Fix for issue 5223 : Import 'dart:core' implicitly only if it has not been

tests/language/import_core_prefix-test.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.
+// Test explicit import of dart:core in the source code..
+
+#library("ImportCorePrefixTest.dart");
+#import("dart:core", prefix:"mycore");
+
+void main() {
+  var test = new Map<int,String>();

[hausner, 2012/09/20 22:25:32]

I don't think new Map() should work in this case. You import core with a prefix,
so you should have to write new mycore.Map().

[siva, 2012/09/21 00:42:35]

Good point. I had named the file import_core_prefix-test.dart and hence it was
not getting picked up by the test harness. Fixed the file name verified that
these were flagged as errors and fixed them by adding the prefix.

On 2012/09/20 22:25:32, hausner wrote:

+  bool boolval = false;
+  int variable = 10;
+  num value = 10;
+}