---

yaml
---
r: 232553
b: refs/heads/try
c: c0c6af7
h: refs/heads/master
i:
  232551: a6b0b70
v: v3

Author: GSam

[refs]

@@ -1,7 +1,7 @@
 ---
 refs/heads/master: edeb4f1c86cbf6af8ef9874d4b3af50f721ea1b8
 refs/heads/snap-stage3: 1af31d4974e33027a68126fa5a5a3c2c6491824f
-refs/heads/try: c67a34b9e509b76ff145526f28a20f9495c2ab61
+refs/heads/try: c0c6af7f073620aacfb103c070e997a8d50b7201
 refs/tags/release-0.1: 1f5c5126e96c79d22cb7862f75304136e204f105
 refs/tags/release-0.2: c870d2dffb391e14efb05aa27898f1f6333a9596
 refs/tags/release-0.3: b5f0d0f648d9a6153664837026ba1be43d3e2503

branches/try/src/libsyntax/print/pprust.rs

@@ -1555,6 +1555,21 @@ impl<'a> State<'a> {
         self.pclose()
     }
 
+    pub fn check_expr_bin_needs_paren(&mut self, sub_expr: &ast::Expr,
+                                      binop: ast::BinOp) -> bool {
+        match sub_expr.node {
+            ast::ExprBinary(ref sub_op, _, _) => {
+                if ast_util::operator_prec(sub_op.node) <
+                    ast_util::operator_prec(binop.node) {
+                    true
+                } else {
+                    false
+                }
+            }
+            _ => true
+        }
+    }
+
     pub fn print_expr_maybe_paren(&mut self, expr: &ast::Expr) -> io::Result<()> {
         let needs_par = needs_parentheses(expr);
         if needs_par {
@@ -1670,10 +1685,18 @@ impl<'a> State<'a> {
                          op: ast::BinOp,
                          lhs: &ast::Expr,
                          rhs: &ast::Expr) -> io::Result<()> {
-        try!(self.print_expr_maybe_paren(lhs));
+        if self.check_expr_bin_needs_paren(lhs, op) {
+            try!(self.print_expr_maybe_paren(lhs));
+        } else {
+            try!(self.print_expr(lhs));
+        }
         try!(space(&mut self.s));
         try!(self.word_space(ast_util::binop_to_string(op.node)));
-        self.print_expr_maybe_paren(rhs)
+        if self.check_expr_bin_needs_paren(rhs, op) {
+            self.print_expr_maybe_paren(rhs)
+        } else {
+            self.print_expr(rhs)
+        }
     }
 
     fn print_expr_unary(&mut self,