Enable '--strictNullChecks'

Gulpfile.js

@@ -260,6 +260,7 @@ function getCompilerSettings(base, useBuiltCompiler) {
     for (const key in base) {
         copy[key] = base[key];
     }
+    copy.strictNullChecks = true;
     if (!useDebugMode) {
         if (copy.removeComments === undefined) copy.removeComments = true;
     }

Jakefile.js

@@ -251,7 +251,7 @@ function compileFile(outFile, sources, prereqs, prefixes, useBuiltCompiler, opts
         else {
             options += " --lib es5";
         }
-        options += " --noUnusedLocals --noUnusedParameters";
+        options += " --noUnusedLocals --noUnusedParameters --strictNullChecks";
 
         var cmd = host + " " + compilerPath + " " + options + " ";
         cmd = cmd + sources.join(" ");

scripts/buildProtocol.ts

@@ -8,7 +8,7 @@ function endsWith(s: string, suffix: string) {
 }
 
 function isStringEnum(declaration: ts.EnumDeclaration) {
-    return declaration.members.length && declaration.members.every(m => m.initializer && m.initializer.kind === ts.SyntaxKind.StringLiteral);
+    return declaration.members.length && declaration.members.every(m => !!m.initializer && m.initializer.kind === ts.SyntaxKind.StringLiteral);
 }
 
 class DeclarationsWalker {
@@ -30,7 +30,7 @@ class DeclarationsWalker {
             text += "\ndeclare namespace ts {\n";
             text += "    // these types are empty stubs for types from services and should not be used directly\n"
             for (const type of walker.removedTypes) {
-                text += `    export type ${type.symbol.name} = never;\n`;
+                text += `    export type ${type.symbol!.name} = never;\n`;
             }
             text += "}"
         }
@@ -130,7 +130,7 @@ function writeProtocolFile(outputFile: string, protocolTs: string, typeScriptSer
     function getInitialDtsFileForProtocol() {
         const program = ts.createProgram([protocolTs, typeScriptServicesDts], options);
 
-        let protocolDts: string;
+        let protocolDts: string | undefined;
         program.emit(program.getSourceFile(protocolTs), (file, content) => {
             if (endsWith(file, ".d.ts")) {
                 protocolDts = content;
@@ -162,7 +162,7 @@ function writeProtocolFile(outputFile: string, protocolTs: string, typeScriptSer
     let protocolDts = getInitialDtsFileForProtocol();
     const program = getProgramWithProtocolText(protocolDts, /*includeTypeScriptServices*/ true);
 
-    const protocolFile = program.getSourceFile("protocol.d.ts");
+    const protocolFile = program.getSourceFile("protocol.d.ts")!;
     const extraDeclarations = DeclarationsWalker.getExtraDeclarations(program.getTypeChecker(), protocolFile);
     if (extraDeclarations) {
         protocolDts += extraDeclarations;

scripts/processDiagnosticMessages.ts

@@ -22,7 +22,7 @@ function main(): void {
     }
 
     const inputFilePath = sys.args[0].replace(/\\/g, "/");
-    const inputStr = sys.readFile(inputFilePath);
+    const inputStr = sys.readFile(inputFilePath)!;
 
     const diagnosticMessagesJson: { [key: string]: DiagnosticDetails } = JSON.parse(inputStr);
 

scripts/tslint/rules/noInOperatorRule.ts

@@ -12,7 +12,7 @@ export class Rule extends Lint.Rules.AbstractRule {
 function walk(ctx: Lint.WalkContext<void>): void {
     ts.forEachChild(ctx.sourceFile, recur);
     function recur(node: ts.Node): void {
-        if (node.kind === ts.SyntaxKind.InKeyword && node.parent.kind === ts.SyntaxKind.BinaryExpression) {
+        if (node.kind === ts.SyntaxKind.InKeyword && node.parent!.kind === ts.SyntaxKind.BinaryExpression) {
             ctx.addFailureAtNode(node, Rule.FAILURE_STRING);
         }
     }