Better newtypes for Scala based on the following two articles:
addCompilerPlugin("org.scalameta" % "paradise" % "3.0.0-M10" cross CrossVersion.full) resolvers += Resolver.bintrayRepo("alexknvl", "maven") libraryDependencies += "com.alexknvl" %% "newtypes" % "0.3.0"Use this fork of scalameta/paradise until https://github.com/scalameta/paradise/pull/207 is merged in if you need companion object support and can't use paradise-3.0.0-M10 (it supports only 2.12.3+). Clone it and publishM2 in sbt, then change the paradise plugin to:
addCompilerPlugin("org.scalameta" % "paradise" % "3.0.0-alex" cross CrossVersion.full)| Features | AnyVal | @newtypes.opaque | @newtypes.translucent |
|---|---|---|---|
isInstanceOf | Yes | No | No |
Generics box AnyRef subtypes | Yes | No | No |
| Generics box primitives | Yes | Yes | Yes |
| Primitives box | No | Yes | No |
| Up-cast works | No | No | Yes |
| Down-cast works | No | No | No |
| Any methods | Yes | Yes | Yes |
| Overrides | Yes | No | No |
| Virtual dispatch | Yes | No | No |
| Typeclass-based dispatch | Yes | Yes | Yes |
Wrap List elements | O(N) | O(1) (using subst) | O(1) (using subst) |
Unwrap List elements | O(N) | O(1) (using subst and Is) | O(1) (automatic widening) |
| Supports HK parameters | Yes | Yes | Yes |
| Supports existential parameters | Yes | Yes | Yes |
@opaque type ArrayWrapper[A] = Array[A] @translucent type Flags = Intbecomes
type ArrayWrapper[A] = ArrayWrapper.Type[A] object ArrayWrapper { type Base$$1 trait Tag$$1 extends Any type Type[A] <: Base$$1 with Tag$$1 object Impl { def apply[A](value: Array[A]): Type[A] = value.asInstanceOf[Type[A]] def unwrap[A](value: Type[A]): Array[A] = value.asInstanceOf[Array[A]] def subst[F[_], A](value: F[Array[A]]): F[Type[A]] = value.asInstanceOf[F[Type[A]]] } } type Flags = Flags.Type object Flags { trait Tag$$1 extends Any type Type <: Int with Tag$$1 object Impl { def apply(value: Int): Type = value.asInstanceOf[Type] def unwrap(value: Type): Int = value.asInstanceOf[Int] def subst[F[_]](value: F[Int]): F[Type] = value.asInstanceOf[F[Type]] } }Code is provided under the MIT license available at https://opensource.org/licenses/MIT, as well as in the LICENSE file.