---

yaml
---
r: 157660
b: refs/heads/snap-stage3
c: fb00015
h: refs/heads/master
v: v3

Author: ftxqxd

[refs]

@@ -1,7 +1,7 @@
 ---
 refs/heads/master: 065caf34f5ff29e04605f95d9c5d511af219439a
 refs/heads/snap-stage1: e33de59e47c5076a89eadeb38f4934f58a3618a6
-refs/heads/snap-stage3: 2a7be1b209a4ceea42418f55baf68774571ed9a2
+refs/heads/snap-stage3: fb00015246824313e8882935c9ba175ea6daf9d4
 refs/heads/try: 0ee4d8b0b112c608646fa75463ab4dc59132efd9
 refs/tags/release-0.1: 1f5c5126e96c79d22cb7862f75304136e204f105
 refs/heads/ndm: f3868061cd7988080c30d6d5bf352a5a5fe2460b

branches/snap-stage3/src/libsyntax/parse/parser.rs

@@ -2730,6 +2730,8 @@ impl<'a> Parser<'a> {
                 return self.parse_dot_or_call_expr();
             }
 
+            let lo = self.span.lo;
+
             self.bump();
 
             // Check for a place: `box(PLACE) EXPR`.
@@ -2738,6 +2740,18 @@ impl<'a> Parser<'a> {
                 if !self.eat(&token::RParen) {
                     let place = self.parse_expr();
                     self.expect(&token::RParen);
+                    // Give a suggestion to use `box()` when a parenthesised expression is used
+                    if !self.token.can_begin_expr() {
+                        let span = self.span;
+                        let this_token_to_string = self.this_token_to_string();
+                        self.span_err(span,
+                                      format!("expected expression, found `{}`",
+                                              this_token_to_string).as_slice());
+                        let box_span = mk_sp(lo, self.last_span.hi);
+                        self.span_help(box_span,
+                                       "perhaps you meant `box() (foo)` instead?");
+                        self.abort_if_errors();
+                    }
                     let subexpression = self.parse_prefix_expr();
                     hi = subexpression.span.hi;
                     ex = ExprBox(place, subexpression);

branches/snap-stage3/src/test/compile-fail/parenthesized-box-expr-message.rs

@@ -0,0 +1,14 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+fn main() {
+    box(1 + 1) //~ HELP perhaps you meant `box() (foo)` instead?
+    ; //~ ERROR expected expression, found `;`
+}