add test, fixes #27807

this appears to have been already working correctly

[email protected]

Review URL: https://codereview.chromium.org/2517193004 .

Author: Jennifer Messerly

pkg/dev_compiler/test/codegen/language/void_subtype_test.dart

@@ -0,0 +1,59 @@
+// 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.
+// Dart test for type checks involving the void type.
+
+import "package:expect/expect.dart";
+
+var _str = new StringBuffer();
+
+/*=T*/ run/*<T>*/(/*=T*/ f()) {
+  _str.write("+");
+  var t = f();
+  _str.write("-");
+  return t;
+}
+
+void writeV() { _str.write("V"); }
+
+main() {
+  {
+    var x = run/*<dynamic>*/(writeV);
+    Expect.equals('+V-', _str.toString());
+    Expect.equals(null, x);
+    _str.clear();
+
+    var y = run(writeV);
+    Expect.equals('+V-', _str.toString());
+    Expect.equals(null, y);
+    _str.clear();
+  }
+
+  // implicit cast
+  {
+    dynamic d = writeV;
+    var x = run/*<dynamic>*/(d);
+    Expect.equals('+V-', _str.toString());
+    Expect.equals(null, x);
+    _str.clear();
+
+    var y = run(d);
+    Expect.equals('+V-', _str.toString());
+    Expect.equals(null, y);
+    _str.clear();
+  }
+
+  // dynamic dispatch
+  {
+    dynamic d = run;
+    var x = d/*<dynamic>*/(writeV);
+    Expect.equals('+V-', _str.toString());
+    Expect.equals(null, x);
+    _str.clear();
+
+    var y = d(writeV);
+    Expect.equals('+V-', _str.toString());
+    Expect.equals(null, y);
+    _str.clear();
+  }
+}