FA-4540 / Iterator consumption / Member archive

Islice leaves unrequested tail · case 05

The operation returns a result or retained state that violates this contract: Take at most n values from a one-pass iterator and return [taken,unconsumed tail]; taking zero consumes nothing.

Member previewVariant 5 · 3 implementations · 4 checks per implementation

Case scope

A controlled failure with recorded boundary checks.

Why this case matters

A controlled local-runtime regression for collection APIs, language semantics, or ownership wrappers. Fixtures include boundary and interaction cases.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
bounded prefix	`[["a"], []]`	`[["a"], ["b", "c"]]`	Failed

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