Throw when cancellation is requested

Author: JsonFreeman

src/compiler/types.ts

@@ -1174,6 +1174,7 @@ module ts {
 
     export interface CancellationToken {
         isCancellationRequested(): boolean;
+        throwIfCancellationRequested?(): void;
     }
 
     export interface CompilerHost {

src/services/services.ts

@@ -3487,7 +3487,7 @@ module ts {
             var sourceFile = getSourceFile(fileName);
             var node = getNodeAtPosition(sourceFile, position);
 
-            return SignatureHelp.getSignatureHelpItems(sourceFile, position, node, typeInfoResolver);
+            return SignatureHelp.getSignatureHelpItems(sourceFile, position, node, typeInfoResolver, cancellationToken);
         }
 
         function getSignatureHelpCurrentArgumentState(fileName: string, position: number, applicableSpanStart: number): SignatureHelpState {

src/services/signatureHelp.ts

@@ -333,15 +333,18 @@ module ts.SignatureHelp {
     //}
     var emptyArray: any[] = [];
 
-    export function getSignatureHelpItems(sourceFile: SourceFile, position: number, startingNode: Node, typeInfoResolver: TypeChecker): SignatureHelpItems {
+    export function getSignatureHelpItems(sourceFile: SourceFile, position: number, startingNode: Node, typeInfoResolver: TypeChecker, cancellationToken: CancellationToken): SignatureHelpItems {
         // Decide whether to show signature help
         var argumentList = getContainingArgumentList(startingNode);
+        cancellationToken.throwIfCancellationRequested();
 
         // Semantic filtering of signature help
         if (argumentList) {
             var call = <CallExpression>argumentList.parent;
             var candidates = <Signature[]>[];
             var resolvedSignature = typeInfoResolver.getResolvedSignature(call, candidates);
+            cancellationToken.throwIfCancellationRequested();
+
             return candidates.length
                 ? createSignatureHelpItems(candidates, resolvedSignature, argumentList)
                 : undefined;