#2037: Inner type declaration causes GHC panic
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Reporter: basvandijk | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler (Type checker) | Version: 6.8.2
Severity: blocker | Resolution:
Keywords: | Testcase:
Architecture: x86 | Os: Linux
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Comment (by basvandijk):
I just discovered a bug in my module:
All the applications of 'union' in 'unify' have to be replaced by
'unionWithKey f' like so:
{{{
unify :: k -> Value k a -> Value k a -> Value k a
unify x (NoValue dl) (NoValue dr) = NoValue(unionWithKey f dl
dr)
unify x (NoValue dl) (AValue (dr, yr)) = AValue (unionWithKey f dl
dr, yr)
unify x (AValue (dl, yl)) (NoValue dr) = AValue (unionWithKey f dl
dr, yl)
unify x (AValue (dl, yl)) (AValue (dr, yr)) = AValue (unionWithKey f dl
dr, f x yl yr)
}}}
The interesting thing is that with this the module compiles just fine!
Of course the orginal bug is still a bug. It probably has something to do
with the interaction between the explicit type of 'unify' and the type of
'union'. It also doesn't matter if I add a 'forall k a' to 'union'.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2037#comment:2>
GHC <http://www.haskell.org/ghc/>
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