Merge pull request #8697 from Microsoft/Fix8694

Fix #8694: check for singatures before calling a type empty

src/compiler/checker.ts

@@ -6030,7 +6030,7 @@ namespace ts {
                 if (type.flags & TypeFlags.ObjectType) {
                     const resolved = resolveStructuredTypeMembers(type);
                     if ((relation === assignableRelation || relation === comparableRelation) &&
-                        (type === globalObjectType || resolved.properties.length === 0) ||
+                        (type === globalObjectType || isEmptyObjectType(resolved)) ||
                         resolved.stringIndexInfo || resolved.numberIndexInfo || getPropertyOfType(type, name)) {
                         return true;
                     }
@@ -6045,6 +6045,14 @@ namespace ts {
                 return false;
             }
 
+            function isEmptyObjectType(t: ResolvedType) {
+                return t.properties.length === 0 &&
+                    t.callSignatures.length === 0 &&
+                    t.constructSignatures.length === 0 &&
+                    !t.stringIndexInfo &&
+                    !t.numberIndexInfo;
+            }
+
             function hasExcessProperties(source: FreshObjectLiteralType, target: Type, reportErrors: boolean): boolean {
                 if (!(target.flags & TypeFlags.ObjectLiteralPatternWithComputedProperties) && maybeTypeOfKind(target, TypeFlags.ObjectType)) {
                     for (const prop of getPropertiesOfObjectType(source)) {

tests/baselines/reference/excessPropertyErrorForFunctionTypes.errors.txt

@@ -0,0 +1,12 @@
+tests/cases/compiler/excessPropertyErrorForFunctionTypes.ts(4,44): error TS2322: Type '{ a: number; c: number; d: number; }' is not assignable to type '{ a: number; c: number; } | (() => any)'.
+  Object literal may only specify known properties, and 'd' does not exist in type '{ a: number; c: number; } | (() => any)'.
+
+
+==== tests/cases/compiler/excessPropertyErrorForFunctionTypes.ts (1 errors) ====
+    type FunctionType = () => any;
+    type DoesntWork = { a: number, c: number } | FunctionType;
+    
+    let doesntWork: DoesntWork = { a: 1, c: 2, d: 3 }
+                                               ~~~~
+!!! error TS2322: Type '{ a: number; c: number; d: number; }' is not assignable to type '{ a: number; c: number; } | (() => any)'.
+!!! error TS2322:   Object literal may only specify known properties, and 'd' does not exist in type '{ a: number; c: number; } | (() => any)'.

tests/baselines/reference/excessPropertyErrorForFunctionTypes.js

@@ -0,0 +1,8 @@
+//// [excessPropertyErrorForFunctionTypes.ts]
+type FunctionType = () => any;
+type DoesntWork = { a: number, c: number } | FunctionType;
+
+let doesntWork: DoesntWork = { a: 1, c: 2, d: 3 }
+
+//// [excessPropertyErrorForFunctionTypes.js]
+var doesntWork = { a: 1, c: 2, d: 3 };

tests/cases/compiler/excessPropertyErrorForFunctionTypes.ts

@@ -0,0 +1,4 @@
+type FunctionType = () => any;
+type DoesntWork = { a: number, c: number } | FunctionType;
+
+let doesntWork: DoesntWork = { a: 1, c: 2, d: 3 }