I have rebased a patch onto HEAD, and I'm getting this

Reading interface for ghc-internal:GHC.Exception.Type;
    reason: Need decl for SomeException
...not found
updating EPS
/home/simonpj/code/HEAD-12/_build/stage1/inplace/../libraries/ghc-internal/build/GHC/Err.hi
Declaration for errorWithoutStackTrace
Unfolding of errorWithoutStackTrace:
  SomeException ErrorWithoutFlag
                  Failed to load interface for ‘GHC.Exception.Type’.
                  There are files missing in the ‘ghc-internal-0.1.0.0’ package,
                  try running 'ghc-pkg check'.
                  Use -v to see a list of the files searched for.
forkM failed: Unfolding of errorWithoutStackTrace IOEnv failure
} ending fork (badly) Unfolding of errorWithoutStackTrace
Cannot continue after interface file error

Does anyone have any idea what is going on?  I have made no changes to GHC.Err or exceptions etc.


Thanks

Simon