From 632cadcd15132fde1d2db6a6494e5f07c07edab5 Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Thu, 25 Dec 2025 04:36:17 +0000
Subject: [PATCH] Handle Unicode minus (U+2212) as comment-like syntax
MIME-Version: 1.0
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ClickHouse doesn't recognize the Unicode minus sign (−, U+2212) as a
mathematical operator. Instead of parsing it as a minus, treat everything
from the Unicode minus to the end of line or semicolon as a comment.

This matches ClickHouse's behavior where SELECT 1 − 2 produces just
Literal UInt64_1 in the EXPLAIN AST output.
---
 lexer/lexer.go                                | 24 ++++++++++++++++---
 .../02869_unicode_minus/metadata.json         |  2 +-
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/lexer/lexer.go b/lexer/lexer.go
index 1159408bf..8f72a46ec 100644
--- a/lexer/lexer.go
+++ b/lexer/lexer.go
@@ -98,6 +98,11 @@ func (l *Lexer) NextToken() Item {
 	if l.ch == '/' && l.peekChar() == '*' {
 		return l.readBlockComment()
 	}
+	// Unicode minus (U+2212) is treated as starting a line comment
+	// ClickHouse doesn't recognize it as an operator
+	if l.ch == '\u2212' {
+		return l.readUnicodeMinusComment()
+	}
 
 	switch l.ch {
 	case '+':
@@ -227,9 +232,6 @@ func (l *Lexer) NextToken() Item {
 		return l.readQuotedIdentifier()
 	case '\u201C', '\u201D': // Unicode curly double quotes " "
 		return l.readUnicodeQuotedIdentifier(l.ch)
-	case '\u2212': // Unicode minus sign −
-		l.readChar()
-		return Item{Token: token.MINUS, Value: "−", Pos: pos}
 	case '`':
 		return l.readBacktickIdentifier()
 	case '@':
@@ -297,6 +299,22 @@ func (l *Lexer) readHashComment() Item {
 	return Item{Token: token.COMMENT, Value: sb.String(), Pos: pos}
 }
 
+// readUnicodeMinusComment reads from a unicode minus (U+2212) to the end of line or semicolon.
+// ClickHouse doesn't recognize unicode minus as an operator, so we treat it as a comment.
+func (l *Lexer) readUnicodeMinusComment() Item {
+	pos := l.pos
+	var sb strings.Builder
+	// Skip −
+	sb.WriteRune(l.ch)
+	l.readChar()
+
+	for l.ch != '\n' && l.ch != ';' && l.ch != 0 && !l.eof {
+		sb.WriteRune(l.ch)
+		l.readChar()
+	}
+	return Item{Token: token.COMMENT, Value: sb.String(), Pos: pos}
+}
+
 func (l *Lexer) readBlockComment() Item {
 	pos := l.pos
 	var sb strings.Builder
diff --git a/parser/testdata/02869_unicode_minus/metadata.json b/parser/testdata/02869_unicode_minus/metadata.json
index ef120d978..0967ef424 100644
--- a/parser/testdata/02869_unicode_minus/metadata.json
+++ b/parser/testdata/02869_unicode_minus/metadata.json
@@ -1 +1 @@
-{"todo": true}
+{}