Proposal for Opaque Type Aliases

Scala Improvement Process
55

I wish they had gone with inline class instead of the weird opaque type syntax.

inline class MyString(self: String) { def greet = s"hello $self" }

First, it would generally require less boilerplate, and second, it makes more sense conceptually with respect to companion objects: types cannot have companion objects, but classes can. The fact that opaque types are an exception and can have companion objects is fairly ugly.

For the first point, compare:

implicit inline class MyString(self: String) { def greet = s"hello $self" }

With:

opaque type MyString = String
object MyString {
  implicit def apply(self: String): MyString = self
  implied MyStringOps {
    def (self: MyString) greet = s"hello $self"
  }
}
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