A variable is declared as string | number and currently narrowed to string. Why may a lat…

A variable is declared as string | number and currently narrowed to string. Why may a later assignment of 42 still compile?

1. Assignments are checked against the declared type, while the observed type can change along control flow.
2. Narrowing permanently changes the declaration to any.
3. Every number is implicitly converted to a string.
4. The assignment is accepted only when strict mode is disabled.