删除所有左值转换运算符 [英] Deleting all lvalue conversion operators

问题描述

我想避免所有左值从一种类型转换为另一种类型:

I want to avoid all lvalue conversions from a type to another type:

struct A
{};

struct T
{
    A a;
    operator A() { return a; }
    //operator A&() = delete; how to delete lvalue conversions to A?
};

void bar(A)
{}

void foo(const A&)
{}

void foo2(A&)
{}

int main()
{
    T t;

    bar(t); // fine
    foo(t); // should never convert to ref-to-const A
    foo2(t); // should never convert to ref-to A

    return 0;
}

这可能吗?我需要如何以及删除哪些转换运算符?

Is this possible? How and which conversion operators do I need to delete?

godbolt

推荐答案

您可能会

struct T
{
    A a;
    operator A() { return a; }
    
    template <typename T> operator const T&() = delete;
};

演示

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