Otherwise, the following code would not compile:
constexpr Array<int, 3> array { 4, 5, 6 };
Vector<int> vector { 4, 5, 6 };
if (array == vector.span()) { }
We do such comparisons in tests quite a bit. But it currently doesn't
become an issue because of the way EXPECT_EQ copies its input parameters
to non-const locals. In a future patch, that copying will be removed,
and the compiler would otherwise complain about not finding a suitable
comparison operator.