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[GHC] #6066: Constraint Kinds don't work with Template Haskell

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[GHC] #6066: Constraint Kinds don't work with Template Haskell

GHC
#6066: Constraint Kinds don't work with Template Haskell
------------------------------+---------------------------------------------
 Reporter:  sseverance        |          Owner:                  
     Type:  bug               |         Status:  new            
 Priority:  normal            |      Component:  Compiler        
  Version:  7.4.1             |       Keywords:                  
       Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
  Failure:  None/Unknown      |       Testcase:                  
Blockedby:                    |       Blocking:                  
  Related:                    |  
------------------------------+---------------------------------------------
 If I have a record with a constraint kind that has multiple constraints
 such as:

 {{{
 type MyConstraint a = (Show a, Eq a, Typeable a)
 data MyConstraint a => MyType a =  MyType {
   someField :: a
 }
 }}}

 If I try to use template haskell on the type (in my case mkLabels from
 fclabels) you get the following error:  Can't represent tuple predicates
 in Template Haskell: MyConstraint a

 Complete Repro Case:

 {{{
 {-# LANGUAGE ConstraintKinds #-}
 {-# LANGUAGE DatatypeContexts #-}
 {-# LANGUAGE ExistentialQuantification #-}
 {-# LANGUAGE TemplateHaskell #-}

 import Data.Label
 import Data.Typeable

 type MyConstraint a = (Show a, Eq a, Typeable a)

 data MyConstraint a => MyType a = MyType {
   myField :: a
 } deriving (Show, Eq)

 mkLabels [''MyType]
 }}}

--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6066>
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Re: [GHC] #6066: Constraint Kinds don't work with Template Haskell

GHC
#6066: Constraint Kinds don't work with Template Haskell
------------------------------+---------------------------------------------
 Reporter:  sseverance        |          Owner:                  
     Type:  bug               |         Status:  new            
 Priority:  normal            |      Component:  Compiler        
  Version:  7.4.1             |       Keywords:                  
       Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
  Failure:  None/Unknown      |       Testcase:                  
Blockedby:                    |       Blocking:                  
  Related:                    |  
------------------------------+---------------------------------------------

Comment(by dreixel):

 Maybe this is also fixed with the patches for #5612?

--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6066#comment:1>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler

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Re: [GHC] #6066: Constraint Kinds don't work with Template Haskell

GHC
In reply to this post by GHC
#6066: Constraint Kinds don't work with Template Haskell
---------------------------------+------------------------------------------
    Reporter:  sseverance        |        Owner:                  
        Type:  bug               |       Status:  closed          
    Priority:  normal            |    Component:  Compiler        
     Version:  7.4.1             |   Resolution:  duplicate      
    Keywords:                    |           Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  |      Failure:  None/Unknown    
    Testcase:                    |    Blockedby:                  
    Blocking:                    |      Related:                  
---------------------------------+------------------------------------------
Changes (by sseverance):

  * status:  new => closed
  * resolution:  => duplicate


Comment:

 It would appear so. I have marked as duplicate.

--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6066#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler

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