docs: function renderExpressionMemoized(expr, traverse, path, state) {
    var evaluated;
    if (expr.type === Syntax.Identifier) {
      evaluated = expr.name;
    } else if (isString(expr)) {
      evaluated = expr;
    } else {
      evaluated = genID('var');
      utils.append(evaluated + ' = ', state);
      render(expr, traverse, path, state);
  
      utils.append(', ', state);
    }
    return evaluated;
  }