I think the simplifier is doing something iffy with types, because
when I try to call exprType from SimplUtils.interestingArg, I get
this:
ghc-6.5: panic! (the 'impossible' happened)
(GHC version 6.5 for i386-unknown-linux):
applyTypeToArgs
a98{v a1eB} [lid] ex{v aqZ} [lid]
a{tv a1et} [tv]
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
make: *** [GHC/TopHandler.o] Error 1
I think you only need to add this code:
interestingArg expr | pprTrace "interestingArg" (ppr expr) $
isUnLiftedType (exprType expr) =
-- Unlifted args are only ever interesting if we know what
they are
case expr of
Lit lit -> True
_ -> False
at the top of the "interestingArg" function to get this error.
The call chain looks like:
completeCall -> interestingArg -> exprType -> applyTypeToArgs
I think somehow an ill-typed variable has been stuffed into the
SimplCont? Or perhaps contArgs isn't substituting right? Anyway I
can't find anything in the immediate area to indicate what the problem
might be caused by... and I really hope it *is* a bug.
Btw, here is some relevant trace info:
completeCall
var: base:GHC.IOBase.>>{v rgF} [gid]
cont: ApplyTo nodup TYPE base:GHC.Base.(){(w) tc 40}
ApplyTo nodup TYPE a{tv a13f} [sk]
ApplyTo nodup handler{v ar2} [lid] ex{v aqZ} [lid]
ApplyTo nodup lvl_s1dT{v} [lid] @ a{tv a13f} [sk]
CoerceIt (base:GHC.IOBase.:CoIO{tc r3v}) a{tv a13f} [sk]
ApplyTo nodup new_s{v a1eg} [lid]
Stop[arg] (# base:GHC.Prim.State#{(w) tc 32q}
base:GHC.Prim.RealWorld{(w) tc 31E},
a{tv a13f} [sk] #)
contArgs
-> ([TYPE base:GHC.Base.(){(w) tc 40}, TYPE a{tv a13f} [sk],
a98{v a1eh} [lid] ex{v aqZ} [lid],
lvl_s1dT{v} [lid] @ a{tv a13f} [sk]],
CoerceIt (base:GHC.IOBase.:CoIO{tc r3v}) a{tv a13f} [sk]
ApplyTo nodup new_s{v a1eg} [lid]
Stop[arg] (# base:GHC.Prim.State#{(w) tc 32q}
base:GHC.Prim.RealWorld{(w) tc 31E},
a{tv a13f} [sk] #))
If you can guess what that might mean, great. If not, well, you could
do your own tracing. Now if you'll excuse me I have a headache :-(.
Potentially related to trying to follow the simplifier.
This definately didn't happen before the recent simplifier changes.
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