在编译时将 this 指针和类方法的参数传递给本地 lambda 函数

假设您有一个场景，当您想要创建一个constexprlambda 在编译时计算某些内容的方法中。

struct A {
    int a;
    constexpr A(int a) : a(a) {}
    constexpr auto operator+(const A& rhs) {
        constexpr auto l = [&]() {
            return A(this->a + rhs.a);
        };
        return l();
    }
};

这段代码无法编译，因为编译器说this and rhs不是常量表达式。有没有办法可以通过this and rhs给当地人constexpr lambda?

You can't capture the a members of this and rhs (by reference) and maintain constexpr validity¹; however, you can pass those members as by (const) reference arguments to your lambda:

struct A {
    int a;
    constexpr A(int a) : a(a) { }
    constexpr auto operator+(const A rhs) {
        constexpr auto l = [](const int& ta, const int& ra) {
            return A(ta + ra);
        };
        return l(a, rhs.a); // Or return l(this->a, rhs.a) if you prefer
    }
};

¹ Or maybe you can, but it's messy: Lambda capture as const reference? https://stackoverflow.com/q/3772867/10871073