shapeless

the

object the extends Dynamic

An enhanced alternative to Predef.implicitly.

Used as a term the[T] yields the unique implicit value of type T in the current implicit scope, if any. It is a compile time error if there is no such value. Its primary advantage over Predef.implicitly is that it will preserve any refinement that the implicit definition has, resulting in more precisely typed, and hence often more useful, values,

scala> trait Foo { type T ; val t: T }
defined trait Foo

scala> implicit val intFoo: Foo { type T = Int } = new Foo { type T = Int ; val t = 23 }
intFoo: Foo{type T = Int} = $anon$1@6067b682

scala> implicitly[Foo].t  // implicitly loses precision
res0: Foo#T = 23

scala> implicitly[Foo].t+13
<console>:13: error: type mismatch;
 found   : Int(13)
 required: String
              implicitly[Foo].t+13
                                ^

scala> the[Foo].t         // the retains it
res1: Int = 23

scala> the[Foo].t+13
res2: Int = 36

Unlike implicitly, the can also be used in type position, thanks to a trick due to Denys Shabalin (@den_sh) and Eugene Burmako (@xeno_by). Here we use a combination of selectDynamic and backticks to embed a type in a path which appears to the compiler as stable,

scala> val i: implicitly[Foo].T = 23  // syntax error
<console>:1: error: ';' expected but '.' found.
       val i: implicitly[Foo].T = 23
                             ^
scala> val i: the.`Foo`.T = 23        // OK
i: Int = 23
Linear Supertypes
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  1. final def !=(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef

  2. final def !=(arg0: Any): Boolean

    Definition Classes
    Any

  3. final def ##(): Int

    Definition Classes
    AnyRef → Any

  4. final def ==(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef

  5. final def ==(arg0: Any): Boolean

    Definition Classes
    Any

  6. def apply[T](implicit t: T): T

    Annotations
    @macroImpl( ... )

  7. final def asInstanceOf[T0]: T0

    Definition Classes
    Any

  8. def clone(): AnyRef

    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )

  9. final def eq(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef

  10. def equals(arg0: Any): Boolean

    Definition Classes
    AnyRef → Any

  11. def finalize(): Unit

    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] )

  12. final def getClass(): Class[_]

    Definition Classes
    AnyRef → Any

  13. def hashCode(): Int

    Definition Classes
    AnyRef → Any

  14. final def isInstanceOf[T0]: Boolean

    Definition Classes
    Any

  15. final def ne(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef

  16. final def notify(): Unit

    Definition Classes
    AnyRef

  17. final def notifyAll(): Unit

    Definition Classes
    AnyRef

  18. def selectDynamic(tpeSelector: String): Any

    Annotations
    @macroImpl( ... )

  19. final def synchronized[T0](arg0: ⇒ T0): T0

    Definition Classes
    AnyRef

  20. def toString(): String

    Definition Classes
    AnyRef → Any

  21. final def wait(): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws( ... )

  22. final def wait(arg0: Long, arg1: Int): Unit

    Definition Classes
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    @throws( ... )

  23. final def wait(arg0: Long): Unit

    Definition Classes
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    @throws( ... )

Inherited from Dynamic

Inherited from AnyRef

Inherited from Any

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