Function guards_without_terms 

pub fn guards_without_terms<'a>(
    consequences: &'a [Consequence],
    terms: &[Term],
) -> Vec<&'a str>

Guards that name a value the vocabulary doesn’t have — a lint, run when an embedder loads its schema, not part of validation.

A guard is silent when it is wrong: Consequence::when("none", …) against a vocabulary spelling it off simply never fires, and the user commits the expensive change with no warning at all. Nothing else in the crate can notice, because a guard that matches nothing is indistinguishable from a guard for a value the user hasn’t chosen yet.

Only Some(Value::Str(_)) guards are checked: an unguarded consequence has no value to look up, and a bool or numeric guard is not a vocabulary term. A retired term counts as present — it is still a known value, and warning about one is exactly what a retirement wants.

use fig_schema::{Consequence, Term, guards_without_terms};

let terms = [Term::value("off"), Term::value("registry")];
let declared = [
    Consequence::when("none", "History will be discarded."),
    Consequence::when("off", "History will be discarded."),
];
assert_eq!(guards_without_terms(&declared, &terms), vec!["none"]);