Hmm. I suppose that F _ = Int
should mean just the same as F a = Int But what about F _a = _a -> _a Does that mean anything different from F a = a -> a If F _a = .. is allowed at all, I guess it should mean just the same as an ordinary type variable. Would you like to implement that, and document it? (My wildcard refactoring patch is about to land.) Simon | -----Original Message----- | From: Jan Stolarek [mailto:jan.stola...@p.lodz.pl] | Sent: 01 December 2015 12:21 | To: Simon Peyton Jones <simo...@microsoft.com> | Cc: ghc-devs@haskell.org; Michał Sośnicki <180...@edu.p.lodz.pl> | Subject: Wildcards in type functions vs. named wild cards | | 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 | | Treść tej wiadomości zawiera informacje przeznaczone tylko dla | adresata. | Jeżeli nie jesteście Państwo jej adresatem, bądź otrzymaliście ją | przez pomyłkę prosimy o powiadomienie o tym nadawcy oraz trwałe jej | usunięcie. | | This email contains information intended solely for the use of the | individual to whom it is addressed. | If you are not the intended recipient or if you have received this | message in error, please notify the sender and delete it from your | system. _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs
