#5581: ConstraintKinds lets you put the typechecker into a loop
---------------------------------+------------------------------------------
Reporter: pumpkin | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler (Type checker)
Version: 7.3 | Keywords: ConstraintKinds
Testcase: | Blockedby:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: Compile-time crash
---------------------------------+------------------------------------------
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))
-}
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5581>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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