Point at match when a parse failure ocurrs inside of it

Author: estebank

src/libsyntax/parse/parser.rs

@@ -2474,7 +2474,11 @@ impl<'a> Parser<'a> {
                     return Ok(self.mk_expr(lo.to(hi), ex, attrs));
                 }
                 if self.eat_keyword(keywords::Match) {
-                    return self.parse_match_expr(attrs);
+                    let match_sp = self.prev_span;
+                    return self.parse_match_expr(attrs).map_err(|mut err| {
+                        err.span_label(match_sp, "while parsing this match expression");
+                        err
+                    });
                 }
                 if self.eat_keyword(keywords::Unsafe) {
                     return self.parse_block_expr(

src/test/ui/label/label_break_value_illegal_uses.stderr

@@ -25,7 +25,9 @@ error: expected one of `.`, `?`, `{`, or an operator, found `'b`
   --> $DIR/label_break_value_illegal_uses.rs:28:17
    |
 LL |     match false 'b: {} //~ ERROR expected one of `.`, `?`, `{`, or an operator
-   |                 ^^ expected one of `.`, `?`, `{`, or an operator here
+   |     -----       ^^ expected one of `.`, `?`, `{`, or an operator here
+   |     |
+   |     while parsing this match expression
 
 error: aborting due to 4 previous errors
 

src/test/ui/parser/match-refactor-to-expr.rs

@@ -12,7 +12,7 @@
 
 fn main() {
     let foo =
-        match
+        match //~ NOTE while parsing this match expression
         Some(4).unwrap_or_else(5)
         //~^ NOTE expected one of `.`, `?`, `{`, or an operator here
         ; //~ NOTE unexpected token

src/test/ui/parser/match-refactor-to-expr.stderr

@@ -1,8 +1,11 @@
 error: expected one of `.`, `?`, `{`, or an operator, found `;`
   --> $DIR/match-refactor-to-expr.rs:18:9
    |
-LL |         match
-   |         ----- help: try removing this `match`
+LL |         match //~ NOTE while parsing this match expression
+   |         -----
+   |         |
+   |         while parsing this match expression
+   |         help: try removing this `match`
 LL |         Some(4).unwrap_or_else(5)
    |                                  - expected one of `.`, `?`, `{`, or an operator here
 LL |         //~^ NOTE expected one of `.`, `?`, `{`, or an operator here

src/test/ui/try-block/try-block-in-match.stderr

@@ -2,7 +2,9 @@ error: expected expression, found reserved keyword `try`
   --> $DIR/try-block-in-match.rs:16:11
    |
 LL |     match try { false } { _ => {} } //~ ERROR expected expression, found reserved keyword `try`
-   |           ^^^ expected expression
+   |     ----- ^^^ expected expression
+   |     |
+   |     while parsing this match expression
 
 error: aborting due to previous error