Add tests for block scope

tests/language/src/BlockScopeTest.dart

+// Copyright (c) 2011, 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.
+
+foo() => 123;
+
+void testShadowingScope1() {
+  var foo = foo();
+  Expect.equals(123, foo);
+}
+
+void testShadowingScope2() {
+  {
+    var foo = foo() + 444;
+    Expect.equals(567, foo);
+  }
+  Expect.equals(123, foo());
+}
+
+void testShadowingCapture1() {
+  var f;
+  {
+    var foo = 888;
+    f = () => foo;
+  }
+  var foo = -888;
+  Expect.equals(888, f());
+}
+
+void testShadowingCapture2() {
+  var f = null;
+  // this one uses a reentrent block
+  for (int i = 0; i < 2; i++) {
+    var foo = i + 888;
+    if (f == null) f = () => foo;
+  } while(false);
+  var foo = -888;
+
+  // this could break if it doesn't bind the right "foo"
+  Expect.equals(888, f());
+}
+
+class BlockScopeTest1 {
+  void testShadowingInstanceVar() {
+    if (true) {
+      var foo = foo() + 444;
+      Expect.equals(1221, foo);
+    }
+    Expect.equals(777, foo());
+  }
+  static void testShadowingStatic() {
+    if (true) {
+      var bar = bar() + 444;
+      Expect.equals(1221, bar);
+    }
+    Expect.equals(777, bar());
+  }
+
+  foo() => 777;
+  static bar() => 777;
+}
+
+main() {
+  testShadowingScope1();
+  testShadowingScope2();
+  testShadowingCapture1();
+  testShadowingCapture2();
+  new BlockScopeTest1().testShadowingInstanceVar();
+  BlockScopeTest1.testShadowingStatic();
+}