all: use the new types with old syntax (#6922)

vlib/v/doc/doc.v

@@ -122,7 +122,7 @@ pub fn (mut d Doc) stmt(stmt ast.Stmt, filename string) ?DocNode {
 	if node.name.len == 0 && node.comment.len == 0 && node.content.len == 0 {
 		return error('empty stmt')
 	}
-	match stmt {
+	match union stmt {
 		ast.ConstDecl {
 			node.kind = .const_group
 			node.parent_name = 'Constants'

vlib/v/doc/utils.v

@@ -77,7 +77,7 @@ fn (mut d Doc) convert_pos(filename string, pos token.Position) DocPos {
 }
 
 pub fn (mut d Doc) stmt_signature(stmt ast.Stmt) string {
-	match stmt {
+	match union stmt {
 		ast.Module {
 			return 'module $stmt.name'
 		}
@@ -93,9 +93,9 @@ pub fn (mut d Doc) stmt_signature(stmt ast.Stmt) string {
 }
 
 pub fn (d Doc) stmt_name(stmt ast.Stmt) string {
-	match stmt {
+	match union stmt {
 		ast.FnDecl, ast.StructDecl, ast.EnumDecl, ast.InterfaceDecl { return stmt.name }
-		ast.TypeDecl { match stmt {
+		ast.TypeDecl { match union stmt {
 				ast.SumTypeDecl, ast.FnTypeDecl, ast.AliasTypeDecl, ast.UnionSumTypeDecl { return stmt.name }
 			} }
 		ast.ConstDecl { return '' } // leave it blank