Datatype TypeTag

Types inferred by the flow analysis, represented as type tags.

These type tags are similar to the type tags returned by typeof, except that

• null has type tag null, not object;
• classes have type tag class, not function;
• Date objects have type tag date, not object.

We treat Date objects separately since they have some semantic peculiarities; in particular, their primitive coercion yields a number (not a string, as for most other objects).