FA-43947 / Borrow checking / Member archive

A lending item remains usable across the next iterator call · case 02

A lending item remains usable across the next iterator call.

Member previewVariant 2 · 3 implementations · 21 checks per implementation

Case contract

Check iterator lifetime summaries. Yielded shared items borrow backing storage; lending items borrow the iterator until next call; mutable yields must have disjoint element footprints; next consumes the prior lending-item loan; double-ended iteration cannot yield a crossed element twice; chunked iteration retains remainder ownership; adapter closures cannot extend item lifetime; collection of lending references cannot outlive iteration; empty iterator yields no loan; iterator destruction releases its backing borrow but not independently owned items. 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
lending-call-bound regression 0	`[]`	`["lending-call-bound"]`	Failed

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