#7527: Couldn't match kind `*' with `*' with PolyKinds & GADTs.
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Reporter: Ashley Yakeley | Owner:
Type: bug | Status: closed
Priority: normal | Component: Compiler (Type checker)
Version: 7.6.1 | Resolution: fixed
Keywords: | Os: Unknown/Multiple
Architecture: Unknown/Multiple | Failure: GHC rejects valid program
Blockedby: | Blocking:
Related: |
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Changes (by goldfire):
* status: new => closed
* resolution: => fixed
Comment:
Fixed in HEAD:
{{{
Couldn't match type `t0' with `f'
`t0' is untouchable
inside the constraints ('WrapType * a ~ 'WrapType * a1)
bound by a pattern with constructor
MkW :: forall (k :: BOX) (f :: k -> *) (a :: k).
f a -> W k f ('WrapType k a),
in a case alternative
at /Users/rae/temp/Scratch.hs:21:9-14
`f' is a rigid type variable bound by
the type signature for thing :: T ('WrapType * a) -> f a
at /Users/rae/temp/Scratch.hs:19:30
Expected type: f a
Actual type: t0 a1
Relevant bindings include
thing :: T ('WrapType * a) -> f a
(bound at /Users/rae/temp/Scratch.hs:20:5)
cw :: t0 a1 (bound at /Users/rae/temp/Scratch.hs:21:13)
In the expression: cw
In a case alternative: MkW cw -> cw
In the expression: case (get t) of { MkW cw -> cw }
}}}
Are you claiming that this should type check? Or, just stating that the
error message is unhelpful? I agree with GHC that it shouldn't, and I can
explain if that would be helpful...
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7527#comment:1>
GHC <http://www.haskell.org/ghc/>
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