FillInto method
Fills a tracked slot of count structs by calling init(i, struct)
which writes directly into the native struct fields.
Implementation
Pointer<T> FillInto(int count, void Function(int, T) init, {String? key}) {
final p = At(_slotKey(key), count);
for (int i = 0; i < count; i++) init(i, indexerFunc(p, i));
return p;
}