Opened 9 years ago

Closed 9 years ago

#2503 closed bug (worksforme)

Panic related to MPTC's and type equality

Reported by: Benja Owned by:
Priority: normal Milestone:
Component: Compiler Version: 6.8.2
Keywords: Cc:
Operating System: Linux Architecture: x86
Type of failure: None/Unknown Test Case:
Blocked By: Blocking:
Related Tickets: Differential Rev(s):
Wiki Page:


The following code:

{-# OPTIONS_GHC -fglasgow-exts #-}

class Foo a b where
    foo :: a

instance (a ~ ()) => Foo [a] b where
    foo = undefined

main = print "hello"

gives this:

ghc-6.8.2: panic! (the 'impossible' happened)
  (GHC version 6.8.2 for i386-unknown-linux):
	nameModule $dFoo{v aqY}

Change History (1)

comment:1 Changed 9 years ago by chak

Resolution: worksforme
Status: newclosed

I am pretty sure that bug has long been fixed in the HEAD. Please try with that. Equality constraints are not really a supported feature in the 6.8 branch.

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