Hey, I ran into this earlier today, though it was in a where clause. :)
Luckily I already knew what to google, since there are multiple ways to
handle it and I wasn't sure which was best (I went with "just give it a
signature").
You're looking at the storied Monomorphism Restriction!
https://wiki.haskell.org/Monomorphism_restriction
On Tue, Aug 14, 2018, 8:33 PM Jeffrey Brown
Today I was writing a lot of Hashable instances, and found it hard to read code littered long lines mostly consisting of `hashWithSalt`, so I made a synonym:
infixl 5 ## (##) = hashWithSalt
But when I replaced all the `hashWithSalt`s with ##, I got lots of weird errors -- GHC kept wanting things to be Strings that were Ints, or vice verse. The problem vanished when I added this type signature:
(##) :: Hashable a => Int -> a -> Int
That's exactly the same type signature that hashWithSalt has.
Is this expected behavior? Desirable?
-- Jeff Brown | Jeffrey Benjamin Brown Website https://msu.edu/~brown202/ | Facebook https://www.facebook.com/mejeff.younotjeff | LinkedIn https://www.linkedin.com/in/jeffreybenjaminbrown(spammy, so I often miss messages here) | Github https://github.com/jeffreybenjaminbrown
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