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  • Glasgow Haskell CompilerGlasgow Haskell Compiler
  • GHCGHC
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  • #7282
Closed
Open
Issue created Sep 30, 2012 by HolgerReinhardt@trac-HolgerReinhardt

polykinds error: Found `k' but expected `k'

{-# 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.

Trac metadata
Trac field Value
Version 7.6.1
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler (Type checker)
Test case
Differential revisions
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