[commit: ghc] master: Tidy up treatment of FlexibleContexts (b83160d)

[git at git.haskell.org]

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

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/b83160d07e626bee685f329a9a73e90a4a6074ae/ghc

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

commit b83160d07e626bee685f329a9a73e90a4a6074ae
Author: Simon Peyton Jones <simonpj at microsoft.com>
Date:   Thu Apr 30 09:18:49 2015 +0100

    Tidy up treatment of FlexibleContexts
    
    Previously (Trac #10351) we could get
    
        Non type-variable argument in the constraint: C [t]
        (Use FlexibleContexts to permit this)
        When checking that `f' has the inferred type
          f :: forall t. C [t] => t -> ()
    
    which is a bit stupid: we have *inferred* a type that we
    immediately *reject*.  This patch arranges that that the
    generalisation mechanism (TcSimplify.decideQuantification)
    doesn't pick a predicate that will be rejected by the
    subsequent validity check.
    
    This forced some minor refactoring, as usual.


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

b83160d07e626bee685f329a9a73e90a4a6074ae
 compiler/main/DynFlags.hs                          |   5 -
 compiler/typecheck/TcBinds.hs                      |   5 +-
 compiler/typecheck/TcSimplify.hs                   |  57 ++++++-----
 compiler/typecheck/TcType.hs                       |  31 ++++++
 compiler/typecheck/TcValidity.hs                   | 109 +++++++++------------
 testsuite/tests/typecheck/should_fail/T10351.hs    |   6 ++
 .../tests/typecheck/should_fail/T10351.stderr      |   5 +
 testsuite/tests/typecheck/should_fail/T6022.stderr |  11 ++-
 testsuite/tests/typecheck/should_fail/T8883.stderr |  16 +--
 testsuite/tests/typecheck/should_fail/all.T        |   1 +
 .../tests/typecheck/should_fail/tcfail108.stderr   |   9 +-
 11 files changed, 147 insertions(+), 108 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 b83160d07e626bee685f329a9a73e90a4a6074ae