Function tw_outcome_located 

pub fn tw_outcome_located(source: &str) -> RunOutcome

tw_outcome, with a failed run’s error LOCATED (see locate_runtime_failure) — same front- end, same interpreter, same error TEXT; this only decides what goes in FRONT of it. A concurrent program (many Interpreter instances, one per task) has no single “the current site” to show, so it falls back to tw_outcome’s own unlocated shape rather than guessing which task’s site to name.