FA-4719 / Scoped mappings / Member archive

Chainmap write always top scope · case 04

The operation returns a result or retained state that violates this contract: Assignment always writes the first scope, even when the key exists only in an outer scope; return all scopes.

Member previewVariant 4 · 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
shadow outer binding	`[{}, {"a": 2}]`	`[{"a": 2}, {"a": 1}]`	Failed

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

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