fix checking of dsend generic type bounds

tests/language_strong/generic_function_bounds_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 'dart:math';
 import 'package:expect/expect.dart';
 
 void testInstantiateToBounds() {
   f<T extends num, U extends T>() => [T, U];
   g<T extends List<U>, U extends int>() => [T, U];
   h<T extends num, U extends T>(T x, U y) => h.runtimeType.toString();
 
   Expect.listEquals((f as dynamic)(), [num, num]);
   Expect.equals((g as dynamic)().join('|'), 'List<int>|int');
   Expect.equals((h as dynamic)(null, null),
       '<T extends num, U extends T>(T, U) -> String');
 
   i<T extends Iterable<T>>() => null;
   j<T extends Iterable<S>, S extends T>() => null;
-  Expect.throws(() => (i as dynamic)(),
-      (e) => '$e'.contains('Instantiate to bounds'));
-  Expect.throws(() => (j as dynamic)(),
-      (e) => '$e'.contains('Instantiate to bounds'));
+  Expect.throws(
+      () => (i as dynamic)(), (e) => '$e'.contains('Instantiate to bounds'));
+  Expect.throws(
+      () => (j as dynamic)(), (e) => '$e'.contains('Instantiate to bounds'));
 }
 
 void testChecksBound() {
   f<T extends num>(T x) => x;
   Expect.equals((f as dynamic)(42), 42);
   Expect.throws(() => (f as dynamic)('42'));
 
+  msg(t1, t2, tf) => Expect.throws(() => (f as dynamic)<Object>(42),
+      (e) => '$e' == 'type `Object` does not extend `num` of `T');
+
   g<T extends U, U extends num>(T x, U y) => x;
   Expect.equals((g as dynamic)(42.0, 100), 42.0);
   Expect.throws(() => (g as dynamic)('hi', 100));
+  Expect.throws(() => (g as dynamic)<double, int>(42.0, 100),
+      (e) => '$e' == 'type `double` does not extend `int` of `T`.');
+
+  Expect.throws(() => (g as dynamic)<num, Object>(42.0, 100),
+      (e) => '$e' == 'type `Object` does not extend `num` of `U`.');
 }
 
 typedef G<U> = T Function<T extends U>(T x);
 
 void testSubtype() {
   f<T extends num>(T x) => x + 2;
 
   dynamic d = f;
   Expect.equals(d(40.0), 42.0);
   Expect.equals((f as G<int>)(40), 42);
   Expect.equals((d as G<int>)(40), 42);
   Expect.equals((f as G<double>)(40.0), 42.0);
   Expect.equals((d as G<double>)(40.0), 42.0);
 
   d as G<Null>;
   Expect.throws(() => d as G);
   Expect.throws(() => d as G<Object>);
   Expect.throws(() => d as G<String>);
 }
 
 void testToString() {
   // TODO(jmesserly): I don't think the cast on `y` should be required.
   num f<T extends num, U extends T>(T x, U y) => min(x, y as num);
   num g<T, U>(T x, U y) => max(x as num, y as num);
   String h<T, U>(T x, U y) => h.runtimeType.toString();
-  Expect.equals(f.runtimeType.toString(),
-      '<T extends num, U extends T>(T, U) -> num');
+  Expect.equals(
+      f.runtimeType.toString(), '<T extends num, U extends T>(T, U) -> num');
   Expect.equals(g.runtimeType.toString(), '<T, U>(T, U) -> num');
   Expect.equals(h(42, 123.0), '<T, U>(T, U) -> String');
 }
 
 main() {
   testInstantiateToBounds();
   testToString();
   testChecksBound();
   testSubtype();
 }