provide MISSING_RETURN on factory constructors

provide MISSING_RETURN on factory constructors

BUG=https://github.com/dart-lang/sdk/issues/17121
R=brianwilkerson@google.com, scheglov@google.com

Committed: https://github.com/dart-lang/sdk/commit/7cb775f149b488f9aaba48cb811248d53c27e13f

[srawlins, 2016-04-26 18:43:56]

srawlins@google.com changed reviewers:
+ brianwilkerson@google.com, scheglov@google.com

[srawlins, 2016-04-26 18:43:57]

Two notes:

* I couldn't use the existing _checkForMissingReturn because it uses a TypeName
with a DartType, which I could not find at all for constructors or
ClassElements, etc. Most of _checkForImssingReturn was null checks that were not
necessary for this impl anyways.

* I had to adjust a lot of tests to _not_ produce this hint, by adding a named
constructor, and using it in the factory, instead of `factory A() {}`. Let me
know if you'd like me to avoid the error in a different way.

[Brian Wilkerson, 2016-04-26 19:10:33]

lgtm

[scheglov, 2016-04-27 15:52:02]

LGTM after rolling back test changes and replacing with "=> null".

https://codereview.chromium.org/1923593002/diff/1/pkg/analyzer/test/generated...
File pkg/analyzer/test/generated/compile_time_error_code_test.dart (left):

https://codereview.chromium.org/1923593002/diff/1/pkg/analyzer/test/generated...
pkg/analyzer/test/generated/compile_time_error_code_test.dart:2212: factory
A(this.x) {}
I think you could replace this with:

factory A(this.x) => null;

...and it would not trigger the new hint.

[srawlins, 2016-04-27 19:33:07]

Description was changed from

==========
provide MISSING_RETURN on factory constructors

BUG=https://github.com/dart-lang/sdk/issues/17121
==========

to

==========
provide MISSING_RETURN on factory constructors

BUG=https://github.com/dart-lang/sdk/issues/17121
R=brianwilkerson@google.com, scheglov@google.com

Committed:
https://github.com/dart-lang/sdk/commit/7cb775f149b488f9aaba48cb811248d53c27e13f
==========

[srawlins, 2016-04-27 19:33:09]

Committed patchset #2 (id:10001) manually as
7cb775f149b488f9aaba48cb811248d53c27e13f (presubmit successful).

[srawlins, 2016-04-27 19:52:34]

https://codereview.chromium.org/1923593002/diff/1/pkg/analyzer/test/generated...
File pkg/analyzer/test/generated/compile_time_error_code_test.dart (left):

https://codereview.chromium.org/1923593002/diff/1/pkg/analyzer/test/generated...
pkg/analyzer/test/generated/compile_time_error_code_test.dart:2212: factory
A(this.x) {}
On 2016/04/27 15:52:01, scheglov wrote:
> I think you could replace this with:
> 
> factory A(this.x) => null;
> 
> ...and it would not trigger the new hint.

Great suggestion!