Error message, instead of segfault, when recursive types are used.

src/comp/front/ast.rs

@@ -503,6 +503,14 @@ fn is_constraint_arg(@expr e) -> bool {
     }
 }
 
+fn eq_ty(&@ty a, &@ty b) -> bool {
+    ret a == b;
+}
+
+fn hash_ty(&@ty t) -> uint {
+    ret t.span.lo << 16u + t.span.hi;
+}
+
 //
 // Local Variables:
 // mode: rust