Add WITH clause support in projection definitions (#116)

Parse and explain WITH clause in ProjectionSelectQuery for CREATE TABLE
statements with projections.

Author: claude

ast/ast.go

@@ -637,6 +637,7 @@ func (p *Projection) End() token.Position { return p.Position }
 // ProjectionSelectQuery represents the SELECT part of a projection.
 type ProjectionSelectQuery struct {
 	Position token.Position   `json:"-"`
+	With     []Expression     `json:"with,omitempty"` // WITH clause expressions
 	Columns  []Expression     `json:"columns"`
 	GroupBy  []Expression     `json:"group_by,omitempty"`
 	OrderBy  []Expression     `json:"order_by,omitempty"` // ORDER BY columns

internal/explain/statements.go

@@ -1914,6 +1914,9 @@ func explainProjection(sb *strings.Builder, p *ast.Projection, indent string, de
 
 func explainProjectionSelectQuery(sb *strings.Builder, q *ast.ProjectionSelectQuery, indent string, depth int) {
 	children := 0
+	if len(q.With) > 0 {
+		children++
+	}
 	if len(q.Columns) > 0 {
 		children++
 	}
@@ -1924,6 +1927,13 @@ func explainProjectionSelectQuery(sb *strings.Builder, q *ast.ProjectionSelectQu
 		children++
 	}
 	fmt.Fprintf(sb, "%sProjectionSelectQuery (children %d)\n", indent, children)
+	// Output WITH clause first
+	if len(q.With) > 0 {
+		fmt.Fprintf(sb, "%s ExpressionList (children %d)\n", indent, len(q.With))
+		for _, w := range q.With {
+			Node(sb, w, depth+2)
+		}
+	}
 	if len(q.Columns) > 0 {
 		fmt.Fprintf(sb, "%s ExpressionList (children %d)\n", indent, len(q.Columns))
 		for _, col := range q.Columns {

parser/parser.go

@@ -7785,6 +7785,12 @@ func (p *Parser) parseProjection() *ast.Projection {
 		Position: p.current.Pos,
 	}
 
+	// Parse WITH clause if present
+	if p.currentIs(token.WITH) {
+		p.nextToken() // skip WITH
+		proj.Select.With = p.parseWithClause()
+	}
+
 	// Parse SELECT keyword (optional in projection)
 	if p.currentIs(token.SELECT) {
 		p.nextToken()

parser/testdata/03340_projections_formatting/metadata.json

@@ -1,6 +1 @@
-{
-  "explain_todo": {
-    "stmt1": true,
-    "stmt4": true
-  }
-}
+{}