From 9772545dd0fc684cb1c784f7f18dba6804359096 Mon Sep 17 00:00:00 2001
From: Ulrich Stark <github@ustark.de>
Date: Sun, 31 Aug 2025 20:46:59 +0200
Subject: [PATCH] fix(parser): reset popped lexer errors when rewinding

---
 crates/oxc_parser/src/lexer/mod.rs        | 17 +++++++----------
 tasks/coverage/misc/fail/oxc-12816.ts     |  1 +
 tasks/coverage/snapshots/parser_misc.snap |  8 +++++++-
 3 files changed, 15 insertions(+), 11 deletions(-)
 create mode 100644 tasks/coverage/misc/fail/oxc-12816.ts

diff --git a/crates/oxc_parser/src/lexer/mod.rs b/crates/oxc_parser/src/lexer/mod.rs
index f2292d7129f5a..2bbc1ff0529c9 100644
--- a/crates/oxc_parser/src/lexer/mod.rs
+++ b/crates/oxc_parser/src/lexer/mod.rs
@@ -40,14 +40,11 @@ pub use token::Token;
 use source::{Source, SourcePosition};
 use trivia_builder::TriviaBuilder;
 
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, Clone)]
 pub struct LexerCheckpoint<'a> {
-    /// Current position in source
-    position: SourcePosition<'a>,
-
+    source_position: SourcePosition<'a>,
     token: Token,
-
-    errors_pos: usize,
+    errors: Vec<OxcDiagnostic>,
 }
 
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
@@ -141,16 +138,16 @@ impl<'a> Lexer<'a> {
     /// Use `rewind` to restore the lexer to the state stored in the checkpoint.
     pub fn checkpoint(&self) -> LexerCheckpoint<'a> {
         LexerCheckpoint {
-            position: self.source.position(),
+            source_position: self.source.position(),
             token: self.token,
-            errors_pos: self.errors.len(),
+            errors: self.errors.clone(),
         }
     }
 
     /// Rewinds the lexer to the same state as when the passed in `checkpoint` was created.
     pub fn rewind(&mut self, checkpoint: LexerCheckpoint<'a>) {
-        self.errors.truncate(checkpoint.errors_pos);
-        self.source.set_position(checkpoint.position);
+        self.errors = checkpoint.errors;
+        self.source.set_position(checkpoint.source_position);
         self.token = checkpoint.token;
     }
 
diff --git a/tasks/coverage/misc/fail/oxc-12816.ts b/tasks/coverage/misc/fail/oxc-12816.ts
new file mode 100644
index 0000000000000..747246cfef609
--- /dev/null
+++ b/tasks/coverage/misc/fail/oxc-12816.ts
@@ -0,0 +1 @@
+{if(\ ()<1){}}
\ No newline at end of file
diff --git a/tasks/coverage/snapshots/parser_misc.snap b/tasks/coverage/snapshots/parser_misc.snap
index 3f4579684208f..6ebc70330f1b2 100644
--- a/tasks/coverage/snapshots/parser_misc.snap
+++ b/tasks/coverage/snapshots/parser_misc.snap
@@ -1,7 +1,7 @@
 parser_misc Summary:
 AST Parsed     : 48/48 (100.00%)
 Positive Passed: 48/48 (100.00%)
-Negative Passed: 78/78 (100.00%)
+Negative Passed: 79/79 (100.00%)
 
   × Cannot assign to 'arguments' in strict mode
    ╭─[misc/fail/arguments-eval.ts:1:10]
@@ -437,6 +437,12 @@ Negative Passed: 78/78 (100.00%)
    ·  ──────────────────────
    ╰────
 
+  × Invalid Unicode escape sequence
+   ╭─[misc/fail/oxc-12816.ts:1:6]
+ 1 │ {if(\ ()<1){}}
+   ·      ─
+   ╰────
+
   × 'super' can only be referenced in members of derived classes or object literal expressions.
    ╭─[misc/fail/oxc-13284.ts:5:9]
  4 │       bar() {