[commit: ghc] master: Kind variables in RHS of an associated type instances should be bound on LHS (171101b)

[git at git.haskell.org]

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

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/171101beca39befde191baff5027c417bcc709ee/ghc

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commit 171101beca39befde191baff5027c417bcc709ee
Author: Simon Peyton Jones <simonpj at microsoft.com>
Date:   Fri Nov 28 17:23:08 2014 +0000

    Kind variables in RHS of an associated type instances should be bound on LHS
    
    This patche fixes Trac #9574.
    
    The previous Note [Renaming associated types] in RnTypes appears to me to be wrong;
    it confused class and instance declarations.
    
    I have:
    
     * Treated kind and type variables uniformly. Both must be bound on the LHS
       of an associated type instance.  Eg
           instance C ('KProxy :: KProxy o) where
              type F 'KProxy = NatTr (Proxy :: o -> *)
       is illegal because 'o' is not bound on the LHS of the instance.
    
     * Moved the Note to RnSource and fixed it up
    
    This improves the error message from T7938. However it made the code in
    T6118 incorrect. We had:
      instance SingE (a :: Maybe k) where
        type Demote a = Maybe (Demote (Any :: k))
    and that is now rejected, rightly I think.


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171101beca39befde191baff5027c417bcc709ee
 compiler/rename/RnSource.lhs                       | 53 +++++++++++++++++-----
 compiler/rename/RnTypes.lhs                        | 25 ----------
 compiler/typecheck/TcInstDcls.lhs                  | 14 +-----
 .../tests/indexed-types/should_fail/T5515.stderr   |  4 +-
 .../tests/indexed-types/should_fail/T7938.stderr   |  8 ++--
 testsuite/tests/polykinds/T6118.hs                 |  2 +-
 testsuite/tests/polykinds/T9574.hs                 | 18 ++++++++
 testsuite/tests/polykinds/T9574.stderr             |  4 ++
 testsuite/tests/polykinds/all.T                    |  1 +
 9 files changed, 72 insertions(+), 57 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 171101beca39befde191baff5027c417bcc709ee