Throw a type error in production mode when the type of the type test is not

tests/language/src/Instanceof3Test.dart

+// Copyright (c) 2012, 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 testing the instanceof operation.
+
+// In the type test 'e is T', it is a run-time error if T does not denote a type
+// available in the current lexical scope.
+
+isCheckedMode() {
+  try {
+    var i = 1;
+    String s = i;
+    return false;
+  } catch(var e) {
+    return true;
+  }
+}
+
+main() {
+  {
+    bool got_type_error = false;
+    var x = null;
+    try {
+      Expect.isFalse(x is UndeclaredType);  // x is null.
+    } catch (TypeError error) {
+      got_type_error = true;
+    }
+    // Type error in production mode and in checked mode.
+    Expect.isTrue(got_type_error);
+  }
+  {
+    bool got_type_error = false;
+    var x = 1;
+    try {
+      Expect.isFalse(x is UndeclaredType);  // x is not null.
+    } catch (TypeError error) {
+      got_type_error = true;
+    }
+    // Type error in production mode and in checked mode.
+    Expect.isTrue(got_type_error);
+  }
+  {
+    bool got_type_error = false;
+    var x = null;
+    try {
+      Expect.isFalse(x is List<UndeclaredType>);  // x is null.
+    } catch (TypeError error) {
+      got_type_error = true;
+    }
+    // Type error in checked mode only.
+    Expect.isTrue(got_type_error == isCheckedMode());
+  }
+  {
+    bool got_type_error = false;
+    var x = 1;
+    try {
+      Expect.isFalse(x is List<UndeclaredType>);  // x is not a List.
+    } catch (TypeError error) {
+      got_type_error = true;
+    }
+    // Type error in checked mode only.
+    Expect.isTrue(got_type_error == isCheckedMode());
+  }
+  {
+    bool got_type_error = false;
+    var x = new List();
+    try {
+      Expect.isTrue(x is List<UndeclaredType>);  // x is a List<Dynamic>.
+    } catch (TypeError error) {
+      got_type_error = true;
+    }
+    // Type error in checked mode only.
+    Expect.isTrue(got_type_error == isCheckedMode());
+  }
+  {
+    bool got_type_error = false;
+    var x = new List<int>();
+    try {
+      Expect.isTrue(x is List<UndeclaredType>);  // x is a List<int>.
+    } catch (TypeError error) {
+      got_type_error = true;
+    }
+    // Type error in checked mode only.
+    Expect.isTrue(got_type_error == isCheckedMode());
+  }
+}