Add AT TIME ZONE expression parsing

- Add AtTimeZoneCall AST type for AT TIME ZONE expressions
- Add parsePostfixExpression to handle postfix operators
- Support chained AT TIME ZONE expressions
- Enable AtTimeZoneTests130 and Baselines130_AtTimeZoneTests130 tests

Author: claude

ast/at_time_zone.go

@@ -0,0 +1,10 @@
+package ast
+
+// AtTimeZoneCall represents an AT TIME ZONE expression
+type AtTimeZoneCall struct {
+	DateValue ScalarExpression
+	TimeZone  ScalarExpression
+}
+
+func (*AtTimeZoneCall) node()             {}
+func (*AtTimeZoneCall) scalarExpression() {}

parser/marshal.go

@@ -1697,6 +1697,17 @@ func scalarExpressionToJSON(expr ast.ScalarExpression) jsonNode {
 			node["Increment"] = scalarExpressionToJSON(e.Increment)
 		}
 		return node
+	case *ast.AtTimeZoneCall:
+		node := jsonNode{
+			"$type": "AtTimeZoneCall",
+		}
+		if e.DateValue != nil {
+			node["DateValue"] = scalarExpressionToJSON(e.DateValue)
+		}
+		if e.TimeZone != nil {
+			node["TimeZone"] = scalarExpressionToJSON(e.TimeZone)
+		}
+		return node
 	case *ast.BinaryExpression:
 		node := jsonNode{
 			"$type": "BinaryExpression",

parser/parse_select.go

@@ -709,7 +709,7 @@ func (p *Parser) parseAdditiveExpression() (ast.ScalarExpression, error) {
 }
 
 func (p *Parser) parseMultiplicativeExpression() (ast.ScalarExpression, error) {
-	left, err := p.parsePrimaryExpression()
+	left, err := p.parsePostfixExpression()
 	if err != nil {
 		return nil, err
 	}
@@ -726,7 +726,7 @@ func (p *Parser) parseMultiplicativeExpression() (ast.ScalarExpression, error) {
 		}
 		p.nextToken()
 
-		right, err := p.parsePrimaryExpression()
+		right, err := p.parsePostfixExpression()
 		if err != nil {
 			return nil, err
 		}
@@ -741,6 +741,36 @@ func (p *Parser) parseMultiplicativeExpression() (ast.ScalarExpression, error) {
 	return left, nil
 }
 
+// parsePostfixExpression handles postfix operators like AT TIME ZONE
+func (p *Parser) parsePostfixExpression() (ast.ScalarExpression, error) {
+	expr, err := p.parsePrimaryExpression()
+	if err != nil {
+		return nil, err
+	}
+
+	// Check for AT TIME ZONE - only if followed by "TIME"
+	for strings.ToUpper(p.curTok.Literal) == "AT" && strings.ToUpper(p.peekTok.Literal) == "TIME" {
+		p.nextToken() // consume AT
+		p.nextToken() // consume TIME
+		if strings.ToUpper(p.curTok.Literal) != "ZONE" {
+			return nil, fmt.Errorf("expected ZONE after TIME, got %s", p.curTok.Literal)
+		}
+		p.nextToken() // consume ZONE
+
+		timezone, err := p.parsePrimaryExpression()
+		if err != nil {
+			return nil, err
+		}
+
+		expr = &ast.AtTimeZoneCall{
+			DateValue: expr,
+			TimeZone:  timezone,
+		}
+	}
+
+	return expr, nil
+}
+
 func (p *Parser) parsePrimaryExpression() (ast.ScalarExpression, error) {
 	switch p.curTok.Type {
 	case TokenNull:

parser/testdata/AtTimeZoneTests130/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}

parser/testdata/Baselines130_AtTimeZoneTests130/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}