#1174: Impredicative type-class context causes stack overflow or non-termination
in type checker
-------------------------+--------------------------------------------------
Reporter: ccshan | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 6.6
Severity: normal | Keywords:
Difficulty: Unknown | Testcase:
Architecture: Unknown | Os: Unknown
-------------------------+--------------------------------------------------
This program makes GHC loop. The first time the stack overflows; the
second time GHCi just hangs.
{{{
$ cat Bug.hs
{-# OPTIONS -fglasgow-exts #-}
module Bug where
data T t where
T :: (forall a. T (f a)) -> T (forall a. f a)
instance Show (T t) where
show (T t) = show t
$ ghci Bug.hs
___ ___ _
/ _ \ /\ /\/ __(_)
/ /_\// /_/ / / | | GHC Interactive, version 6.6, for Haskell 98.
/ /_\\/ __ / /___| | http://www.haskell.org/ghc/
\____/\/ /_/\____/|_| Type :? for help.
Loading package base ... linking ... done.
[1 of 1] Compiling Bug ( Bug.hs, interpreted )
*** Exception: stack overflow
> :reload
[1 of 1] Compiling Bug ( Bug.hs, interpreted )
Interrupted.
>
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1174>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler_______________________________________________
Glasgow-haskell-bugs mailing list
[email protected]
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
