This test uses wholesale impredicative polymorphism, and now fails.
That's ok.

..accidentally omitted from previous commit.

This patch fixes Trac #12616.

Dignosis.  In TcUnify.tc_sub_type_ds we were going to some trouble to
support co- and contra-variance even for impredicative types.  With
-XImpredicativeTYpes, this allowed a unification variable to be
unified with a polytype (probably wrongly) and that caused later
trouble in the constraint solver, where -XImpredicativeTypes was /not/
on.  In effect, -XImpredicativeTypes can't be switched on locally.

Why did we want ImpredicativeTypes locally?  Because the program
generated by GND for a higher-rank method involved impredicative
instantation of 'coerce':
      op = coerce op   -- where op has a higher rank type
See Note [Newtype-deriving instances] in TcGenDeriv.

Cure.

1.  It is ghastly to rely on ImpredicativeTypes (a 100% flaky
    feature) to instantiate coerce polymorphically.  Happily we
    now have Visible Type Application, so I've used that instead
    which should be solid and reliable.

2.  I deleted the code in tc_sub_type_ds that allows the constraint
    solver to "look through" a unification variable to find a
    polytype.  That used to be essential in the days of ReturnTv,
    but it's utterly unreliable and should be consigned to the dustbin
    of history.  (We have ExpType now for the essential uses.)

Tests involving ImpredicativeTypes are affected, but I'm not worried
about them... it's advertised as a feature you can't rely on, and
I want to reform it outright.

...just for debug output

1. Trac #12593 exposed a long-standing bug in the occurs
   checking machinery.  When unifying two type variables
          a ~ b
   where a /= b, we were assuming that there could be
   no occurs-check error.  But there can: 'a' can occur
   in b's kind!  When the RHS was a non-tyvar we used
   occurCheckExpand, which /did/ look in kinds, but not
   when the RHS was a tyvar.

   This bug has been lurking ever since TypeInType, maybe
   longer.  And it was present both in TcUnify (the on-the-fly
   unifier), and in TcInteract.

   I ended up refactoring both so that the tyvar/tyvar
   path naturally goes through the same occurs-check as
   non-tyvar rhss.  It's simpler and more robust now.

   One good thing is that both unifiers now share
       TcType.swapOverVars
       TcType.canSolveByUnification
   previously they had different logic for the same goals

2. Fixing this bug exposed another!  In T11635 we end
   up unifying
   (alpha :: forall k. k->*) ~ (beta :: forall k. k->*)
   Now that the occurs check is done for tyvars too, we
   look inside beta's kind.  And then reject the program
   becuase of the forall inside there.  But in fact that
   forall is fine -- it does not count as impredicative
   polymoprhism.   See Note [Checking for foralls]
   in TcType.

3. All this fuss around occurrence checking forced me
   to look at TcUnify.checkTauTvUpdate
          and TcType.occurCheckExpand
   There's a lot of duplication there, and I managed
   to elminate quite a bit of it. For example,
   checkTauTvUpdate called a local 'defer_me'; and then
   called occurCheckExpand, which then used a very
   similar 'fast_check'.

   Things are better, but there is more to do.

This patch fixes Trac #12595.  The problem was with a
pattern binding like
     !x = e
For a start it's silly to match that pattern and build
a unit tuple (the General Case of mkSelectorBinds); but
that's what was happening because the bang fell through
to the general case.  But for a variable pattern building
any auxiliary bindings is stupid.  So the patch
introduces a new case in mkSelectorBinds for variable
patterns.

Then it turned out that if 'e' was a plain variable, and
moreover was imported GlobalId, then matchSinglePat made
it a /bound/ variable, which should never happen.  That
ultimately caused a linker error, but the original bug
was much earlier.

This prevents the possibility of race conditions when creating fresh
names.

Test Plan: validate

Reviewers: goldfire, austin, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2548

With this patch we stop generating virtual semicolons in MultiWayIf
guards. Fixes #10807.

Test Plan:

Reviewers: simonmar, austin, bgamari

Reviewed By: simonmar

Subscribers: mpickering, thomie

Differential Revision: https://phabricator.haskell.org/D2524

GHC Trac Issues: #10807

__GLASGOW_HASKELL is a typo (should be __GLASGOW_HASKELL__), obviously,
but nobody noticed.

This fixes Trac #12597: in RnNames.warnMissingSignatures,
use pprSigmaType not pprType

as the latter is the official, correct spelling, and the former just a
misspelling accepted by GHC.

Also document in the user’s guide that the alternative spelling is
accepted

This commit was brough to you by HIW 2016.

It is a self-recursive function so will always be the loop-breaker
and hence never able to be inlined. It is dubious whether the INLINABLE
pragma will ever help as it is not a very polymorphic function
but some specialisation could occur.

The problem is described in the ticket.

This patch adds new variants of the access points to the pure
unifier that allow unification of types only when the caller
wants this behavior. (The unifier used to also unify kinds.)
This behavior is appropriate when the kinds are either already
known to be the same, or the list of types provided are a
list of well-typed arguments to some type constructor. In the
latter case, unifying earlier types in the list will unify the
kinds of any later (dependent) types.

At use sites, I went through and chose the unification function
according to the criteria above.

This patch includes some modest performance improvements as we
are now doing less work.

We had better docs for the underlying functions in GHC.ForeignPtr, but
this wasn't propagated to the re-exported versions in
Foreign.Concurrent.

Summary: And document it.  See the docmentation for the reason I want this.

Test Plan: It's an existing API, just exposing it.

Reviewers: bgamari, niteria, austin, erikd

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2531

If we want to keep the RTS alive a bit longer by having another
hs_init()/hs_exit() pair in a library that will destruct itself after
main() has exited, then the forced shutdown here thwarts that.

I think we just "fixed" #5402 in the wrong way before, this should be
better.

Summary:
Test T12504 does it's checking in the Makefile using grep but still specified an stdout.
the stdout has the old output and would always fail.

Since the stdout isn't needed, let's not check it.

Test Plan: make test TEST=T12504

Reviewers: bgamari, austin, erikd, rcook

Reviewed By: rcook

Subscribers: thomie, #ghc_windows_task_force

Differential Revision: https://phabricator.haskell.org/D2537

GHC Trac Issues: #12504

Fixes #12519

New unarise (714bebff) eliminates void binders in patterns already, so no
need to eliminate them here. I leave assertions to make sure this is the
case.

Assertion failure -> bug in unarise

Reviewers: bgamari, simonpj, austin, simonmar, hvr

Reviewed By: simonpj

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2416

Ben Gamari authored 8 years ago and Ben Gamari committed 8 years ago

Previously this was a relative path which worked in the GHC tree, but
failed elsewhere. This caused trouble for out-of-tree users as well as
Hadrian, which wants to move build artifacts out of the working
directory. Fixes #8040.

Test Plan: Validate

Reviewers: thomie, austin, snowleopard, hvr

Reviewed By: snowleopard, hvr

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2530

GHC Trac Issues: #8040

basically using the machinery from the test case of #2110.

See Note [Data for non-algebraic types]

Here we introduce compatibility wrappers for HasCallStack constraints.
This is necessary as we must support GHC 7.10.1 which lacks sane call
stack support. We also introduce another constraint synonym,
HasDebugCallStack, which only provides a call stack when DEBUG is set.

Summary:
* getNonClobberedReg instead of getSomeReg, because the reg needs to
  survive across t_code
* Use a new reg for the table offset calculation instead of clobbering
  the reg returned by expr (this was the bug affecting #12433)

Test Plan: New unit test; validate

Reviewers: rwbarton, bgamari, austin, erikd

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2529

GHC Trac Issues: #12433

Sigh.  I added some comments to the source files,
and failed to revalidate.  But the comments change the
line number in the error messages.  Doh.

I must have failed to validate properly, sorry.
These testsuite wibbles belong with

  commit 03541cba
  Author: Simon Peyton Jones <simonpj@microsoft.com>
  Date:   Fri Sep 9 17:42:42 2016 +0100

      Be less picky about reporing inaccessible code

Ben Gamari authored 8 years ago and Ben Gamari committed 8 years ago

Biographical profiling is not thread-safe as documented in #12019. Throw
an error when it is used in this way.

Test Plan: Validate

Reviewers: simonmar, austin, erikd

Reviewed By: erikd

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2516

GHC Trac Issues: #12019

As requested in #10267. However we still lack support in typed splices.
See #10945 and #10946.