Hi! > On 13 Jan 2014, at 02:56, Krzysztof Gogolewski <krz.gogolew...@gmail.com> > wrote: > > Hello, > > I propose to enable -XTypeHoles in GHC by default. > > Unlike other -X* flags, holes do not really change meaning of the program, > they only change error messages. Instead of "_x not in scope", we effectively > get "_x not in scope, its expected type is a -> a". You get it only if you > precede the identifier not in scope with underscore, so in some sense you > declare the intention of using holes. > > Two possible issues: > > (a) If you use -fdefer-type-errors, then a program might compile, while > previously it did not. However, we should facilitate compiling with > defer-type-errors, so I don't think this is a disadvantage. > > (b) The identifier _ becomes both a pattern and a hole by default, which > might confuse new users. > Reply: I have never seen anyone ask why code such as "Just _ -> _" does not > work. >
I do think that having _ both as a pattern and a hole might be confusing, I can see that. However that's more of a syntax issue, than an issue about default extensions IMO > IMO the productivity boost by having holes by default outweighs those two > objections. I am open to hearing any other possible issues others might find. > > The change is trivial implementation-wise; add Opt_TypeHoles to the list in > languageExtensions Nothing in DynFlags. > > -KG > _______________________________________________ > ghc-devs mailing list > ghc-devs@haskell.org > http://www.haskell.org/mailman/listinfo/ghc-devs _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://www.haskell.org/mailman/listinfo/ghc-devs
