Rust frontend RTL — println!/format!/vec!/assert!/panic! runtime

• Type: feature — Track B
• Status: backlog
• Owner: —
• Opened: 2026-07-03
• Umbrella: [[feature-rust-frontend]] — sub-ticket 12/12. Depends on [[feature-rust-macro-rules]] (intrinsic recognition, Track A side) and [[feature-rust-misc-semantics]] (format-string parser, Track A side).

What it does

RTL-side bodies backing the builtin-macro intrinsics parsed by [[feature-rust-macro-rules]]:

• println!/eprintln!/format! — call the format-string parser ([[feature-rust-misc-semantics]]) then write to stdout/stderr/build a String, respectively.
• vec! — literal-array-ctor over Vec<T> ([[feature-rust-rtl-core-types]]).
• assert!/assert_eq!/debug_assert! — condition check + panic! with a formatted message on failure.
• panic! — formatted message + abort. Per [[feature-rust-drop-move-tracking]]'s non-goals: ~/nextlevel's Cargo.toml sets panic="abort", so this maps straight to existing Halt/exception machinery — no unwind-and-run-Drop-along-the-stack behavior needed for that target. A future program that doesn't set panic="abort" would need real unwinding — explicitly not this ticket.

Acceptance

• All 6 macros produce correct runtime behavior against the format-string and Vec sub-tickets once those land.
• panic! aborts with the formatted message printed, matching panic="abort" semantics exactly (no partial unwind, no Drop calls during the abort — consistent with the non-goal above).

Log

• 2026-07-09 — println!/print! landed on master (ports-back pass, commit bbd15a52) as parser intrinsics over the shared write machinery — no RTL involved. format!/vec!/assert!/panic! remain open (need string values / dynarrays / halt wiring respectively).

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