Wildcards in type functions vs. named wild cards
Jan Stolarek
jan.stolarek at p.lodz.pl
Tue Dec 1 12:21:15 UTC 2015
Simon,
One of my students (Michał, CCd) is hacking on #10982 and he noticed a rather unexpected
behaviour. If I say:
{-# LANGUAGE TypeFamilies #-}
module T10982 where
type family F a where
F _t = Int
Then everything is fine. But if I enable NamedWildCards extension then suddenly this code is
rejected:
T10982.hs:7:7: error:
Unexpected wild card: ‘_t’
In the declaration for type synonym ‘F’
I am 99% sure this is a bug and the program should be accepted even with NamedWildCards. Am I
correct? Does this interact in any way with your upcomming refactoring of wildcards?
Janek
---
Politechnika Łódzka
Lodz University of Technology
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