Demand analyser is unpacking too deeply

The demand analyser reports that fixpoint iterations are sometimes going on forever; in particular, this debug trace trips:

| +      = -- pprTrace "dmdFix loop" (ppr n <+> (vcat
| +        --                 [ text "Sigs:" <+> ppr [ (id,lookupVarEnv
| (sigEnv env) id,
| +        --                                              lookupVarEnv
| (sigEnv env') id)
| +        --                                          | (id,_) <- pairs],
| +        --                   text "env:" <+> ppr env,
| +        --                   text "binds:" <+> pprCoreBinding (Rec

This happens during bootsrapping GHC itself, and maybe somewhere in the testsuite; I forget.

The reason is that I thought a neater way to control unpacking of recursive products would work (see the ae_rec_tc field of AnalEnv) but I was wrong.

This doesn't bite often but it's plainly wrong and needs fixing.

Trac metadata

Trac field	Value
Version	7.6.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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