From type/Iterator

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method sink-all(Iterator:D: --> IterationEnd)

Should exhaust the iterator purely for the side-effects of producing the values, without actually saving them in any way. Should always return IterationEnd. If there are no side-effects associated with producing a value, then it can be implemented by a consuming class to be a virtual no-op.

say (1 .. 1000).iterator.sink-all;  # OUTPUT: «IterationEnd␤»

The Iterator role implements this method as a loop that calls pull-one until it is exhausted.