add a test for #28079, dynamic calls to generic functions and other RTTI

tests/language_strong/generic_function_dcall_test.dart

+// Copyright (c) 2017, 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.
+
+import 'package:expect/expect.dart';
+
+void testCallsToGenericFn() {
+  T f<T>(T a, T b) => ((a as dynamic) + b) as T;
+
+  var x = (f as dynamic)<int>(40, 2);
+  Expect.equals(x, 42);
+
+  var y = (f as dynamic)<String>('hi', '!');
+  Expect.equals(y, 'hi!');
+
+  var dd2d = (x, y) => x;
+  dd2d = f; // implicit <dynamic>
+  x = (dd2d as dynamic)(40, 2);
+  Expect.equals(x, 42);
+  y = (dd2d as dynamic)('hi', '!');
+  Expect.equals(y, 'hi!');
+}
+
+void testGenericFnAsArg() {
+  h<T>(a) => a as T;
+  Object foo(f(Object a), Object a) => f(a);
+  Expect.throws(() => foo(h as dynamic, 42));
+
+  var int2int = (int x) => x;
+  T bar<T>(x) => x as T;
+  dynamic list = <Object>[1, 2, 3];
+  Expect.throws(() => list.map(bar));
+  int2int = bar;
+  Expect.listEquals(list.map(int2int).toList(), [1, 2, 3]);
+}
+
+typedef T2T = T Function<T>(T t);
+void testGenericFnAsGenericFnArg() {
+  h<T>(a) => a as T;
+  S foo<S>(T2T f, S a) => f<S>(a);
+  Expect.equals(foo<int>(h, 42), 42);
+  Expect.equals(foo<dynamic>(h, 42), 42);
+  Expect.equals(foo<int>(h as dynamic, 42), 42);
+  Expect.equals(foo<dynamic>(h as dynamic, 42), 42);
+}
+
+void testGenericFnTypeToString() {
+  T f<T>(T a) => a;
+  // TODO(jmesserly): other Dart implementations use `=>` arrow, so we may need
+  // to change this in DDC at some point.
+  Expect.equals(f.runtimeType.toString(), "<T>(T) -> T");
+}
+
+main() {
+  testCallsToGenericFn();
+  testGenericFnAsArg();
+  testGenericFnAsGenericFnArg();
+  testGenericFnTypeToString();
+}