Bad eta expand during building

[Axel Simon]

Hi,

I'm just trying to compile ghc 6.4. I was a bit put off by ton's of "Bad
eta expand" messages scrolling off my screen. It looks like this:

Bad eta expand
    1
    __coerce GHCziBase.Z0T{(w) tc 40}
    (CmmParse.zgzg{v rej3}
       @ GHCziBase.Z0T{(w) tc 40}
       @ GHCziBase.Z0T{(w) tc 40}
       (__coerce CmmParse.ExtCode{tc r3CA} happyzuxzu1{v a3WU})
       (__coerce CmmParse.ExtCode{tc r3CA} happyzuxzu2{v a3WT})
       (__coerce CmmParse.Env{tc r3CI} eta{v sb4W}))
    GHCziBase.Z0T{(w) tc 40}
<<ghc: 1194327916 bytes, 3628 GCs, 13332977/21631780 avg/max bytes
residency (11 samples), 57M in use, 0.00 INIT (0.00 elapsed), 5.13 MUT
(39.72 elapsed), 2.47 GC (2.59 elapsed) :ghc>>
../../ghc/compiler/stage1/ghc-inplace -H16m -O  -istage2/utils  -
istage2/basicTypes  -istage2/types  -istage2/hsSyn  -istage2/prelude  -
istage2/rename  -istage2/typecheck  -istage2/deSugar  -istage2/coreSyn
-istage2/specialise  -istage2/simplCore  -istage2/stranal  -
istage2/stgSyn  -istage2/simplStg  -istage2/codeGen  -istage2/main  -
istage2/profiling  -istage2/parser  -istage2/cprAnalysis  -
istage2/compMan  -istage2/ndpFlatten  -istage2/iface  -istage2/cmm  -
istage2/nativeGen  -istage2/ghci -Istage2 -DGHCI -package template-
haskell -package readline -DUSE_READLINE -cpp -fglasgow-exts -fno-
generics -Rghc-timing -I. -IcodeGen -InativeGen -Iparser -package unix -
package Cabal -recomp -Rghc-timing  -H16M '-#include "hschooks.h"'    -c
utils/FiniteMap.lhs -o stage2/utils/FiniteMap.o  -ohi
stage2/utils/FiniteMap.hi

I don't know which files this refers to as there were way too many of
these messages to scroll back. But the next file is obviously
FiniteMap.lhs

Does this message have to scare me? And if yes, why does the build
proceed?

Axel.