Unify untyped call checking between decorators and template tags.

Author: DanielRosenwasser

src/compiler/checker.ts

@@ -11943,18 +11943,12 @@ namespace ts {
             // Function interface, since they have none by default. This is a bit of a leap of faith
             // that the user will not add any.
             const callSignatures = getSignaturesOfType(apparentType, SignatureKind.Call);
-
             const constructSignatures = getSignaturesOfType(apparentType, SignatureKind.Construct);
-            // TS 1.0 spec: 4.12
-            // If FuncExpr is of type Any, or of an object type that has no call or construct signatures
-            // but is a subtype of the Function interface, the call is an untyped function call. In an
-            // untyped function call no TypeArgs are permitted, Args can be any argument list, no contextual
+
+            // TS 1.0 Spec: 4.12
+            // In an untyped function call no TypeArgs are permitted, Args can be any argument list, no contextual
             // types are provided for the argument expressions, and the result is always of type Any.
-            // We exclude union types because we may have a union of function types that happen to have
-            // no common signatures.
-            if (isTypeAny(funcType) ||
-                (isTypeAny(apparentType) && funcType.flags & TypeFlags.TypeParameter) ||
-                (!callSignatures.length && !constructSignatures.length && !(funcType.flags & TypeFlags.Union) && isTypeAssignableTo(funcType, globalFunctionType))) {
+            if (isUntypedFunctionCall(funcType, apparentType, callSignatures.length, constructSignatures.length)) {
                 // The unknownType indicates that an error already occurred (and was reported).  No
                 // need to report another error in this case.
                 if (funcType !== unknownType && node.typeArguments) {
@@ -11977,6 +11971,29 @@ namespace ts {
             return resolveCall(node, callSignatures, candidatesOutArray);
         }
 
+        /**
+         * TS 1.0 spec: 4.12
+         * If FuncExpr is of type Any, or of an object type that has no call or construct signatures
+         * but is a subtype of the Function interface, the call is an untyped function call.
+         */
+        function isUntypedFunctionCall(funcType: Type, apparentFuncType: Type, numCallSignatures: number, numConstructSignatures: number) {
+            if (isTypeAny(funcType)) {
+                return true;
+            }
+            if (isTypeAny(apparentFuncType) && funcType.flags & TypeFlags.TypeParameter) {
+                return true;
+            }
+            if (!numCallSignatures && !numConstructSignatures) {
+                // We exclude union types because we may have a union of function types that happen to have
+                // no common signatures.
+                if (funcType.flags & TypeFlags.Union) {
+                    return false;
+                }
+                return isTypeAssignableTo(funcType, globalFunctionType);
+            }
+            return false;
+        }
+
         function resolveNewExpression(node: NewExpression, candidatesOutArray: Signature[]): Signature {
             if (node.arguments && languageVersion < ScriptTarget.ES5) {
                 const spreadIndex = getSpreadArgumentIndex(node.arguments);
@@ -12102,8 +12119,9 @@ namespace ts {
             }
 
             const callSignatures = getSignaturesOfType(apparentType, SignatureKind.Call);
+            const constructSignatures = getSignaturesOfType(apparentType, SignatureKind.Construct);
 
-            if (isTypeAny(tagType) || (!callSignatures.length && !(tagType.flags & TypeFlags.Union) && isTypeAssignableTo(tagType, globalFunctionType))) {
+            if (isUntypedFunctionCall(tagType, apparentType, callSignatures.length, constructSignatures.length)) {
                 return resolveUntypedCall(node);
             }
 
@@ -12148,7 +12166,8 @@ namespace ts {
             }
 
             const callSignatures = getSignaturesOfType(apparentType, SignatureKind.Call);
-            if (funcType === anyType || (!callSignatures.length && !(funcType.flags & TypeFlags.Union) && isTypeAssignableTo(funcType, globalFunctionType))) {
+            const constructSignatures = getSignaturesOfType(apparentType, SignatureKind.Construct);
+            if (isUntypedFunctionCall(funcType, apparentType, callSignatures.length, constructSignatures.length)) {
                 return resolveUntypedCall(node);
             }