I'm a bit confused about understanding of what type in scala means.
In documents I read that List[Int] is a type and List is a type constructor.
but what keyword type means when I write the following?
val ls: scala.collection.immutable.List.type = scala.collection.immutable.List
And how this type related to type that can be defined as a field in a trait for example.
In type-level programming you’d think of a List[+A] being a type constructor:
That is:
-List[+A] takes a type parameter (A),
-by itself it’s not a valid type, you need to fill in the A somehow - "construct the type",
-by filling it in with String you’d get List[String] which is a concrete type.
In Scala it is not valid to say something is of type List. Scala is more strict here, and won’t allow us to use just a List in the place of a type, as it’s expecting a real type - not a type constructor.
In brief: List[+A] is a type constructor whereas List[String] is a real type.