Compile time error if name is used before variable is declared

tests/language/bailout3_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.
-
-import "package:expect/expect.dart";
-
-// Test that the return type of a method is being registered for both
-// its bailout and optimized version in dart2js.
-
-var a;
-
-bar() {
-  if (a[0] == 0) {
-    // Force bailout version.
-    bar();
-    // Avoid inlining.
-    throw 0;
-  }
-  for (int i = 0; i < 10; i++) {
-    a[0] = 42;
-  }
-  // This return should say that bar can return an array or unknown.
-  return a;
-}
-
-foo() {
-  if (a[0] == 0) {
-    // Avoid inlining.
-    throw 0;
-  }
-  var a = bar();

[ngeoffray, 2013/11/01 21:41:06]

This should be var b = bar().

-  // This check used to fail because dart2js was assuming [a] was an
-  // array.
-  Expect.equals(1, a.length);

[ngeoffray, 2013/11/01 21:41:06]

-> b.length.

-}
-
-main() {
-  a = new Map();
-  bar();
-  foo();
-}