Refuses a candidate table the id encoding cannot express (§85; RFC 0005
§3): a pass over it must fail loudly, never wrap an index back to a wrong
node.
A separate, pure function rather than an inline comparison in the backend so
the refusal is testable without constructing 2³² nodes — the backend calls
it with the table it just built; a test calls it with a number.
Refuses a candidate table the id encoding cannot express (§85; RFC 0005 §3): a pass over it must fail loudly, never wrap an index back to a wrong node.
A separate, pure function rather than an inline comparison in the backend so the refusal is testable without constructing 2³² nodes — the backend calls it with the table it just built; a test calls it with a number.