source file that compiled fine fails to recompile after touching it (yes, another one)

I'm using the development snapshot ghc-6.11.20090107 and ran into a bug very similar to #2888 (closed), but I think it is different because I could not reproduce that bug in my version.

The setup is very similar: File A.hs contains

{-# LANGUAGE TypeFamilies #-}
module A where
class Foo a where
  data Bar a :: * -> *

and file B.hs contains

{-# LANGUAGE TypeFamilies #-}
module B where
import A
instance Foo Int where
  data Bar Int x where
    Baz :: Bar Int String

Then:

rwbarton@functor:/tmp/a$ ghc --make B
[1 of 2] Compiling A                ( A.hs, A.o )
[2 of 2] Compiling B                ( B.hs, B.o )
rwbarton@functor:/tmp/a$ touch B.hs
rwbarton@functor:/tmp/a$ ghc --make B
[2 of 2] Compiling B                ( B.hs, B.o )

B.hs:8:2:
    Arguments that do not correspond to a class parameter must be variables
    Instead of a variable, found Int
    In the associated type instance for `Bar'
    In the instance declaration for `Foo Int'

Trac metadata

Trac field	Value
Version	6.11
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture