I recently read (and unfortunately forgot where), that the best way to write operator= is like this:

foo &operator=(foo other)
{
    swap(*this, other);
    return *this;
}

instead of this:

foo &operator=(const foo &other)
{
    foo copy(other);
    swap(*this, copy);
    return *this;
}

The idea is that if operator= is called with an rvalue, the first version can optimize away construction of a copy. So when called with a rvalue, the first version is faster and when called with an lvalue the two are equivalent.

I'm curious as to what other people think about this? Would people avoid the first version because of lack of explicitness? Am I correct that the first version can be better and can never be worse?