maeder at tzi.de
Tue Nov 30 06:48:26 EST 2004
The attached module does not compile and yields the following error:
Could not deduce (Confuse a) from the context (Typeable a)
arising from use of `breakFn' at InCoherentInst.hs:17
Add (Confuse a) to the type signature(s) for `addGeneralFallOut'
In the first argument of `GeneralBreakFn', namely `breakFn'
In the definition of `addGeneralFallOut':
addGeneralFallOut = let
breakFn a = throwDyn (GeneralFallOutExcep a)
in GeneralBreakFn breakFn
The same source compiles ok without -fallow-incoherent-instances (or
If, furthermore, the "confusing instance" is commented out, the source
even compiles without extensions.
I don't know if this is a bug, possibly related to the import of
Typeable stuff. I don't need a fix. I only want to point out that
globally switching on the option -fallow-incoherent-instances is likely
to break existing code, currently (ghc 6.2.2).
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