FA-44009 / Borrow checking / Member archive

Array-to-slice borrow omits the final owned element · case 04

Array-to-slice borrow omits the final owned element.

Member previewVariant 4 · 3 implementations · 21 checks per implementation

Case contract

Check reference coercion proof steps. Unique-to-shared freeze is one-way; unsizing preserves owner; trait unsizing retains metadata; array-to-slice length equals array extent; nested mutable references cannot shorten inner lifetime; shared outer references may shorten; deref coercion records every intermediate loan; implicit coercion cannot execute a moving deref; reification of a borrowed function pointer preserves captured lifetimes; never-type branch coercion contributes no invented loan. 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
array-slice-extent regression 0	`[]`	`["array-slice-extent"]`	Failed

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