[GHC] #1849: Template Haskell: reify is not consistent with the special constructors ListT and TupleT

[GHC]

#1849: Template Haskell: reify is not consistent with the special constructors
ListT and TupleT
----------------------+-----------------------------------------------------
 Reporter:  guest     |          Owner:         
     Type:  bug       |         Status:  new    
 Priority:  normal    |      Milestone:         
Component:  Compiler  |        Version:  6.8.1  
 Severity:  normal    |       Keywords:         
 Testcase:            |   Architecture:  Unknown
       Os:  Unknown   |  
----------------------+-----------------------------------------------------
 While reify provides consistent type information for arrows (i.e. returns
 the special ArrowT constructor and not ConT "GHC.Prim.(->)"), that doesn't
 happen with ListT and TupleT.

 {{{
 Prelude> :m +Language.Haskell.TH
 Prelude Language.Haskell.TH> let seeType n = do {VarI _ t _ _ <- reify n;
 runIO $ putStrLn $ show t; [|1|]}
 Prelude Language.Haskell.TH> let {f = undefined :: Int -> Int; g =
 undefined :: [Int]; h = undefined :: (Int, Int)}
 Prelude Language.Haskell.TH> $(seeType (mkName "f"))
 AppT (AppT ArrowT (ConT GHC.Base.Int)) (ConT GHC.Base.Int)
 AppT (AppT ArrowT (ConT GHC.Base.Int)) (ConT GHC.Base.Int)
 AppT (AppT ArrowT (ConT GHC.Base.Int)) (ConT GHC.Base.Int)
 AppT (AppT ArrowT (ConT GHC.Base.Int)) (ConT GHC.Base.Int)
 1
 Prelude Language.Haskell.TH> $(seeType (mkName "g"))
 AppT (ConT GHC.Base.[]) (ConT GHC.Base.Int)
 AppT (ConT GHC.Base.[]) (ConT GHC.Base.Int)
 AppT (ConT GHC.Base.[]) (ConT GHC.Base.Int)
 AppT (ConT GHC.Base.[]) (ConT GHC.Base.Int)
 1
 Prelude Language.Haskell.TH> $(seeType (mkName "h"))
 AppT (AppT (ConT Data.Tuple.(,)) (ConT GHC.Base.Int)) (ConT GHC.Base.Int)
 AppT (AppT (ConT Data.Tuple.(,)) (ConT GHC.Base.Int)) (ConT GHC.Base.Int)
 AppT (AppT (ConT Data.Tuple.(,)) (ConT GHC.Base.Int)) (ConT GHC.Base.Int)
 AppT (AppT (ConT Data.Tuple.(,)) (ConT GHC.Base.Int)) (ConT GHC.Base.Int)
 1
 }}}

 For g and h the expected returned types are:

 {{{
 AppT ListT (ConT GHC.Base.Int)
 AppT (AppT (TupleT 2) (ConT GHC.Base.Int)) (ConT GHC.Base.Int)
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1849>
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The Glasgow Haskell Compiler