ANNOUNCE: GHC 7.0.1 Release Candidate 1
ml at isaac.cedarswampstudios.org
Wed Sep 29 01:59:33 EDT 2010
>>> Couldn't match type `s' with `s3'
>>> because this skolem type variable would escape: `s3'
> I have to say, as an everyday joe programmer, that the obscurity of
> this message disturbs me. I hope I don't see it very often.
"Rigid" type variable seemed obscure before. Now a new different
obscure thing to learn!
I wonder if there's a reasonable way for the message to notice when it
might be a situation involving local bindings and new typechecking
behavior. Even adding "Possible fix: add a type-signature to
such-and-such local binding in 'f'", if the message could be arranged to
make that actually be a likely fix, might be helpful. (We want to make
sure that the message will still be usually-helpful 2 years in the
future when everyone's used to this type-checker. Hmm.)
I don't know: do "skolem" errors always imply that: either it's possible
to add more type-signatures to fix them: or if that's impossible then
the code is seriously type-incorrect?
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