bsl::basic_string<char16_t>::assign

Assign to this string the value of the specified replacement string, propagate to this object the allocator of replacement if the ALLOCATOR type has trait propagate_on_container_move_assignment, and return a reference providing modifiable access to this string. The content of replacement is moved (in constant time) to this string if get_allocator() == rhs.get_allocator() (after accounting for the aforementioned trait). replacement is left in a valid but unspecified state. Note that this method has exactly the same behavior as the corresponding operator=.