From 99ecf4e2c94a72a68294111ecdf6a82c150c378a Mon Sep 17 00:00:00 2001
From: Kevin Butler <haqkrs@gmail.com>
Date: Tue, 27 Oct 2015 13:41:55 +0000
Subject: [PATCH] libsyntax: improve error message when a statement is prefixed
 with a match keyword

---
 src/libsyntax/parse/parser.rs                 |  8 +++++++-
 src/test/parse-fail/match-refactor-to-expr.rs | 18 ++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100644 src/test/parse-fail/match-refactor-to-expr.rs

diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 6cee7b86a61..d1fc8ac2002 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -2941,9 +2941,15 @@ impl<'a> Parser<'a> {
     }
 
     fn parse_match_expr(&mut self) -> PResult<P<Expr>> {
+        let match_span = self.last_span;
         let lo = self.last_span.lo;
         let discriminant = try!(self.parse_expr_res(Restrictions::RESTRICTION_NO_STRUCT_LITERAL));
-        try!(self.commit_expr_expecting(&*discriminant, token::OpenDelim(token::Brace)));
+        if let Err(e) = self.commit_expr_expecting(&*discriminant, token::OpenDelim(token::Brace)) {
+            if self.token == token::Token::Semi {
+                self.span_note(match_span, "did you mean to remove this `match` keyword?");
+            }
+            return Err(e)
+        }
         let mut arms: Vec<Arm> = Vec::new();
         while self.token != token::CloseDelim(token::Brace) {
             arms.push(try!(self.parse_arm_nopanic()));
diff --git a/src/test/parse-fail/match-refactor-to-expr.rs b/src/test/parse-fail/match-refactor-to-expr.rs
new file mode 100644
index 00000000000..e85fb3c9dd5
--- /dev/null
+++ b/src/test/parse-fail/match-refactor-to-expr.rs
@@ -0,0 +1,18 @@
+// Copyright 2015 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() {
+    let foo =
+        match //~ NOTE did you mean to remove this `match` keyword?
+        Some(4).unwrap_or_else(5)
+        ; //~ ERROR expected one of `.`, `{`, or an operator, found `;`
+
+    println!("{}", foo)
+}