diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 2375d52a6e9..0ee3d549d48 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -6361,7 +6361,7 @@ namespace ts {
          * @param typeParameters The requested type parameters.
          * @param minTypeArgumentCount The minimum number of required type arguments.
          */
-        function fillMissingTypeArguments(typeArguments: Type[] | undefined, typeParameters: TypeParameter[] | undefined, minTypeArgumentCount: number, isJavaScript?: boolean) {
+        function fillMissingTypeArguments(typeArguments: Type[] | undefined, typeParameters: TypeParameter[] | undefined, minTypeArgumentCount: number, isJavaScript: boolean) {
             const numTypeParameters = length(typeParameters);
             if (numTypeParameters) {
                 const numTypeArguments = length(typeArguments);
@@ -6622,7 +6622,7 @@ namespace ts {
             return anyType;
         }
 
-        function getSignatureInstantiation(signature: Signature, typeArguments: Type[], isJavascript?: boolean): Signature {
+        function getSignatureInstantiation(signature: Signature, typeArguments: Type[], isJavascript: boolean): Signature {
             typeArguments = fillMissingTypeArguments(typeArguments, signature.typeParameters, getMinTypeArgumentCount(signature.typeParameters), isJavascript);
             const instantiations = signature.instantiations || (signature.instantiations = createMap<Signature>());
             const id = getTypeListId(typeArguments);
@@ -6661,7 +6661,10 @@ namespace ts {
             // where different generations of the same type parameter are in scope). This leads to a lot of new type
             // identities, and potentially a lot of work comparing those identities, so here we create an instantiation
             // that uses the original type identities for all unconstrained type parameters.
-            return getSignatureInstantiation(signature, map(signature.typeParameters, tp => tp.target && !getConstraintOfTypeParameter(tp.target) ? tp.target : tp));
+            return getSignatureInstantiation(
+                signature,
+                map(signature.typeParameters, tp => tp.target && !getConstraintOfTypeParameter(tp.target) ? tp.target : tp),
+                isInJavaScriptFile(signature.declaration));
         }
 
         function getOrCreateTypeFromSignature(signature: Signature): ObjectType {
@@ -6843,7 +6846,7 @@ namespace ts {
             const id = getTypeListId(typeArguments);
             let instantiation = links.instantiations.get(id);
             if (!instantiation) {
-                links.instantiations.set(id, instantiation = instantiateType(type, createTypeMapper(typeParameters, fillMissingTypeArguments(typeArguments, typeParameters, getMinTypeArgumentCount(typeParameters)))));
+                links.instantiations.set(id, instantiation = instantiateType(type, createTypeMapper(typeParameters, fillMissingTypeArguments(typeArguments, typeParameters, getMinTypeArgumentCount(typeParameters), isInJavaScriptFile(symbol.valueDeclaration)))));
             }
             return instantiation;
         }
@@ -13999,8 +14002,9 @@ namespace ts {
             const instantiatedSignatures = [];
             for (const signature of signatures) {
                 if (signature.typeParameters) {
-                    const typeArguments = fillMissingTypeArguments(/*typeArguments*/ undefined, signature.typeParameters, /*minTypeArgumentCount*/ 0);
-                    instantiatedSignatures.push(getSignatureInstantiation(signature, typeArguments));
+                    const isJavascript = isInJavaScriptFile(node);
+                    const typeArguments = fillMissingTypeArguments(/*typeArguments*/ undefined, signature.typeParameters, /*minTypeArgumentCount*/ 0, isJavascript);
+                    instantiatedSignatures.push(getSignatureInstantiation(signature, typeArguments, isJavascript));
                 }
                 else {
                     instantiatedSignatures.push(signature);
@@ -15257,7 +15261,7 @@ namespace ts {
             if (!contextualMapper) {
                 inferTypes(context.inferences, getReturnTypeOfSignature(contextualSignature), getReturnTypeOfSignature(signature), InferencePriority.ReturnType);
             }
-            return getSignatureInstantiation(signature, getInferredTypes(context));
+            return getSignatureInstantiation(signature, getInferredTypes(context), isInJavaScriptFile(contextualSignature.declaration));
         }
 
         function inferTypeArguments(node: CallLikeExpression, signature: Signature, args: ReadonlyArray<Expression>, excludeArgument: boolean[], context: InferenceContext): Type[] {
@@ -15292,7 +15296,7 @@ namespace ts {
                     // Above, the type of the 'value' parameter is inferred to be 'A'.
                     const contextualSignature = getSingleCallSignature(instantiatedType);
                     const inferenceSourceType = contextualSignature && contextualSignature.typeParameters ?
-                        getOrCreateTypeFromSignature(getSignatureInstantiation(contextualSignature, contextualSignature.typeParameters)) :
+                        getOrCreateTypeFromSignature(getSignatureInstantiation(contextualSignature, contextualSignature.typeParameters, isInJavaScriptFile(node))) :
                         instantiatedType;
                     const inferenceTargetType = getReturnTypeOfSignature(signature);
                      // Inferences made from return types have lower priority than all other inferences.
@@ -16008,8 +16012,9 @@ namespace ts {
                         candidate = originalCandidate;
                         if (candidate.typeParameters) {
                             let typeArgumentTypes: Type[];
+                            const isJavascript = isInJavaScriptFile(candidate.declaration);
                             if (typeArguments) {
-                                typeArgumentTypes = fillMissingTypeArguments(map(typeArguments, getTypeFromTypeNode), candidate.typeParameters, getMinTypeArgumentCount(candidate.typeParameters));
+                                typeArgumentTypes = fillMissingTypeArguments(map(typeArguments, getTypeFromTypeNode), candidate.typeParameters, getMinTypeArgumentCount(candidate.typeParameters), isJavascript);
                                 if (!checkTypeArguments(candidate, typeArguments, typeArgumentTypes, /*reportErrors*/ false)) {
                                     candidateForTypeArgumentError = originalCandidate;
                                     break;
@@ -16018,7 +16023,7 @@ namespace ts {
                             else {
                                 typeArgumentTypes = inferTypeArguments(node, candidate, args, excludeArgument, inferenceContext);
                             }
-                            candidate = getSignatureInstantiation(candidate, typeArgumentTypes);
+                            candidate = getSignatureInstantiation(candidate, typeArgumentTypes, isJavascript);
                         }
                         if (!checkApplicableSignature(node, args, candidate, relation, excludeArgument, /*reportErrors*/ false)) {
                             candidateForArgumentError = candidate;
@@ -18782,7 +18787,7 @@ namespace ts {
                 const constraint = getConstraintOfTypeParameter(typeParameters[i]);
                 if (constraint) {
                     if (!typeArguments) {
-                        typeArguments = fillMissingTypeArguments(map(typeArgumentNodes, getTypeFromTypeNode), typeParameters, minTypeArgumentCount);
+                        typeArguments = fillMissingTypeArguments(map(typeArgumentNodes, getTypeFromTypeNode), typeParameters, minTypeArgumentCount, isInJavaScriptFile(typeArgumentNodes[i]));
                         mapper = createTypeMapper(typeParameters, typeArguments);
                     }
                     const typeArgument = typeArguments[i];
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index ee450344827..7eaf99c68e2 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -1325,11 +1325,11 @@ namespace ts {
         return isInJavaScriptFile(file);
     }
 
-    export function isInJavaScriptFile(node: Node): boolean {
+    export function isInJavaScriptFile(node: Node | undefined): boolean {
         return node && !!(node.flags & NodeFlags.JavaScriptFile);
     }
 
-    export function isInJSDoc(node: Node): boolean {
+    export function isInJSDoc(node: Node | undefined): boolean {
         return node && !!(node.flags & NodeFlags.JSDoc);
     }