    "======== Resolving type reference directive 'alpha', containing file '/node_modules/foo/index.d.ts', root directory not set. ========",
+    "Root directory cannot be determined, skipping primary search paths.",
+    "Looking up in 'node_modules' folder, initial location '/node_modules/foo'",
+    "File '/node_modules/foo/node_modules/alpha.ts' does not exist.",
+    "File '/node_modules/foo/node_modules/alpha.d.ts' does not exist.",
+    "File '/node_modules/foo/node_modules/alpha/package.json' does not exist.",
+    "File '/node_modules/foo/node_modules/alpha/index.ts' does not exist.",
+    "File '/node_modules/foo/node_modules/alpha/index.d.ts' exist - use it as a name resolution result.",
+    "======== Type reference directive 'alpha' was successfully resolved to '/node_modules/foo/node_modules/alpha/index.d.ts', primary: false. ========",
+    "======== Resolving type reference directive 'alpha', containing file '/node_modules/bar/index.d.ts', root directory not set. ========",
+    "Root directory cannot be determined, skipping primary search paths.",
+    "Looking up in 'node_modules' folder, initial location '/node_modules/bar'",
+    "File '/node_modules/bar/node_modules/alpha.ts' does not exist.",
+    "File '/node_modules/bar/node_modules/alpha.d.ts' does not exist.",
+    "File '/node_modules/bar/node_modules/alpha/package.json' does not exist.",
+    "File '/node_modules/bar/node_modules/alpha/index.ts' does not exist.",
+    "File '/node_modules/bar/node_modules/alpha/index.d.ts' exist - use it as a name resolution result.",
+    "======== Type reference directive 'alpha' was successfully resolved to '/node_modules/bar/node_modules/alpha/index.d.ts', primary: false. ========"
+]
\ No newline at end of file
diff --git a/tests/baselines/reference/library-reference-6.js b/tests/baselines/reference/library-reference-6.js
new file mode 100644
index 0000000000000..d78a3a131a1ce
--- /dev/null
+++ b/tests/baselines/reference/library-reference-6.js
@@ -0,0 +1,16 @@
+//// [tests/cases/conformance/references/library-reference-6.ts] ////
+
+//// [index.d.ts]
+
+// The primary lookup folder is relative to tsconfig.json, if present
+
+declare var alpha: { a: string };
+
+//// [foo.ts]
+/// <reference types="alpha" />
+var x: string = alpha.a;
+
+
+//// [foo.js]
+/// <reference types="alpha" />
+var x = alpha.a;
diff --git a/tests/baselines/reference/library-reference-6.symbols b/tests/baselines/reference/library-reference-6.symbols
new file mode 100644
index 0000000000000..328842f804c56
--- /dev/null
+++ b/tests/baselines/reference/library-reference-6.symbols
@@ -0,0 +1,16 @@
+=== /src/foo.ts ===
+/// <reference types="alpha" />
+var x: string = alpha.a;
+>x : Symbol(x, Decl(foo.ts, 1, 3))
+>alpha.a : Symbol(a, Decl(index.d.ts, 3, 20))
+>alpha : Symbol(alpha, Decl(index.d.ts, 3, 11))
+>a : Symbol(a, Decl(index.d.ts, 3, 20))
+
+=== /types/alpha/index.d.ts ===
+
+// The primary lookup folder is relative to tsconfig.json, if present
+
+declare var alpha: { a: string };
+>alpha : Symbol(alpha, Decl(index.d.ts, 3, 11))
+>a : Symbol(a, Decl(index.d.ts, 3, 20))
+
diff --git a/tests/baselines/reference/library-reference-6.trace.json b/tests/baselines/reference/library-reference-6.trace.json
new file mode 100644
index 0000000000000..426214fdcfc7f
--- /dev/null
+++ b/tests/baselines/reference/library-reference-6.trace.json
@@ -0,0 +1,7 @@
+[
+    "======== Resolving type reference directive 'alpha', containing file '/src/foo.ts', root directory '/'. ========",
+    "Resolving with primary search path '/types/'",
+    "File '/types/alpha/package.json' does not exist.",
+    "File '/types/alpha/index.d.ts' exist - use it as a name resolution result.",
+    "======== Type reference directive 'alpha' was successfully resolved to '/types/alpha/index.d.ts', primary: true. ========"
+]
\ No newline at end of file
diff --git a/tests/baselines/reference/library-reference-6.types b/tests/baselines/reference/library-reference-6.types
new file mode 100644
index 0000000000000..2f6c1e49b891f
--- /dev/null
+++ b/tests/baselines/reference/library-reference-6.types
@@ -0,0 +1,16 @@
+=== /src/foo.ts ===
+/// <reference types="alpha" />
+var x: string = alpha.a;
+>x : string
+>alpha.a : string
+>alpha : { a: string; }
+>a : string
+
+=== /types/alpha/index.d.ts ===
+
+// The primary lookup folder is relative to tsconfig.json, if present
+
+declare var alpha: { a: string };
+>alpha : { a: string; }
+>a : string
+
diff --git a/tests/baselines/reference/library-reference-7.js b/tests/baselines/reference/library-reference-7.js
new file mode 100644
index 0000000000000..f1ef6ca4eab8a
--- /dev/null
+++ b/tests/baselines/reference/library-reference-7.js
@@ -0,0 +1,16 @@
+//// [tests/cases/conformance/references/library-reference-7.ts] ////
+
+//// [index.d.ts]
+
+// Secondary references are possible
+
+declare var $: { foo(): void };
+
+//// [consumer.ts]
+/// <reference types="jquery" />
+$.foo();
+
+
+//// [consumer.js]
+/// <reference types="jquery" />
+$.foo();
diff --git a/tests/baselines/reference/library-reference-7.symbols b/tests/baselines/reference/library-reference-7.symbols
new file mode 100644
index 0000000000000..a1785fd77c9a5
--- /dev/null
+++ b/tests/baselines/reference/library-reference-7.symbols
@@ -0,0 +1,15 @@
+=== /src/consumer.ts ===
+/// <reference types="jquery" />
+$.foo();
+>$.foo : Symbol(foo, Decl(index.d.ts, 3, 16))
+>$ : Symbol($, Decl(index.d.ts, 3, 11))
+>foo : Symbol(foo, Decl(index.d.ts, 3, 16))
+
+=== /src/node_modules/jquery/index.d.ts ===
+
+// Secondary references are possible
+
+declare var $: { foo(): void };
+>$ : Symbol($, Decl(index.d.ts, 3, 11))
+>foo : Symbol(foo, Decl(index.d.ts, 3, 16))
+
diff --git a/tests/baselines/reference/library-reference-7.trace.json b/tests/baselines/reference/library-reference-7.trace.json
new file mode 100644
index 0000000000000..419fe6d055d72
--- /dev/null
+++ b/tests/baselines/reference/library-reference-7.trace.json
@@ -0,0 +1,11 @@
+[
+    "======== Resolving type reference directive 'jquery', containing file '/src/consumer.ts', root directory not set. ========",
+    "Root directory cannot be determined, skipping primary search paths.",
+    "Looking up in 'node_modules' folder, initial location '/src'",
+    "File '/src/node_modules/jquery.ts' does not exist.",
+    "File '/src/node_modules/jquery.d.ts' does not exist.",
+    "File '/src/node_modules/jquery/package.json' does not exist.",
+    "File '/src/node_modules/jquery/index.ts' does not exist.",
+    "File '/src/node_modules/jquery/index.d.ts' exist - use it as a name resolution result.",
+    "======== Type reference directive 'jquery' was successfully resolved to '/src/node_modules/jquery/index.d.ts', primary: false. ========"
+]
\ No newline at end of file
diff --git a/tests/baselines/reference/library-reference-7.types b/tests/baselines/reference/library-reference-7.types
new file mode 100644
index 0000000000000..ed7da59525f32
--- /dev/null
+++ b/tests/baselines/reference/library-reference-7.types
@@ -0,0 +1,16 @@
+=== /src/consumer.ts ===
+/// <reference types="jquery" />
+$.foo();
+>$.foo() : void
+>$.foo : () => void
+>$ : { foo(): void; }
+>foo : () => void
+
+=== /src/node_modules/jquery/index.d.ts ===
+
+// Secondary references are possible
+
+declare var $: { foo(): void };
+>$ : { foo(): void; }
+>foo : () => void
+
diff --git a/tests/baselines/reference/library-reference-8.js b/tests/baselines/reference/library-reference-8.js
new file mode 100644
index 0000000000000..a48b226cb62fc
--- /dev/null
+++ b/tests/baselines/reference/library-reference-8.js
@@ -0,0 +1,24 @@
+//// [tests/cases/conformance/references/library-reference-8.ts] ////
+
+//// [index.d.ts]
+
+// Don't crash in circular library reference situations
+
+/// <reference types="beta" />
+declare var alpha: { a: string };
+
+//// [index.d.ts]
+/// <reference types="alpha" />
+declare var beta: { b: string };
+
+//// [foo.ts]
+/// <reference types="alpha" />
+/// <reference types="beta" />
+var x: string = alpha.a + beta.b;
+
+
+
+//// [foo.js]
+/// <reference types="alpha" />
+/// <reference types="beta" />
+var x = alpha.a + beta.b;
diff --git a/tests/baselines/reference/library-reference-8.symbols b/tests/baselines/reference/library-reference-8.symbols
new file mode 100644
index 0000000000000..299a60f1b1dcb
--- /dev/null
+++ b/tests/baselines/reference/library-reference-8.symbols
@@ -0,0 +1,28 @@
+=== /foo.ts ===
+/// <reference types="alpha" />
+/// <reference types="beta" />
+var x: string = alpha.a + beta.b;
+>x : Symbol(x, Decl(foo.ts, 2, 3))
+>alpha.a : Symbol(a, Decl(index.d.ts, 4, 20))
+>alpha : Symbol(alpha, Decl(index.d.ts, 4, 11))
+>a : Symbol(a, Decl(index.d.ts, 4, 20))
+>beta.b : Symbol(b, Decl(index.d.ts, 1, 19))
+>beta : Symbol(beta, Decl(index.d.ts, 1, 11))
+>b : Symbol(b, Decl(index.d.ts, 1, 19))
+
+
+=== /types/alpha/index.d.ts ===
+
+// Don't crash in circular library reference situations
+
+/// <reference types="beta" />
+declare var alpha: { a: string };
+>alpha : Symbol(alpha, Decl(index.d.ts, 4, 11))
+>a : Symbol(a, Decl(index.d.ts, 4, 20))
+
+=== /types/beta/index.d.ts ===
+/// <reference types="alpha" />
+declare var beta: { b: string };
+>beta : Symbol(beta, Decl(index.d.ts, 1, 11))
+>b : Symbol(b, Decl(index.d.ts, 1, 19))
+
diff --git a/tests/baselines/reference/library-reference-8.trace.json b/tests/baselines/reference/library-reference-8.trace.json
new file mode 100644
index 0000000000000..b1dc64786880d
--- /dev/null
+++ b/tests/baselines/reference/library-reference-8.trace.json
@@ -0,0 +1,22 @@
+[
+    "======== Resolving type reference directive 'alpha', containing file '/foo.ts', root directory '/'. ========",
+    "Resolving with primary search path '/types/'",
+    "File '/types/alpha/package.json' does not exist.",
+    "File '/types/alpha/index.d.ts' exist - use it as a name resolution result.",
+    "======== Type reference directive 'alpha' was successfully resolved to '/types/alpha/index.d.ts', primary: true. ========",
+    "======== Resolving type reference directive 'beta', containing file '/foo.ts', root directory '/'. ========",
+    "Resolving with primary search path '/types/'",
+    "File '/types/beta/package.json' does not exist.",
+    "File '/types/beta/index.d.ts' exist - use it as a name resolution result.",
+    "======== Type reference directive 'beta' was successfully resolved to '/types/beta/index.d.ts', primary: true. ========",
+    "======== Resolving type reference directive 'beta', containing file '/types/alpha/index.d.ts', root directory '/'. ========",
+    "Resolving with primary search path '/types/'",
+    "File '/types/beta/package.json' does not exist.",
+    "File '/types/beta/index.d.ts' exist - use it as a name resolution result.",
+    "======== Type reference directive 'beta' was successfully resolved to '/types/beta/index.d.ts', primary: true. ========",
+    "======== Resolving type reference directive 'alpha', containing file '/types/beta/index.d.ts', root directory '/'. ========",
+    "Resolving with primary search path '/types/'",
+    "File '/types/alpha/package.json' does not exist.",
+    "File '/types/alpha/index.d.ts' exist - use it as a name resolution result.",
+    "======== Type reference directive 'alpha' was successfully resolved to '/types/alpha/index.d.ts', primary: true. ========"
+]
\ No newline at end of file
diff --git a/tests/baselines/reference/library-reference-8.types b/tests/baselines/reference/library-reference-8.types
new file mode 100644
index 0000000000000..b0780d90f63ac
--- /dev/null
+++ b/tests/baselines/reference/library-reference-8.types
@@ -0,0 +1,29 @@
+=== /foo.ts ===
+/// <reference types="alpha" />
+/// <reference types="beta" />
+var x: string = alpha.a + beta.b;
+>x : string
+>alpha.a + beta.b : string
+>alpha.a : string
+>alpha : { a: string; }
+>a : string
+>beta.b : string
+>beta : { b: string; }
+>b : string
+
+
+=== /types/alpha/index.d.ts ===
+
+// Don't crash in circular library reference situations
+
+/// <reference types="beta" />
+declare var alpha: { a: string };
+>alpha : { a: string; }
+>a : string
+
+=== /types/beta/index.d.ts ===
+/// <reference types="alpha" />
+declare var beta: { b: string };
+>beta : { b: string; }
+>b : string
+
diff --git a/tests/baselines/reference/library-reference-9.js b/tests/baselines/reference/library-reference-9.js
new file mode 100644
index 0000000000000..ccb3b3213a9f1
--- /dev/null
+++ b/tests/baselines/reference/library-reference-9.js
@@ -0,0 +1,16 @@
+//// [tests/cases/conformance/references/library-reference-9.ts] ////
+
+//// [index.d.ts]
+
+// Use types search path
+
+declare var alpha: { a: string };
+
+//// [foo.ts]
+/// <reference types="alpha" />
+var x: string = alpha.a;
+
+
+//// [foo.js]
+/// <reference types="alpha" />
+var x = alpha.a;
diff --git a/tests/baselines/reference/library-reference-9.symbols b/tests/baselines/reference/library-reference-9.symbols
new file mode 100644
index 0000000000000..62cde2117dff6
--- /dev/null
+++ b/tests/baselines/reference/library-reference-9.symbols
@@ -0,0 +1,16 @@
+=== /base/src/foo.ts ===
+/// <reference types="alpha" />
+var x: string = alpha.a;
+>x : Symbol(x, Decl(foo.ts, 1, 3))
+>alpha.a : Symbol(a, Decl(index.d.ts, 3, 20))
+>alpha : Symbol(alpha, Decl(index.d.ts, 3, 11))
+>a : Symbol(a, Decl(index.d.ts, 3, 20))
+
+=== /share/typelib/alpha/index.d.ts ===
+
+// Use types search path
+
+declare var alpha: { a: string };
+>alpha : Symbol(alpha, Decl(index.d.ts, 3, 11))
+>a : Symbol(a, Decl(index.d.ts, 3, 20))
+
diff --git a/tests/baselines/reference/library-reference-9.trace.json b/tests/baselines/reference/library-reference-9.trace.json
new file mode 100644
index 0000000000000..e2fdfdc05500c
--- /dev/null
+++ b/tests/baselines/reference/library-reference-9.trace.json
@@ -0,0 +1,7 @@
+[
+    "======== Resolving type reference directive 'alpha', containing file '/base/src/foo.ts', root directory '/'. ========",
+    "Resolving with primary search path '/share/typelib'",
+    "File '/share/typelib/alpha/package.json' does not exist.",
+    "File '/share/typelib/alpha/index.d.ts' exist - use it as a name resolution result.",
+    "======== Type reference directive 'alpha' was successfully resolved to '/share/typelib/alpha/index.d.ts', primary: true. ========"
+]
\ No newline at end of file
diff --git a/tests/baselines/reference/library-reference-9.types b/tests/baselines/reference/library-reference-9.types
new file mode 100644
index 0000000000000..8df2179e24995
--- /dev/null
+++ b/tests/baselines/reference/library-reference-9.types
@@ -0,0 +1,16 @@
+=== /base/src/foo.ts ===
+/// <reference types="alpha" />
+var x: string = alpha.a;
+>x : string
+>alpha.a : string
+>alpha : { a: string; }
+>a : string
+
+=== /share/typelib/alpha/index.d.ts ===
+
+// Use types search path
+
+declare var alpha: { a: string };
+>alpha : { a: string; }
+>a : string
+
diff --git a/tests/baselines/reference/pathMappingBasedModuleResolution3_classic.trace.json b/tests/baselines/reference/pathMappingBasedModuleResolution3_classic.trace.json
index 513198c50b0c4..8b003e05e8f04 100644
--- a/tests/baselines/reference/pathMappingBasedModuleResolution3_classic.trace.json
+++ b/tests/baselines/reference/pathMappingBasedModuleResolution3_classic.trace.json
@@ -3,11 +3,11 @@
     "Explicitly specified module resolution kind: 'Classic'.",
     "'baseUrl' option is set to 'c:/root', using this value to resolve non-relative module name 'folder2/file2'",
     "Resolving module name 'folder2/file2' relative to base url 'c:/root' - 'c:/root/folder2/file2'.",
-    "File 'c:/root/folder2/file2.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/folder2/file2.ts' exist - use it as a name resolution result.",
     "======== Module name 'folder2/file2' was successfully resolved to 'c:/root/folder2/file2.ts'. ========",
     "======== Resolving module './file3' from 'c:/root/folder2/file2.ts'. ========",
     "Explicitly specified module resolution kind: 'Classic'.",
-    "File 'c:/root/folder2/file3.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/folder2/file3.ts' exist - use it as a name resolution result.",
     "======== Module name './file3' was successfully resolved to 'c:/root/folder2/file3.ts'. ========",
     "======== Resolving module 'file4' from 'c:/root/folder2/file2.ts'. ========",
     "Explicitly specified module resolution kind: 'Classic'.",
@@ -19,6 +19,6 @@
     "File 'c:/root/folder2/file4.d.ts' does not exist.",
     "File 'c:/root/file4.ts' does not exist.",
     "File 'c:/root/file4.d.ts' does not exist.",
-    "File 'c:/file4.ts' exist - use it as a module resolution result.",
+    "File 'c:/file4.ts' exist - use it as a name resolution result.",
     "======== Module name 'file4' was successfully resolved to 'c:/file4.ts'. ========"
 ]
\ No newline at end of file
diff --git a/tests/baselines/reference/pathMappingBasedModuleResolution3_node.trace.json b/tests/baselines/reference/pathMappingBasedModuleResolution3_node.trace.json
index 6d0de807bc03c..af5e20a3cc30c 100644
--- a/tests/baselines/reference/pathMappingBasedModuleResolution3_node.trace.json
+++ b/tests/baselines/reference/pathMappingBasedModuleResolution3_node.trace.json
@@ -4,12 +4,12 @@
     "'baseUrl' option is set to 'c:/root', using this value to resolve non-relative module name 'folder2/file2'",
     "Resolving module name 'folder2/file2' relative to base url 'c:/root' - 'c:/root/folder2/file2'.",
     "Loading module as file / folder, candidate module location 'c:/root/folder2/file2'.",
-    "File 'c:/root/folder2/file2.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/folder2/file2.ts' exist - use it as a name resolution result.",
     "======== Module name 'folder2/file2' was successfully resolved to 'c:/root/folder2/file2.ts'. ========",
     "======== Resolving module './file3' from 'c:/root/folder2/file2.ts'. ========",
     "Explicitly specified module resolution kind: 'NodeJs'.",
     "Loading module as file / folder, candidate module location 'c:/root/folder2/file3'.",
-    "File 'c:/root/folder2/file3.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/folder2/file3.ts' exist - use it as a name resolution result.",
     "======== Module name './file3' was successfully resolved to 'c:/root/folder2/file3.ts'. ========",
     "======== Resolving module 'file4' from 'c:/root/folder2/file2.ts'. ========",
     "Explicitly specified module resolution kind: 'NodeJs'.",
@@ -31,6 +31,13 @@
     "File 'c:/root/folder2/node_modules/file4/index.ts' does not exist.",
     "File 'c:/root/folder2/node_modules/file4/index.tsx' does not exist.",
     "File 'c:/root/folder2/node_modules/file4/index.d.ts' does not exist.",
+    "File 'c:/root/folder2/node_modules/@types/file4.ts' does not exist.",
+    "File 'c:/root/folder2/node_modules/@types/file4.tsx' does not exist.",
+    "File 'c:/root/folder2/node_modules/@types/file4.d.ts' does not exist.",
+    "File 'c:/root/folder2/node_modules/@types/file4/package.json' does not exist.",
+    "File 'c:/root/folder2/node_modules/@types/file4/index.ts' does not exist.",
+    "File 'c:/root/folder2/node_modules/@types/file4/index.tsx' does not exist.",
+    "File 'c:/root/folder2/node_modules/@types/file4/index.d.ts' does not exist.",
     "File 'c:/root/node_modules/file4.ts' does not exist.",
     "File 'c:/root/node_modules/file4.tsx' does not exist.",
     "File 'c:/root/node_modules/file4.d.ts' does not exist.",
@@ -38,12 +45,19 @@
     "File 'c:/root/node_modules/file4/index.ts' does not exist.",
     "File 'c:/root/node_modules/file4/index.tsx' does not exist.",
     "File 'c:/root/node_modules/file4/index.d.ts' does not exist.",
+    "File 'c:/root/node_modules/@types/file4.ts' does not exist.",
+    "File 'c:/root/node_modules/@types/file4.tsx' does not exist.",
+    "File 'c:/root/node_modules/@types/file4.d.ts' does not exist.",
+    "File 'c:/root/node_modules/@types/file4/package.json' does not exist.",
+    "File 'c:/root/node_modules/@types/file4/index.ts' does not exist.",
+    "File 'c:/root/node_modules/@types/file4/index.tsx' does not exist.",
+    "File 'c:/root/node_modules/@types/file4/index.d.ts' does not exist.",
     "File 'c:/node_modules/file4.ts' does not exist.",
     "File 'c:/node_modules/file4.tsx' does not exist.",
     "File 'c:/node_modules/file4.d.ts' does not exist.",
     "File 'c:/node_modules/file4/package.json' does not exist.",
     "File 'c:/node_modules/file4/index.ts' does not exist.",
     "File 'c:/node_modules/file4/index.tsx' does not exist.",
-    "File 'c:/node_modules/file4/index.d.ts' exist - use it as a module resolution result.",
+    "File 'c:/node_modules/file4/index.d.ts' exist - use it as a name resolution result.",
     "======== Module name 'file4' was successfully resolved to 'c:/node_modules/file4/index.d.ts'. ========"
 ]
\ No newline at end of file
diff --git a/tests/baselines/reference/pathMappingBasedModuleResolution4_classic.trace.json b/tests/baselines/reference/pathMappingBasedModuleResolution4_classic.trace.json
index 513198c50b0c4..8b003e05e8f04 100644
--- a/tests/baselines/reference/pathMappingBasedModuleResolution4_classic.trace.json
+++ b/tests/baselines/reference/pathMappingBasedModuleResolution4_classic.trace.json
@@ -3,11 +3,11 @@
     "Explicitly specified module resolution kind: 'Classic'.",
     "'baseUrl' option is set to 'c:/root', using this value to resolve non-relative module name 'folder2/file2'",
     "Resolving module name 'folder2/file2' relative to base url 'c:/root' - 'c:/root/folder2/file2'.",
-    "File 'c:/root/folder2/file2.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/folder2/file2.ts' exist - use it as a name resolution result.",
     "======== Module name 'folder2/file2' was successfully resolved to 'c:/root/folder2/file2.ts'. ========",
     "======== Resolving module './file3' from 'c:/root/folder2/file2.ts'. ========",
     "Explicitly specified module resolution kind: 'Classic'.",
-    "File 'c:/root/folder2/file3.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/folder2/file3.ts' exist - use it as a name resolution result.",
     "======== Module name './file3' was successfully resolved to 'c:/root/folder2/file3.ts'. ========",
     "======== Resolving module 'file4' from 'c:/root/folder2/file2.ts'. ========",
     "Explicitly specified module resolution kind: 'Classic'.",
@@ -19,6 +19,6 @@
     "File 'c:/root/folder2/file4.d.ts' does not exist.",
     "File 'c:/root/file4.ts' does not exist.",
     "File 'c:/root/file4.d.ts' does not exist.",
-    "File 'c:/file4.ts' exist - use it as a module resolution result.",
+    "File 'c:/file4.ts' exist - use it as a name resolution result.",
     "======== Module name 'file4' was successfully resolved to 'c:/file4.ts'. ========"
 ]
\ No newline at end of file
diff --git a/tests/baselines/reference/pathMappingBasedModuleResolution4_node.trace.json b/tests/baselines/reference/pathMappingBasedModuleResolution4_node.trace.json
index 6d0de807bc03c..af5e20a3cc30c 100644
--- a/tests/baselines/reference/pathMappingBasedModuleResolution4_node.trace.json
+++ b/tests/baselines/reference/pathMappingBasedModuleResolution4_node.trace.json
@@ -4,12 +4,12 @@
     "'baseUrl' option is set to 'c:/root', using this value to resolve non-relative module name 'folder2/file2'",
     "Resolving module name 'folder2/file2' relative to base url 'c:/root' - 'c:/root/folder2/file2'.",
     "Loading module as file / folder, candidate module location 'c:/root/folder2/file2'.",
-    "File 'c:/root/folder2/file2.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/folder2/file2.ts' exist - use it as a name resolution result.",
     "======== Module name 'folder2/file2' was successfully resolved to 'c:/root/folder2/file2.ts'. ========",
     "======== Resolving module './file3' from 'c:/root/folder2/file2.ts'. ========",
     "Explicitly specified module resolution kind: 'NodeJs'.",
     "Loading module as file / folder, candidate module location 'c:/root/folder2/file3'.",
-    "File 'c:/root/folder2/file3.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/folder2/file3.ts' exist - use it as a name resolution result.",
     "======== Module name './file3' was successfully resolved to 'c:/root/folder2/file3.ts'. ========",
     "======== Resolving module 'file4' from 'c:/root/folder2/file2.ts'. ========",
     "Explicitly specified module resolution kind: 'NodeJs'.",
@@ -31,6 +31,13 @@
     "File 'c:/root/folder2/node_modules/file4/index.ts' does not exist.",
     "File 'c:/root/folder2/node_modules/file4/index.tsx' does not exist.",
     "File 'c:/root/folder2/node_modules/file4/index.d.ts' does not exist.",
+    "File 'c:/root/folder2/node_modules/@types/file4.ts' does not exist.",
+    "File 'c:/root/folder2/node_modules/@types/file4.tsx' does not exist.",
+    "File 'c:/root/folder2/node_modules/@types/file4.d.ts' does not exist.",
+    "File 'c:/root/folder2/node_modules/@types/file4/package.json' does not exist.",
+    "File 'c:/root/folder2/node_modules/@types/file4/index.ts' does not exist.",
+    "File 'c:/root/folder2/node_modules/@types/file4/index.tsx' does not exist.",
+    "File 'c:/root/folder2/node_modules/@types/file4/index.d.ts' does not exist.",
     "File 'c:/root/node_modules/file4.ts' does not exist.",
     "File 'c:/root/node_modules/file4.tsx' does not exist.",
     "File 'c:/root/node_modules/file4.d.ts' does not exist.",
@@ -38,12 +45,19 @@
     "File 'c:/root/node_modules/file4/index.ts' does not exist.",
     "File 'c:/root/node_modules/file4/index.tsx' does not exist.",
     "File 'c:/root/node_modules/file4/index.d.ts' does not exist.",
+    "File 'c:/root/node_modules/@types/file4.ts' does not exist.",
+    "File 'c:/root/node_modules/@types/file4.tsx' does not exist.",
+    "File 'c:/root/node_modules/@types/file4.d.ts' does not exist.",
+    "File 'c:/root/node_modules/@types/file4/package.json' does not exist.",
+    "File 'c:/root/node_modules/@types/file4/index.ts' does not exist.",
+    "File 'c:/root/node_modules/@types/file4/index.tsx' does not exist.",
+    "File 'c:/root/node_modules/@types/file4/index.d.ts' does not exist.",
     "File 'c:/node_modules/file4.ts' does not exist.",
     "File 'c:/node_modules/file4.tsx' does not exist.",
     "File 'c:/node_modules/file4.d.ts' does not exist.",
     "File 'c:/node_modules/file4/package.json' does not exist.",
     "File 'c:/node_modules/file4/index.ts' does not exist.",
     "File 'c:/node_modules/file4/index.tsx' does not exist.",
-    "File 'c:/node_modules/file4/index.d.ts' exist - use it as a module resolution result.",
+    "File 'c:/node_modules/file4/index.d.ts' exist - use it as a name resolution result.",
     "======== Module name 'file4' was successfully resolved to 'c:/node_modules/file4/index.d.ts'. ========"
 ]
\ No newline at end of file
diff --git a/tests/baselines/reference/pathMappingBasedModuleResolution5_classic.trace.json b/tests/baselines/reference/pathMappingBasedModuleResolution5_classic.trace.json
index 099acae2aca50..d1709c82dc676 100644
--- a/tests/baselines/reference/pathMappingBasedModuleResolution5_classic.trace.json
+++ b/tests/baselines/reference/pathMappingBasedModuleResolution5_classic.trace.json
@@ -5,7 +5,7 @@
     "'paths' option is specified, looking for a pattern to match module name 'folder2/file1'.",
     "Module name 'folder2/file1', matched pattern '*'.",
     "Trying substitution '*', candidate module location: 'folder2/file1'.",
-    "File 'c:/root/folder2/file1.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/folder2/file1.ts' exist - use it as a name resolution result.",
     "======== Module name 'folder2/file1' was successfully resolved to 'c:/root/folder2/file1.ts'. ========",
     "======== Resolving module 'folder3/file2' from 'c:/root/folder1/file1.ts'. ========",
     "Module resolution kind is not specified, using 'Classic'.",
@@ -16,7 +16,7 @@
     "File 'c:/root/folder3/file2.ts' does not exist.",
     "File 'c:/root/folder3/file2.d.ts' does not exist.",
     "Trying substitution 'generated/*', candidate module location: 'generated/folder3/file2'.",
-    "File 'c:/root/generated/folder3/file2.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/generated/folder3/file2.ts' exist - use it as a name resolution result.",
     "======== Module name 'folder3/file2' was successfully resolved to 'c:/root/generated/folder3/file2.ts'. ========",
     "======== Resolving module 'components/file3' from 'c:/root/folder1/file1.ts'. ========",
     "Module resolution kind is not specified, using 'Classic'.",
@@ -24,7 +24,7 @@
     "'paths' option is specified, looking for a pattern to match module name 'components/file3'.",
     "Module name 'components/file3', matched pattern 'components/*'.",
     "Trying substitution 'shared/components/*', candidate module location: 'shared/components/file3'.",
-    "File 'c:/root/shared/components/file3.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/shared/components/file3.ts' exist - use it as a name resolution result.",
     "======== Module name 'components/file3' was successfully resolved to 'c:/root/shared/components/file3.ts'. ========",
     "======== Resolving module 'file4' from 'c:/root/folder1/file1.ts'. ========",
     "Module resolution kind is not specified, using 'Classic'.",
@@ -41,6 +41,6 @@
     "File 'c:/root/folder1/file4.d.ts' does not exist.",
     "File 'c:/root/file4.ts' does not exist.",
     "File 'c:/root/file4.d.ts' does not exist.",
-    "File 'c:/file4.ts' exist - use it as a module resolution result.",
+    "File 'c:/file4.ts' exist - use it as a name resolution result.",
     "======== Module name 'file4' was successfully resolved to 'c:/file4.ts'. ========"
 ]
\ No newline at end of file
diff --git a/tests/baselines/reference/pathMappingBasedModuleResolution5_node.trace.json b/tests/baselines/reference/pathMappingBasedModuleResolution5_node.trace.json
index 398d15839de92..cebd59f01b41a 100644
--- a/tests/baselines/reference/pathMappingBasedModuleResolution5_node.trace.json
+++ b/tests/baselines/reference/pathMappingBasedModuleResolution5_node.trace.json
@@ -6,7 +6,7 @@
     "Module name 'folder2/file1', matched pattern '*'.",
     "Trying substitution '*', candidate module location: 'folder2/file1'.",
     "Loading module as file / folder, candidate module location 'c:/root/folder2/file1'.",
-    "File 'c:/root/folder2/file1.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/folder2/file1.ts' exist - use it as a name resolution result.",
     "======== Module name 'folder2/file1' was successfully resolved to 'c:/root/folder2/file1.ts'. ========",
     "======== Resolving module 'folder3/file2' from 'c:/root/folder1/file1.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
@@ -24,7 +24,7 @@
     "File 'c:/root/folder3/file2/index.d.ts' does not exist.",
     "Trying substitution 'generated/*', candidate module location: 'generated/folder3/file2'.",
     "Loading module as file / folder, candidate module location 'c:/root/generated/folder3/file2'.",
-    "File 'c:/root/generated/folder3/file2.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/generated/folder3/file2.ts' exist - use it as a name resolution result.",
     "======== Module name 'folder3/file2' was successfully resolved to 'c:/root/generated/folder3/file2.ts'. ========",
     "======== Resolving module 'components/file3' from 'c:/root/folder1/file1.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
@@ -39,7 +39,7 @@
     "File 'c:/root/shared/components/file3/package.json' does not exist.",
     "File 'c:/root/shared/components/file3/index.ts' does not exist.",
     "File 'c:/root/shared/components/file3/index.tsx' does not exist.",
-    "File 'c:/root/shared/components/file3/index.d.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/shared/components/file3/index.d.ts' exist - use it as a name resolution result.",
     "======== Module name 'components/file3' was successfully resolved to 'c:/root/shared/components/file3/index.d.ts'. ========",
     "======== Resolving module 'file4' from 'c:/root/folder1/file1.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
@@ -72,6 +72,13 @@
     "File 'c:/root/folder1/node_modules/file4/index.ts' does not exist.",
     "File 'c:/root/folder1/node_modules/file4/index.tsx' does not exist.",
     "File 'c:/root/folder1/node_modules/file4/index.d.ts' does not exist.",
+    "File 'c:/root/folder1/node_modules/@types/file4.ts' does not exist.",
+    "File 'c:/root/folder1/node_modules/@types/file4.tsx' does not exist.",
+    "File 'c:/root/folder1/node_modules/@types/file4.d.ts' does not exist.",
+    "File 'c:/root/folder1/node_modules/@types/file4/package.json' does not exist.",
+    "File 'c:/root/folder1/node_modules/@types/file4/index.ts' does not exist.",
+    "File 'c:/root/folder1/node_modules/@types/file4/index.tsx' does not exist.",
+    "File 'c:/root/folder1/node_modules/@types/file4/index.d.ts' does not exist.",
     "File 'c:/root/node_modules/file4.ts' does not exist.",
     "File 'c:/root/node_modules/file4.tsx' does not exist.",
     "File 'c:/root/node_modules/file4.d.ts' does not exist.",
@@ -79,6 +86,13 @@
     "File 'c:/root/node_modules/file4/index.ts' does not exist.",
     "File 'c:/root/node_modules/file4/index.tsx' does not exist.",
     "File 'c:/root/node_modules/file4/index.d.ts' does not exist.",
-    "File 'c:/node_modules/file4.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/node_modules/@types/file4.ts' does not exist.",
+    "File 'c:/root/node_modules/@types/file4.tsx' does not exist.",
+    "File 'c:/root/node_modules/@types/file4.d.ts' does not exist.",
+    "File 'c:/root/node_modules/@types/file4/package.json' does not exist.",
+    "File 'c:/root/node_modules/@types/file4/index.ts' does not exist.",
+    "File 'c:/root/node_modules/@types/file4/index.tsx' does not exist.",
+    "File 'c:/root/node_modules/@types/file4/index.d.ts' does not exist.",
+    "File 'c:/node_modules/file4.ts' exist - use it as a name resolution result.",
     "======== Module name 'file4' was successfully resolved to 'c:/node_modules/file4.ts'. ========"
 ]
\ No newline at end of file
diff --git a/tests/baselines/reference/pathMappingBasedModuleResolution6_classic.trace.json b/tests/baselines/reference/pathMappingBasedModuleResolution6_classic.trace.json
index 0493e9c216b3c..20fc416ccd479 100644
--- a/tests/baselines/reference/pathMappingBasedModuleResolution6_classic.trace.json
+++ b/tests/baselines/reference/pathMappingBasedModuleResolution6_classic.trace.json
@@ -10,7 +10,7 @@
     "File 'c:/root/src/project/file3.d.ts' does not exist.",
     "Trying other entries in 'rootDirs'",
     "Loading 'project/file3' from the root dir 'c:/root/generated/src', candidate location 'c:/root/generated/src/project/file3'",
-    "File 'c:/root/generated/src/project/file3.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/generated/src/project/file3.ts' exist - use it as a name resolution result.",
     "======== Module name './project/file3' was successfully resolved to 'c:/root/generated/src/project/file3.ts'. ========",
     "======== Resolving module '../file2' from 'c:/root/generated/src/project/file3.ts'. ========",
     "Module resolution kind is not specified, using 'Classic'.",
@@ -24,6 +24,6 @@
     "Trying other entries in 'rootDirs'",
     "Loading 'file2' from the root dir 'c:/root/src', candidate location 'c:/root/src/file2'",
     "File 'c:/root/src/file2.ts' does not exist.",
-    "File 'c:/root/src/file2.d.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/src/file2.d.ts' exist - use it as a name resolution result.",
     "======== Module name '../file2' was successfully resolved to 'c:/root/src/file2.d.ts'. ========"
 ]
\ No newline at end of file
diff --git a/tests/baselines/reference/pathMappingBasedModuleResolution6_node.trace.json b/tests/baselines/reference/pathMappingBasedModuleResolution6_node.trace.json
index 4ea2f12a63c35..7c5e76a28474e 100644
--- a/tests/baselines/reference/pathMappingBasedModuleResolution6_node.trace.json
+++ b/tests/baselines/reference/pathMappingBasedModuleResolution6_node.trace.json
@@ -17,7 +17,7 @@
     "Trying other entries in 'rootDirs'",
     "Loading 'project/file3' from the root dir 'c:/root/generated/src', candidate location 'c:/root/generated/src/project/file3'",
     "Loading module as file / folder, candidate module location 'c:/root/generated/src/project/file3'.",
-    "File 'c:/root/generated/src/project/file3.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/generated/src/project/file3.ts' exist - use it as a name resolution result.",
     "======== Module name './project/file3' was successfully resolved to 'c:/root/generated/src/project/file3.ts'. ========",
     "======== Resolving module '../file2' from 'c:/root/generated/src/project/file3.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
@@ -43,6 +43,6 @@
     "File 'c:/root/src/file2/package.json' does not exist.",
     "File 'c:/root/src/file2/index.ts' does not exist.",
     "File 'c:/root/src/file2/index.tsx' does not exist.",
-    "File 'c:/root/src/file2/index.d.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/src/file2/index.d.ts' exist - use it as a name resolution result.",
     "======== Module name '../file2' was successfully resolved to 'c:/root/src/file2/index.d.ts'. ========"
 ]
\ No newline at end of file
diff --git a/tests/baselines/reference/pathMappingBasedModuleResolution7_classic.trace.json b/tests/baselines/reference/pathMappingBasedModuleResolution7_classic.trace.json
index b45cd4754c7ef..2d72108210e21 100644
--- a/tests/baselines/reference/pathMappingBasedModuleResolution7_classic.trace.json
+++ b/tests/baselines/reference/pathMappingBasedModuleResolution7_classic.trace.json
@@ -10,7 +10,7 @@
     "File 'c:/root/src/project/file2.d.ts' does not exist.",
     "Trying other entries in 'rootDirs'",
     "Loading 'project/file2' from the root dir 'c:/root/generated/src', candidate location 'c:/root/generated/src/project/file2'",
-    "File 'c:/root/generated/src/project/file2.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/generated/src/project/file2.ts' exist - use it as a name resolution result.",
     "======== Module name './project/file2' was successfully resolved to 'c:/root/generated/src/project/file2.ts'. ========",
     "======== Resolving module 'module3' from 'c:/root/src/file1.ts'. ========",
     "Module resolution kind is not specified, using 'Classic'.",
@@ -28,7 +28,7 @@
     "File 'c:/root/module3.ts' does not exist.",
     "File 'c:/root/module3.d.ts' does not exist.",
     "File 'c:/module3.ts' does not exist.",
-    "File 'c:/module3.d.ts' exist - use it as a module resolution result.",
+    "File 'c:/module3.d.ts' exist - use it as a name resolution result.",
     "======== Module name 'module3' was successfully resolved to 'c:/module3.d.ts'. ========",
     "======== Resolving module 'module1' from 'c:/root/generated/src/project/file2.ts'. ========",
     "Module resolution kind is not specified, using 'Classic'.",
@@ -40,7 +40,7 @@
     "File 'c:/root/module1.d.ts' does not exist.",
     "Trying substitution 'c:/shared/*', candidate module location: 'c:/shared/module1'.",
     "File 'c:/shared/module1.ts' does not exist.",
-    "File 'c:/shared/module1.d.ts' exist - use it as a module resolution result.",
+    "File 'c:/shared/module1.d.ts' exist - use it as a name resolution result.",
     "======== Module name 'module1' was successfully resolved to 'c:/shared/module1.d.ts'. ========",
     "======== Resolving module 'templates/module2' from 'c:/root/generated/src/project/file2.ts'. ========",
     "Module resolution kind is not specified, using 'Classic'.",
@@ -48,7 +48,7 @@
     "'paths' option is specified, looking for a pattern to match module name 'templates/module2'.",
     "Module name 'templates/module2', matched pattern 'templates/*'.",
     "Trying substitution 'generated/src/templates/*', candidate module location: 'generated/src/templates/module2'.",
-    "File 'c:/root/generated/src/templates/module2.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/generated/src/templates/module2.ts' exist - use it as a name resolution result.",
     "======== Module name 'templates/module2' was successfully resolved to 'c:/root/generated/src/templates/module2.ts'. ========",
     "======== Resolving module '../file3' from 'c:/root/generated/src/project/file2.ts'. ========",
     "Module resolution kind is not specified, using 'Classic'.",
@@ -62,6 +62,6 @@
     "Trying other entries in 'rootDirs'",
     "Loading 'file3' from the root dir 'c:/root/src', candidate location 'c:/root/src/file3'",
     "File 'c:/root/src/file3.ts' does not exist.",
-    "File 'c:/root/src/file3.d.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/src/file3.d.ts' exist - use it as a name resolution result.",
     "======== Module name '../file3' was successfully resolved to 'c:/root/src/file3.d.ts'. ========"
 ]
\ No newline at end of file
diff --git a/tests/baselines/reference/pathMappingBasedModuleResolution7_node.trace.json b/tests/baselines/reference/pathMappingBasedModuleResolution7_node.trace.json
index 39d5c25c92a12..99d4bf244db23 100644
--- a/tests/baselines/reference/pathMappingBasedModuleResolution7_node.trace.json
+++ b/tests/baselines/reference/pathMappingBasedModuleResolution7_node.trace.json
@@ -17,7 +17,7 @@
     "Trying other entries in 'rootDirs'",
     "Loading 'project/file2' from the root dir 'c:/root/generated/src', candidate location 'c:/root/generated/src/project/file2'",
     "Loading module as file / folder, candidate module location 'c:/root/generated/src/project/file2'.",
-    "File 'c:/root/generated/src/project/file2.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/generated/src/project/file2.ts' exist - use it as a name resolution result.",
     "======== Module name './project/file2' was successfully resolved to 'c:/root/generated/src/project/file2.ts'. ========",
     "======== Resolving module 'module3' from 'c:/root/src/file1.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
@@ -50,6 +50,13 @@
     "File 'c:/root/src/node_modules/module3/index.ts' does not exist.",
     "File 'c:/root/src/node_modules/module3/index.tsx' does not exist.",
     "File 'c:/root/src/node_modules/module3/index.d.ts' does not exist.",
+    "File 'c:/root/src/node_modules/@types/module3.ts' does not exist.",
+    "File 'c:/root/src/node_modules/@types/module3.tsx' does not exist.",
+    "File 'c:/root/src/node_modules/@types/module3.d.ts' does not exist.",
+    "File 'c:/root/src/node_modules/@types/module3/package.json' does not exist.",
+    "File 'c:/root/src/node_modules/@types/module3/index.ts' does not exist.",
+    "File 'c:/root/src/node_modules/@types/module3/index.tsx' does not exist.",
+    "File 'c:/root/src/node_modules/@types/module3/index.d.ts' does not exist.",
     "File 'c:/root/node_modules/module3.ts' does not exist.",
     "File 'c:/root/node_modules/module3.tsx' does not exist.",
     "File 'c:/root/node_modules/module3.d.ts' does not exist.",
@@ -57,9 +64,16 @@
     "File 'c:/root/node_modules/module3/index.ts' does not exist.",
     "File 'c:/root/node_modules/module3/index.tsx' does not exist.",
     "File 'c:/root/node_modules/module3/index.d.ts' does not exist.",
+    "File 'c:/root/node_modules/@types/module3.ts' does not exist.",
+    "File 'c:/root/node_modules/@types/module3.tsx' does not exist.",
+    "File 'c:/root/node_modules/@types/module3.d.ts' does not exist.",
+    "File 'c:/root/node_modules/@types/module3/package.json' does not exist.",
+    "File 'c:/root/node_modules/@types/module3/index.ts' does not exist.",
+    "File 'c:/root/node_modules/@types/module3/index.tsx' does not exist.",
+    "File 'c:/root/node_modules/@types/module3/index.d.ts' does not exist.",
     "File 'c:/node_modules/module3.ts' does not exist.",
     "File 'c:/node_modules/module3.tsx' does not exist.",
-    "File 'c:/node_modules/module3.d.ts' exist - use it as a module resolution result.",
+    "File 'c:/node_modules/module3.d.ts' exist - use it as a name resolution result.",
     "======== Module name 'module3' was successfully resolved to 'c:/node_modules/module3.d.ts'. ========",
     "======== Resolving module 'module1' from 'c:/root/generated/src/project/file2.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
@@ -83,7 +97,7 @@
     "File 'c:/shared/module1/package.json' does not exist.",
     "File 'c:/shared/module1/index.ts' does not exist.",
     "File 'c:/shared/module1/index.tsx' does not exist.",
-    "File 'c:/shared/module1/index.d.ts' exist - use it as a module resolution result.",
+    "File 'c:/shared/module1/index.d.ts' exist - use it as a name resolution result.",
     "======== Module name 'module1' was successfully resolved to 'c:/shared/module1/index.d.ts'. ========",
     "======== Resolving module 'templates/module2' from 'c:/root/generated/src/project/file2.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
@@ -92,7 +106,7 @@
     "Module name 'templates/module2', matched pattern 'templates/*'.",
     "Trying substitution 'generated/src/templates/*', candidate module location: 'generated/src/templates/module2'.",
     "Loading module as file / folder, candidate module location 'c:/root/generated/src/templates/module2'.",
-    "File 'c:/root/generated/src/templates/module2.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/generated/src/templates/module2.ts' exist - use it as a name resolution result.",
     "======== Module name 'templates/module2' was successfully resolved to 'c:/root/generated/src/templates/module2.ts'. ========",
     "======== Resolving module '../file3' from 'c:/root/generated/src/project/file2.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
@@ -118,6 +132,6 @@
     "File 'c:/root/src/file3/package.json' does not exist.",
     "File 'c:/root/src/file3/index.ts' does not exist.",
     "File 'c:/root/src/file3/index.tsx' does not exist.",
-    "File 'c:/root/src/file3/index.d.ts' exist - use it as a module resolution result.",
+    "File 'c:/root/src/file3/index.d.ts' exist - use it as a name resolution result.",
     "======== Module name '../file3' was successfully resolved to 'c:/root/src/file3/index.d.ts'. ========"
 ]
\ No newline at end of file
diff --git a/tests/cases/compiler/pathMappingBasedModuleResolution1_classic.ts b/tests/cases/compiler/pathMappingBasedModuleResolution1_classic.ts
index 20845a49372ab..054d6ed8a0b68 100644
--- a/tests/cases/compiler/pathMappingBasedModuleResolution1_classic.ts
+++ b/tests/cases/compiler/pathMappingBasedModuleResolution1_classic.ts
@@ -1,5 +1,5 @@
 // @module: amd
-// @traceModuleResolution: true
+// @traceResolution: true
 
 // paths should error in the absence of baseurl
 
diff --git a/tests/cases/compiler/pathMappingBasedModuleResolution1_node.ts b/tests/cases/compiler/pathMappingBasedModuleResolution1_node.ts
index 392e85bd7c39c..a0ce95f2c1a7f 100644
--- a/tests/cases/compiler/pathMappingBasedModuleResolution1_node.ts
+++ b/tests/cases/compiler/pathMappingBasedModuleResolution1_node.ts
@@ -1,5 +1,5 @@
 // @module: commonjs
-// @traceModuleResolution: true
+// @traceResolution: true
 
 // paths should error in the absence of baseurl
 // @filename: c:/root/tsconfig.json
diff --git a/tests/cases/compiler/pathMappingBasedModuleResolution2_classic.ts b/tests/cases/compiler/pathMappingBasedModuleResolution2_classic.ts
index 6c84a197eeb13..f24e857fa416f 100644
--- a/tests/cases/compiler/pathMappingBasedModuleResolution2_classic.ts
+++ b/tests/cases/compiler/pathMappingBasedModuleResolution2_classic.ts
@@ -1,5 +1,5 @@
 // @module: amd
-// @traceModuleResolution: true
+// @traceResolution: true
 
 // baseurl is defined in tsconfig.json
 // paths has errors
diff --git a/tests/cases/compiler/pathMappingBasedModuleResolution2_node.ts b/tests/cases/compiler/pathMappingBasedModuleResolution2_node.ts
index 78ef7215e737e..ac4d51bacf50d 100644
--- a/tests/cases/compiler/pathMappingBasedModuleResolution2_node.ts
+++ b/tests/cases/compiler/pathMappingBasedModuleResolution2_node.ts
@@ -1,5 +1,5 @@
 // @module: commonjs
-// @traceModuleResolution: true
+// @traceResolution: true
 
 // baseurl is defined in tsconfig.json
 // paths has errors
diff --git a/tests/cases/compiler/pathMappingBasedModuleResolution3_classic.ts b/tests/cases/compiler/pathMappingBasedModuleResolution3_classic.ts
index d46308d089fb0..350346adebcf0 100644
--- a/tests/cases/compiler/pathMappingBasedModuleResolution3_classic.ts
+++ b/tests/cases/compiler/pathMappingBasedModuleResolution3_classic.ts
@@ -1,7 +1,7 @@
 // @moduleResolution: classic
 // @module: amd
 // @baseUrl: c:/root
-// @traceModuleResolution: true
+// @traceResolution: true
 
 // baseUrl set via command line
 
diff --git a/tests/cases/compiler/pathMappingBasedModuleResolution3_node.ts b/tests/cases/compiler/pathMappingBasedModuleResolution3_node.ts
index 30e95c9303ee6..6cab1df06b064 100644
--- a/tests/cases/compiler/pathMappingBasedModuleResolution3_node.ts
+++ b/tests/cases/compiler/pathMappingBasedModuleResolution3_node.ts
@@ -1,7 +1,7 @@
 // @moduleResolution: node
 // @module: commonjs
 // @baseUrl: c:/root
-// @traceModuleResolution: true
+// @traceResolution: true
 
 // baseUrl set via command line
 
diff --git a/tests/cases/compiler/pathMappingBasedModuleResolution4_classic.ts b/tests/cases/compiler/pathMappingBasedModuleResolution4_classic.ts
index 723de05b70c14..fbf11e6171646 100644
--- a/tests/cases/compiler/pathMappingBasedModuleResolution4_classic.ts
+++ b/tests/cases/compiler/pathMappingBasedModuleResolution4_classic.ts
@@ -1,6 +1,6 @@
 // @moduleResolution: classic
 // @module: amd
-// @traceModuleResolution: true
+// @traceResolution: true
 
 // baseUrl set via command line
 
diff --git a/tests/cases/compiler/pathMappingBasedModuleResolution4_node.ts b/tests/cases/compiler/pathMappingBasedModuleResolution4_node.ts
index e68635e205e57..cfb90ca1cc5c0 100644
--- a/tests/cases/compiler/pathMappingBasedModuleResolution4_node.ts
+++ b/tests/cases/compiler/pathMappingBasedModuleResolution4_node.ts
@@ -1,6 +1,6 @@
 // @moduleResolution: node
 // @module: commonjs
-// @traceModuleResolution: true
+// @traceResolution: true
 
 // baseUrl set via command line
 
diff --git a/tests/cases/compiler/pathMappingBasedModuleResolution5_classic.ts b/tests/cases/compiler/pathMappingBasedModuleResolution5_classic.ts
index a7662688e373a..9779f0ca64494 100644
--- a/tests/cases/compiler/pathMappingBasedModuleResolution5_classic.ts
+++ b/tests/cases/compiler/pathMappingBasedModuleResolution5_classic.ts
@@ -1,5 +1,5 @@
 // @module: amd
-// @traceModuleResolution: true
+// @traceResolution: true
 
 // paths is defined in tsconfig.json
 // @filename: c:/root/tsconfig.json
diff --git a/tests/cases/compiler/pathMappingBasedModuleResolution5_node.ts b/tests/cases/compiler/pathMappingBasedModuleResolution5_node.ts
index ef5ef0afd6a52..3606ab08cd10c 100644
--- a/tests/cases/compiler/pathMappingBasedModuleResolution5_node.ts
+++ b/tests/cases/compiler/pathMappingBasedModuleResolution5_node.ts
@@ -1,5 +1,5 @@
 // @module: commonjs
-// @traceModuleResolution: true
+// @traceResolution: true
 
 // paths is defined in tsconfig.json
 // @filename: c:/root/tsconfig.json
diff --git a/tests/cases/compiler/pathMappingBasedModuleResolution6_classic.ts b/tests/cases/compiler/pathMappingBasedModuleResolution6_classic.ts
index adaba8478c997..5ce4bd2a18f54 100644
--- a/tests/cases/compiler/pathMappingBasedModuleResolution6_classic.ts
+++ b/tests/cases/compiler/pathMappingBasedModuleResolution6_classic.ts
@@ -1,5 +1,5 @@
 // @module: amd
-// @traceModuleResolution: true
+// @traceResolution: true
 
 // @filename: c:/root/src/tsconfig.json
 {
diff --git a/tests/cases/compiler/pathMappingBasedModuleResolution6_node.ts b/tests/cases/compiler/pathMappingBasedModuleResolution6_node.ts
index a3d0feadf7c9e..29a82e5412d9e 100644
--- a/tests/cases/compiler/pathMappingBasedModuleResolution6_node.ts
+++ b/tests/cases/compiler/pathMappingBasedModuleResolution6_node.ts
@@ -1,5 +1,5 @@
 // @module: commonjs
-// @traceModuleResolution: true
+// @traceResolution: true
 
 // @filename: c:/root/src/tsconfig.json
 {
diff --git a/tests/cases/compiler/pathMappingBasedModuleResolution7_classic.ts b/tests/cases/compiler/pathMappingBasedModuleResolution7_classic.ts
index af092df5ce95f..81c2328df670f 100644
--- a/tests/cases/compiler/pathMappingBasedModuleResolution7_classic.ts
+++ b/tests/cases/compiler/pathMappingBasedModuleResolution7_classic.ts
@@ -1,5 +1,5 @@
 // @module: amd
-// @traceModuleResolution: true
+// @traceResolution: true
 
 // @filename: c:/root/src/tsconfig.json
 {
diff --git a/tests/cases/compiler/pathMappingBasedModuleResolution7_node.ts b/tests/cases/compiler/pathMappingBasedModuleResolution7_node.ts
index faecbe4adb91e..1ba9630e0cfab 100644
--- a/tests/cases/compiler/pathMappingBasedModuleResolution7_node.ts
+++ b/tests/cases/compiler/pathMappingBasedModuleResolution7_node.ts
@@ -1,5 +1,5 @@
 // @module: commonjs
-// @traceModuleResolution: true
+// @traceResolution: true
 
 // @filename: c:/root/src/tsconfig.json
 {
diff --git a/tests/cases/conformance/references/library-reference-1.ts b/tests/cases/conformance/references/library-reference-1.ts
new file mode 100644
index 0000000000000..ca25441521fcc
--- /dev/null
+++ b/tests/cases/conformance/references/library-reference-1.ts
@@ -0,0 +1,13 @@
+// @noImplicitReferences: true
+// @traceResolution: true
+// @typesRoot: /
+
+// We can find typings in the ./types folder
+
+// @filename: /types/jquery/index.d.ts
+declare var $: { foo(): void };
+
+
+// @filename: /consumer.ts
+/// <reference types="jquery" />
+$.foo();
diff --git a/tests/cases/conformance/references/library-reference-10.ts b/tests/cases/conformance/references/library-reference-10.ts
new file mode 100644
index 0000000000000..11e065b0a7db9
--- /dev/null
+++ b/tests/cases/conformance/references/library-reference-10.ts
@@ -0,0 +1,18 @@
+// @noImplicitReferences: true
+// @traceResolution: true
+// @typesRoot: /
+
+// package.json in a primary reference can refer to another file
+
+// @filename: /types/jquery/package.json
+{
+    "typings": "jquery.d.ts"
+}
+
+// @filename: /types/jquery/jquery.d.ts
+declare var $: { foo(): void };
+
+
+// @filename: /consumer.ts
+/// <reference types="jquery" />
+$.foo();
diff --git a/tests/cases/conformance/references/library-reference-11.ts b/tests/cases/conformance/references/library-reference-11.ts
new file mode 100644
index 0000000000000..39c8af5654311
--- /dev/null
+++ b/tests/cases/conformance/references/library-reference-11.ts
@@ -0,0 +1,17 @@
+// @noImplicitReferences: true
+// @traceResolution: true
+
+// package.json in a secondary reference can refer to another file
+
+// @filename: /a/node_modules/jquery/package.json
+{
+    "typings": "jquery.d.ts"
+}
+
+// @filename: /a/node_modules/jquery/jquery.d.ts
+declare var $: { foo(): void };
+
+
+// @filename: /a/b/consumer.ts
+/// <reference types="jquery" />
+$.foo();
diff --git a/tests/cases/conformance/references/library-reference-12.ts b/tests/cases/conformance/references/library-reference-12.ts
new file mode 100644
index 0000000000000..c61d6d916ff16
--- /dev/null
+++ b/tests/cases/conformance/references/library-reference-12.ts
@@ -0,0 +1,17 @@
+// @noImplicitReferences: true
+// @traceResolution: true
+
+// package.json in a secondary reference can refer to another file
+
+// @filename: /a/node_modules/jquery/package.json
+{
+    "types": "dist/jquery.d.ts"
+}
+
+// @filename: /a/node_modules/jquery/dist/jquery.d.ts
+declare var $: { foo(): void };
+
+
+// @filename: /a/b/consumer.ts
+/// <reference types="jquery" />
+$.foo();
diff --git a/tests/cases/conformance/references/library-reference-13.ts b/tests/cases/conformance/references/library-reference-13.ts
new file mode 100644
index 0000000000000..a96437f9b2c3b
--- /dev/null
+++ b/tests/cases/conformance/references/library-reference-13.ts
@@ -0,0 +1,18 @@
+// @noImplicitReferences: true
+// @traceResolution: true
+
+// load type declarations from types section of tsconfig
+
+// @filename: /a/tsconfig.json
+{
+    "compilerOptions": {
+        "types": [ "jquery" ]
+    }
+}
+
+// @filename: /a/types/jquery/index.d.ts
+declare var $: { foo(): void };
+
+
+// @filename: /a/b/consumer.ts
+$.foo();
diff --git a/tests/cases/conformance/references/library-reference-14.ts b/tests/cases/conformance/references/library-reference-14.ts
new file mode 100644
index 0000000000000..53bca2ab40d16
--- /dev/null
+++ b/tests/cases/conformance/references/library-reference-14.ts
@@ -0,0 +1,11 @@
+// @noImplicitReferences: true
+// @traceResolution: true
+// @types: jquery
+// @typesRoot: /a
+
+// @filename: /a/types/jquery/index.d.ts
+declare var $: { foo(): void };
+
+
+// @filename: /a/b/consumer.ts
+$.foo();
diff --git a/tests/cases/conformance/references/library-reference-15.ts b/tests/cases/conformance/references/library-reference-15.ts
new file mode 100644
index 0000000000000..92c96e74c9795
--- /dev/null
+++ b/tests/cases/conformance/references/library-reference-15.ts
@@ -0,0 +1,10 @@
+// @noImplicitReferences: true
+// @traceResolution: true
+// @types: jquery
+
+// @filename: /a/types/jquery/index.d.ts
+declare var $: { foo(): void };
+
+
+// @filename: /a/b/consumer.ts
+$.foo();
diff --git a/tests/cases/conformance/references/library-reference-2.ts b/tests/cases/conformance/references/library-reference-2.ts
new file mode 100644
index 0000000000000..d8975664428cb
--- /dev/null
+++ b/tests/cases/conformance/references/library-reference-2.ts
@@ -0,0 +1,18 @@
+// @noImplicitReferences: true
+// @traceResolution: true
+// @typesRoot: /
+
+// package.json in a primary reference can refer to another file
+
+// @filename: /types/jquery/package.json
+{
+    "types": "jquery.d.ts"
+}
+
+// @filename: /types/jquery/jquery.d.ts
+declare var $: { foo(): void };
+
+
+// @filename: /consumer.ts
+/// <reference types="jquery" />
+$.foo();
diff --git a/tests/cases/conformance/references/library-reference-3.ts b/tests/cases/conformance/references/library-reference-3.ts
new file mode 100644
index 0000000000000..1af6df89d19d6
--- /dev/null
+++ b/tests/cases/conformance/references/library-reference-3.ts
@@ -0,0 +1,12 @@
+// @noImplicitReferences: true
+// @traceResolution: true
+// @typesRoot: /src
+
+// Secondary references are possible
+
+// @filename: /src/node_modules/jquery/index.d.ts
+declare var $: { foo(): void };
+
+// @filename: /src/consumer.ts
+/// <reference types="jquery" />
+$.foo();
diff --git a/tests/cases/conformance/references/library-reference-4.ts b/tests/cases/conformance/references/library-reference-4.ts
new file mode 100644
index 0000000000000..92f1b4008beb6
--- /dev/null
+++ b/tests/cases/conformance/references/library-reference-4.ts
@@ -0,0 +1,23 @@
+// @noImplicitReferences: true
+// @traceResolution: true
+// @typesRoot: /src
+
+// Secondary references may be duplicated if they agree in content
+
+// @filename: /node_modules/foo/index.d.ts
+/// <reference types="alpha" />
+declare var foo: any;
+
+// @filename: /node_modules/foo/node_modules/alpha/index.d.ts
+declare var alpha: any;
+
+// @filename: /node_modules/bar/index.d.ts
+/// <reference types="alpha" />
+declare var bar: any;
+
+// @filename: /node_modules/bar/node_modules/alpha/index.d.ts
+declare var alpha: any;
+
+// @filename: /src/root.ts
+/// <reference types="foo" />
+/// <reference types="bar" />
diff --git a/tests/cases/conformance/references/library-reference-5.ts b/tests/cases/conformance/references/library-reference-5.ts
new file mode 100644
index 0000000000000..4660da00a2a20
--- /dev/null
+++ b/tests/cases/conformance/references/library-reference-5.ts
@@ -0,0 +1,22 @@
+// @noImplicitReferences: true
+// @traceResolution: true
+
+// Secondary references may not be duplicated if they disagree in content
+
+// @filename: /node_modules/foo/index.d.ts
+/// <reference types="alpha" />
+declare var foo: any;
+
+// @filename: /node_modules/foo/node_modules/alpha/index.d.ts
+declare var alpha: any;
+
+// @filename: /node_modules/bar/index.d.ts
+/// <reference types="alpha" />
+declare var bar: any;
+
+// @filename: /node_modules/bar/node_modules/alpha/index.d.ts
+declare var alpha: {};
+
+// @filename: /src/root.ts
+/// <reference types="foo" />
+/// <reference types="bar" />
diff --git a/tests/cases/conformance/references/library-reference-6.ts b/tests/cases/conformance/references/library-reference-6.ts
new file mode 100644
index 0000000000000..a746262dd73b1
--- /dev/null
+++ b/tests/cases/conformance/references/library-reference-6.ts
@@ -0,0 +1,15 @@
+// @noImplicitReferences: true
+// @traceResolution: true
+
+// The primary lookup folder is relative to tsconfig.json, if present
+
+// @filename: /types/alpha/index.d.ts
+declare var alpha: { a: string };
+
+// @filename: /src/foo.ts
+/// <reference types="alpha" />
+var x: string = alpha.a;
+
+// @filename: /tsconfig.json
+{
+}
diff --git a/tests/cases/conformance/references/library-reference-7.ts b/tests/cases/conformance/references/library-reference-7.ts
new file mode 100644
index 0000000000000..e938aef7d3a68
--- /dev/null
+++ b/tests/cases/conformance/references/library-reference-7.ts
@@ -0,0 +1,11 @@
+// @noImplicitReferences: true
+// @traceResolution: true
+
+// Secondary references are possible
+
+// @filename: /src/node_modules/jquery/index.d.ts
+declare var $: { foo(): void };
+
+// @filename: /src/consumer.ts
+/// <reference types="jquery" />
+$.foo();
diff --git a/tests/cases/conformance/references/library-reference-8.ts b/tests/cases/conformance/references/library-reference-8.ts
new file mode 100644
index 0000000000000..9de93776989b5
--- /dev/null
+++ b/tests/cases/conformance/references/library-reference-8.ts
@@ -0,0 +1,19 @@
+// @noImplicitReferences: true
+// @traceResolution: true
+// @typesRoot: /
+
+// Don't crash in circular library reference situations
+
+// @filename: /types/alpha/index.d.ts
+/// <reference types="beta" />
+declare var alpha: { a: string };
+
+// @filename: /types/beta/index.d.ts
+/// <reference types="alpha" />
+declare var beta: { b: string };
+
+// @filename: /foo.ts
+/// <reference types="alpha" />
+/// <reference types="beta" />
+var x: string = alpha.a + beta.b;
+
diff --git a/tests/cases/conformance/references/library-reference-9.ts b/tests/cases/conformance/references/library-reference-9.ts
new file mode 100644
index 0000000000000..a187d3c23b91f
--- /dev/null
+++ b/tests/cases/conformance/references/library-reference-9.ts
@@ -0,0 +1,20 @@
+// @noImplicitReferences: true
+// @traceResolution: true
+
+// Use types search path
+
+// @filename: /share/typelib/alpha/index.d.ts
+declare var alpha: { a: string };
+
+// @filename: /base/src/foo.ts
+/// <reference types="alpha" />
+var x: string = alpha.a;
+
+// @filename: /tsconfig.json
+{
+    "compilerOptions": {
+        "typesSearchPaths": [
+            "./share/typelib"
+        ]
+    }
+}
diff --git a/tests/cases/fourslash/goToDefinitionTypeReferenceDirective.ts b/tests/cases/fourslash/goToDefinitionTypeReferenceDirective.ts
new file mode 100644
index 0000000000000..3aaa3ab980f08
--- /dev/null
+++ b/tests/cases/fourslash/goToDefinitionTypeReferenceDirective.ts
@@ -0,0 +1,13 @@
+/// <reference path="fourslash.ts"/>
+
+// @typesRoot: src
+// @Filename: src/types/lib/index.d.ts
+/////*0*/declare let $: {x: number};
+
+// @Filename: src/app.ts
+//// /// <reference types="lib/*1*/"/>
+//// $.x;
+
+goTo.marker("1");
+goTo.definition();
+verify.caretAtMarker("0");
\ No newline at end of file
diff --git a/tests/cases/fourslash/shims-pp/goToDefinitionTypeReferenceDirective.ts b/tests/cases/fourslash/shims-pp/goToDefinitionTypeReferenceDirective.ts
new file mode 100644
index 0000000000000..3aaa3ab980f08
--- /dev/null
+++ b/tests/cases/fourslash/shims-pp/goToDefinitionTypeReferenceDirective.ts
@@ -0,0 +1,13 @@
+/// <reference path="fourslash.ts"/>
+
+// @typesRoot: src
+// @Filename: src/types/lib/index.d.ts
+/////*0*/declare let $: {x: number};
+
+// @Filename: src/app.ts
+//// /// <reference types="lib/*1*/"/>
+//// $.x;
+
+goTo.marker("1");
+goTo.definition();
+verify.caretAtMarker("0");
\ No newline at end of file
diff --git a/tests/cases/fourslash/shims/goToDefinitionTypeReferenceDirective.ts b/tests/cases/fourslash/shims/goToDefinitionTypeReferenceDirective.ts
new file mode 100644
index 0000000000000..3aaa3ab980f08
--- /dev/null
+++ b/tests/cases/fourslash/shims/goToDefinitionTypeReferenceDirective.ts
@@ -0,0 +1,13 @@
+/// <reference path="fourslash.ts"/>
+
+// @typesRoot: src
+// @Filename: src/types/lib/index.d.ts
+/////*0*/declare let $: {x: number};
+
+// @Filename: src/app.ts
+//// /// <reference types="lib/*1*/"/>
+//// $.x;
+
+goTo.marker("1");
+goTo.definition();
+verify.caretAtMarker("0");
\ No newline at end of file
diff --git a/tests/cases/unittests/convertToBase64.ts b/tests/cases/unittests/convertToBase64.ts
index 76f56f7747779..c73d7531c405b 100644
--- a/tests/cases/unittests/convertToBase64.ts
+++ b/tests/cases/unittests/convertToBase64.ts
@@ -8,26 +8,28 @@ module ts {
             assert.equal(actual, expected, "Encoded string using convertToBase64 does not match buffer.toString('base64')");
         }
 
-        it("Converts ASCII charaters correctly", () => {
-            runTest(" !\"#$ %&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~");
-        });
+        if (Buffer) {
+            it("Converts ASCII charaters correctly", () => {
+                runTest(" !\"#$ %&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~");
+            });
 
-        it("Converts escape sequences correctly", () => {
-            runTest("\t\n\r\\\"\'\u0062");
-        });
+            it("Converts escape sequences correctly", () => {
+                runTest("\t\n\r\\\"\'\u0062");
+            });
 
-        it("Converts simple unicode characters correctly", () => {
-            runTest("ΠΣ ٵپ औठ ⺐⺠");
-        });
+            it("Converts simple unicode characters correctly", () => {
+                runTest("ΠΣ ٵپ औठ ⺐⺠");
+            });
 
-        it("Converts simple code snippet correctly", () => {
-            runTest(`/// <reference path="file.ts" /> 
+            it("Converts simple code snippet correctly", () => {
+                runTest(`/// <reference path="file.ts" /> 
 var x: string = "string";
 console.log(x);`);
-        });
+            });
 
-        it("Converts simple code snippet with unicode characters correctly", () => {
-            runTest(`var Π = 3.1415; console.log(Π);`);
-        });
+            it("Converts simple code snippet with unicode characters correctly", () => {
+                runTest(`var Π = 3.1415; console.log(Π);`);
+            });
+        }
     });
 }
diff --git a/tests/cases/unittests/moduleResolution.ts b/tests/cases/unittests/moduleResolution.ts
index 9a52d9896e490..29fde3318928d 100644
--- a/tests/cases/unittests/moduleResolution.ts
+++ b/tests/cases/unittests/moduleResolution.ts
@@ -204,6 +204,13 @@ module ts {
                     "/a/b/c/d/node_modules/foo/index.ts",
                     "/a/b/c/d/node_modules/foo/index.tsx",
                     "/a/b/c/d/node_modules/foo/index.d.ts",
+                    "/a/b/c/d/node_modules/@types/foo.ts",
+                    "/a/b/c/d/node_modules/@types/foo.tsx",
+                    "/a/b/c/d/node_modules/@types/foo.d.ts",
+                    "/a/b/c/d/node_modules/@types/foo/package.json",
+                    "/a/b/c/d/node_modules/@types/foo/index.ts",
+                    "/a/b/c/d/node_modules/@types/foo/index.tsx",
+                    "/a/b/c/d/node_modules/@types/foo/index.d.ts",
                     "/a/b/c/node_modules/foo.ts",
                     "/a/b/c/node_modules/foo.tsx",
                     "/a/b/c/node_modules/foo.d.ts",
@@ -211,6 +218,13 @@ module ts {
                     "/a/b/c/node_modules/foo/index.ts",
                     "/a/b/c/node_modules/foo/index.tsx",
                     "/a/b/c/node_modules/foo/index.d.ts",
+                    "/a/b/c/node_modules/@types/foo.ts",
+                    "/a/b/c/node_modules/@types/foo.tsx",
+                    "/a/b/c/node_modules/@types/foo.d.ts",
+                    "/a/b/c/node_modules/@types/foo/package.json",
+                    "/a/b/c/node_modules/@types/foo/index.ts",
+                    "/a/b/c/node_modules/@types/foo/index.tsx",
+                    "/a/b/c/node_modules/@types/foo/index.d.ts",
                 ])
             }
         });
@@ -246,6 +260,13 @@ module ts {
                     "/a/node_modules/b/c/node_modules/d/node_modules/foo/index.ts",
                     "/a/node_modules/b/c/node_modules/d/node_modules/foo/index.tsx",
                     "/a/node_modules/b/c/node_modules/d/node_modules/foo/index.d.ts",
+                    "/a/node_modules/b/c/node_modules/d/node_modules/@types/foo.ts",
+                    "/a/node_modules/b/c/node_modules/d/node_modules/@types/foo.tsx",
+                    "/a/node_modules/b/c/node_modules/d/node_modules/@types/foo.d.ts",
+                    "/a/node_modules/b/c/node_modules/d/node_modules/@types/foo/package.json",
+                    "/a/node_modules/b/c/node_modules/d/node_modules/@types/foo/index.ts",
+                    "/a/node_modules/b/c/node_modules/d/node_modules/@types/foo/index.tsx",
+                    "/a/node_modules/b/c/node_modules/d/node_modules/@types/foo/index.d.ts",
                     "/a/node_modules/b/c/node_modules/foo.ts",
                     "/a/node_modules/b/c/node_modules/foo.tsx",
                     "/a/node_modules/b/c/node_modules/foo.d.ts",
@@ -253,6 +274,13 @@ module ts {
                     "/a/node_modules/b/c/node_modules/foo/index.ts",
                     "/a/node_modules/b/c/node_modules/foo/index.tsx",
                     "/a/node_modules/b/c/node_modules/foo/index.d.ts",
+                    "/a/node_modules/b/c/node_modules/@types/foo.ts",
+                    "/a/node_modules/b/c/node_modules/@types/foo.tsx",
+                    "/a/node_modules/b/c/node_modules/@types/foo.d.ts",
+                    "/a/node_modules/b/c/node_modules/@types/foo/package.json",
+                    "/a/node_modules/b/c/node_modules/@types/foo/index.ts",
+                    "/a/node_modules/b/c/node_modules/@types/foo/index.tsx",
+                    "/a/node_modules/b/c/node_modules/@types/foo/index.d.ts",
                     "/a/node_modules/b/node_modules/foo.ts",
                     "/a/node_modules/b/node_modules/foo.tsx",
                     "/a/node_modules/b/node_modules/foo.d.ts",
@@ -260,6 +288,13 @@ module ts {
                     "/a/node_modules/b/node_modules/foo/index.ts",
                     "/a/node_modules/b/node_modules/foo/index.tsx",
                     "/a/node_modules/b/node_modules/foo/index.d.ts",
+                    "/a/node_modules/b/node_modules/@types/foo.ts",
+                    "/a/node_modules/b/node_modules/@types/foo.tsx",
+                    "/a/node_modules/b/node_modules/@types/foo.d.ts",
+                    "/a/node_modules/b/node_modules/@types/foo/package.json",
+                    "/a/node_modules/b/node_modules/@types/foo/index.ts",
+                    "/a/node_modules/b/node_modules/@types/foo/index.tsx",
+                    "/a/node_modules/b/node_modules/@types/foo/index.d.ts",
                     "/a/node_modules/foo.ts",
                     "/a/node_modules/foo.tsx",
                     "/a/node_modules/foo.d.ts",
@@ -267,7 +302,6 @@ module ts {
                     "/a/node_modules/foo/index.ts",
                     "/a/node_modules/foo/index.tsx"
                 ]);
-
             }
         });
     });
@@ -664,6 +698,13 @@ import b = require("./moduleB.ts");
                     "/root/folder1/node_modules/file6/index.ts",
                     "/root/folder1/node_modules/file6/index.tsx",
                     "/root/folder1/node_modules/file6/index.d.ts",
+                    "/root/folder1/node_modules/@types/file6.ts",
+                    "/root/folder1/node_modules/@types/file6.tsx",
+                    "/root/folder1/node_modules/@types/file6.d.ts",
+                    "/root/folder1/node_modules/@types/file6/package.json",
+                    "/root/folder1/node_modules/@types/file6/index.ts",
+                    "/root/folder1/node_modules/@types/file6/index.tsx",
+                    "/root/folder1/node_modules/@types/file6/index.d.ts"
                     // success on /root/node_modules/file6.ts
                 ]);
 
@@ -913,4 +954,119 @@ import b = require("./moduleB.ts");
             assert(!result.resolvedModule);
         });
     });
+
+    describe("Type reference directive resolution: ", () => {
+        function test(typesRoot: string, typeDirective: string, primary: boolean, initialFile: File, targetFile: File, ...otherFiles: File[]) {
+            const host = createModuleResolutionHost(false, ...[initialFile, targetFile].concat(...otherFiles));
+            const result = resolveTypeReferenceDirective(typeDirective, initialFile.name, {typesRoot}, host);
+            assert(result.resolvedTypeReferenceDirective.resolvedFileName !== undefined, "expected type directive to be resolved");
+            assert.equal(result.resolvedTypeReferenceDirective.resolvedFileName, targetFile.name, "unexpected result of type reference resolution");
+            assert.equal(result.resolvedTypeReferenceDirective.primary, primary, "unexpected 'primary' value");
+        }
+
+        it("Can be resolved from primary location", () => {
+            {
+                const f1 = { name: "/root/src/app.ts" }
+                const f2 = { name: "/root/src/types/lib/index.d.ts" }; 
+                test(/*typesRoot*/"/root/src", /* typeDirective */"lib", /*primary*/ true, f1, f2);
+            }
+            {
+                const f1 = { name: "/root/src/app.ts" }
+                const f2 = { name: "/root/src/types/lib/typings/lib.d.ts" };
+                const package = { name: "/root/src/types/lib/package.json", content: JSON.stringify({types: "typings/lib.d.ts"}) }; 
+                test(/*typesRoot*/"/root/src", /* typeDirective */"lib", /*primary*/ true, f1, f2, package);
+            }
+            {
+                const f1 = { name: "/root/src/app.ts" }
+                const f2 = { name: "/root/src/node_modules/lib/index.d.ts" }; 
+                test(/*typesRoot*/"/root/src", /* typeDirective */"lib", /*primary*/ true, f1, f2);
+            }
+            {
+                const f1 = { name: "/root/src/app.ts" }
+                const f2 = { name: "/root/src/node_modules/lib/typings/lib.d.ts" };
+                const package = { name: "/root/src/node_modules/lib/package.json", content: JSON.stringify({types: "typings/lib.d.ts"}) }; 
+                test(/*typesRoot*/"/root/src", /* typeDirective */"lib", /*primary*/ true, f1, f2, package);
+            }
+            {
+                const f1 = { name: "/root/src/app.ts" }
+                const f2 = { name: "/root/src/node_modules/@types/lib/index.d.ts" }; 
+                test(/*typesRoot*/"/root/src", /* typeDirective */"lib", /*primary*/ true, f1, f2);
+            }
+            {
+                const f1 = { name: "/root/src/app.ts" }
+                const f2 = { name: "/root/src/node_modules/@types/lib/typings/lib.d.ts" };
+                const package = { name: "/root/src/node_modules/@types/lib/package.json", content: JSON.stringify({types: "typings/lib.d.ts"}) }; 
+                test(/*typesRoot*/"/root/src", /* typeDirective */"lib", /*primary*/ true, f1, f2, package);
+            }
+        });
+        it("Can be resolved from secondary location", () => {
+            {
+                const f1 = { name: "/root/src/app.ts" }
+                const f2 = { name: "/root/node_modules/lib.d.ts" };
+                test(/*typesRoot*/"/root/src", /* typeDirective */"lib", /*primary*/ false, f1, f2);
+            }
+            {
+                const f1 = { name: "/root/src/app.ts" }
+                const f2 = { name: "/root/node_modules/lib/index.d.ts" };
+                test(/*typesRoot*/"/root/src", /* typeDirective */"lib", /*primary*/ false, f1, f2);
+            }
+            {
+                const f1 = { name: "/root/src/app.ts" }
+                const f2 = { name: "/root/node_modules/lib/typings/lib.d.ts" };
+                const package = { name: "/root/node_modules/lib/package.json", content: JSON.stringify({typings: "typings/lib.d.ts"}) };
+                test(/*typesRoot*/"/root/src", /* typeDirective */"lib", /*primary*/ false, f1, f2, package);
+            }
+            {
+                const f1 = { name: "/root/src/app.ts" }
+                const f2 = { name: "/root/node_modules/@types/lib/index.d.ts" };
+                test(/*typesRoot*/"/root/src", /* typeDirective */"lib", /*primary*/ false, f1, f2);
+            }
+            {
+                const f1 = { name: "/root/src/app.ts" }
+                const f2 = { name: "/root/node_modules/@types/lib/typings/lib.d.ts" };
+                const package = { name: "/root/node_modules/@types/lib/package.json", content: JSON.stringify({typings: "typings/lib.d.ts"}) };
+                test(/*typesRoot*/"/root/src", /* typeDirective */"lib", /*primary*/ false, f1, f2, package);
+            }
+        });
+        it("Primary resolution overrides secondary resolutions", () => {
+            {
+                const f1 = { name: "/root/src/a/b/c/app.ts" };
+                const f2 = { name: "/root/src/types/lib/index.d.ts" };
+                const f3 = { name: "/root/src/a/b/node_modules/lib.d.ts" }
+                test(/*typesRoot*/"/root/src", /* typeDirective */"lib", /*primary*/ true, f1, f2, f3);
+            }
+        })
+        it("Reused program keeps errors", () => {
+            const f1 = { name: "/root/src/a/b/c/d/e/app.ts", content: `/// <reference types="lib"/>` };
+            const f2 = { name: "/root/src/a/b/c/d/node_modules/lib/index.d.ts", content: `declare var x: number;` };
+            const f3 = { name: "/root/src/a/b/c/d/f/g/app.ts", content: `/// <reference types="lib"/>` };
+            const f4 = { name: "/root/src/a/b/c/d/f/node_modules/lib/index.d.ts", content: `declare var x: number;` };
+            const files = [f1, f2, f3, f4];
+            
+            const names = map(files, f => f.name);
+            const sourceFiles = arrayToMap(map(files, f => createSourceFile(f.name, f.content, ScriptTarget.ES6)), f => f.fileName);
+            const compilerHost: CompilerHost = {
+                fileExists : fileName => hasProperty(sourceFiles, fileName),
+                getSourceFile: fileName => sourceFiles[fileName],
+                getDefaultLibFileName: () => "lib.d.ts",
+                writeFile(file, text) {
+                    throw new Error("NYI");
+                },
+                getCurrentDirectory: () => "/",
+                getCanonicalFileName: f => f.toLowerCase(),
+                getNewLine: () => "\r\n",
+                useCaseSensitiveFileNames: () => false,
+                readFile: fileName => hasProperty(sourceFiles, fileName) ? sourceFiles[fileName].text : undefined
+            };
+            const program1 = createProgram(names, {}, compilerHost);
+            const diagnostics1 = program1.getFileProcessingDiagnostics().getDiagnostics();
+            assert.equal(diagnostics1.length, 1, "expected one diagnostic");
+
+            const program2 = createProgram(names, {}, compilerHost, program1);
+            assert.isTrue(program1.structureIsReused);
+            const diagnostics2 = program1.getFileProcessingDiagnostics().getDiagnostics();
+            assert.equal(diagnostics2.length, 1, "expected one diagnostic");
+            assert.equal(diagnostics1[0].messageText, diagnostics2[0].messageText, "expected one diagnostic");
+        })
+    });
 }
\ No newline at end of file
diff --git a/tests/cases/unittests/reuseProgramStructure.ts b/tests/cases/unittests/reuseProgramStructure.ts
index 5f313eeae2b32..036a58e0c99bd 100644
--- a/tests/cases/unittests/reuseProgramStructure.ts
+++ b/tests/cases/unittests/reuseProgramStructure.ts
@@ -118,13 +118,13 @@ module ts {
                 return "";
             },
             getCanonicalFileName(fileName): string {
-                return sys.useCaseSensitiveFileNames ? fileName : fileName.toLowerCase();
+                return sys && sys.useCaseSensitiveFileNames ? fileName : fileName.toLowerCase();
             },
             useCaseSensitiveFileNames(): boolean {
-                return sys.useCaseSensitiveFileNames;
+                return sys && sys.useCaseSensitiveFileNames;
             },
             getNewLine(): string {
-                return sys.newLine;
+                return sys ? sys.newLine : newLine;
             },
             fileExists: fileName => hasProperty(files, fileName),
             readFile: fileName => {
@@ -160,36 +160,55 @@ module ts {
         return size;
     }
 
-    function checkResolvedModulesCache(program: Program, fileName: string, expectedContent: Map<ResolvedModule>): void {
+    function checkResolvedModule(expected: ResolvedModule, actual: ResolvedModule): void {
+        assert.isTrue(actual !== undefined);
+        assert.isTrue(expected.resolvedFileName === actual.resolvedFileName, `'resolvedFileName': expected '${expected.resolvedFileName}' to be equal to '${actual.resolvedFileName}'`);
+        assert.isTrue(expected.isExternalLibraryImport === actual.isExternalLibraryImport, `'isExternalLibraryImport': expected '${expected.isExternalLibraryImport}' to be equal to '${actual.isExternalLibraryImport}'`);
+    }
+
+    function checkResolvedTypeDirective(expected: ResolvedTypeReferenceDirective, actual: ResolvedTypeReferenceDirective): void {
+        assert.isTrue(actual !== undefined);
+        assert.isTrue(expected.resolvedFileName === actual.resolvedFileName, `'resolvedFileName': expected '${expected.resolvedFileName}' to be equal to '${actual.resolvedFileName}'`);
+        assert.isTrue(expected.primary === actual.primary, `'primary': expected '${expected.primary}' to be equal to '${actual.primary}'`);
+    }
+
+    function checkCache<T>(caption: string, program: Program, fileName: string, expectedContent: Map<T>, getCache: (f: SourceFile) => Map<T>, entryChecker: (expected: T, original:T) => void): void {
         let file = program.getSourceFile(fileName);
         assert.isTrue(file !== undefined, `cannot find file ${fileName}`);
+        const cache = getCache(file)
         if (expectedContent === undefined) {
-            assert.isTrue(file.resolvedModules === undefined, "expected resolvedModules to be undefined");
+            assert.isTrue(cache === undefined, `expected ${caption} to be undefined`);
         }
         else {
-            assert.isTrue(file.resolvedModules !== undefined, "expected resolvedModuled to be set");
-            let actualCacheSize = getSizeOfMap(file.resolvedModules);
+            assert.isTrue(cache !== undefined, `expected ${caption} to be set`);
+            let actualCacheSize = getSizeOfMap(cache);
             let expectedSize = getSizeOfMap(expectedContent);
             assert.isTrue(actualCacheSize === expectedSize, `expected actual size: ${actualCacheSize} to be equal to ${expectedSize}`);
 
             for (let id in expectedContent) {
                 if (hasProperty(expectedContent, id)) {
-                    assert.isTrue(hasProperty(file.resolvedModules, id), `expected ${id} to be found in resolved modules`);
+
                     if (expectedContent[id]) {
                         const expected = expectedContent[id];
-                        const actual = file.resolvedModules[id];
-                        assert.isTrue(actual !== undefined);
-                        assert.isTrue(expected.resolvedFileName === actual.resolvedFileName, `'resolvedFileName': expected '${expected.resolvedFileName}' to be equal to '${actual.resolvedFileName}'`);
-                        assert.isTrue(expected.isExternalLibraryImport === actual.isExternalLibraryImport, `'shouldBeProperExternalModule': expected '${expected.isExternalLibraryImport}' to be equal to '${actual.isExternalLibraryImport}'`);
-                    }
-                    else {
-                        assert.isTrue(file.resolvedModules[id] === undefined);
+                        const actual = cache[id];
+                        entryChecker(expected, actual);
                     }
                 }
+                else {
+                    assert.isTrue(cache[id] === undefined);
+                }
             }
         }
     }
 
+    function checkResolvedModulesCache(program: Program, fileName: string, expectedContent: Map<ResolvedModule>): void {
+        checkCache("resolved modules", program, fileName, expectedContent, f => f.resolvedModules, checkResolvedModule);
+    }
+
+    function checkResolvedTypeDirectivesCache(program: Program, fileName: string, expectedContent: Map<ResolvedTypeReferenceDirective>): void {
+        checkCache("resolved type directives", program, fileName, expectedContent, f => f.resolvedTypeReferenceDirectiveNames, checkResolvedTypeDirective);
+    }
+
     describe("Reuse program structure", () => {
         let target = ScriptTarget.Latest;
         let files = [
@@ -197,9 +216,11 @@ module ts {
                 `
 /// <reference path='b.ts'/>
 /// <reference path='non-existing-file.ts'/>
+/// <reference types="typerefs" />
 `, "",`var x = 1`) },
             { name: "b.ts", text: SourceText.New(`/// <reference path='c.ts'/>`, "", `var y = 2`) },
             { name: "c.ts", text: SourceText.New("", "", `var z = 1;`) },
+            { name: "types/typerefs/index.d.ts", text: SourceText.New("", "", `declare let z: number;`) },
         ]
 
         it("successful if change does not affect imports", () => {
@@ -213,6 +234,17 @@ module ts {
             assert.equal(program1Diagnostics.length, program2Diagnostics.length);
         });
 
+        it("successful if change does not affect type reference directives", () => {
+            var program_1 = newProgram(files, ["a.ts"], { target });
+            var program_2 = updateProgram(program_1, ["a.ts"], { target }, files => {
+                files[0].text = files[0].text.updateProgram("var x = 100");
+            });
+            assert.isTrue(program_1.structureIsReused);
+            let program1Diagnostics = program_1.getSemanticDiagnostics(program_1.getSourceFile("a.ts"))
+            let program2Diagnostics = program_2.getSemanticDiagnostics(program_1.getSourceFile("a.ts"))
+            assert.equal(program1Diagnostics.length, program2Diagnostics.length);
+        });
+
         it("fails if change affects tripleslash references", () => {
             var program_1 = newProgram(files, ["a.ts"], { target });
             var program_2 = updateProgram(program_1, ["a.ts"], { target }, files => {
@@ -232,11 +264,35 @@ module ts {
             assert.isTrue(!program_1.structureIsReused);
         });
 
+        it("fails if change affects type directives", () => {
+            var program_1 = newProgram(files, ["a.ts"], { target });
+            var program_2 = updateProgram(program_1, ["a.ts"], { target }, files => {
+                let newReferences = `
+/// <reference path='b.ts'/>
+/// <reference path='non-existing-file.ts'/>
+/// <reference types="typerefs1" />`;
+                files[0].text = files[0].text.updateReferences(newReferences);
+            });
+            assert.isTrue(!program_1.structureIsReused);
+        });
+
         it("fails if module kind changes", () => {
             var program_1 = newProgram(files, ["a.ts"], { target, module: ModuleKind.CommonJS });
             var program_2 = updateProgram(program_1, ["a.ts"], { target, module: ModuleKind.AMD }, files => void 0);
             assert.isTrue(!program_1.structureIsReused);
         });
+        
+        it("fails if rootdir changes", () => {
+            var program_1 = newProgram(files, ["a.ts"], { target, module: ModuleKind.CommonJS, rootDir: "/a/b" });
+            var program_2 = updateProgram(program_1, ["a.ts"], { target, module: ModuleKind.CommonJS, rootDir: "/a/c" }, files => void 0);
+            assert.isTrue(!program_1.structureIsReused);
+        });
+
+        it("fails if config path changes", () => {
+            var program_1 = newProgram(files, ["a.ts"], { target, module: ModuleKind.CommonJS, configFilePath: "/a/b/tsconfig.json" });
+            var program_2 = updateProgram(program_1, ["a.ts"], { target, module: ModuleKind.CommonJS, configFilePath: "/a/c/tsconfig.json" }, files => void 0);
+            assert.isTrue(!program_1.structureIsReused);
+        });
 
         it("resolution cache follows imports", () => {
             let files = [
@@ -274,5 +330,43 @@ module ts {
             assert.isTrue(!program_3.structureIsReused);
             checkResolvedModulesCache(program_4, "a.ts", { "b": { resolvedFileName: "b.ts" }, "c": undefined });
         });
+
+        it("resolved type directives cache follows type directives", () => {
+            let files = [
+                { name: "/a.ts", text: SourceText.New("/// <reference types='typedefs'/>", "", "var x = $") },
+                { name: "/types/typedefs/index.d.ts", text: SourceText.New("", "", "declare var $: number") },
+            ];
+            var options: CompilerOptions = { target, typesRoot: "/" };
+
+            var program_1 = newProgram(files, ["/a.ts"], options);
+            checkResolvedTypeDirectivesCache(program_1, "/a.ts", { "typedefs": { resolvedFileName: "/types/typedefs/index.d.ts", primary: true } });
+            checkResolvedTypeDirectivesCache(program_1, "/types/typedefs/index.d.ts", undefined);
+
+            var program_2 = updateProgram(program_1, ["/a.ts"], options, files => {
+                files[0].text = files[0].text.updateProgram("var x = 2");
+            });
+            assert.isTrue(program_1.structureIsReused);
+
+            // content of resolution cache should not change
+            checkResolvedTypeDirectivesCache(program_1, "/a.ts", { "typedefs": { resolvedFileName: "/types/typedefs/index.d.ts", primary: true } });
+            checkResolvedTypeDirectivesCache(program_1, "/types/typedefs/index.d.ts", undefined);
+
+            // type reference directives has changed - program is not reused
+            var program_3 = updateProgram(program_2, ["/a.ts"], options, files => {
+                files[0].text = files[0].text.updateReferences("");
+            });
+
+            assert.isTrue(!program_2.structureIsReused);
+            checkResolvedTypeDirectivesCache(program_3, "/a.ts", undefined);
+
+            var program_4 = updateProgram(program_3, ["/a.ts"], options, files => {
+                let newReferences = `/// <reference types="typedefs"/>
+                /// <reference types="typedefs2"/>
+                `;
+                files[0].text = files[0].text.updateReferences(newReferences);
+            });
+            assert.isTrue(!program_3.structureIsReused);
+            checkResolvedTypeDirectivesCache(program_1, "/a.ts", { "typedefs": { resolvedFileName: "/types/typedefs/index.d.ts", primary: true } });
+        });
     })
 }
\ No newline at end of file
diff --git a/tests/cases/unittests/services/preProcessFile.ts b/tests/cases/unittests/services/preProcessFile.ts
index a648a3c4b26fb..7fa25b440c557 100644
--- a/tests/cases/unittests/services/preProcessFile.ts
+++ b/tests/cases/unittests/services/preProcessFile.ts
@@ -9,18 +9,11 @@ describe('PreProcessFile:', function () {
     function test(sourceText: string, readImportFile: boolean, detectJavaScriptImports: boolean, expectedPreProcess: ts.PreProcessedFileInfo): void {
         var resultPreProcess = ts.preProcessFile(sourceText, readImportFile, detectJavaScriptImports);
 
-        var resultIsLibFile = resultPreProcess.isLibFile;
-        var resultImportedFiles = resultPreProcess.importedFiles;
-        var resultReferencedFiles = resultPreProcess.referencedFiles;
+        assert.equal(resultPreProcess.isLibFile, expectedPreProcess.isLibFile, "Pre-processed file has different value for isLibFile. Expected: " + expectedPreProcess.isLibFile + ". Actual: " + resultPreProcess.isLibFile);
 
-        var expectedIsLibFile = expectedPreProcess.isLibFile;
-        var expectedImportedFiles = expectedPreProcess.importedFiles;
-        var expectedReferencedFiles = expectedPreProcess.referencedFiles;
-
-        assert.equal(resultIsLibFile, expectedIsLibFile, "Pre-processed file has different value for isLibFile. Expected: " + expectedPreProcess + ". Actual: " + resultIsLibFile);
-
-        checkFileReferenceList("Imported files", expectedImportedFiles, resultImportedFiles);
-        checkFileReferenceList("Referenced files", expectedReferencedFiles, resultReferencedFiles);
+        checkFileReferenceList("Imported files", expectedPreProcess.importedFiles, resultPreProcess.importedFiles);
+        checkFileReferenceList("Referenced files", expectedPreProcess.referencedFiles, resultPreProcess.referencedFiles);
+        checkFileReferenceList("Type reference directives", expectedPreProcess.typeReferenceDirectives, resultPreProcess.typeReferenceDirectives);
 
         assert.deepEqual(resultPreProcess.ambientExternalModules, expectedPreProcess.ambientExternalModules);
     }
@@ -52,6 +45,7 @@ describe('PreProcessFile:', function () {
                     referencedFiles: [{ fileName: "refFile1.ts", pos: 0, end: 37 }, { fileName: "refFile2.ts", pos: 38, end: 73 },
                         { fileName: "refFile3.ts", pos: 74, end: 109 }, { fileName: "..\\refFile4d.ts", pos: 110, end: 150 }],
                     importedFiles: <ts.FileReference[]>[],
+                    typeReferenceDirectives: [],
                     ambientExternalModules: undefined,
                     isLibFile: false
                 });
@@ -64,6 +58,7 @@ describe('PreProcessFile:', function () {
                 {
                     referencedFiles: <ts.FileReference[]>[],
                     importedFiles: <ts.FileReference[]>[],
+                    typeReferenceDirectives: [],
                     ambientExternalModules: undefined,
                     isLibFile: false
                 });
@@ -75,6 +70,7 @@ describe('PreProcessFile:', function () {
                 /* detectJavaScriptImports */ false,
                 {
                     referencedFiles: <ts.FileReference[]>[],
+                    typeReferenceDirectives: [],
                     importedFiles: [{ fileName: "r1.ts", pos: 20, end: 25 }, { fileName: "r2.ts", pos: 49, end: 54 }, { fileName: "r3.ts", pos: 78, end: 83 },
                         { fileName: "r4.ts", pos: 106, end: 111 }, { fileName: "r5.ts", pos: 138, end: 143 }],
                     ambientExternalModules: undefined,
@@ -88,6 +84,7 @@ describe('PreProcessFile:', function () {
                 /* detectJavaScriptImports */ false,
                 {
                     referencedFiles: <ts.FileReference[]>[],
+                    typeReferenceDirectives: [],
                     importedFiles: <ts.FileReference[]>[],
                     ambientExternalModules: undefined,
                     isLibFile: false
@@ -100,6 +97,7 @@ describe('PreProcessFile:', function () {
                 /* detectJavaScriptImports */ false,
                 {
                     referencedFiles: <ts.FileReference[]>[],
+                    typeReferenceDirectives: [],
                     importedFiles: [{ fileName: "r3.ts", pos: 73, end: 78 }],
                     ambientExternalModules: undefined,
                     isLibFile: false
@@ -112,6 +110,7 @@ describe('PreProcessFile:', function () {
                 /* detectJavaScriptImports */ false,
                 {
                     referencedFiles: [{ fileName: "refFile1.ts", pos: 0, end: 35 }, { fileName: "refFile2.ts", pos: 36, end: 71 }],
+                    typeReferenceDirectives: [],
                     importedFiles: [{ fileName: "r1.ts", pos: 92, end: 97 }, { fileName: "r2.ts", pos: 121, end: 126 }],
                     ambientExternalModules: undefined,
                     isLibFile: false
@@ -124,6 +123,7 @@ describe('PreProcessFile:', function () {
                 /* detectJavaScriptImports */ false,
                 {
                     referencedFiles: [{ fileName: "refFile1.ts", pos: 0, end: 35 }],
+                    typeReferenceDirectives: [],
                     importedFiles: [{ fileName: "r1.ts", pos: 91, end: 96 }, { fileName: "r3.ts", pos: 148, end: 153 }],
                     ambientExternalModules: undefined,
                     isLibFile: false
@@ -142,6 +142,7 @@ describe('PreProcessFile:', function () {
                 /* detectJavaScriptImports */ false,
                 {
                     referencedFiles: [],
+                    typeReferenceDirectives: [],
                     importedFiles: [
                         { fileName: "m1", pos: 20, end: 22 },
                         { fileName: "m2", pos: 51, end: 53 },
@@ -165,6 +166,7 @@ describe('PreProcessFile:', function () {
                 /* detectJavaScriptImports */ false,
                 {
                     referencedFiles: [],
+                    typeReferenceDirectives: [],
                     importedFiles: [
                         { fileName: "m1", pos: 14, end: 16 },
                         { fileName: "m2", pos: 36, end: 38 },
@@ -188,6 +190,7 @@ describe('PreProcessFile:', function () {
  
                {
                    referencedFiles: [],
+                   typeReferenceDirectives: [],
                    importedFiles: [],
                    ambientExternalModules: ["B"],
                    isLibFile: false
@@ -200,6 +203,7 @@ describe('PreProcessFile:', function () {
                 /* detectJavaScriptImports */ false,
                 {
                     referencedFiles: [],
+                    typeReferenceDirectives: [],
                     importedFiles: [
                         { fileName: "m1", pos: 26, end: 28 }
                     ],
@@ -218,6 +222,7 @@ describe('PreProcessFile:', function () {
                 /* detectJavaScriptImports */ true,
                 {
                     referencedFiles: [],
+                    typeReferenceDirectives: [],
                     importedFiles: [
                         { fileName: "m1", pos: 39, end: 41 },
                         { fileName: "m2", pos: 74, end: 76 },
@@ -237,6 +242,7 @@ describe('PreProcessFile:', function () {
                 /* detectJavaScriptImports */ true,
                 {
                     referencedFiles: [],
+                    typeReferenceDirectives: [],
                     importedFiles: [
                         { fileName: "mod1", pos: 21, end: 25 },
                         { fileName: "mod2", pos: 29, end: 33 },
@@ -254,6 +260,7 @@ describe('PreProcessFile:', function () {
                 /* detectJavaScriptImports */ true,
                 {
                     referencedFiles: [],
+                    typeReferenceDirectives: [],
                     importedFiles: [
                         { fileName: "mod1", pos: 28, end: 32 },
                         { fileName: "mod2", pos: 36, end: 40 },
@@ -274,6 +281,7 @@ describe('PreProcessFile:', function () {
             /*detectJavaScriptImports*/ false,
             {
                 referencedFiles: [],
+                typeReferenceDirectives: [],
                 importedFiles: [
                     { "fileName": "../Observable", "pos": 28, "end": 41 }
                 ],
@@ -293,6 +301,7 @@ describe('PreProcessFile:', function () {
             /*detectJavaScriptImports*/ false,
             {
                 referencedFiles: [],
+                typeReferenceDirectives: [],
                 importedFiles: [
                     { "fileName": "m", "pos": 135, "end": 136 },
                     { "fileName": "../Observable", "pos": 28, "end": 41 }
@@ -313,6 +322,7 @@ describe('PreProcessFile:', function () {
             /*detectJavaScriptImports*/ false,
             {
                 referencedFiles: [],
+                typeReferenceDirectives: [],
                 importedFiles: [
                     { "fileName": "m", "pos": 135, "end": 136 },
                     { "fileName": "../Observable", "pos": 28, "end": 41 }
@@ -333,6 +343,7 @@ describe('PreProcessFile:', function () {
             /*detectJavaScriptImports*/ false,
             {
                 referencedFiles: [],
+                typeReferenceDirectives: [],
                 importedFiles: [
                     { "fileName": "../Observable", "pos": 28, "end": 41 }
                 ],
@@ -352,6 +363,7 @@ describe('PreProcessFile:', function () {
             /*detectJavaScriptImports*/ false,
             {
                 referencedFiles: [],
+                typeReferenceDirectives: [],
                 importedFiles: [
                     { "fileName": "../Observable", "pos": 28, "end": 41 }
                 ],
@@ -370,6 +382,7 @@ describe('PreProcessFile:', function () {
             /*detectJavaScriptImports*/ false,
             {
                 referencedFiles: [],
+                typeReferenceDirectives: [],
                 importedFiles: [
                     { "fileName": "../Observable", "pos": 28, "end": 41 }
                 ],
@@ -390,6 +403,7 @@ describe('PreProcessFile:', function () {
             /*detectJavaScriptImports*/ false,
             {
                 referencedFiles: [],
+                typeReferenceDirectives: [],
                 importedFiles: [
                     { "fileName": "m2", "pos": 65, "end": 67 },
                     { "fileName": "augmentation", "pos": 102, "end": 114 }
@@ -413,6 +427,7 @@ describe('PreProcessFile:', function () {
             /*detectJavaScriptImports*/ false,
             {
                 referencedFiles: [],
+                typeReferenceDirectives: [],
                 importedFiles: [
                     { "fileName": "m2", "pos": 127, "end": 129 },
                     { "fileName": "augmentation", "pos": 164, "end": 176 }
@@ -420,7 +435,30 @@ describe('PreProcessFile:', function () {
                 ambientExternalModules: ["m1"],
                 isLibFile: false
             });
-        });        
+        });
+        it ("correctly recognizes type reference directives", () => {
+            test(`
+            /// <reference path="a"/>
+            /// <reference types="a1"/>
+            /// <reference path="a2"/>
+            /// <reference types="a3"/>
+            `,
+            /*readImportFile*/ true,
+            /*detectJavaScriptImports*/ false,
+            {
+                referencedFiles: [
+                    { "pos": 13, "end": 38, "fileName": "a" },
+                    { "pos": 91, "end": 117, "fileName": "a2" }
+                ],
+                typeReferenceDirectives: [
+                    { "pos": 51, "end": 78, "fileName": "a1" },
+                    { "pos": 130, "end": 157, "fileName": "a3" }
+                ],
+                importedFiles: [],
+                ambientExternalModules: undefined,
+                isLibFile: false
+            });
+        })
     });
 });
 
diff --git a/tests/cases/unittests/session.ts b/tests/cases/unittests/session.ts
index 41f4bc599f65d..ee9742482cd5e 100644
--- a/tests/cases/unittests/session.ts
+++ b/tests/cases/unittests/session.ts
@@ -36,7 +36,7 @@ namespace ts.server {
         let lastSent: protocol.Message;
 
         beforeEach(() => {
-            session = new Session(mockHost, Buffer.byteLength, process.hrtime, mockLogger);
+            session = new Session(mockHost, Utils.byteLength, process.hrtime, mockLogger);
             session.send = (msg: protocol.Message) => {
                 lastSent = msg;
             };
@@ -161,7 +161,7 @@ namespace ts.server {
             it("is an overrideable handle which sends protocol messages over the wire", () => {
                 const msg = {seq: 0, type: "none"};
                 const strmsg = JSON.stringify(msg);
-                const len = 1 + Buffer.byteLength(strmsg, "utf8");
+                const len = 1 + Utils.byteLength(strmsg, "utf8");
                 const resultMsg = `Content-Length: ${len}\r\n\r\n${strmsg}\n`;
 
                 session.send = Session.prototype.send;
@@ -253,7 +253,7 @@ namespace ts.server {
             lastSent: protocol.Message;
             customHandler = "testhandler";
             constructor() {
-                super(mockHost, Buffer.byteLength, process.hrtime, mockLogger);
+                super(mockHost, Utils.byteLength, process.hrtime, mockLogger);
                 this.addProtocolHandler(this.customHandler, () => {
                     return {response: undefined, responseRequired: true};
                 });
@@ -311,7 +311,7 @@ namespace ts.server {
         class InProcSession extends Session {
             private queue: protocol.Request[] = [];
             constructor(private client: InProcClient) {
-                super(mockHost, Buffer.byteLength, process.hrtime, mockLogger);
+                super(mockHost, Utils.byteLength, process.hrtime, mockLogger);
                 this.addProtocolHandler("echo", (req: protocol.Request) => ({
                     response: req.arguments,
                     responseRequired: true