InstanceSigs -- rationale for the "must be more polymorphic than"

Anthony Clayden anthony.d.clayden at gmail.com
Sat Sep 18 02:29:53 UTC 2021


> If you would like to offer a patch for the user manual to explain this
better, that would be great.

Thank you Simon for the invitation.

On further investigation https://gitlab.haskell.org/ghc/ghc/-/issues/20357,
what I'd like the user manual to say is:

"InstanceSigs is a mis-feature. Don't use it. It is less confusing to just
give no signature at all. If you really, really want to bind tyvars, use
PatternSignatures."
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