Rust frontend RTL — Option<T> / Result<T,E> / Box<T> / Vec<T>

• Type: feature — Track B
• Status: backlog
• Owner: —
• Opened: 2026-07-03
• Umbrella: [[feature-rust-frontend]] — sub-ticket 10/12. Depends on [[feature-rust-match-enum-payload]] (tagged union, for Option/Result) and [[feature-rust-generics-trait-bounds]] (generic specialization).

What it does

Four RTL types, all thin wrappers over machinery Track A already provides once its sub-tickets land — no new compiler primitives, just lib/rtl surface:

• Option<T>/Result<T,E> — RTL-level generic over the new tagged-union type ([[feature-rust-match-enum-payload]]).
• Box<T> — thin wrapper over existing heap alloc, single-owner (no refcount — Drop from [[feature-rust-drop-move-tracking]] handles the free, not a counter).
• Vec<T> — maps directly onto existing dynarray + generic specialization; RTL wrapper supplies the .push/.pop/.len/iterator API surface Rust code expects.

Acceptance

• Option<T>/Result<T,E> round-trip through match correctly (depends on the match sub-ticket landing first).
• Box<T> allocates/frees exactly once per real ownership lifetime, no leak, no double-free (stress-test alongside [[feature-rust-drop-move-tracking]]'s corpus).
• Vec<T> push/pop/index/iterate match Rust's observable semantics (growth need not match Rust's exact capacity-doubling curve — only correctness, not the exact reallocation schedule, is the bar).

Log

• 2026-07-03 — split from [[feature-rust-frontend]] umbrella at ticket-craft time. No code written yet.