Method swap

common/expr.h:544–548

  ABSL_MUST_USE_RESULT std::vector<StructExprField> release_fields();

  friend void swap(StructExpr& lhs, StructExpr& rhs) noexcept {
    using std::swap;
    swap(lhs.name_, rhs.name_);
    swap(lhs.fields_, rhs.fields_);
  }

 private:
  friend class Expr;