From 7f816b7ef4c617eec3d03397f4013c06c9f98ce2 Mon Sep 17 00:00:00 2001
From: Patrick Walton <pcwalton@mimiga.net>
Date: Sun, 22 Dec 2013 14:26:36 -0800
Subject: [PATCH] librustc: De-`@mut` the `idstack` in constant checking

---
 src/librustc/middle/check_const.rs | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/src/librustc/middle/check_const.rs b/src/librustc/middle/check_const.rs
index 840f9ec2475..3922d338f3e 100644
--- a/src/librustc/middle/check_const.rs
+++ b/src/librustc/middle/check_const.rs
@@ -15,6 +15,7 @@
 use middle::typeck;
 use util::ppaux;
 
+use std::cell::RefCell;
 use syntax::ast::*;
 use syntax::codemap;
 use syntax::{ast_util, ast_map};
@@ -215,7 +216,7 @@ struct env {
     sess: Session,
     ast_map: ast_map::map,
     def_map: resolve::DefMap,
-    idstack: @mut ~[NodeId]
+    idstack: @RefCell<~[NodeId]>,
 }
 
 struct CheckItemRecursionVisitor {
@@ -233,7 +234,7 @@ pub fn check_item_recursion(sess: Session,
         sess: sess,
         ast_map: ast_map,
         def_map: def_map,
-        idstack: @mut ~[]
+        idstack: @RefCell::new(~[]),
     };
 
     let mut visitor = CheckItemRecursionVisitor { env: env };
@@ -242,12 +243,19 @@ pub fn check_item_recursion(sess: Session,
 
 impl Visitor<()> for CheckItemRecursionVisitor {
     fn visit_item(&mut self, it: @item, _: ()) {
-        if self.env.idstack.iter().any(|x| x == &(it.id)) {
-            self.env.sess.span_fatal(self.env.root_it.span, "recursive constant");
+        {
+            let mut idstack = self.env.idstack.borrow_mut();
+            if idstack.get().iter().any(|x| x == &(it.id)) {
+                self.env.sess.span_fatal(self.env.root_it.span,
+                                         "recursive constant");
+            }
+            idstack.get().push(it.id);
         }
-        self.env.idstack.push(it.id);
         visit::walk_item(self, it, ());
-        self.env.idstack.pop();
+        {
+            let mut idstack = self.env.idstack.borrow_mut();
+            idstack.get().pop();
+        }
     }
 
     fn visit_expr(&mut self, e: @Expr, _: ()) {
-- 
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