When encountering unclosed delimiters during parsing, check for diff markers

Fix #116252.

3 files changed, 63 insertions, 27 deletions

diff --git a/compiler/rustc_parse/src/lexer/mod.rs b/compiler/rustc_parse/src/lexer/mod.rs
index a375a1d69cd..f2eed5c9be5 100644
--- a/compiler/rustc_parse/src/lexer/mod.rs
+++ b/compiler/rustc_parse/src/lexer/mod.rs
@@ -64,10 +64,10 @@ pub(crate) fn parse_token_trees<'a>(
         override_span,
         nbsp_is_whitespace: false,
     };
-    let (token_trees, unmatched_delims) =
+    let (stream, res, unmatched_delims) =
         tokentrees::TokenTreesReader::parse_all_token_trees(string_reader);
-    match token_trees {
-        Ok(stream) if unmatched_delims.is_empty() => Ok(stream),
+    match res {
+        Ok(()) if unmatched_delims.is_empty() => Ok(stream),
         _ => {
             // Return error if there are unmatched delimiters or unclosed delimiters.
             // We emit delimiter mismatch errors first, then emit the unclosing delimiter mismatch
@@ -79,9 +79,11 @@ pub(crate) fn parse_token_trees<'a>(
                     err.buffer(&mut buffer);
                 }
             }
-            if let Err(err) = token_trees {
-                // Add unclosing delimiter error
-                err.buffer(&mut buffer);
+            if let Err(errs) = res {
+                // Add unclosing delimiter or diff marker errors
+                for err in errs {
+                    err.buffer(&mut buffer);
+                }
             }
             Err(buffer)
         }
diff --git a/compiler/rustc_parse/src/lexer/tokentrees.rs b/compiler/rustc_parse/src/lexer/tokentrees.rs
index 1d9dbfe4b89..31d91fe80bd 100644
--- a/compiler/rustc_parse/src/lexer/tokentrees.rs
+++ b/compiler/rustc_parse/src/lexer/tokentrees.rs
@@ -5,7 +5,7 @@ use super::{StringReader, UnmatchedDelim};
 use rustc_ast::token::{self, Delimiter, Token};
 use rustc_ast::tokenstream::{DelimSpan, Spacing, TokenStream, TokenTree};
 use rustc_ast_pretty::pprust::token_to_string;
-use rustc_errors::{PErr, PResult};
+use rustc_errors::PErr;
 
 pub(super) struct TokenTreesReader<'a> {
     string_reader: StringReader<'a>,
@@ -18,36 +18,42 @@ pub(super) struct TokenTreesReader<'a> {
 impl<'a> TokenTreesReader<'a> {
     pub(super) fn parse_all_token_trees(
         string_reader: StringReader<'a>,
-    ) -> (PResult<'a, TokenStream>, Vec<UnmatchedDelim>) {
+    ) -> (TokenStream, Result<(), Vec<PErr<'a>>>, Vec<UnmatchedDelim>) {
         let mut tt_reader = TokenTreesReader {
             string_reader,
             token: Token::dummy(),
             diag_info: TokenTreeDiagInfo::default(),
         };
-        let res = tt_reader.parse_token_trees(/* is_delimited */ false);
-        (res, tt_reader.diag_info.unmatched_delims)
+        let (stream, res) = tt_reader.parse_token_trees(/* is_delimited */ false);
+        (stream, res, tt_reader.diag_info.unmatched_delims)
     }
 
     // Parse a stream of tokens into a list of `TokenTree`s.
-    fn parse_token_trees(&mut self, is_delimited: bool) -> PResult<'a, TokenStream> {
+    fn parse_token_trees(
+        &mut self,
+        is_delimited: bool,
+    ) -> (TokenStream, Result<(), Vec<PErr<'a>>>) {
         self.token = self.string_reader.next_token().0;
         let mut buf = Vec::new();
         loop {
             match self.token.kind {
-                token::OpenDelim(delim) => buf.push(self.parse_token_tree_open_delim(delim)?),
+                token::OpenDelim(delim) => {
+                    buf.push(match self.parse_token_tree_open_delim(delim) {
+                        Ok(val) => val,
+                        Err(errs) => return (TokenStream::new(buf), Err(errs)),
+                    })
+                }
                 token::CloseDelim(delim) => {
-                    return if is_delimited {
-                        Ok(TokenStream::new(buf))
-                    } else {
-                        Err(self.close_delim_err(delim))
-                    };
+                    return (
+                        TokenStream::new(buf),
+                        if is_delimited { Ok(()) } else { Err(vec![self.close_delim_err(delim)]) },
+                    );
                 }
                 token::Eof => {
-                    return if is_delimited {
-                        Err(self.eof_err())
-                    } else {
-                        Ok(TokenStream::new(buf))
-                    };
+                    return (
+                        TokenStream::new(buf),
+                        if is_delimited { Err(vec![self.eof_err()]) } else { Ok(()) },
+                    );
                 }
                 _ => {
                     // Get the next normal token. This might require getting multiple adjacent
@@ -97,7 +103,10 @@ impl<'a> TokenTreesReader<'a> {
         err
     }
 
-    fn parse_token_tree_open_delim(&mut self, open_delim: Delimiter) -> PResult<'a, TokenTree> {
+    fn parse_token_tree_open_delim(
+        &mut self,
+        open_delim: Delimiter,
+    ) -> Result<TokenTree, Vec<PErr<'a>>> {
         // The span for beginning of the delimited section
         let pre_span = self.token.span;
 
@@ -106,7 +115,26 @@ impl<'a> TokenTreesReader<'a> {
         // Parse the token trees within the delimiters.
         // We stop at any delimiter so we can try to recover if the user
         // uses an incorrect delimiter.
-        let tts = self.parse_token_trees(/* is_delimited */ true)?;
+        let (tts, res) = self.parse_token_trees(/* is_delimited */ true);
+        if let Err(mut errs) = res {
+            // If there are unclosed delims, see if there are diff markers and if so, point them
+            // out instead of complaining about the unclosed delims.
+            let mut parser = crate::stream_to_parser(self.string_reader.sess, tts, None);
+            let mut diff_errs = vec![];
+            while parser.token != token::Eof {
+                if let Err(diff_err) = parser.err_diff_marker() {
+                    diff_errs.push(diff_err);
+                }
+                parser.bump();
+            }
+            if !diff_errs.is_empty() {
+                errs.iter_mut().for_each(|err| {
+                    err.delay_as_bug();
+                });
+                return Err(diff_errs);
+            }
+            return Err(errs);
+        }
 
         // Expand to cover the entire delimited token tree
         let delim_span = DelimSpan::from_pair(pre_span, self.token.span);
diff --git a/compiler/rustc_parse/src/parser/diagnostics.rs b/compiler/rustc_parse/src/parser/diagnostics.rs
index 7b5bb319ed8..2a8eb6edd23 100644
--- a/compiler/rustc_parse/src/parser/diagnostics.rs
+++ b/compiler/rustc_parse/src/parser/diagnostics.rs
@@ -2808,8 +2808,15 @@ impl<'a> Parser<'a> {
     }
 
     pub fn recover_diff_marker(&mut self) {
+        if let Err(mut err) = self.err_diff_marker() {
+            err.emit();
+            FatalError.raise();
+        }
+    }
+
+    pub fn err_diff_marker(&mut self) -> PResult<'a, ()> {
         let Some(start) = self.diff_marker(&TokenKind::BinOp(token::Shl), &TokenKind::Lt) else {
-            return;
+            return Ok(());
         };
         let mut spans = Vec::with_capacity(3);
         spans.push(start);
@@ -2856,8 +2863,7 @@ impl<'a> Parser<'a> {
             "for an explanation on these markers from the `git` documentation, visit \
              <https://git-scm.com/book/en/v2/Git-Tools-Advanced-Merging#_checking_out_conflicts>",
         );
-        err.emit();
-        FatalError.raise()
+        Err(err)
     }
 
     /// Parse and throw away a parenthesized comma separated