Special types (Self, Super)

Self represents its own type. You can just use it as an alias, but note that the meaning changes in derived types (refers to the own type).

C = Class()
    new_self() = Self. new()
    new_c() = C.new()
D = Inherit C

classof D. new_self() # D
classof D. new_c() # C

Super represents the type of the base class. The method itself refers to the base class, but the instance uses its own type.

C = Class()

D = Inherit(C)
    new_super() = Super.new()
    new_c() = C.new()

classof D. new_super() # D
classof D. new_c() # C

special type variables

Self and Super can be used as type variables in structured types and traits. This refers to classes that are subtypes of that type. That is, Self in type T means Self <: T.

Add R = Trait {
    .AddO = Type
    .`_+_`: Self, R -> Self.AddO
ClosedAdd = Subsume Add(Self)

ClosedAddForInt = Patch(Int, Impl := ClosedAdd)
    AddO = Int

assert 1 in Add(Int, Int)
assert 1 in ClosedAdd
assert Int < Add(Int, Int)
assert Int < ClosedAdd