VarSet -- Locally-defined free vars of *both* LHS and RHS
-- of rules. I don't think it needs to include the
-- ru_fn though.
- -- Note [Rule dependency info]
+ -- Note [Rule dependency info] in OccurAnal
emptySpecInfo :: SpecInfo
emptySpecInfo = SpecInfo [] emptyVarSet
seqSpecInfo (SpecInfo rules fvs) = seqRules rules `seq` seqVarSet fvs
\end{code}
-Note [Rule dependency info]
-~~~~~~~~~~~~~~~~~~~~~~~~~~~
-THe VarSet in a SpecInfo is used for dependency analysis in the
-occurrence analyser. We must track free vars in *both* lhs and rhs. Why both?
-Consider
- x = y
- RULE f x = 4
-Then if we substitute y for x, we'd better do so in the
- rule's LHS too, so we'd better ensure the dependency is respected
-
%************************************************************************