[GHC] #8507: ConstraintKinds TH regression from 7.6 -> 7.7

6 Nov 2013

      #8507: ConstraintKinds TH regression from 7.6 -> 7.7
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       Reporter:  errge     |             Owner:
           Type:  bug       |            Status:  new
       Priority:  normal    |         Milestone:
      Component:  Template  |           Version:  7.7
  Haskell                   |  Operating System:  Unknown/Multiple
       Keywords:            |   Type of failure:  GHC rejects valid program
   Architecture:            |         Test Case:
  Unknown/Multiple          |          Blocking:
     Difficulty:  Unknown   |
     Blocked By:            |
Related Tickets:            |
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 {{{
 {-# LANGUAGE TemplateHaskell #-}
 {-# LANGUAGE ConstraintKinds #-}

 module ConstraintKindUser where

 -- type Stringy a = (Read a, Show a)
 $([d|type Stringy a = (Read a, Show a) |])
 }}}

 Results in this error message:
 {{{
 ConstraintKindUser.hs:7:3:
     The first argument of a tuple should have kind ‛*’,
       but ‛Read a_a2ZZ’ has kind ‛Constraint’
     In the type ‛(Read a_a2ZZ, Show a_a2ZZ)’
     In the type declaration for ‛Stringy’
 }}}

 This is a regression compared to 7.6.3.

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8507
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