Add --skipLibCheck compiler option

src/compiler/checker.ts

@@ -16383,14 +16383,11 @@ namespace ts {
         function checkSourceFileWorker(node: SourceFile) {
             const links = getNodeLinks(node);
             if (!(links.flags & NodeCheckFlags.TypeChecked)) {
-                // Check whether the file has declared it is the default lib,
-                // and whether the user has specifically chosen to avoid checking it.
-                if (compilerOptions.skipDefaultLibCheck) {
-                    // If the user specified '--noLib' and a file has a '/// <reference no-default-lib="true"/>',
-                    // then we should treat that file as a default lib.
-                    if (node.hasNoDefaultLib) {
-                        return;
-                    }
+                // If skipLibCheck is enabled, skip type checking if file is a declaration file.
+                // If skipDefaultLibCheck is enabled, skip type checking if file contains a
+                // '/// <reference no-default-lib="true"/>' directive.
+                if (compilerOptions.skipLibCheck && node.isDeclarationFile || compilerOptions.skipDefaultLibCheck && node.hasNoDefaultLib) {
+                    return;
                 }
 
                 // Grammar checking

src/compiler/commandLineParser.ts

@@ -139,6 +139,11 @@ namespace ts {
             name: "skipDefaultLibCheck",
             type: "boolean",
         },
+        {
+            name: "skipLibCheck",
+            type: "boolean",
+            description: Diagnostics.Skip_type_checking_of_declaration_files,
+        },
         {
             name: "out",
             type: "string",

src/compiler/diagnosticMessages.json

@@ -2348,6 +2348,10 @@
         "category": "Message",
         "code": 6011
     },
+    "Skip type checking of declaration files.": {
+        "category": "Message",
+        "code": 6012
+    },
     "Specify ECMAScript target version: 'ES3' (default), 'ES5', or 'ES2015'": {
         "category": "Message",
         "code": 6015

src/compiler/types.ts

@@ -2505,6 +2505,7 @@ namespace ts {
         allowJs?: boolean;
         noImplicitUseStrict?: boolean;
         strictNullChecks?: boolean;
+        skipLibCheck?: boolean;
         listEmittedFiles?: boolean;
         lib?: string[];
         /* @internal */ stripInternal?: boolean;