Currently, the bounds check in `std::ranges::advance(it, n, s)` is done
_before_ `n` is checked. This results in one extra, unneeded bounds
check.
Thus, `std::ranges::advance(it, 1, s)` currently is _not_ simply
equivalent to:
```c++
if (it != s) {
++it;
}
```
This difference in behavior matters when the check involves some
"expensive" logic. For example, the `==` operator of
`std::istreambuf_iterator` may actually have to read the underlying
`streambuf`.
Swapping around the checks in the `while` results in the expected
behavior.
84ae8cb4af