foldr/single no longer firing in GHC 6.10

consider the following module

module Foo where x = ['x']++"haskell"

when ghc --make -O2 Foo.hs -ddump-simpl-stats is run using GHC 6.8.2, the output show that the foldr/single rule is fired

5 RuleFired
    1 ++
    1 augment/build
    1 foldr/single
    1 unpack
    1 unpack-list

However, I am told that this does not happen in GHC 6.10.2 nor GHC 6.10.3 where foldr/app is fired instead

6 RuleFired
     1 ++
     1 augment/build
     1 fold/build
     1 foldr/app
     1 unpack
     1 unpack-list

Thus it appears that the above module is no longer properly optimized in GHC 6.10

(thanks to dons and Jedai for helping with this)

Trac metadata

Trac field	Value
Version	6.10.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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