#7282: polykinds error: Found `k' but expected `k'
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Reporter: HolgerReinhardt | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler (Type
checker)
Version: 7.6.1 | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: GHC rejects valid program | Testcase:
Blockedby: | Blocking:
Related: |
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{{{
{-# OPTIONS -XTypeFamilies -XDataKinds -XPolyKinds #-}
class Foo (xs :: [k]) where
type Bar xs :: *
instance Foo '[] where
type Bar '[] = Int
}}}
fails with:
{{{
I:\a.hs:7:5:
Type indexes must match class instance head
Found `k' but expected `k'
In the type instance declaration for `Bar'
In the instance declaration for `Foo '[]'
}}}
If I change the kind of xs from [k] to [*], the program is accepted.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7282>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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