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  • #8020

Closed
Open
Created Jun 28, 2013 by Richard Eisenberg@raeDeveloper

Closed type families break substitution

This code causes a Core Lint error:

{-# LANGUAGE TypeFamilies #-}

type family F a b where
  F (Maybe a) [a] = Int
  F b c           = Bool

data Proxy a = P

type family G

foo :: Proxy d -> F d d -> Bool
foo _ = not

bar :: Bool -> Bool
bar = foo (P :: Proxy G)

The solution needs to freshen variables before doing apartness checking. I will fix in due course.

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Version 7.7
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler
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