FA-4393 / Mapping semantics / Member archive

Map pop preserves present default value · case 03

The operation returns a result or retained state that violates this contract: Pop a key if present and return [value,remaining map], using fallback only when absent.

Member previewVariant 3 · 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
present value	`["v", {"a": "v"}]`	`["v", {}]`	Failed

MEMBER ARCHIVE

The complete case is available to members.

This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

Member access is invitation-based. Sign in with your invited account to inspect the sources.