Hello,

With MSVC, the following code compiles. The char overload is selected by overload resolution.

struct S
{
	operator int() const & { return 0; }
	operator char() && { return 0; }
};

void foo(int) {}
void foo(char) {}

int main()
{
	foo(S{}); //OK, calls 'void foo(char)'. 
}

However, the following code won't compile.

struct S
{
	int i = 0;
	operator const int &() const & { return i; }
	operator int &&() && { return (int &&)(i); }
};

void foo(const int &) {}
void foo(int &&) {}

int main()
{
	foo(S{}); //error C2668: 'foo': ambiguous call to overloaded function
                  //message : could be 'void foo(int &&)'
                  //message : or       'void foo(const int &)'
}

What is exactly the difference that makes the second sample fail to compile?

Given that 'operator int &&() &&' is an exact match to the conversion required to call 'void foo(int &&)', I expected the compiler to select it. It is strange if the C++ rules will not allow the compiler to select a conversion function that exactly matches the required conversion, both in terms of the provided argument 'S &&' and the result of conversion 'int &&'.

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