dart2js: capture type variables in closures, if they are only used in literals.

tests/language/type_variable_closure2_test.dart

Index: tests/language/type_variable_closure2_test.dart
diff --git a/tests/language/type_variable_closure2_test.dart b/tests/language/type_variable_closure2_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..1b55ff9aca86a202fb0bafdca3fe49f398da92c4
--- /dev/null
+++ b/tests/language/type_variable_closure2_test.dart
@@ -0,0 +1,31 @@
+// Copyright (c) 2013, 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";
+
+class A<T> {}
+
+class C<T> {
+  a() {
+    return () => new A<T>();
+  }
+
+  list() {
+    return () => <T>[];
+  }
+
+  map() {
+    return () => <T, T>{};
+  }

[sra1, 2015/01/20 20:25:30]

Also add a function uses the type argument in an is-check

  check() {
    return (x) => x is T;
  }

and in type assertion positions.

  validate1() {
    return (x) { T y = x; }
  }

  validate2() {
    return (T x) { }
  }

  validate3() {
    T foo(x) => x;
    return foo;
  }

You would only use these in checked mode

bool get inCheckedMode {
  bool checked = false;
  assert(checked = true);
  return checked;
}

+}
+
+main() {
+  Expect.isTrue(new C<int>().a()() is A<int>);
+  Expect.isFalse(new C<int>().a()() is A<String>);
+  Expect.isTrue(new C<int>().list()() is List<int>);
+  Expect.isFalse(new C<int>().list()() is List<String>);
+  Expect.isTrue(new C<int>().map()() is Map<int, int>);
+  Expect.isFalse(new C<int>().map()() is Map<String, int>);
+  Expect.isFalse(new C<int>().map()() is Map<int, String>);
+}