Method setLast

tests/framework/src/doctest.cpp:524–524

void String::setOnHeap() noexcept { *reinterpret_cast<unsigned char*>(&buf[last]) = 128; }
void String::setLast(size_type in) noexcept { buf[last] = char(in); }
void String::setSize(size_type sz) noexcept {
    if (isOnStack()) { buf[sz] = '\0'; setLast(last - sz); }
    else { data.ptr[sz] = '\0'; data.size = sz; }