Put union types behind a flag.

Put union types behind a flag.

I added two union types related flags:

- enableUnionTypes: whether or not union types should be used.

- strictUnionTypes: whether or not union types should have "strict"
  semantics. The default, non-strict semantics are more like
  intersection types: they're less sound than the strict semantics but
  generate fewer warnings, by saying e.g. that a method is defined on
  the union if it's defined on *any* of the members. For the strict
  semantics we want the method to be defined on *all* the members.

I surfaced the flags in the static [AnalysisEngine] instance and added a helper function
for setting them in the resolver tests.  The next step is to use the "strict" flag to implement the
optional strict semantics for union types.

I don't know where setting the options for the Dart Editor is
documented, so I'm summarizing @brianwilkerson's instructions here. In
Eclipse, assuming you already have a Dart Editor configuration, do

  run configurations ->
  launch dart editor ->
  tracing ->
  enable tracing ->
  enable com.google.dart.tools.core ->
  enable experimental/enableUnionTypes and (optionally)
  enable experimental/strictUnionTypes

R=brianwilkerson@google.com, jwren@google.com
BUG=

Committed: https://code.google.com/p/dart/source/detail?r=40635

[Brian Wilkerson, 2014-09-23 13:49:08]

https://codereview.chromium.org/592923002/diff/1/editor/tools/plugins/com.goo...
File
editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/resolver/ResolverVisitor.java
(right):

https://codereview.chromium.org/592923002/diff/1/editor/tools/plugins/com.goo...
editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/resolver/ResolverVisitor.java:733:
// dependencies.
You need to access the option from the AnalysisOptions for the context that is
running this resolver. (Then, in ProjectImpl in the core plug-in, initialize the
analysis options from the flag in DartCoreDebug.)

[Nathan Collins, 2014-09-23 21:07:21]

https://codereview.chromium.org/592923002/diff/1/editor/tools/plugins/com.goo...
File
editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/resolver/ResolverVisitor.java
(right):

https://codereview.chromium.org/592923002/diff/1/editor/tools/plugins/com.goo...
editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/resolver/ResolverVisitor.java:733:
// dependencies.
On 2014/09/23 13:49:08, Brian Wilkerson wrote:
> You need to access the option from the AnalysisOptions for the context that is
> running this resolver. (Then, in ProjectImpl in the core plug-in, initialize
the
> analysis options from the flag in DartCoreDebug.)

Done.

[Nathan Collins, 2014-09-23 21:12:46]

PTAL.

[Brian Wilkerson, 2014-09-23 22:04:51]

LGTM

https://codereview.chromium.org/592923002/diff/20001/editor/tools/plugins/com...
File
editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/resolver/ResolverVisitor.java
(right):

https://codereview.chromium.org/592923002/diff/20001/editor/tools/plugins/com...
editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/resolver/ResolverVisitor.java:742:
// TODO(collinsn): If I import this class then Eclipse complains about circular
I assume this TODO is obsolete and should be removed.

[Nathan Collins, 2014-09-24 00:34:06]

PTAL.

I removed the union type options from [AnalysisOptions] and surfaced them in
[AnalysisEngine] instead, as discussed.  They still come into Eclipse through
[DartCoreDebug] and [ProjectImpl] and the .options file.

https://codereview.chromium.org/592923002/diff/20001/editor/tools/plugins/com...
File
editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/resolver/ResolverVisitor.java
(right):

https://codereview.chromium.org/592923002/diff/20001/editor/tools/plugins/com...
editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/resolver/ResolverVisitor.java:742:
// TODO(collinsn): If I import this class then Eclipse complains about circular
On 2014/09/23 22:04:51, Brian Wilkerson wrote:
> I assume this TODO is obsolete and should be removed.

Done.

[Brian Wilkerson, 2014-09-24 13:28:43]

LGTM

[Nathan Collins, 2014-09-24 17:31:47]

Committed patchset #3 manually as 40635 (presubmit successful).