Changes between Version 33 and Version 34 of GhcKinds


Ignore:
Timestamp:
Jun 7, 2012 12:23:03 PM (3 years ago)
Author:
simonpj
Comment:

--

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  • GhcKinds

    v33 v34  
    1212------------------------
    1313= Future work =
     14
     15== Promoting data families ==
     16
     17Consider this:
     18{{{
     19  data family T a
     20  data instance T Int = MkT
     21  data Proxy (a :: k)
     22  data S = MkS (Proxy 'MkT)
     23}}}
     24Is it ok to use the promoted data family instance constructor `MkT` in
     25the data declaration for `S`?  No, we don't allow this. It ''might'' make
     26sense, but at least it would mean that we'd have to interleave
     27typechecking instances and data types, whereas at present we do data
     28types ''then'' instances.
     29
     30A couple of people have asked about this
     31 * http://hackage.haskell.org/trac/ghc/wiki/Commentary/Compiler/GenericDeriving#Digression
     32 * http://www.reddit.com/r/haskell/comments/u7oxb/is_it_possible_to_datakindlift_a_data_family/
     33 
    1434
    1535== [http://hackage.haskell.org/trac/ghc/ticket/5682 #5682] (proper handling of infix promoted constructors) ==