[commit: ghc] master: Fix egregious error in eta-reduction of data families (1160dc5)

[git at git.haskell.org]

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

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/1160dc516f8b27249d819665883409ee270a743f/ghc

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

commit 1160dc516f8b27249d819665883409ee270a743f
Author: Simon Peyton Jones <simonpj at microsoft.com>
Date:   Fri Dec 4 12:08:37 2015 +0000

    Fix egregious error in eta-reduction of data families
    
    This terrible and long-standing bug was shown up by Trac #11148.
    We are trying to eta-reduce a data family instance, so that we
    can then derive Functor or Generic.  But we were assuming, for
    absolutely not reason whatsoever, that the type variables were
    lined up in a convenient order.  The fact that it ever worked
    was a fluke.
    
    This patch fixes it properly.  Main change is in eta_reduce
    in TcInstDcls.tcDataFamInstDecl


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1160dc516f8b27249d819665883409ee270a743f
 compiler/typecheck/TcInstDcls.hs                  | 92 +++++++++--------------
 compiler/types/FamInstEnv.hs                      | 60 ++++++++++++---
 testsuite/tests/deriving/should_compile/Makefile  | 10 ++-
 testsuite/tests/deriving/should_compile/T11148.hs | 11 +++
 testsuite/tests/deriving/should_compile/all.T     |  2 +
 5 files changed, 109 insertions(+), 66 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 1160dc516f8b27249d819665883409ee270a743f