FA-11497 / Static analysis soundness / Member archive

Widening retains an escaping lower bound · case 02

Widening retains an escaping lower bound.

Member previewVariant 2 · 3 implementations · 6 checks per implementation

Case contract

Widen finite old and next integer intervals; return [lower,upper], with None representing an unbounded endpoint. Preserve each old bound unless that direction expands.

Why this case matters

A deterministic offline analysis model exposing a specific soundness or precision boundary; it does not implement a complete language analyzer.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
lower expands alone	`[0, 2]`	`[null, 2]`	Failed

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