Add early bail out for call expressions that are never type predicates

ahejlsberg · ahejlsberg · commit 24567445d6dc · 2016-11-13T08:29:21.000-08:00
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -8981,6 +8981,28 @@ namespace ts {
             return isLengthPushOrUnshift || isElementAssignment;
         }
 
+        function maybeTypePredicateCall(node: CallExpression) {
+            const links = getNodeLinks(node);
+            if (links.maybeTypePredicate === undefined) {
+                links.maybeTypePredicate = getMaybeTypePredicate(node);
+            }
+            return links.maybeTypePredicate;
+        }
+
+        function getMaybeTypePredicate(node: CallExpression) {
+            if (node.expression.kind !== SyntaxKind.SuperKeyword) {
+                const funcType = checkNonNullExpression(node.expression);
+                if (funcType !== silentNeverType) {
+                    const apparentType = getApparentType(funcType);
+                    if (apparentType !== unknownType) {
+                        const callSignatures = getSignaturesOfType(apparentType, SignatureKind.Call);
+                        return !!forEach(callSignatures, sig => sig.typePredicate);
+                    }
+                }
+            }
+            return false;
+        }
+
         function getFlowTypeOfReference(reference: Node, declaredType: Type, assumeInitialized: boolean, flowContainer: Node) {
             let key: string;
             if (!reference.flowNode || assumeInitialized && !(declaredType.flags & TypeFlags.Narrowable)) {
@@ -9495,7 +9517,7 @@ namespace ts {
             }
 
             function narrowTypeByTypePredicate(type: Type, callExpression: CallExpression, assumeTrue: boolean): Type {
-                if (!hasMatchingArgument(callExpression, reference)) {
+                if (!hasMatchingArgument(callExpression, reference) || !maybeTypePredicateCall(callExpression)) {
                     return type;
                 }
                 const signature = getResolvedSignature(callExpression);
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
@@ -2668,6 +2668,7 @@ namespace ts {
         resolvedSignature?: Signature;    // Cached signature of signature node or call expression
         resolvedSymbol?: Symbol;          // Cached name resolution result
         resolvedIndexInfo?: IndexInfo;    // Cached indexing info resolution result
+        maybeTypePredicate?: boolean;     // Cached check whether call expression might reference a type predicate 
         enumMemberValue?: number;         // Constant value of enum member
         isVisible?: boolean;              // Is this node visible
         hasReportedStatementInAmbientContext?: boolean;  // Cache boolean if we report statements in ambient context
