From 3f1884ac5e3cfee1b99563ebd593687c388acf51 Mon Sep 17 00:00:00 2001
From: Matthew Saw <matthew.saw@systemearth.com>
Date: Mon, 28 Sep 2026 21:52:36 +0800
Subject: [PATCH] fix(scanner): insert semicolon before identifiers starting
 with `in`

The automatic semicolon check treats a line starting with `in` or
`instanceof` as a binary operator unless the next character is a letter.
Digits, `_` and `$` also continue an identifier, so a line starting with
`in_b`, `in1`, `in$` or `instanceof_` suppressed the semicolon and the
statement failed to parse.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 src/scanner.c                       |  6 ++++--
 test/corpus/semicolon_insertion.txt | 24 ++++++++++++++++++++++++
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/src/scanner.c b/src/scanner.c
index 795916dd..78ac80e1 100644
--- a/src/scanner.c
+++ b/src/scanner.c
@@ -26,6 +26,8 @@ static inline void advance(TSLexer *lexer) { lexer->advance(lexer, false); }
 
 static inline void skip(TSLexer *lexer) { lexer->advance(lexer, true); }
 
+static inline bool is_identifier_char(int32_t c) { return iswalnum(c) || c == '_' || c == '$'; }
+
 static bool scan_template_chars(TSLexer *lexer) {
     lexer->result_symbol = TEMPLATE_CHARS;
     for (bool has_content = false;; has_content = true) {
@@ -199,7 +201,7 @@ static bool scan_automatic_semicolon(TSLexer *lexer, bool comment_condition, boo
             }
             skip(lexer);
 
-            if (!iswalpha(lexer->lookahead)) {
+            if (!is_identifier_char(lexer->lookahead)) {
                 return false;
             }
 
@@ -210,7 +212,7 @@ static bool scan_automatic_semicolon(TSLexer *lexer, bool comment_condition, boo
                 skip(lexer);
             }
 
-            if (!iswalpha(lexer->lookahead)) {
+            if (!is_identifier_char(lexer->lookahead)) {
                 return false;
             }
             break;
diff --git a/test/corpus/semicolon_insertion.txt b/test/corpus/semicolon_insertion.txt
index 75cca226..f7367245 100644
--- a/test/corpus/semicolon_insertion.txt
+++ b/test/corpus/semicolon_insertion.txt
@@ -130,6 +130,18 @@ a
 a
   instanceofX;
 
+a
+  in_b;
+
+a
+  in1;
+
+a
+  in$;
+
+a
+  instanceof_;
+
 ---
 
 (program
@@ -146,6 +158,18 @@ a
 
   (expression_statement (binary_expression (identifier) (identifier)))
 
+  (expression_statement (identifier))
+  (expression_statement (identifier))
+
+  (expression_statement (identifier))
+  (expression_statement (identifier))
+
+  (expression_statement (identifier))
+  (expression_statement (identifier))
+
+  (expression_statement (identifier))
+  (expression_statement (identifier))
+
   (expression_statement (identifier))
   (expression_statement (identifier)))