#3950: panic: Unify.uTys_s: mismatched type lists!
---------------------------------+------------------------------------------
Reporter: ganesh | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler (Type checker)
Version: 6.8.3 | Keywords:
Os: Unknown/Multiple | Testcase:
Architecture: Unknown/Multiple | Failure: Compile-time crash
---------------------------------+------------------------------------------
This erroneous program provokes a panic instead of a type error, with GHC
6.8.3, 6.10.4 and 6.12.1. I don't have any recent snapshots to hand to
try.
{{{
{-# LANGUAGE GADTs #-}
data Id p x y = Id (p x y)
data Sealed p where
Sealed :: p x -> Sealed p
rp :: Bool -> Maybe (w (Id p))
rp _ = Just rp'
where rp' :: Sealed (Id p x)
rp' = undefined
}}}
{{{
ghc: panic! (the 'impossible' happened)
(GHC version 6.12.1 for x86_64-unknown-linux):
Unify.uTys_s: mismatched type lists!
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3950>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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