From: simonpj@microsoft.com <unknown>
Date: Mon, 6 Nov 2006 15:59:01 +0000 (+0000)
Subject: Tidy up substitutions
X-Git-Url: http://git.megacz.com/?a=commitdiff_plain;h=94b170a053c161d1e0cc4418b37a6a4807872a5f;hp=94b170a053c161d1e0cc4418b37a6a4807872a5f;p=ghc-hetmet.git

Tidy up substitutions

The new simplifer stuff exposed the fact that the invariants on the
TvSubstEnv and IdSubstEnv were insufficiently explicit.  (Resulted in
a bug found by Sam Brosnon.)

This patch fixes the bug, and tries to document the invariants pretty
thoroughly. See
	Note [Extending the TvSubst] in Type
	Note [Extenting the Subst]   in CoreSubst

(Most of the new lines are comments.)
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