overriding checks should normalise type aliases #144
Description
when reporting a problem with overriding an abstract type with a concrete type, the involved type should be normalised so the error message becomes more explicit
trait Lists { // developed by Func Inc.
type TList[x] <: List[x]
trait List[T]
}
// Our component
trait MyComponent { self: Lists with MyComponent =>
val input: TList[Int]
}
trait SpecialLists extends Lists {
// The following does not type check:
type TList[x <: B] <: BoundedList[x]
trait B
trait BoundedList[T <: B] extends List[T]
}error message:
error: error overriding type TList in trait Lists with bounds [x]>: Nothing <: SpecialLists.this.List[x];
type TList has incompatible type SpecialLists.this.TList[x]
type TList[x <: B] <: BoundedList[x]
^