https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108645
--- Comment #1 from Evan Teran <eteran at alum dot rit.edu> ---
To further experiment, i factored out `std::accumulate`:
```
#include <vector>
#include <iostream>
#include <string>
#include <iterator>
void print_v(const char *rem, const std::vector<std::string> &v) {
std::cout << rem;
for (const std::string &s : v)
std::cout << '"' << s << '"' << ' ';
std::cout << '\n';
}
int main() {
std::vector<std::string> v = {"this", "_", "is", "_", "an", "_",
"example"};
print_v("Old contents of the vector: ", v);
std::string concat;
auto first = std::make_move_iterator(v.begin());
auto last = std::make_move_iterator(v.end());
for (; first != last; ++first) {
#if __cplusplus >= 202002L
concat = std::move(concat) + *first;
#else
concat = concat + *first;
#endif
}
print_v("New contents of the vector: ", v);
std::cout << "Concatenated as string: " << '"' << concat << '"' <<
'\n';
}
```
Which results in the same behavior, so it appears to be that the:
```
basic_string operator+(basic_string &&, basic_string &&)
```
Overload doesn't steal the guts of the rhs at all?
But the
```
basic_string operator+(const basic_string &, basic_string &&)
```
overload does?
