Inference casts to dynamic, fuzzy types handled

Inference casts to dynamic, fuzzy types handled

During inference, allow sub-expressions of type dynamic to be cast to the inferred type.

This CL also adds special case support for the case where we are trying to infer a type for a closure literal with a fuzzy type - often these closures are already well-typed (or easily inferable) if we eliminate the fuzziness.

This gets rid of two of the static errors on angular hello world, along with most of the InferableClosure warnings (turning them into InferredTypeClosure infos).

Most of the remaining InferableClosure cases are function literals with block function bodies, which I don't handle in general yet.

BUG=
R=vsm@google.com

Committed: https://github.com/dart-lang/dev_compiler/commit/34dc80aa9118c6fd2c1cd468bac09a2ab466c54b

[Leaf, 2015-04-03 22:23:16]

leafp@google.com changed reviewers:
+ vsm@google.com

[Leaf, 2015-04-03 22:23:23]

https://codereview.chromium.org/1059763003/diff/1/test/checker/inferred_type_...
File test/checker/inferred_type_test.dart (right):

https://codereview.chromium.org/1059763003/diff/1/test/checker/inferred_type_...
test/checker/inferred_type_test.dart:1503: Function2<int, int> l1 =
/*info:InferredTypeClosure*/(x) => x+1;
This now succeeds, though arguably for the wrong reason.

https://codereview.chromium.org/1059763003/diff/1/test/checker/inferred_type_...
test/checker/inferred_type_test.dart:1504: Function2<int, String> l2 =
/*info:InferredTypeClosure should be severe:StaticTypeError*/(x) => x;
This is an example of a case where allowing casts from dynamic makes things
worse - it would be nice to reject this case statically.

[vsm, 2015-04-03 22:32:59]

lgtm

https://codereview.chromium.org/1059763003/diff/1/lib/src/checker/rules.dart
File lib/src/checker/rules.dart (right):

https://codereview.chromium.org/1059763003/diff/1/lib/src/checker/rules.dart#...
lib/src/checker/rules.dart:774: // succeed and treat it as a succesful inference
s/succesful/successful/

[Leaf, 2015-04-03 22:36:31]

Committed patchset #1 (id:1) manually as
34dc80aa9118c6fd2c1cd468bac09a2ab466c54b (presubmit successful).