dart:collection

setRange method

void setRange(int start, int end, Iterable<E> iterable, [ int skipCount = 0 ])

This operation is not supported by an unmodifiable list.

Source

void setRange(int start, int end, Iterable<E> iterable, [int skipCount = 0]) {
  throw new UnsupportedError("Cannot modify an unmodifiable list");
}