Closed
Description
When trying to define HasThisType trait in following form
// this is compile-able code in both Scala and Dotty compilers
type HasThisTypeLoverBounded[PThis] = HasThisType { type This <: PThis }
trait HasThisType {
type This >: this.type <: HasThisTypeLoverBounded[This]
}Dotty compiler crashes when that snippet is grown to several bigger snippets.
(1) While attempting to verify that "that.This#This <: that.This" like
(complete snippet, same snippet with commented problematic lines)
val that: HasThisType = ???
// this line works in both Dotty and Scala
val that1: that.This = that
// this like fails in both Dotty and Scala but in Dotty it also makes compiler runtime crash
val that2: that1.This = that1(2) While trying to define abstract subclass with qualities similar to original HasThisType:
(complete snippet)
// this code is compile-able in Scala while in Dotty it makes compiler runtime crash
type FooLikeTypeLoverBounded[PThis] = FooLike { type This <: PThis }
class FooLike extends HasThisType {
type This >: this.type <: FooLikeTypeLoverBounded[This]
}However simple instantiation/subclassing of such HasThisType is still possible in Dotty:
(complete snippet)
// this code is compile-able in both Scala and Dotty compiler
class Foo extends HasThisType {
type This = Foo
}FYI: positive case (snippet which compiles and works as expected with Scala compiler)
could be found here