From 7849d4a5be50796cda506c5d92ca2ccb0d15dd90 Mon Sep 17 00:00:00 2001
From: simonpj <unknown>
Date: Mon, 2 Jun 2003 13:27:53 +0000
Subject: [PATCH] [project @ 2003-06-02 13:27:53 by simonpj] Add comments

---
 ghc/compiler/typecheck/TcIfaceSig.lhs |   12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/ghc/compiler/typecheck/TcIfaceSig.lhs b/ghc/compiler/typecheck/TcIfaceSig.lhs
index e1d3230..5295fec 100644
--- a/ghc/compiler/typecheck/TcIfaceSig.lhs
+++ b/ghc/compiler/typecheck/TcIfaceSig.lhs
@@ -55,8 +55,20 @@ signatures.
 tcInterfaceSigs :: [RenamedTyClDecl]	-- Ignore non-sig-decls in these decls
 		-> TcM TcGblEnv
 		
+-- May 2003: 
+--	NOTE 1: careful about the side-effected EPS
+--		in the two tcExtendGlobalValueEnv calls
+--	NOTE 2: no point in tying the knot with fixM; all
+--		the important knot-tying comes via the PCS global variable
+
 tcInterfaceSigs decls = 
   zapEnv (fixM (tc_interface_sigs decls)) `thenM` \ (_,sig_ids) ->
+	-- The zapEnv dramatically trims the environment, solely
+	-- to plug the space leak that would otherwise be caused
+	-- by a rich environment bound into lots of lazy thunks
+	-- The thunks are the lazily-typechecked IdInfo of the 
+	-- imported things.
+
   tcExtendGlobalValEnv sig_ids getGblEnv  `thenM` \ gbl_env ->
   returnM gbl_env
 	-- We tie a knot so that the Ids read out of interfaces are in scope
-- 
1.7.10.4