From a7e0eb35819bb9171b60f2854753f7784da6a087 Mon Sep 17 00:00:00 2001
From: Niko Matsakis <niko@alum.mit.edu>
Date: Thu, 3 May 2012 17:07:57 -0700
Subject: [PATCH] allow enums that ref themselves via unsafe pointers

---
 src/rustc/middle/ty.rs | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/rustc/middle/ty.rs b/src/rustc/middle/ty.rs
index cf8f223afd9..a64c1a5a777 100644
--- a/src/rustc/middle/ty.rs
+++ b/src/rustc/middle/ty.rs
@@ -1475,11 +1475,14 @@ fn is_instantiable(cx: ctxt, r_ty: t) -> bool {
 
           ty_box(mt) |
           ty_uniq(mt) |
-          ty_ptr(mt) |
           ty_rptr(_, mt) {
             be type_requires(cx, seen, r_ty, mt.ty);
           }
 
+          ty_ptr(mt) {
+            false           // unsafe ptrs can always be NULL
+          }
+
           ty_rec(fields) {
             vec::any(fields) {|field|
                 type_requires(cx, seen, r_ty, field.mt.ty)