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  • Glasgow Haskell CompilerGlasgow Haskell Compiler
  • GHCGHC
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  • #7073
Closed
Open
Issue created Jul 13, 2012 by Richard Eisenberg@raeDeveloper

Kind variable problem when declaring associated type family

The following code fails to compile:

{-# LANGUAGE PolyKinds, TypeFamilies #-}

class Foo a where
  type Bar a
  type Bar a = Int

The error I get is

    Type indexes must match class instance head
    Found `k' but expected `k'
    In the type synonym instance default declaration for `Bar'
    In the class declaration for `Foo'

When I remove -XPolyKinds, the code compiles without a hiccup.

This was tested on 7.5.2012.0710

Trac metadata
Trac field Value
Version 7.5
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler (Type checker)
Test case
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