Fix type checks with malformed types

tests/language/is_malformed_type_test.dart

Index: tests/language/is_malformed_type_test.dart
===================================================================
--- tests/language/is_malformed_type_test.dart	(revision 0)
+++ tests/language/is_malformed_type_test.dart	(working copy)
@@ -0,0 +1,94 @@
+// Copyright (c) 2014, 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 program for the "is" and "as" operator with malformed type.
+
+import "package:expect/expect.dart";
+
+var evalCount = 0;
+testEval(x) { evalCount++; return x; }
+
+test99(e) {
+  // Test that a runtime error is thrown when the 'is' operator checks for a
+  // malformed type.
+  try {
+    if (e is Undefined) Expect.fail("unreachable");
+    Expect.fail("unreachable");
+  } catch(exc) {
+    Expect.isTrue(exc is TypeError);
+  }
+}
+
+test98(e) {
+  // Test that a runtime error is thrown when the 'as' operator checks for a
+  // malformed type.
+  try {
+    if (e as Undefined) Expect.fail("unreachable");
+    Expect.fail("unreachable");
+  } catch(exc) {
+    Expect.isTrue(exc is TypeError);
+  }
+}
+
+test97(e) {
+  try {
+    // Check that the remaining expression after the type test
+    // with malformed type is parsed, but not executed at runtime.
+    // Regression test for issue 16985.
+    evalCount = 0;
+    if (e is Undefined && testEval(e)) Expect.fail("unreachable");
+    Expect.fail("unreachable");
+  } catch(exc) {
+    Expect.isTrue(exc is TypeError);
+    Expect.equals(0, evalCount);
+  }
+}
+
+test96(e) {
+  try {
+    // Check that the remaining expression after the type test
+    // with malformed type is parsed, but not executed at runtime.
+    // Regression test for issue 16985.
+    evalCount = 0;
+    if (e as Undefined && testEval(e)) Expect.fail("unreachable");
+    Expect.fail("unreachable");
+  } catch(exc) {
+    Expect.isTrue(exc is TypeError);
+    Expect.equals(0, evalCount);
+  }
+}
+
+test95(e) {
+  // Check that the type-tested expression is evaluated before the
+  // runtime error is thrown.
+  try {
+    evalCount = 0;
+    if (testEval(e) is Undefined) Expect.fail("unreachable");
+    Expect.fail("unreachable");
+  } catch(exc) {
+    Expect.isTrue(exc is TypeError);
+    Expect.equals(1, evalCount);
+  }
+}
+
+test94(e) {
+  // Check that the type-tested expression is evaluated before the
+  // runtime error is thrown.
+  try {
+    evalCount = 0;
+    if (testEval(e) as Undefined) Expect.fail("unreachable");
+    Expect.fail("unreachable");
+  } catch(exc) {
+    Expect.isTrue(exc is TypeError);
+    Expect.equals(1, evalCount);
+  }
+}
+
+main() {
+  test99("99 bottles");  /// 99: ok
+  test98("98 bottles");  /// 98: ok
+  test97("97 bottles");  /// 97: ok
+  test96("96 bottles");  /// 96: ok
+  test95("95 bottles");  /// 95: ok
+  test94("94 bottles");  /// 94: ok
+}