Because Delphi doesn't have them and when constraints were implemented they were implemented for Delphi compatibility.
Can they be added? The original announcement ~13 years ago mentioned that those could be added at some point. "object" and "operator X" would be quite useful for me.
I tried to use constraints at some point in my code but they proven too limited in functionality - the biggest issue i faced was that i couldn't use a specialization with a forward declared class (which is the entire point of the forward declaration). For example i have a generic collection that only works on TSerializable subclasses so i gave it that constraint, but in another unit i need to define a specialization for it before it was defined (so the class was available with a forward class declaration) since that specialization also needs to be used by the class itself. In general it seems like having constrained generic work with a tree structure of derived types that use the generic itself is impossible.
Wouldn't storing a list of "specializations to confirm later in this unit" work (with later being when the class is actually defined in the unit)? The language already has forward declarations for a bunch of other things.
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