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Constraining trait type parameters via a super class type parameter constraint ... different instances along different paths
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| import cats.{Applicative, Monad} | |
| import cats.implicits._ | |
| abstract class Foo[+M[_[_]], F[_]](implicit val M: M[F]) | |
| trait Bar[F[_]] extends Foo[Applicative, F] { def bar = Applicative[F] } | |
| trait Baz[F[_]] extends Foo[Monad, F] { def baz = Monad[F] } | |
| class User[F[_]: Monad] extends Bar[F] with Baz[F] | |
| object Test { | |
| val u = new User[List] | |
| u.bar: Applicative[List] | |
| u.baz: Monad[List] | |
| } | |
| // scala> val u = new User[List] | |
| // val u: constrain.User[List] = constrain.User@5a70669f | |
| // | |
| // scala> u.bar | |
| // val res0: cats.Applicative[List] = cats.instances.ListInstances$$anon$1@577b462b | |
| // | |
| // scala> u.baz | |
| // val res1: cats.Monad[List] = cats.instances.ListInstances$$anon$1@577b462b |
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