[GHC] #4459: Polymorphic Data.Dynamic

[GHC]

#4459: Polymorphic Data.Dynamic
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    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):

 Replying to [comment:21 simonpj]:
 > The way to generate dictionaries is to call the type checker.  As
 described in the Commentary
 http://hackage.haskell.org/trac/ghc/wiki/Commentary/Compiler/HscMain, and
 http://hackage.haskell.org/trac/ghc/wiki/Commentary/Compiler, the type
 checker takes a `(HsExpr Name)`, with no `HsWrap` constructors, and
 returns an `(HsExpr Id)`, replete with `HsWrap` constructors that do the
 dictionary application.
 >
 This paragraph is from
 [http://hackage.haskell.org/trac/ghc/wiki/Commentary/Compiler/TypeChecker].
 The functions referred to, including `sourceTypeRep` are maybe part of the
 old typechecker?

 Of particular interest are the variants SourceTy and NoteTy of
 TypeRep.Type. The constructor SourceTy :: SourceType -> Type represents a
 type constraint; that is, a predicate over types represented by a
 dictionary. The type checker treats a SourceTy as opaque, but during the
 translation to core it will be expanded into its concrete representation
 (i.e., a dictionary type) by the function
 [[GhcModule(compiler/types/Type.lhs])).sourceTypeRep. Note that newtypes
 are not covered by SourceTypes anymore, even if some comments in GHC still
 suggest this. Instead, all newtype applications are initially represented
 as a NewTcApp, until they are eliminated by calls to
 [[GhcModule(compiler/types/Type.lhs])).newTypeRep.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4459#comment:23>
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