FA-44093 / Borrow checking / Member archive

Aggregate lowering reorders a borrow before its owner-producing field expression · case 03

Aggregate lowering reorders a borrow before its owner-producing field expression.

Member previewVariant 3 · 3 implementations · 21 checks per implementation

Case contract

Validate lowering of aggregate expressions containing owned and borrowed fields. Evaluation order follows source field order; struct update moves only omitted fields; explicit fields override update sources; failed construction drops initialized fields in reverse initialization order; borrowed fields preserve their source origin; spread cannot duplicate exclusive fields; tuple projection indices remain positional; enum payload loans require matching discriminant; moving an aggregate remaps every contained reference owner slot; zero-field aggregates create no synthetic borrowed field. 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
field-evaluation-order regression 0	`[]`	`["field-evaluation-order"]`	Failed

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