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Template Haskell's newName no longer works properly, with GHC HEAD. Consider:

{-# LANGUAGE TemplateHaskell #-}

module B where

import Language.Haskell.TH

data D = D

-- declare 'data E = D' with a fresh name 'D'
$(do
    nm <- newName "D"
    return $ [DataD [] (mkName "E") [] [NormalC nm []] []]
 )

With ghc-7.0.3, this compiles without error, as it should. However, with ghc-7.3.20110803, we get:

B.hs:8:3:
    Multiple declarations of `D'
    Declared at: B.hs:7:10
                 B.hs:8:3

which is wrong.

The following might also be related. Given:

{-# LANGUAGE TemplateHaskell #-}

module C where

import Language.Haskell.TH

g = $(do 
        nm <- newName "f"
        return $ VarE nm
     )

with ghc-7.0.3 we get the correct error message

C.hs:7:7:
    Not in scope: `f[aK5]'
    In the result of the splice:
      $(do { nm <- newName "f";
               return $ VarE nm })
    To see what the splice expanded to, use -ddump-splices
    In the expression:
      $(do { nm <- newName "f";
               return $ VarE nm })
    In an equation for `g':
        g = $(do { nm <- newName "f";
                     return $ VarE nm })

but with ghc-7.3.20110803 we get a GHC internal error message:

C.hs:7:7:
    GHC internal error: `f_aOw' is not in scope during type checking, but it passed the renamer
    tcg_type_env of environment: []
    tcl_env of environment: [(rgQ, Identifier[g::t_a, 1])]
    In the expression: f_aOw
    In the result of the splice:
      $(do { nm <- newName "f";
             return $ VarE nm })
    To see what the splice expanded to, use -ddump-splices
    In the expression:
      $(do { nm <- newName "f";
             return $ VarE nm })

Trac metadata

Trac field	Value
Version	7.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Template Haskell
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