Panic with TemplateHaskell and duplicate indentifiers

This code causes GHC panic under 7.8.1-RC2:

{-# LANGUAGE TemplateHaskell #-}

module TXXXX where

$([d|
  foo :: a -> a
  foo x = x
 |])

foo :: a
foo = undefined

[killy@xerxes : /dane/projekty/sandbox/haskell] ghc -fforce-recomp TXXXX.hs
[1 of 1] Compiling TXXXX            ( TXXXX.hs, TXXXX.o )
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Loading package array-0.5.0.0 ... linking ... done.
Loading package deepseq-1.3.0.2 ... linking ... done.
Loading package containers-0.5.4.0 ... linking ... done.
Loading package pretty-1.1.1.1 ... linking ... done.
Loading package template-haskell ... linking ... done.
ghc: panic! (the 'impossible' happened)
  (GHC version 7.8.0.20140226 for x86_64-unknown-linux):
        lookupExactOcc
    foo_a2kL{v}
    [main:TXXXX.foo{v a2kL} defined at TXXXX.hs:11:1,
     main:TXXXX.foo{v a2kL} defined at TXXXX.hs:5:3]

Trac metadata

Trac field	Value
Version	7.8.1-rc2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Template Haskell
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture

mentioned in issue #7241 (closed)

changed weight to 5

added Tbug TemplateHaskell Trac import labels

mentioned in commit d8d798b1

Thanks for discovering this. Now fixed.

Merge to the 7.8 branch, but don't hold up the release for it. 7.8.2 would do.

Simon

Trac metadata

Trac field	Value
Test case	→ th/T8932

added 1 deleted label

closed

Merged in 7.8, thanks!

Trac metadata

Trac field	Value
Resolution	Unresolved → ResolvedFixed

removed 1 deleted label

changed milestone to %7.8.3

added compiler crash label

added Pnormal label