scala/scala — pull request #1869 by retronym (2013-01-08 18:21:24+00:00)
Title: Backport of SI-6846.

Squashed commit of the following:

commit 55806cc0e6177820c12a35a18b4f2a12dc07bb39
Author: Paul Phillips
Date: Wed Dec 19 07:32:19 2012 -0800

SI-6846, regression in type constructor inference.

In 658ba1b4e6 some inference was gained and some was lost.
In this commit we regain what was lost and gain even more.
Dealiasing and widening should be fully handled now, as
illustrated by the test case.
(cherry picked from commit dbebcd509e4013ce02655a2687b27d0967b3650e)

commit e6ef58447d0f4ef6de956fcc03ee283bb9028c02
Author: Paul Phillips
Date: Fri Dec 21 15:11:29 2012 -0800

Cleaning up type alias usage.

I determined that many if not most of the calls to .normalize
have no intent beyond dealiasing the type. In light of this I
went call site to call site knocking on doors and asking why
exactly they were calling any of

.normalize
.widen.normalize
.normalize.widen

and if I didn't like their answers they found themselves
introduced to 'dropAliasesAndSingleTypes', the recursive widener
and dealiaser which I concluded is necessary after all.

Discovered that the object called 'deAlias' actually depends
upon calling 'normalize', not 'dealias'. Decided this was
sufficient cause to rename it to 'normalizeAliases'.

Created dealiasWiden and dealiasWidenChain.

Dropped dropAliasesAndSingleTypes in favor of methods
on Type alongside dealias and widen (Type#dealiasWiden).
These should reduce the number of "hey, the type alias doesn't work" bugs.

(cherry picked from commit 3bf51189f979eb0dd41744ca844fd12dfdaa0dee)

Conflicts:
src/compiler/scala/tools/nsc/interpreter/CompletionOutput.scala

commit c1d8803cea1523f458730103386d8e14324a9446
Author: Paul Phillips
Date: Sat Dec 22 08:13:48 2012 -0800

Shored up a hidden dealiasing dependency.

Like the comment says:

// This way typedNew always returns a dealiased type. This
// used to happen by accident for instantiations without type
// arguments due to ad hoc code in typedTypeConstructor, and
// annotations depended on it (to the extent that they worked,
// which they did not when given a parameterized type alias
// which dealiased to an annotation.) typedTypeConstructor
// dealiases nothing now, but it makes sense for a "new" to
// always be given a dealiased type.

PS:
Simply running the test suite is becoming more difficult all
the time. Running "ant test" includes time consuming activities
of niche interest such as all the osgi tests, but test.suite
manages to miss the continuations tests.
(cherry picked from commit 422f461578ae0547181afe6d2c0c52ea1071d37b)

commit da4748502792b260161baa10939554564c488051
Author: Paul Phillips
Date: Fri Dec 21 12:39:02 2012 -0800

Fix and simplify typedTypeConstructor.

Investigating the useful output of devWarning (-Xdev people,
it's good for you) led back to this comment:

"normalize to get rid of type aliases"

You may know that this is not all the normalizing does.
Normalizing also turns TypeRefs with unapplied arguments
(type constructors) into PolyTypes. That means that when
typedParentType would call typedTypeConstructor it would
find its parent had morphed into a PolyType. Not that it
noticed; it would blithely continue and unwittingly discard
the type arguments by way of appliedType (which smoothly
logged the incident, thank you appliedType.)

The simplification of typedTypeConstructor:

There was a whole complicated special treatment of AnyRef
here which appears to have become unnecessary. Removed special
treatment and lit a candle for regularity.

Updated lots of tests regarding newly not-so-special AnyRef.
(cherry picked from commit 394cc426c1ff1da53146679b4e2995ece52a133e)

commit 1f3c77bacb2fbb3ba9e4ad0a8a733e0f9263b234
Author: Paul Phillips
Date: Fri Dec 21 15:06:10 2012 -0800

Removed dead implementation.

Another "attractive nuisance" burning off time until I
realized it was commented out.
(cherry picked from commit ed40f5cbdf35d09b02898e9c0950b9bd34c1f858)

Review by @paulp