Distinguish delim kind to decide whether to emit unexpected closing delimiter

compiler/rustc_parse/src/lexer/diagnostics.rs

@@ -34,9 +34,12 @@ pub(super) fn same_indentation_level(sm: &SourceMap, open_sp: Span, close_sp: Sp
 
 // When we get a `)` or `]` for `{`, we should emit help message here
 // it's more friendly compared to report `unmatched error` in later phase
-fn report_missing_open_delim(err: &mut Diag<'_>, unmatched_delims: &[UnmatchedDelim]) -> bool {
+fn report_missing_open_delim(
+    err: &mut Diag<'_>,
+    unmatched_delims: &mut Vec<UnmatchedDelim>,
+) -> bool {
     let mut reported_missing_open = false;
-    for unmatch_brace in unmatched_delims.iter() {
+    unmatched_delims.retain(|unmatch_brace| {
         if let Some(delim) = unmatch_brace.found_delim
             && matches!(delim, Delimiter::Parenthesis | Delimiter::Bracket)
         {
@@ -50,18 +53,21 @@ fn report_missing_open_delim(err: &mut Diag<'_>, unmatched_delims: &[UnmatchedDe
                 format!("missing open `{missed_open}` for this delimiter"),
             );
             reported_missing_open = true;
+            false
+        } else {
+            true
         }
-    }
+    });
     reported_missing_open
 }
 
 pub(super) fn report_suspicious_mismatch_block(
     err: &mut Diag<'_>,
-    diag_info: &TokenTreeDiagInfo,
+    diag_info: &mut TokenTreeDiagInfo,
     sm: &SourceMap,
     delim: Delimiter,
 ) {
-    if report_missing_open_delim(err, &diag_info.unmatched_delims) {
+    if report_missing_open_delim(err, &mut diag_info.unmatched_delims) {
         return;
     }
 

compiler/rustc_parse/src/lexer/tokentrees.rs

@@ -77,12 +77,12 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
             );
         }
 
-        if let Some((delim, _)) = self.diag_info.open_delimiters.last() {
+        if let Some((delim, _)) = self.diag_info.open_delimiters.last().cloned() {
             report_suspicious_mismatch_block(
                 &mut err,
-                &self.diag_info,
+                &mut self.diag_info,
                 self.psess.source_map(),
-                *delim,
+                delim,
             )
         }
         err
@@ -154,15 +154,12 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
                             candidate = Some(*delimiter_span);
                         }
                     }
-                    let (_, _) = self.diag_info.open_delimiters.pop().unwrap();
                     self.diag_info.unmatched_delims.push(UnmatchedDelim {
                         found_delim: Some(close_delim),
                         found_span: self.token.span,
                         unclosed_span: unclosed_delimiter,
                         candidate_span: candidate,
                     });
-                } else {
-                    self.diag_info.open_delimiters.pop();
                 }
 
                 // If the incorrect delimiter matches an earlier opening
@@ -238,13 +235,29 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
         this_spacing
     }
 
-    fn close_delim_err(&mut self, delim: Delimiter) -> Diag<'psess> {
+    fn close_delim_err(&mut self, close_delim: Delimiter) -> Diag<'psess> {
         // An unexpected closing delimiter (i.e., there is no matching opening delimiter).
         let token_str = token_to_string(&self.token);
         let msg = format!("unexpected closing delimiter: `{token_str}`");
         let mut err = self.dcx().struct_span_err(self.token.span, msg);
 
-        report_suspicious_mismatch_block(&mut err, &self.diag_info, self.psess.source_map(), delim);
+        if let Some((open_delim, open_delim_span)) = self.diag_info.open_delimiters.last().cloned()
+        {
+            if open_delim == close_delim {
+                err.span_label(
+                    open_delim_span,
+                    format!("this closing `{}` may be intended to match here", token_str),
+                );
+                self.diag_info.open_delimiters.pop();
+            }
+        }
+
+        report_suspicious_mismatch_block(
+            &mut err,
+            &mut self.diag_info,
+            self.psess.source_map(),
+            close_delim,
+        );
         err.span_label(self.token.span, "unexpected closing delimiter");
         err
     }

tests/ui/parser/deli-ident-issue-2.rs

@@ -1,6 +1,6 @@
 fn main() {
     if 1 < 2 {
-        let _a = vec!]; //~ ERROR mismatched closing delimiter
+        let _a = vec!];
     }
 } //~ ERROR unexpected closing delimiter
 

tests/ui/parser/deli-ident-issue-2.stderr

@@ -1,19 +1,14 @@
-error: mismatched closing delimiter: `]`
-  --> $DIR/deli-ident-issue-2.rs:2:14
-   |
-LL |     if 1 < 2 {
-   |              ^ unclosed delimiter
-LL |         let _a = vec!];
-   |                      ^ mismatched closing delimiter
-
 error: unexpected closing delimiter: `}`
   --> $DIR/deli-ident-issue-2.rs:5:1
    |
+LL | fn main() {
+   |           - this closing `}` may be intended to match here
+LL |     if 1 < 2 {
 LL |         let _a = vec!];
    |                      - missing open `[` for this delimiter
 LL |     }
 LL | }
    | ^ unexpected closing delimiter
 
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 

tests/ui/parser/issues/issue-104367.rs

@@ -2,5 +2,5 @@
 struct S {
     d: [u32; {
         #![cfg] {
-            #![w,) //~ ERROR mismatched closing delimiter
+            #![w,)
                    //~ ERROR this file contains an unclosed delimiter

tests/ui/parser/issues/issue-104367.stderr

@@ -1,11 +1,3 @@
-error: mismatched closing delimiter: `)`
-  --> $DIR/issue-104367.rs:5:15
-   |
-LL |             #![w,)
-   |               ^  ^ mismatched closing delimiter
-   |               |
-   |               unclosed delimiter
-
 error: this file contains an unclosed delimiter
   --> $DIR/issue-104367.rs:6:71
    |
@@ -18,9 +10,11 @@ LL |     d: [u32; {
 LL |         #![cfg] {
    |                 - unclosed delimiter
 LL |             #![w,)
-   |                  - missing open `(` for this delimiter
+   |               -  - missing open `(` for this delimiter
+   |               |
+   |               unclosed delimiter
 LL |
    |                                                                      ^
 
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 

tests/ui/parser/issues/issue-105209.rs

@@ -1,3 +1,3 @@
 //@ compile-flags: -Zunpretty=ast-tree
-#![c={#![c[)x   //~ ERROR mismatched closing delimiter
-                //~ ERROR this file contains an unclosed delimiter
+//~v ERROR this file contains an unclosed delimiter
+#![c={#![c[)x

tests/ui/parser/issues/issue-105209.stderr

@@ -1,22 +1,14 @@
-error: mismatched closing delimiter: `)`
-  --> $DIR/issue-105209.rs:2:11
-   |
-LL | #![c={#![c[)x
-   |           ^^ mismatched closing delimiter
-   |           |
-   |           unclosed delimiter
-
 error: this file contains an unclosed delimiter
-  --> $DIR/issue-105209.rs:3:68
+  --> $DIR/issue-105209.rs:3:15
    |
 LL | #![c={#![c[)x
-   |   -  -  -  - missing open `(` for this delimiter
-   |   |  |  |
+   |   -  -  - -- ^
+   |   |  |  | ||
+   |   |  |  | |missing open `(` for this delimiter
+   |   |  |  | unclosed delimiter
    |   |  |  unclosed delimiter
    |   |  unclosed delimiter
    |   unclosed delimiter
-LL |
-   |                                                                   ^
 
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 

tests/ui/parser/issues/issue-62895.stderr

@@ -8,10 +8,10 @@ LL | (), w20);
    |        ^ mismatched closing delimiter
 
 error: mismatched closing delimiter: `)`
-  --> $DIR/issue-62895.rs:4:7
+  --> $DIR/issue-62895.rs:5:22
    |
-LL | mod _ {
-   |       ^ unclosed delimiter
+LL | pub fn g() -> isizee {
+   |                      ^ unclosed delimiter
 ...
 LL | (), w20);
    |        ^ mismatched closing delimiter

tests/ui/parser/issues/issue-62973.rs

@@ -2,8 +2,6 @@
 
 fn main() {}
 
-//~vvv ERROR mismatched closing delimiter: `)`
-//~vv ERROR mismatched closing delimiter: `)`
 //~vvv ERROR this file contains an unclosed delimiter
 fn p() { match s { v, E { [) {) }
 

tests/ui/parser/issues/issue-62973.stderr

@@ -1,31 +1,17 @@
-error: mismatched closing delimiter: `)`
-  --> $DIR/issue-62973.rs:8:27
-   |
-LL | fn p() { match s { v, E { [) {) }
-   |                           ^^ mismatched closing delimiter
-   |                           |
-   |                           unclosed delimiter
-
-error: mismatched closing delimiter: `)`
-  --> $DIR/issue-62973.rs:8:30
-   |
-LL | fn p() { match s { v, E { [) {) }
-   |                              ^^ mismatched closing delimiter
-   |                              |
-   |                              unclosed delimiter
-
 error: this file contains an unclosed delimiter
-  --> $DIR/issue-62973.rs:10:2
+  --> $DIR/issue-62973.rs:8:2
    |
 LL | fn p() { match s { v, E { [) {) }
-   |        -         -         -  - missing open `(` for this delimiter
-   |        |         |         |
-   |        |         |         missing open `(` for this delimiter
+   |        -         -      - --  - missing open `(` for this delimiter
+   |        |         |      | ||
+   |        |         |      | |missing open `(` for this delimiter
+   |        |         |      | unclosed delimiter
+   |        |         |      unclosed delimiter
    |        |         unclosed delimiter
    |        unclosed delimiter
 LL |
 LL |
    | ^
 
-error: aborting due to 3 previous errors
+error: aborting due to 1 previous error
 

tests/ui/parser/issues/issue-63116.rs

@@ -1,4 +1,3 @@
 // fixed by #66361
-//~vv ERROR mismatched closing delimiter: `]`
 //~v ERROR this file contains an unclosed delimiter
 impl W <s(f;Y(;]

tests/ui/parser/issues/issue-63116.stderr

@@ -1,19 +1,12 @@
-error: mismatched closing delimiter: `]`
-  --> $DIR/issue-63116.rs:4:14
-   |
-LL | impl W <s(f;Y(;]
-   |              ^ ^ mismatched closing delimiter
-   |              |
-   |              unclosed delimiter
-
 error: this file contains an unclosed delimiter
-  --> $DIR/issue-63116.rs:4:18
+  --> $DIR/issue-63116.rs:3:18
    |
 LL | impl W <s(f;Y(;]
-   |          -     -^
-   |          |     |
-   |          |     missing open `[` for this delimiter
+   |          -   - -^
+   |          |   | |
+   |          |   | missing open `[` for this delimiter
+   |          |   unclosed delimiter
    |          unclosed delimiter
 
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 

tests/ui/parser/issues/issue-67377-invalid-syntax-in-enum-discriminant.rs

@@ -3,21 +3,18 @@ mod a {
 
     enum Bug {
         V = [PhantomData; { [ () ].len() ].len() as isize,
-        //~^ ERROR mismatched closing delimiter: `]`
     }
 }
 
 mod b {
     enum Bug {
         V = [Vec::new; { [].len()  ].len() as isize,
-        //~^ ERROR mismatched closing delimiter: `]`
     }
 }
 
 mod c {
     enum Bug {
         V = [Vec::new; { [0].len() ].len() as isize,
-        //~^ ERROR mismatched closing delimiter: `]`
 }
 
 fn main() {} //~ ERROR this file contains an unclosed delimiter

tests/ui/parser/issues/issue-67377-invalid-syntax-in-enum-discriminant.stderr

@@ -1,47 +1,27 @@
-error: mismatched closing delimiter: `]`
-  --> $DIR/issue-67377-invalid-syntax-in-enum-discriminant.rs:5:27
-   |
-LL |         V = [PhantomData; { [ () ].len() ].len() as isize,
-   |             -             ^              ^ mismatched closing delimiter
-   |             |             |
-   |             |             unclosed delimiter
-   |             closing delimiter possibly meant for this
-
-error: mismatched closing delimiter: `]`
-  --> $DIR/issue-67377-invalid-syntax-in-enum-discriminant.rs:12:24
-   |
-LL |         V = [Vec::new; { [].len()  ].len() as isize,
-   |             -          ^           ^ mismatched closing delimiter
-   |             |          |
-   |             |          unclosed delimiter
-   |             closing delimiter possibly meant for this
-
-error: mismatched closing delimiter: `]`
-  --> $DIR/issue-67377-invalid-syntax-in-enum-discriminant.rs:19:24
-   |
-LL |         V = [Vec::new; { [0].len() ].len() as isize,
-   |             -          ^           ^ mismatched closing delimiter
-   |             |          |
-   |             |          unclosed delimiter
-   |             closing delimiter possibly meant for this
-
 error: this file contains an unclosed delimiter
-  --> $DIR/issue-67377-invalid-syntax-in-enum-discriminant.rs:23:65
+  --> $DIR/issue-67377-invalid-syntax-in-enum-discriminant.rs:20:65
    |
+LL | mod a {
+   |       - unclosed delimiter
+...
 LL |         V = [PhantomData; { [ () ].len() ].len() as isize,
    |                                          - missing open `[` for this delimiter
 ...
+LL | mod b {
+   |       - unclosed delimiter
+LL |     enum Bug {
 LL |         V = [Vec::new; { [].len()  ].len() as isize,
    |                                    - missing open `[` for this delimiter
 ...
 LL | mod c {
    |       - unclosed delimiter
 LL |     enum Bug {
+   |              - unclosed delimiter
 LL |         V = [Vec::new; { [0].len() ].len() as isize,
    |                                    - missing open `[` for this delimiter
 ...
 LL | fn main() {}
    |                                                                ^
 
-error: aborting due to 4 previous errors
+error: aborting due to 1 previous error
 

tests/ui/parser/issues/issue-68987-unmatch-issue-2.rs

@@ -1,7 +1,7 @@
 // FIXME: this case need more work to fix
 // currently the TokenTree matching ')' with '{', which is not user friendly for diagnostics
 async fn obstest() -> Result<> {
-    let obs_connect = || -> Result<(), MyError) { //~ ERROR mismatched closing delimiter
+    let obs_connect = || -> Result<(), MyError) {
         async {
         }
     }