Fix parsing failure with parenthesis in WHERE clause

parser.go

@@ -2807,14 +2807,42 @@ func (p *Parser) parseFrameSpec() (_ *FrameSpec, err error) {
 	return &spec, nil
 }
 
-func (p *Parser) parseParenExpr() (_ *ParenExpr, err error) {
-	var expr ParenExpr
-	expr.Lparen, _, _ = p.scan()
-	if expr.X, err = p.ParseExpr(); err != nil {
-		return &expr, err
+func (p *Parser) parseParenExpr() (Expr, error) {
+	lparen, _, _ := p.scan()
+
+	// Parse the first expression
+	x, err := p.ParseExpr()
+	if err != nil {
+		return nil, err
 	}
-	expr.Rparen, _, _ = p.scan()
-	return &expr, nil
+
+	// If there's no comma after the first expression, treat it as a normal parenthesized expression
+	if p.peek() != COMMA {
+		rparen, _, _ := p.scan()
+		return &ParenExpr{Lparen: lparen, X: x, Rparen: rparen}, nil
+	}
+
+	// If there's a comma, we're dealing with an expression list
+	var list ExprList
+	list.Lparen = lparen
+	list.Exprs = append(list.Exprs, x)
+
+	for p.peek() == COMMA {
+		p.scan() // consume the comma
+
+		expr, err := p.ParseExpr()
+		if err != nil {
+			return &list, err
+		}
+		list.Exprs = append(list.Exprs, expr)
+	}
+
+	if p.peek() != RP {
+		return &list, p.errorExpected(p.pos, p.tok, "right paren")
+	}
+	list.Rparen, _, _ = p.scan()
+
+	return &list, nil
 }
 
 func (p *Parser) parseCastExpr() (_ *CastExpr, err error) {

simple_test.go

@@ -0,0 +1,18 @@
+package sql
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestSimpleParenList(t *testing.T) {
+	s := `UPDATE table1 SET col1 = 'value' WHERE (col1, col2) = ('a', 'b')`
+	stmt, err := NewParser(strings.NewReader(s)).ParseStatement()
+	if err != nil {
+		t.Fatalf("failed: %v", err)
+	}
+	_, ok := stmt.(*UpdateStatement)
+	if !ok {
+		t.Fatalf("failed: expected UpdateStatement")
+	}
+}

update_test.go

@@ -0,0 +1,37 @@
+package sql
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestUpdate(t *testing.T) {
+	s := `UPDATE asynq_tasks
+SET state='active',
+    pending_since=NULL,
+    affinity_timeout=server_affinity,
+    deadline=iif(task_deadline=0, task_timeout+1687276020, task_deadline)    
+WHERE asynq_tasks.state='pending'
+  AND (task_uuid,
+       ndx,
+       pndx,
+       task_msg,
+       task_timeout,
+       task_deadline)=
+    (SELECT task_uuid,
+            ndx,
+            pndx,
+            task_msg,
+            task_timeout,
+            task_deadline
+     FROM asynq_tasks)
+`
+	stmt, err := NewParser(strings.NewReader(s)).ParseStatement()
+	if err != nil {
+		t.Fatalf("failed: %v", err)
+	}
+	_, ok := stmt.(*UpdateStatement)
+	if !ok {
+		t.Fatalf("failed: expected UpdateStatement")
+	}
+}