[GHC] #4459: Polymorphic Data.Dynamic

[GHC]

#4459: Polymorphic Data.Dynamic
-----------------------------------------------------+----------------------
    Reporter:  vivian                                |        Owner:  vivian      
        Type:  feature request                       |       Status:  new         
    Priority:  normal                                |    Milestone:  7.4.1       
   Component:  GHC API                               |      Version:  7.1         
    Keywords:  polymorphic, dynamic, class, linking  |     Testcase:              
   Blockedby:                                        |   Difficulty:              
          Os:  Unknown/Multiple                      |     Blocking:  4316        
Architecture:  Unknown/Multiple                      |      Failure:  None/Unknown
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Comment(by vivian):

 I currently can load a module and bind the `TyThing` and `HValue` of a
 top-level entity
 {{{
 data DynamicHValue = DynamicHValue TyThing HValue
 }}}


 When I want to apply a `DynamicHValue` to another `DynamicHValue` (an App
 operation)

 * I can figure out the resulting type using `mkAppTy` but that takes
 `Type`s not `TyThings`.  What is the correct way of getting a `Type` from
 a `TyThing`?

 * I want to apply one HValue to another.  What is the correct approach?

 The second item is not so straight-forward, because the applied `HValue`
 might cause the resultant type to be less generic.  A class instance might
 specialise the function type, in which case the linker has to link the
 appropriate instance.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4459#comment:7>
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