From 5038f5a70c8fd12703fe5d78b8d04918336e764c Mon Sep 17 00:00:00 2001
From: Jorge Aparicio <japaricious@gmail.com>
Date: Mon, 1 Dec 2014 14:47:06 -0500
Subject: [PATCH] Tell expr_use_visitor which binops are by value

---
 src/librustc/middle/expr_use_visitor.rs | 28 ++++++++++++++++++-------
 1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/src/librustc/middle/expr_use_visitor.rs b/src/librustc/middle/expr_use_visitor.rs
index 8e00c96535b..59872c69462 100644
--- a/src/librustc/middle/expr_use_visitor.rs
+++ b/src/librustc/middle/expr_use_visitor.rs
@@ -30,7 +30,7 @@ use middle::ty::{MethodStatic, MethodStaticUnboxedClosure};
 use util::ppaux::Repr;
 
 use std::kinds;
-use syntax::ast;
+use syntax::{ast, ast_util};
 use syntax::ptr::P;
 use syntax::codemap::Span;
 
@@ -438,7 +438,7 @@ impl<'d,'t,'tcx,TYPER:mc::Typer<'tcx>> ExprUseVisitor<'d,'t,'tcx,TYPER> {
             ast::ExprPath(..) => { }
 
             ast::ExprUnary(ast::UnDeref, ref base) => {      // *base
-                if !self.walk_overloaded_operator(expr, &**base, Vec::new()) {
+                if !self.walk_overloaded_operator(expr, &**base, Vec::new(), None) {
                     self.select_from_expr(&**base);
                 }
             }
@@ -452,7 +452,7 @@ impl<'d,'t,'tcx,TYPER:mc::Typer<'tcx>> ExprUseVisitor<'d,'t,'tcx,TYPER> {
             }
 
             ast::ExprIndex(ref lhs, ref rhs) => {       // lhs[rhs]
-                if !self.walk_overloaded_operator(expr, &**lhs, vec![&**rhs]) {
+                if !self.walk_overloaded_operator(expr, &**lhs, vec![&**rhs], None) {
                     self.select_from_expr(&**lhs);
                     self.consume_expr(&**rhs);
                 }
@@ -465,7 +465,7 @@ impl<'d,'t,'tcx,TYPER:mc::Typer<'tcx>> ExprUseVisitor<'d,'t,'tcx,TYPER> {
                     (&None, &Some(ref e)) => vec![&**e],
                     (&None, &None) => Vec::new()
                 };
-                let overloaded = self.walk_overloaded_operator(expr, &**base, args);
+                let overloaded = self.walk_overloaded_operator(expr, &**base, args, None);
                 assert!(overloaded);
             }
 
@@ -570,13 +570,14 @@ impl<'d,'t,'tcx,TYPER:mc::Typer<'tcx>> ExprUseVisitor<'d,'t,'tcx,TYPER> {
             }
 
             ast::ExprUnary(_, ref lhs) => {
-                if !self.walk_overloaded_operator(expr, &**lhs, Vec::new()) {
+                if !self.walk_overloaded_operator(expr, &**lhs, Vec::new(), None) {
                     self.consume_expr(&**lhs);
                 }
             }
 
-            ast::ExprBinary(_, ref lhs, ref rhs) => {
-                if !self.walk_overloaded_operator(expr, &**lhs, vec![&**rhs]) {
+            ast::ExprBinary(op, ref lhs, ref rhs) => {
+                if !self.walk_overloaded_operator(expr, &**lhs, vec![&**rhs], Some(op))
+                {
                     self.consume_expr(&**lhs);
                     self.consume_expr(&**rhs);
                 }
@@ -911,13 +912,24 @@ impl<'d,'t,'tcx,TYPER:mc::Typer<'tcx>> ExprUseVisitor<'d,'t,'tcx,TYPER> {
     fn walk_overloaded_operator(&mut self,
                                 expr: &ast::Expr,
                                 receiver: &ast::Expr,
-                                rhs: Vec<&ast::Expr>)
+                                rhs: Vec<&ast::Expr>,
+                                binop: Option<ast::BinOp>)
                                 -> bool
     {
         if !self.typer.is_method_call(expr.id) {
             return false;
         }
 
+        match binop {
+            Some(binop) if ast_util::is_by_value_binop(binop) => {
+                self.consume_expr(receiver);
+                self.consume_expr(rhs[0]);
+
+                return true;
+            },
+            _ => {},
+        }
+
         self.walk_expr(receiver);
 
         // Arguments (but not receivers) to overloaded operator