From: simonpj <unknown>
Date: Wed, 17 Dec 2003 11:43:13 +0000 (+0000)
Subject: [project @ 2003-12-17 11:43:13 by simonpj]
X-Git-Tag: Approx_11550_changesets_converted~183
X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=commitdiff_plain;h=9d458d01d2a75b1e452ba00c4e76f3c3d0bc5ba6

[project @ 2003-12-17 11:43:13 by simonpj]
---------------------------------
  Gate in a few more instance decls
  ---------------------------------

When we have
	instance T a where...

we need to suck in the instance decl rather more aggressively than we
were.  (A case I hadn't thought of because it only happens with
undecideable instances.)
---

diff --git a/ghc/compiler/iface/TcIface.lhs b/ghc/compiler/iface/TcIface.lhs
index 51bf028..39eadfb 100644
--- a/ghc/compiler/iface/TcIface.lhs
+++ b/ghc/compiler/iface/TcIface.lhs
@@ -529,8 +529,9 @@ selectInsts pool@(Pool insts n_in n_out) cls tycons
 
 	-- Reverses the gated decls, but that doesn't matter
     choose2 (gis, decls) (gates, decl)
-	| any (`elem` tycons) gates = (gis, 	           decl:decls)
-	| otherwise		    = ((gates,decl) : gis, decls)
+	|  null gates 	-- Happens when we have 'instance T a where ...'
+        || any (`elem` tycons) gates = (gis, 	           decl:decls)
+	| otherwise		     = ((gates,decl) : gis, decls)
 \end{code}
 
 %************************************************************************