Intersection Types
TODO: This page is still a fragment. Contributions welcome!
Intersection types can be useful to say, after the fact, that the input must implement two specific interfaces.
# typed: true
extend T::Sig
module I1
def i1; end
end
module I2
def i2; end
end
class C
include I1
include I2
end
class D
include I1
include I2
end
sig {params(x: T.all(I1, I2)).void}
def foo(x)
x.i1
x.i2
end
foo(C.new)
foo(D.new)
This is useful because we don’t have to know ahead of time all the things that
might implement these two interfaces. It also gets around the problem where
we’d have to make a third interface, I12, like this:
module I12
include I1
include I2
end
and include this interface into C and D (because maybe we don’t have
control over what interfaces C and D can include).