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  • Glasgow Haskell Compiler
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  • #3851
Closed
Open
Created Feb 01, 2010 by Andres Löh@kosmikusReporter

type family does not get expanded in ghc-6.12.1

The following code (which is a trimmed down version of an application of the multirec library) does not compile on ghc-6.12.1, but it does with ghc-6.10.4. Why?

{-# LANGUAGE GADTs, TypeFamilies #-}
type family TF a :: * -> *
type instance TF () = App (Equ ())

data Equ ix ix' where Refl :: Equ ix ix
data App f x = App (f x)

-- does not typecheck in 6.12.1 (but works in 6.10.4)
bar :: TF () () -> ()
bar (App Refl) = ()

-- does typecheck in 6.12.1 and 6.10.4
ar :: App (Equ ()) () -> ()
ar (App Refl) = ()
Trac metadata
Trac field Value
Version 6.12.1
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler (Type checker)
Test case
Differential revisions
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CC andres@cs.uu.nl, jpm@cs.uu.nl, stefan@cs.uu.nl
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