From 3a31576d76f5cab4554da5b511f4a065bf5f92b5 Mon Sep 17 00:00:00 2001
From: llogiq <bogusandre@gmail.com>
Date: Mon, 1 Feb 2016 20:37:07 +0100
Subject: [PATCH] fixed #606

---
 src/escape.rs                         |  8 ++++----
 tests/compile-fail/escape_analysis.rs | 15 +++++++++++++++
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/src/escape.rs b/src/escape.rs
index edc7b5c6fbbd..68dd2307e3fe 100644
--- a/src/escape.rs
+++ b/src/escape.rs
@@ -31,9 +31,9 @@ pub struct EscapePass;
 /// ```
 declare_lint!(pub BOXED_LOCAL, Warn, "using Box<T> where unnecessary");
 
-fn is_box(ty: ty::Ty) -> bool {
+fn is_non_trait_box(ty: ty::Ty) -> bool {
     match ty.sty {
-        ty::TyBox(..) => true,
+        ty::TyBox(ref inner) => !inner.is_trait(),
         _ => false
     }
 }
@@ -90,7 +90,7 @@ impl<'a, 'tcx: 'a> Delegate<'tcx> for EscapeDelegate<'a, 'tcx> {
             if let Some(NodeExpr(..)) = map.find(map.get_parent_node(consume_pat.id)) {
                 return;
             }
-            if is_box(cmt.ty) {
+            if is_non_trait_box(cmt.ty) {
                 self.set.insert(consume_pat.id);
             }
             return;
@@ -101,7 +101,7 @@ impl<'a, 'tcx: 'a> Delegate<'tcx> for EscapeDelegate<'a, 'tcx> {
                     if let DeclLocal(ref loc) = decl.node {
                         if let Some(ref ex) = loc.init {
                             if let ExprBox(..) = ex.node {
-                                if is_box(cmt.ty) {
+                                if is_non_trait_box(cmt.ty) {
                                     // let x = box (...)
                                     self.set.insert(consume_pat.id);
                                 }
diff --git a/tests/compile-fail/escape_analysis.rs b/tests/compile-fail/escape_analysis.rs
index f3aa8bff41c2..c0893bcd767b 100644
--- a/tests/compile-fail/escape_analysis.rs
+++ b/tests/compile-fail/escape_analysis.rs
@@ -11,9 +11,24 @@ impl A {
     fn foo(&self){}
 }
 
+trait Z {
+    fn bar(&self);
+}
+
+impl Z for A {
+    fn bar(&self) {
+        //nothing
+    }
+}
+
 fn main() {
 }
 
+fn ok_box_trait(boxed_trait: &Box<Z>) {
+    let boxed_local = boxed_trait;
+    // done
+}
+
 fn warn_call() {
     let x = box A; //~ ERROR local variable
     x.foo();