[commit: ghc] ghc-7.10: More aggressive Given/Wanted overlap check (49d4282)

[git at git.haskell.org]

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

On branch  : ghc-7.10
Link       : http://ghc.haskell.org/trac/ghc/changeset/49d42827e8875de3d4a953371e98ef5ef71d2038/ghc

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

commit 49d42827e8875de3d4a953371e98ef5ef71d2038
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.
    
    (cherry picked from commit 8b7ceece52d2a0bb8a4ea5609da286fb76d88211)


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49d42827e8875de3d4a953371e98ef5ef71d2038
 compiler/typecheck/TcInteract.hs                   | 141 +++++++++++----------
 compiler/typecheck/TcType.hs                       |   4 +-
 testsuite/tests/typecheck/should_compile/T10195.hs |  31 +++++
 testsuite/tests/typecheck/should_compile/all.T     |   1 +
 4 files changed, 110 insertions(+), 67 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 49d42827e8875de3d4a953371e98ef5ef71d2038