// Flat AST definition.
final VariantT node = ast.toVariant("Node", false);
ast.concretizeTuples(node, UnitT.TYPE);
printer.indent().p("module ").p(m.name.name).p("Tree").pln(';');
printer.pln();
ast.print(node, printer, true, false, null);
printer.pln();
} else {
// Hierarchical AST definition.