From ab1986103738083a5bcf5af4db4be2930459f45f Mon Sep 17 00:00:00 2001
From: Corey Richardson <corey@octayn.net>
Date: Sun, 24 Nov 2013 21:18:20 -0500
Subject: [PATCH] Add a note for unclosed delimiters

Currently, the parser doesn't give any context when it finds an unclosed
delimiter and it's not EOF. Report the most recent unclosed delimiter, to help
the user along.

Closes #10636
---
 src/libsyntax/parse/parser.rs          | 16 +++++++---------
 src/test/compile-fail/issue-10636-1.rs | 13 +++++++++++++
 src/test/compile-fail/issue-10636-2.rs | 13 +++++++++++++
 3 files changed, 33 insertions(+), 9 deletions(-)
 create mode 100644 src/test/compile-fail/issue-10636-1.rs
 create mode 100644 src/test/compile-fail/issue-10636-2.rs

diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 486a7a800a0d9..315872ce8cd1e 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -2086,15 +2086,13 @@ impl Parser {
         fn parse_non_delim_tt_tok(p: &Parser) -> token_tree {
             maybe_whole!(deref p, nt_tt);
             match *p.token {
-              token::RPAREN | token::RBRACE | token::RBRACKET
-              => {
-                p.fatal(
-                    format!(
-                        "incorrect close delimiter: `{}`",
-                        p.this_token_to_str()
-                    )
-                );
-              }
+              token::RPAREN | token::RBRACE | token::RBRACKET => {
+                  // This is a conservative error: only report the last unclosed delimiter. The
+                  // previous unclosed delimiters could actually be closed! The parser just hasn't
+                  // gotten to them yet.
+                  p.open_braces.last_opt().map(|sp| p.span_note(*sp, "unclosed delimiter"));
+                  p.fatal(format!("incorrect close delimiter: `{}`", p.this_token_to_str()));
+              },
               /* we ought to allow different depths of unquotation */
               token::DOLLAR if *p.quote_depth > 0u => {
                 p.bump();
diff --git a/src/test/compile-fail/issue-10636-1.rs b/src/test/compile-fail/issue-10636-1.rs
new file mode 100644
index 0000000000000..710c5a306f377
--- /dev/null
+++ b/src/test/compile-fail/issue-10636-1.rs
@@ -0,0 +1,13 @@
+// Copyright 2013 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.
+
+struct Obj { //~ NOTE: unclosed delimiter
+    member: uint
+) //~ ERROR: incorrect close delimiter
diff --git a/src/test/compile-fail/issue-10636-2.rs b/src/test/compile-fail/issue-10636-2.rs
new file mode 100644
index 0000000000000..2303f858fcc76
--- /dev/null
+++ b/src/test/compile-fail/issue-10636-2.rs
@@ -0,0 +1,13 @@
+// Copyright 2013 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.
+
+pub fn trace_option(option: Option<int>) {
+    option.map(|some| 42; //~ NOTE: unclosed delimiter
+} //~ ERROR: incorrect close delimiter