[commit: ghc] master: More aggressive Given/Wanted overlap check (8b7ceec)

[git at git.haskell.org]

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

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/8b7ceece52d2a0bb8a4ea5609da286fb76d88211/ghc

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

commit 8b7ceece52d2a0bb8a4ea5609da286fb76d88211
Author: Simon Peyton Jones <simonpj at microsoft.com>
Date:   Tue Apr 7 14:29:10 2015 +0100

    More aggressive Given/Wanted overlap check
    
    This fixes Trac #10195
    
    For some reason we considered untouchability before, but Trac #10195
    shows that this is positively worng.
    
    See Note [Instance and Given overlap] in TcInteract.
    
    Looking at the Git log, it seems that this bug was introduced at the
    same time that we introduced the Given/Wanted overlap check in the first
    place.


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

8b7ceece52d2a0bb8a4ea5609da286fb76d88211
 compiler/typecheck/TcInteract.hs                   | 93 ++++++++++++----------
 compiler/typecheck/TcType.hs                       |  4 +-
 testsuite/tests/typecheck/should_compile/T10195.hs | 31 ++++++++
 testsuite/tests/typecheck/should_compile/all.T     |  1 +
 4 files changed, 83 insertions(+), 46 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 8b7ceece52d2a0bb8a4ea5609da286fb76d88211