What is `capture type` , is it related to the `in` and `out` variance? If we have a `foo<out Do...

# compiler

[Icyrockton]

What is capture type , is it related to the in and out variance? If we have a foo<out Double>, TypeApproximator will find all the supertypes of Double (i.e. Double -> Number -> Any) and create ConeCapturedType?

[dmitriy.novozhilov]

Captured types are created based on some type projections and represents "some of possible type for this projection"
E.g. if you have class Inv<T>(val x: T) and Inv<out Number>, then type of x may be any inheritor of Number. And if you have two different Inv<out Number> their x both will be some Number inheritor, but not guaranteed that they are same

[dmitriy.novozhilov]

Type definition for different projections:
• Nothing <: Captured(out T) <: T
• T <: Captured(in T) <: Any?