From: simonpj <unknown>
Date: Mon, 5 Feb 2001 08:48:25 +0000 (+0000)
Subject: [project @ 2001-02-05 08:48:25 by simonpj]
X-Git-Tag: Approximately_9120_patches~2753
X-Git-Url: http://git.megacz.com/?a=commitdiff_plain;h=e19e95429bbcf3f1a408ec39c33aafad74e15b35;p=ghc-hetmet.git

[project @ 2001-02-05 08:48:25 by simonpj]
Add (still incomplete) comment
---

diff --git a/ghc/compiler/types/InstEnv.lhs b/ghc/compiler/types/InstEnv.lhs
index 0586453..a3bb8d4 100644
--- a/ghc/compiler/types/InstEnv.lhs
+++ b/ghc/compiler/types/InstEnv.lhs
@@ -387,6 +387,21 @@ determine the second.  In general, given the same class decl, and given
 
 Then the criterion is: if U=unify(s1,t1) then U(s2) = U(t2).
 
+Matters are a little more complicated if there are free variables in
+the s2/t2.  
+
+	class D a b c | a -> b
+	instance D a b => D [(a,a)] [b] Int
+	instance D a b => D [a]     [b] Bool
+
+The instance decls don't overlap, because the third parameter keeps
+them separate.  But we want to make sure that given any constraint
+	D s1 s2 s3
+if s1 matches 
+
+
+
+
 \begin{code}
 badFunDeps :: ClsInstEnv -> Class
 	   -> TyVarSet -> [Type]	-- Proposed new instance type