Method accept

src/fl/stl/basic_string.cpp.hpp:50–59

        basic_string* self;
        char* result;
        void accept(NotNullStringHolderPtr& heap) {
            if (heap.get().use_count() > 1) {
                // COW: detach from shared data before returning mutable pointer
                self->mStorage = NotNullStringHolderPtr(
                    fl::make_shared<StringHolder>(heap->data(), self->mLength));
                result = self->heapData()->data();
            } else {
                result = heap->data();
            }
        }
        void accept(ConstLiteral&) {
            self->materialize();
            result = self->hasHeapData() ? self->heapData()->data()