Changes between Version 33 and Version 34 of GhcKinds


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Timestamp:
Jun 7, 2012 12:23:03 PM (23 months 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) ==