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  • Glasgow Haskell Compiler
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  • #5581

Closed
Open
Opened Oct 24, 2011 by pumpkin@trac-pumpkin

ConstraintKinds lets you put the typechecker into a loop

Ed Kmett was playing with them the other day and Dan Doel and I reduced the issue to this:

{-# LANGUAGE ConstraintKinds, FlexibleContexts, FlexibleInstances, KindSignatures #-}

class C (p :: Constraint)
class D (p :: Constraint)

instance C (D p) => C (D (D p))

{-
-- This works
data E a = E
class F a
instance F (E a) => F (E (E a))
-}
Trac metadata
Trac field Value
Version 7.3
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler (Type checker)
Test case
Differential revisions
BlockedBy
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Blocking
CC
Operating system
Architecture
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Reference: ghc/ghc#5581