RML002 — a path into a Map, Set or Date

Those hold their contents in internal slots that a copy cannot reach, so a clone of one would look right and throw on first use. They are fine as values — set(new Date()) stores one like any other leaf — but a path cannot descend into one.

Read the value out, rebuild it, and set the result:

const store: { byId: Map<string, { title: string }> } = { byId: new Map() };

focusOn(store).get("byId").set(new Map(store.byId).set(id, { title: "Renamed" }));

Next

• All diagnostics — every code the framework can report.
• Checking your app — the faults proved from the source, before anything runs.