milessabin

scala> class Foo { self: Singleton => }
defined class Foo

scala> class Bar extends Foo
<console>:12: error: illegal inheritance;
 self-type Bar does not conform to Foo's selftype Foo with Singleton
       class Bar extends Foo
                         ^

scala> object Bar extends Foo

milessabin

import scala.language.higherKinds

object cats {
  trait Show[A] {
    def apply(x: A): String
  }

  object Show {
    implicit def stringShow: Show[String] = new Show[String] {
      def apply(x: String): String = x

milessabin

scala> trait Label[T] { val value: Boolean }
defined trait Label

scala> def mkInstance(s: String, v: Boolean): Label[s.type] = new Label[s.type] { val value = v }
mkInstance: (s: String, v: Boolean)Label[s.type]

scala> implicit def lTrue = mkInstance("True", true)
lTrue: Label[String("True")]

scala> implicit def lFalse = mkInstance("False", false)

milessabin

miles@frege:~$ ./shapeless.sh 
Loading...
Welcome to the Ammonite Repl 0.5.2
(Scala 2.11.7 Java 1.8.0_51)
@ val l = 23 :: "foo" :: true :: HNil
l: Int :: String :: Boolean :: HNil = ::(23, ::("foo", ::(true, HNil)))
@

milessabin

sealed trait Dec[+T]
final case class Yes[T](t: T) extends Dec[T]
final case object No extends Dec[Nothing]

object Dec extends Dec0 {
  implicit def yes[T](implicit t: T): Dec[T] = Yes(t)
}

trait Dec0 {
  implicit def no[T]: Dec[T] = No

milessabin

```scala
object Foo {
  bar
}
```

milessabin

[info]  published shapeless_sjs0.6_2.12.0-M3 to https://oss.sonatype.org/service/local/staging/deploy/maven2/com/chuusai/shapeless_sjs0.6_2.12.0-M3/2.3.0-RC4/shapeless_sjs0.6_2.12.0-M3-2.3.0-RC4.jar
[success] Total time: 106 s, completed 23-Feb-2016 16:54:42
[info] Setting scala version to 2.11.7
[info] Set current project to root (in build file:/home/miles/projects/shapeless/)
[info] Setting version to '2.3.0-SNAPSHOT'.
[info] Reapplying settings...
[info] Set current project to root (in build file:/home/miles/projects/shapeless/)
[info] [master f0e0f6c] Setting version to 2.3.0-SNAPSHOT
[info]  1 file changed, 1 insertion(+), 1 deletion(-)
Push changes to the remote repository (y/n)? [y] y

milessabin

import shapeless._
import ops.hlist.Tupler

trait TupleGeneric[C <: Product] extends Serializable {
  type Repr <: Product

  def to(t : C) : Repr

  def from(r : Repr) : C
}

milessabin

import shapeless._
import ops._
import coproduct._

object coproducttest {

  type U = Int :+: String :+: CNil

  type V = Double :+: List[Int] :+: CNil

milessabin

import shapeless._, ops.function._, ops.hlist._

trait Bar {

  trait Wrapper { type T }
  case class A[U]() extends Wrapper { type T = U }

  trait Unwrapper {
    type Args <: HList
    type F[R] = Args => R