[GHC] #13776: -ddump-splices produces unnecessarily qualified names for tuple and list types

1 Jun 2017

      #13776: -ddump-splices produces unnecessarily qualified names for tuple and list
types
-------------------------------------+-------------------------------------
           Reporter:  RyanGlScott    |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Template       |           Version:  8.0.1
  Haskell                            |
           Keywords:  newcomer       |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 If you compile this:

 {{{#!hs
 {-# LANGUAGE TemplateHaskell #-}
 {-# OPTIONS_GHC -ddump-splices #-}
 module Bug where

 import Language.Haskell.TH

 f :: $(conT ''(,) `appT` conT ''Int `appT` conT ''Int)
 f = (1,2)

 g :: $(conT ''[] `appT` conT ''Int)
 g = []
 }}}

 You'll get some unsavory output:

 {{{
 Bug.hs:10:8-34: Splicing type
     conT ''[] `appT` conT ''Int ======> GHC.Types.[] Int
 Bug.hs:7:8-53: Splicing type
     conT ''(,) `appT` conT ''Int `appT` conT ''Int
   ======>
     GHC.Tuple.(,) Int Int
 }}}

 It's unsavory because if you actually try to use the spliced output in
 Haskell code:

 {{{#!hs
 module Bug2 where

 f :: GHC.Tuple.(,) Int Int
 f = (1,2)

 g :: GHC.Types.[] Int
 g = []
 }}}

 Then it won't parse.

 Expressions have the same problem:

 {{{#!hs
 {-# LANGUAGE TemplateHaskell #-}
 {-# OPTIONS_GHC -ddump-splices #-}
 module Bug3 where

 import Language.Haskell.TH

 f :: (Int, Int)
 f = $(conE '(,) `appE` litE (integerL 1) `appE` litE (integerL 1))

 g :: [Int]
 g = $(conE '[])
 }}}

 {{{
 Bug3.hs:8:7-65: Splicing expression
     conE '(,) `appE` litE (integerL 1) `appE` litE (integerL 1)
   ======>
     (GHC.Tuple.(,) 1) 1
 Bug3.hs:11:7-14: Splicing expression conE '[] ======> GHC.Types.[]
 }}}

 And patterns:

 {{{#!hs
 {-# LANGUAGE TemplateHaskell #-}
 {-# OPTIONS_GHC -ddump-splices #-}
 module Bug4 where

 import Language.Haskell.TH

 f :: (Int, Int) -> ()
 f $(conP '(,) [litP (integerL 1), litP (integerL 1)]) = ()

 g :: [Int] -> ()
 g $(conP '[] []) = ()
 }}}

 {{{
 Bug4.hs:8:5-52: Splicing pattern
     conP '(,) [litP (integerL 1), litP (integerL 1)]
   ======>
     GHC.Tuple.(,) 1 1
 Bug4.hs:11:5-15: Splicing pattern conP '[] [] ======> GHC.Types.[]
 }}}

--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13776
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