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

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

BUG= http://dartbug.com/22060
R=asgerf@google.com

Committed: https://code.google.com/p/dart/source/detail?r=42989

[floitsch, 2015-01-16 17:40:20]

floitsch@google.com changed reviewers:
+ asgerf@google.com

[asgerf, 2015-01-19 10:01:52]

lgtm

[floitsch, 2015-01-19 13:32:07]

Committed patchset #2 (id:20001) manually as 42989 (presubmit successful).

[sra1, 2015-01-20 20:25:29]

sra@google.com changed reviewers:
+ sra@google.com

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

https://chromiumcodereview.appspot.com/851303002/diff/20001/tests/language/ty...
File tests/language/type_variable_closure2_test.dart (right):

https://chromiumcodereview.appspot.com/851303002/diff/20001/tests/language/ty...
tests/language/type_variable_closure2_test.dart:20: }
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;
}