restrict generic function type subtyping

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

Index: pkg/analyzer/test/src/task/strong/checker_test.dart
diff --git a/pkg/analyzer/test/src/task/strong/checker_test.dart b/pkg/analyzer/test/src/task/strong/checker_test.dart
index 6c22865f6308266d456bfa7690ae1df59a61ae91..c4c894a698219b09c6839992783621b5cd8c6f08 100644
--- a/pkg/analyzer/test/src/task/strong/checker_test.dart
+++ b/pkg/analyzer/test/src/task/strong/checker_test.dart
@@ -3991,6 +3991,27 @@ void main() {
 ''');
   }
 
+  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('''