Macro thread_local_content_memo 

macro_rules! thread_local_content_memo {
    (
        $(#[$meta:meta])*
        $STATIC:ident : $K:ty => $V:ty ;
        fn $get:ident ;
        fn $clear:ident ;
    ) => { ... };
}

Declare a thread-local ContentMemo plus a memoized accessor and a clear fn — the boilerplate that was hand-rolled at every memo site. Real-easy front: one declaration replaces the thread_local! + get_or_compute wrapper + clear wrapper trio.

use sui_intern::thread_local_content_memo;
use std::collections::HashSet;

thread_local_content_memo! {
    /// referenced idents per (source-id, text-range)
    REFERENCED_IDENTS: (u32, rnix::TextRange) => HashSet<smol_str::SmolStr>;
    fn referenced_idents_memo;   // accessor: (key, || compute) -> Rc<V>
    fn clear_referenced_idents;  // clear the memo (per top-level eval)
}

// hit-or-compute (byte-neutral: value is a pure fn of the key):
let set = referenced_idents_memo(key, || walk_and_collect(expr));
// reset at the eval boundary:
clear_referenced_idents();