restrict generic function type subtyping

pkg/analyzer/test/src/task/strong/checker_test.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library analyzer.test.src.task.strong.checker_test;
 
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import 'strong_test_helper.dart';
 
@@ skipping 3973 matching lines @@
   }
 
   void test_unboundVariable() {
     checkFile('''
 void main() {
    dynamic y = /*error:UNDEFINED_IDENTIFIER*/unboundVariable;
 }
 ''');
   }
 
+  void test_universalFunctionSubtyping() {
+    checkFile(r'''
+T foo<T>(T x) => x;
+
+void takesDtoD(dynamic f(dynamic x)) {}
+
+void test() {
+  // here we currently infer an instantiation.
+  takesDtoD(/*pass should be error:INVALID_ASSIGNMENT*/foo);

[Leaf, 2016/12/02 01:59:10]

I think if you make it

dynamic foo<T>(dynamic x) => x

it might work?

[Jennifer Messerly, 2016/12/02 03:24:00]

hmmm, tried it and it's still too smart to infer. Maybe after that other
inference patch when it treats no information a bit differently than `dynamic`.

+}
+
+class A {
+  dynamic method(dynamic x) => x;
+}
+
+class B extends A {
+  /*error:INVALID_METHOD_OVERRIDE*/T method<T>(T x) => x;
+}
+    ''');
+  }
+
   void test_voidSubtyping() {
     // Regression test for https://github.com/dart-lang/sdk/issues/25069
     checkFile('''
 typedef int Foo();
 void foo() {}
 void main () {
   Foo x = /*error:INVALID_ASSIGNMENT,info:USE_OF_VOID_RESULT*/foo();
 }
 ''');
   }
 }