scala.tools.nsc.typechecker

# Checkable

#### trait Checkable extends AnyRef

On pattern matcher checkability:

Consider a pattern match of this form: (x: X) match { case _: P => }

There are four possibilities to consider: [P1] X will always conform to P [P2] x will never conform to P [P3] X <: P if some runtime test is true [P4] X cannot be checked against P

The first two cases correspond to those when there is enough static information to say X <: P or that (x ∈ X) ⇒ (x ∉ P). The fourth case includes unknown abstract types or structural refinements appearing within a pattern.

The third case is the interesting one. We designate another type, XR, which is essentially the intersection of X and |P|, where |P| is the erasure of P. If XR <: P, then no warning is emitted.

Examples of how this info is put to use: sealed trait A[T] ; class B[T] extends A[T] def f(x: B[Int]) = x match { case _: A[Int] if true => } def g(x: A[Int]) = x match { case _: B[Int] => }

`f` requires no warning because X=B[Int], P=A[Int], and B[Int] <:< A[Int]. `g` requires no warning because X=A[Int], P=B[Int], XR=B[Int], and B[Int] <:< B[Int]. XR=B[Int] because a value of type A[Int] which is tested to be a B can only be a B[Int], due to the definition of B (B[T] extends A[T].)

This is something like asSeenFrom, only rather than asking what a type looks like from the point of view of one of its base classes, we ask what it looks like from the point of view of one of its subclasses.

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  Analyzer

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Analyzer, Duplicator, Duplicators, Erasure, Infer, SpecializationDuplicator, TreeCheckers, erasure, treeChecker
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Implicitly

1. by any2stringadd
2. by StringFormat
3. by Ensuring
4. by ArrowAssoc

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### Type Members

1. #### trait InferCheckable extends AnyRef

### Value Members

1. #### final def !=(arg0: Any): Boolean

   Definition Classes
     AnyRef → Any

2. #### final def ##(): Int

   Definition Classes
     AnyRef → Any

3. #### def +(other: String): String

   Implicit information
     This member is added by an implicit conversion from Checkable to any2stringadd[Checkable] performed by method any2stringadd in scala.Predef.
   Definition Classes
     any2stringadd

4. #### def ->[B](y: B): (Checkable, B)

   Implicit information
     This member is added by an implicit conversion from Checkable to ArrowAssoc[Checkable] performed by method ArrowAssoc in scala.Predef.
   Definition Classes
     ArrowAssoc
   Annotations
     @inline()

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

   Definition Classes
     AnyRef → Any

6. #### final def asInstanceOf[T0]: T0

   Definition Classes
     Any

7. #### def clone(): AnyRef

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

8. #### def ensuring(cond: (Checkable) ⇒ Boolean, msg: ⇒ Any): Checkable

   Implicit information
     This member is added by an implicit conversion from Checkable to Ensuring[Checkable] performed by method Ensuring in scala.Predef.
   Definition Classes
     Ensuring

9. #### def ensuring(cond: (Checkable) ⇒ Boolean): Checkable

   Implicit information
     This member is added by an implicit conversion from Checkable to Ensuring[Checkable] performed by method Ensuring in scala.Predef.
   Definition Classes
     Ensuring

10. #### def ensuring(cond: Boolean, msg: ⇒ Any): Checkable

    Implicit information
      This member is added by an implicit conversion from Checkable to Ensuring[Checkable] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring

11. #### def ensuring(cond: Boolean): Checkable

    Implicit information
      This member is added by an implicit conversion from Checkable to Ensuring[Checkable] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring

12. #### final def eq(arg0: AnyRef): Boolean

    Definition Classes
      AnyRef

13. #### def equals(arg0: Any): Boolean

    Definition Classes
      AnyRef → Any

14. #### def finalize(): Unit

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

15. #### def formatted(fmtstr: String): String

    Implicit information
      This member is added by an implicit conversion from Checkable to StringFormat[Checkable] performed by method StringFormat in scala.Predef.
    Definition Classes
      StringFormat
    Annotations
      @inline()

16. #### final def getClass(): Class[_]

    Definition Classes
      AnyRef → Any

17. #### def hashCode(): Int

    Definition Classes
      AnyRef → Any

18. #### final def isInstanceOf[T0]: Boolean

    Definition Classes
      Any

19. #### final def ne(arg0: AnyRef): Boolean

    Definition Classes
      AnyRef

20. #### final def notify(): Unit

    Definition Classes
      AnyRef

21. #### final def notifyAll(): Unit

    Definition Classes
      AnyRef

22. #### def propagateKnownTypes(from: Global.Type, to: Global.Symbol): Global.Type

    The applied type of class 'to' after inferring anything possible from the knowledge that 'to' must also be of the type given in 'from'.

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

    Definition Classes
      AnyRef

24. #### def toString(): String

    Definition Classes
      AnyRef → Any

25. #### final def wait(): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

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

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

27. #### final def wait(arg0: Long): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

28. #### def →[B](y: B): (Checkable, B)

    Implicit information
      This member is added by an implicit conversion from Checkable to ArrowAssoc[Checkable] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
      ArrowAssoc

### Inherited from AnyRef

### Inherited from Any

### Inherited by implicit conversion any2stringadd from Checkable to any2stringadd[Checkable]

### Inherited by implicit conversion StringFormat from Checkable to StringFormat[Checkable]

### Inherited by implicit conversion Ensuring from Checkable to Ensuring[Checkable]

### Inherited by implicit conversion ArrowAssoc from Checkable to ArrowAssoc[Checkable]

### Ungrouped