From 9cc00d5f6cc85a825e79e29324261daa17e50048 Mon Sep 17 00:00:00 2001
From: Graydon Hoare <graydon@mozilla.com>
Date: Tue, 18 Jan 2011 17:18:51 -0800
Subject: [PATCH] Fix bug (I think) when unifying ty_local and ty_param.

---
 src/comp/middle/ty.rs | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/comp/middle/ty.rs b/src/comp/middle/ty.rs
index e910c23abfa..531e3f855fc 100644
--- a/src/comp/middle/ty.rs
+++ b/src/comp/middle/ty.rs
@@ -889,7 +889,19 @@ fn unify(@ty.t expected, @ty.t actual, &unify_handler handler)
                 ret result;
             }
             case (ty.ty_param(?actual_id)) {
-                ret handler.unify_actual_param(actual_id, expected, actual);
+                alt (expected.struct) {
+
+                    // These two unify via logic lower down. Fall through.
+                    case (ty.ty_local(_)) { }
+                    case (ty.ty_var(_)) { }
+
+                    // More-concrete types can unify against params here.
+                    case (_) {
+                        ret handler.unify_actual_param(actual_id,
+                                                       expected,
+                                                       actual);
+                    }
+                }
             }
             case (_) { /* empty */ }
         }