Add support for //@check directives

src/compiler/parser.ts

@@ -5817,6 +5817,7 @@ namespace ts {
             const typeReferenceDirectives: FileReference[] = [];
             const amdDependencies: { path: string; name: string }[] = [];
             let amdModuleName: string;
+            let hasCheckDirective = false;
 
             // Keep scanning all the leading trivia in the file until we get to something that
             // isn't trivia.  Any single line comment will be analyzed to see if it is a
@@ -5878,6 +5879,9 @@ namespace ts {
                             amdDependencies.push(amdDependency);
                         }
                     }
+
+                    const checkDirectiveRegEx = /^\/\/\s*@check\s*/gim;
+                    hasCheckDirective = hasCheckDirective || !!checkDirectiveRegEx.exec(comment);
                 }
             }
 
@@ -5885,6 +5889,7 @@ namespace ts {
             sourceFile.typeReferenceDirectives = typeReferenceDirectives;
             sourceFile.amdDependencies = amdDependencies;
             sourceFile.moduleName = amdModuleName;
+            sourceFile.hasCheckDirective = hasCheckDirective;
         }
 
         function setExternalModuleIndicator(sourceFile: SourceFile) {

src/compiler/program.ts

@@ -907,7 +907,8 @@ namespace ts {
                 // For JavaScript files, we don't want to report semantic errors.
                 // Instead, we'll report errors for using TypeScript-only constructs from within a
                 // JavaScript file when we get syntactic diagnostics for the file.
-                const checkDiagnostics = !options.checkJsFiles && isSourceFileJavaScript(sourceFile) ? [] : typeChecker.getDiagnostics(sourceFile, cancellationToken);
+                const includeCheckDiagnostics = options.checkJsFiles || sourceFile.hasCheckDirective || !isSourceFileJavaScript(sourceFile);
+                const checkDiagnostics = includeCheckDiagnostics ? typeChecker.getDiagnostics(sourceFile, cancellationToken) : [];
                 const fileProcessingDiagnosticsInFile = fileProcessingDiagnostics.getDiagnostics(sourceFile.fileName);
                 const programDiagnosticsInFile = programDiagnostics.getDiagnostics(sourceFile.fileName);
 

src/compiler/types.ts

@@ -2272,6 +2272,7 @@
         /* @internal */ moduleAugmentations: LiteralExpression[];
         /* @internal */ patternAmbientModules?: PatternAmbientModule[];
         /* @internal */ ambientModuleNames: string[];
+        /* @internal */ hasCheckDirective: boolean;
     }
 
     export interface Bundle extends Node {

src/services/services.ts

@@ -473,6 +473,7 @@ namespace ts {
         public moduleAugmentations: LiteralExpression[];
         private namedDeclarations: Map<Declaration[]>;
         public ambientModuleNames: string[];
+        public hasCheckDirective: boolean;
 
         constructor(kind: SyntaxKind, pos: number, end: number) {
             super(kind, pos, end);