From 1334f2ceaea5e012bba02b6afc0371bf92e976e7 Mon Sep 17 00:00:00 2001
From: Manish Goregaokar <manishsmail@gmail.com>
Date: Sat, 22 Aug 2015 13:01:54 +0530
Subject: [PATCH] Fix doubleborrow of refcell in consts.rs

---
 src/consts.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/consts.rs b/src/consts.rs
index 70d5ff4bc..e54ac77b5 100644
--- a/src/consts.rs
+++ b/src/consts.rs
@@ -330,8 +330,13 @@ impl<'c, 'cc> ConstEvalContext<'c, 'cc> {
     /// lookup a possibly constant expression from a ExprPath
     fn fetch_path(&mut self, e: &Expr) -> Option<Constant> {
         if let Some(lcx) = self.lcx {
+            let mut maybe_id = None;
             if let Some(&PathResolution { base_def: DefConst(id), ..}) =
                 lcx.tcx.def_map.borrow().get(&e.id) {
+                maybe_id = Some(id);
+            }
+            // separate if lets to avoid doubleborrowing the defmap
+            if let Some(id) = maybe_id {
                 if let Some(const_expr) = lookup_const_by_id(lcx.tcx, id, None) {
                     let ret = self.expr(const_expr);
                     if ret.is_some() {