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

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AnyRef → Any
6. final def asInstanceOf[T0]: T0

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Any
7. def clone(): AnyRef

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protected[java.lang]
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AnyRef
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@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

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

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14. def finalize(): Unit

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protected[java.lang]
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@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.
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StringFormat
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@inline()
16. final def getClass(): Class[_]

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17. def hashCode(): Int

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18. final def isInstanceOf[T0]: Boolean

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

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20. final def notify(): Unit

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21. final def notifyAll(): Unit

Definition Classes
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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

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AnyRef
24. def toString(): String

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25. final def wait(): Unit

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AnyRef
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@throws( ... )
26. final def wait(arg0: Long, arg1: Int): Unit

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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