Why is declaring isSmallNumber(value): value is number unsafe when it returns false for n…

Why is declaring isSmallNumber(value): value is number unsafe when it returns false for numbers outside -9 through 9?

1. The false branch may still contain a number, but TypeScript can exclude number from the union.
2. Type predicates are allowed only for object types.
3. The compiler converts large numbers to strings in the false branch.
4. A predicate must throw whenever it returns false.