Avoid using call-through stub on calls to fields.

tests/compiler/dart2js/elide_callthrough_stub_test.dart

Index: tests/compiler/dart2js/elide_callthrough_stub_test.dart
diff --git a/tests/compiler/dart2js/elide_callthrough_stub_test.dart b/tests/compiler/dart2js/elide_callthrough_stub_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..9366df99f1f893d965f640f522dab322b69e18c6
--- /dev/null
+++ b/tests/compiler/dart2js/elide_callthrough_stub_test.dart
@@ -0,0 +1,60 @@
+// Copyright (c) 2016, 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.
+
+// Check that calls through fields elide the call-through stub.  This
+// optimization is done by the simplifier, so inlining does not need to be
+// enabled.
+
+import 'package:async_helper/async_helper.dart';
+import 'package:expect/expect.dart';
+import 'compiler_helper.dart';
+
+const String TEST1 = r'''
+class W {
+  final Function _fun;
+  W(this._fun);
+  foo(zzz) => _fun(zzz);   // this._fun$1(zzz) -->  this._fun.call$1(zzz)
+}
+add1(x) => x + 1;
+main() {
+  var w = new W(add1);
+  var x = w.foo(42);
+}
+''';
+
+const String TEST2 = r'''
+class W {
+  final Function __fun;
+  Function get _fun => __fun;
+  W(this.__fun);
+  foo(zzz) => _fun(zzz);   //  this._fun$1(zzz) stays same.
+}
+add1(x) => x + 1;
+main() {
+  var w = new W(add1);
+  var x = w.foo(42);
+}
+''';
+
+main() {
+  asyncTest(() => compileAll(TEST1).then((generated) {
+    // Direct call through field.
+    Expect.isTrue(generated.contains(r'this._fun.call$1(zzz)'));
+    // No stub.
+    Expect.isFalse(generated.contains(r'_fun$1:'));
+    // No call to stub.
+    Expect.isFalse(generated.contains(r'_fun$1('));
+  }));
+
+  asyncTest(() => compileAll(TEST2).then((generated) {
+    // No call through field.
+    Expect.isFalse(generated.contains(r'this._fun.call$1(zzz)'));
+    // Call through stub.
+    Expect.isTrue(generated.contains(r'this._fun$1(zzz)'));
+    // Stub is generated.
+    Expect.isTrue(generated.contains(r'_fun$1:'));
+    // Call through getter (inside stub).
+    Expect.isTrue(generated.contains(r'get$_fun().call$1'));
+  }));
+}