Bad rule generated in pathological cases
George reports: I am also seeing this on ghc 7.10.1, not sure if this is another instance of this bug (#9160 (closed)):
cabal install bitmap
[ 3 of 10] Compiling Data.Bitmap.IO ( Data/Bitmap/IO.hs, dist/build/Data/Bitmap/IO.o )
Data/Bitmap/IO.hs:1248:1: Warning:
SPECIALISE pragma for non-overloaded function ‘myPlusPtr’
Data/Bitmap/IO.hs:1249:1: Warning:
SPECIALISE pragma for non-overloaded function ‘myPlusPtr’
ghc: panic! (the 'impossible' happened)
(GHC version 7.10.1 for x86_64-apple-darwin):
Template variable unbound in rewrite rule
$fPixelComponentFloat3_X2Rc
[$fPixelComponentFloat3_X2Rc]
[$fPixelComponentFloat3_X2Rc]
[]
[]
But it's not #9160 (closed) at all. So I'm making a new ticket.
Edited by Simon Peyton Jones