An argument is not an integer inside its width, or dest is not a Uint8Array.
start >= end (half-open) or start > end (closed): the reference's assert!.
A signed range longer than its width's MAX: the reference's overflow of end - start.
The full-width early return drew a value the narrower width cannot hold: the reference's unwrap().
A seed or state that is not four u64 words or exactly 32 bytes.
A generator that breaks the RandomNumberGenerator contract.
No Web Crypto API in this environment: the reference's "Failed to seed RNG".
Machine-readable discriminant for a RandError.