FA-4355 / Container mutation / Member archive

List pop returns value and remainder · case 05

The operation returns a result or retained state that violates this contract: Pop a valid index and return [removed value, remaining list].

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
pop second duplicate	`["a", ["b", "a"]]`	`["a", ["a", "b"]]`	Failed

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