[6.8.1 regression] panic: lookupVers1 base:GHC.Prim sym{tc}

When rebuilding the base package you might encounter this:

../../compiler/stage1/ghc-inplace -package-name base-3.0.1.0 -hide-all-packages -split-objs -i -idist/build/autogen -idist/build -i. -Idist/build -Iinclude -#include "HsBase.h" -odir dist/build -hidir dist/build -stubdir dist/build -package rts-1.0 -O -fglasgow-exts -package-name base -XCPP -idist/build  -H16m -O -O -Rghc-timing -fgenerics -c Data/Generics/Twins.hs -o dist/build/Data/Generics/Twins.o  -ohi dist/build/Data/Generics/Twins.hi
ghc-6.8.2: panic! (the 'impossible' happened)
  (GHC version 6.8.2 for powerpc-apple-darwin):
        lookupVers1 base:GHC.Prim sym{tc}

Workaround is to clean in libraries/base.

The problem is that MkIface.computeChangedOccs needs to avoid wired-in names when checking version numbers, because wired-in names are never mentioned in usages.

I believe simonpj has a patch for this in his working tree, we diagnosed it before disappearing for the Christmas period.

Trac metadata

Trac field	Value
Version	6.8.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	high
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system	Unknown
Architecture	Unknown