Emit unclosed delimiters during recovery

Author: estebank

src/libsyntax/parse/parser.rs

@@ -778,6 +778,7 @@ impl<'a> Parser<'a> {
             // leave it in the input
             Ok(false)
         } else if self.last_unexpected_token_span == Some(self.span) {
+            emit_unclosed_delims(&self.unclosed_delims, self.diagnostic());
             FatalError.raise();
         } else {
             let mut expected = edible.iter()

src/test/ui/issues/issue-58856-1.rs

@@ -5,4 +5,8 @@ impl A {
     //~^ ERROR expected one of `)`, `,`, or `:`, found `>`
 }
 
+// verify that mismatched delimiters get emitted
+fn foo(] {}
+//~^ ERROR incorrect close delimiter
+
 fn main() {}

src/test/ui/issues/issue-58856-1.stderr

@@ -7,5 +7,13 @@ LL |     fn b(self> {}
    |         |    help: `)` may belong here
    |         unclosed delimiter
 
-error: aborting due to previous error
+error: incorrect close delimiter: `]`
+  --> $DIR/issue-58856-1.rs:9:8
+   |
+LL | fn foo(] {}
+   |       -^ incorrect close delimiter
+   |       |
+   |       un-closed delimiter
+
+error: aborting due to 2 previous errors