Preparing for a review of pattern synonyms

[Dr. ERDI Gergo]

Hi Simon,

On Mon, 9 Dec 2013, Simon Marlow wrote:

> I think pattern synonyms are great!  A couple of questions:
>
> * what will Haddock show for a pattern export?

Is Haddock a part of GHC? I don't know. If it's not, then whatever parser 
it's using will have to be extended to support pattern synonyms.

> * can we still write pattern matches that GHC can infer
>   to be exhaustive when using pattern synonyms?

No. I don't see how that would be possible without having access to the 
pattern synonym definition when typechecking/compiling a use site. One 
deliberate design decision was to make pattern synonyms proper 
abstractions, in the sense that compiling use sites shouldn't require 
access to its definition details.

> Are we not doing ViewPatternsAlternative any more? 
> https://ghc.haskell.org/trac/ghc/wiki/ViewPatternsAlternative
> Or is that just being treated as an orthogonal issue?  I rather like that 
> proposal, and we originally discussed it in conjunction with pattern 
> synonyms.

It should be treated as orthogonal -- if and when GHC gets support for it, 
they will be available in PatternSynonyms as well.

If there's no separate Trac ticket for ViewPatternsAlternative yet, I'm 
happy 
to open one.

Bye,
 	Gergo

-- 

   .--= ULLA! =-----------------.
    \     http://gergo.erdi.hu   \
     `---= gergo at erdi.hu =-------'
I'm sure the pension plan includes all the starvation I can eat.