[GHC] #11452: Typed Template Haskell sneakily allows impredicativity

[GHC]

#11452: Typed Template Haskell sneakily allows impredicativity
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           Reporter:  goldfire       |             Owner:  goldfire
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.1
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 The following module is accepted:

 {{{#!hs
 {-# LANGUAGE ExplicitForAll, TemplateHaskell #-}

 module Bug where

 impred :: forall a. a -> a
 impred = $$( [|| \x -> x ||] )
 }}}

 But that requires an intermediate `TExp (forall a. a -> a)`.

 Will fix in ongoing work.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11452>
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