[GHC] #11046: lookupTypeName does not support type operators

1 Nov 2015

      #11046: lookupTypeName does not support type operators
-------------------------------------+-------------------------------------
           Reporter:  oerjan         |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Template       |           Version:  7.10.2
  Haskell                            |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  GHC rejects
  Unknown/Multiple                   |  valid program
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 The following non-working code (minus a missing import) was
 [http://stackoverflow.com/questions/33465109/template-haskell-how-to-
 lookup-type-operator-name posted on stackoverflow]:

 `IssueTH.hs`:
 {{{#!hs
 {-# LANGUAGE TemplateHaskell #-}
 module IssueTH where
 import Language.Haskell.TH

 f :: Q [Dec]
 f = do
     Just n <- lookupTypeName "GHC.TypeLits.*"
     return []
 }}}

 `Issue.hs`:
 {{{#!hs
 {-# LANGUAGE TemplateHaskell #-}
 module Issue where
 import IssueTH
 import GHC.TypeLits

 $f
 }}}

 `ghc Issue.hs` fails with message:
 `Pattern match failure in do expression at IssueTH.hs:7:5-10`

 This gives no error if `*` is replaced by an alphanumeric type like `Nat`.
 Similar tests seem to fail whenever attempting to look up a type operator
 with `lookupTypeName`.

--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11046
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