[commit: ghc] master: Better solving for representational equalities (5a66d57)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/5a66d574890ed09859ca912c9e0969dba72f4a23/ghc

>---------------------------------------------------------------

commit 5a66d574890ed09859ca912c9e0969dba72f4a23
Author: Simon Peyton Jones <simonpj at microsoft.com>
Date:   Tue Oct 17 16:32:25 2017 +0100

    Better solving for representational equalities
    
    This patch adds a bit of extra solving power for representational
    equality constraints to fix Trac #14333
    
    The main changes:
    
    * Fix a buglet in TcType.isInsolubleOccursCheck which wrongly
      reported a definite occurs-check error for (a ~R# b a)
    
    * Get rid of TcSMonad.emitInsolubles.  It had an ad-hoc duplicate-removal
      piece that is better handled in interactIrred, now that insolubles
      are Irreds.
    
      We need a little care to keep inert_count (which does not include
      insolubles) accurate.
    
    * Refactor TcInteract.solveOneFromTheOther, to return a much simpler
      type.  It was just over-complicated before.
    
    * Make TcInteract.interactIrred look for constraints that match
      either way around, in TcInteract.findMatchingIrreds
    
    This wasn't hard and it cleaned up quite a bit of code.


>---------------------------------------------------------------

5a66d574890ed09859ca912c9e0969dba72f4a23
 compiler/typecheck/TcCanonical.hs                  |  14 +-
 compiler/typecheck/TcInteract.hs                   | 257 ++++++++++++++-------
 compiler/typecheck/TcSMonad.hs                     |  91 ++------
 compiler/typecheck/TcType.hs                       |  16 +-
 testsuite/tests/typecheck/should_compile/T14333.hs |  20 ++
 testsuite/tests/typecheck/should_compile/all.T     |   1 +
 .../typecheck/should_fail/FrozenErrorTests.hs      |   0
 7 files changed, 236 insertions(+), 163 deletions(-)

Diff suppressed because of size. To see it, use:

    git diff-tree --root --patch-with-stat --no-color --find-copies-harder --ignore-space-at-eol --cc 5a66d574890ed09859ca912c9e0969dba72f4a23