[project @ 2004-12-20 17:16:24 by simonpj]

[project @ 2004-12-20 17:16:24 by simonpj]
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	Deal properly with dual-renaming
	--------------------------------

When comparing types and terms, and during matching, we are faced
with
	\x.e1	~   \y.e2

There are many pitfalls here, and GHC has never done the job properly.
Now, at last it does, using a new abstraction VarEnv.RnEnv2.  See
comments there for how it works.

There are lots of consequential changes to use the new stuff, especially
in
	types/Type (type comparison),
	types/Unify (matching on types)
	coreSyn/CoreUtils (equality on expressions),
	specialise/Rules (matching).

I'm not 100% certain of that I've covered all the bases, so let me
know if something unexpected happens after you update.  Maybe wait until
a nightly build has worked ok first!