What does the underlyingType() represent?

[othercorey]

I'm looking at converting the previous ClassString types I added to psuedo-types. However, I'm not sure how PsuedoType is expected to be used.

underlyingType() returns an empty instance of the type, but False_ and True_ already extend that type. What is the use case for underlyingType()? Is it always supposed to be an empty instance of a type? I'm curious why a type string isn't used instead.

For ClassString which represents a string, but also provides an FQSEN if the class-string includes one, would underlyingType be new String()?

Should psuedo-types always extend the underlying type?

[mvriel]

UnderlyingType is intended for pseudo-types to represent what type or primitive they really are. PseudoTypes are userland constructs that are in reality a primitive (ClassString is a string for example) and UnderlyingType helps parsers, resolvers and analyzers to better validate that type because they can match it to a value.

For example, an analyzer that would want to check if the pseudotype False is a boolean would need to keep track of a list of all pseudotypes and their real types.

This feature has not been applied to all PseudoTypes yet; that is something we intend to expand on or accept Pull Requests to help us with

[othercorey]

How about this question specifically?

Should psuedo-types always extend the underlying type?

[mvriel]

The PseudoTypes classes are designed to extend an underlying type; this mechanism was introduced so that consumers can use instanceof calls to check for the actual type and by choosing which class to instanceof-check you can define your own specificity.

[othercorey]

Ok, I can do that.

I'm still a little confused why underlyingType exists if you can always do an instanceof check on the PsuedoType itself since it extends the same underlying type.

[jaapio]

In case of a String this is very clear. but what about a Collection with a certain key and value? Types can be very complex :-)

[othercorey]

Ok, so psuedo types can just implement PsuedoType without having to extend the underlying type. That should work for me.

[mvriel]

Also: you can do an instanceof; but not use the toString; underlyingType exposes that too

[mvriel]

Ok, so psuedo types can just implement PsuedoType without having to extend the underlying type. That should work for me.

If at all possible; I would prefer it to extend if it has a real world counterpart; such as String for ClassString; mixed would be more difficult but since recently it is a real type