FA-43602 / Borrow checking / Member archive

A borrowed trait object defaults to a lifetime unrelated to its outer reference · case 02

A borrowed trait object defaults to a lifetime unrelated to its outer reference.

Member previewVariant 2 · 3 implementations · 21 checks per implementation

Case contract

Check erased borrowed trait objects in a stipulated object calculus. Erasure retains referent lifetime and ownership capability; default object bound inside reference inherits reference bound; object method return aliases must be represented in the vtable summary; mutable methods require exclusive object access; upcasting cannot enlarge lifetime or change data-address provenance; thin conversion cannot discard lifetime metadata; associated borrowed output includes owner lifetime; object-safe methods cannot expose a locally quantified lifetime as an unbound output; dynamic destruction observes declared borrowed fields. Input is a fully explicit descriptor of the stated toy IR. Return rule identifiers in declaration order; absent optional obligations use the provided neutral defaults. No rule is an assertion about a production language.

Why this case matters

A finite offline static-analysis model of ownership and borrowing; it does not execute the analyzed program.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
reference-default-bound regression 0	`[]`	`["reference-default-bound"]`	Failed

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