Scala Compiler 2.13.16 - scala.tools.nsc.transform.patmat.PatternExpansion
Keywords: Scala Compiler 2.13.16 scala.tools.nsc.transform.patmat.PatternExpansion

Scala Compiler2.13.16 < Back
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# Packages

-  package root

  The Scala compiler and reflection APIs.

  The Scala compiler and reflection APIs.

  Definition Classes
    root
-  package scala
  Definition Classes
    root
-  package tools
  Definition Classes
    scala
-  package nsc
  Definition Classes
    tools
-  package transform
  Definition Classes
    nsc
-  package patmat
  Definition Classes
    transform
- Debugging
- Interface
- Logic
- MatchAnalysis
- MatchApproximation
- MatchCodeGen
- MatchCps
- MatchOptimization
- MatchTranslation
- MatchTreeMaking
- MatchWarnings
- PatternExpansion
- PatternMatching
- PatternMatchingStats
- ScalaLogic
- Solving
- TreeAndTypeAnalysis

t

scala.tools.nsc.transform.patmat

# PatternExpansion

###

#### trait PatternExpansion extends AnyRef

An 'extractor' can be a case class or an unapply or unapplySeq method.

In a case class, the class is the unextracted type and the fixed and repeated types are derived from its constructor parameters.

In an unapply, this is reversed: the parameter to the unapply is the unextracted type, and the other types are derived based on the return type of the unapply method.

An extractor returns: F1, F2, ..., Fi, opt[Seq[E] or E*] A case matches: P1, P2, ..., Pj, opt[Seq[E]] Put together: P1/F1, P2/F2, ... Pi/Fi, Pi+1/E, Pi+2/E, ... Pj/E, opt[Seq[E]]

Here Pm/Fi is the last pattern to match the fixed arity section.

productArity: the value of i, i.e. the number of non-sequence types in the extractor nonStarArity: the value of j, i.e. the number of non-star patterns in the case definition elementArity: j - i, i.e. the number of non-star patterns which must match sequence elements starArity: 1 or 0 based on whether there is a star (sequence-absorbing) pattern totalArity: nonStarArity + starArity, i.e. the number of patterns in the case definition

Note that productArity is a function only of the extractor, and nonStar/star/totalArity are all functions of the patterns. The key value for aligning and typing the patterns is elementArity, as it is derived from both sets of information.

If elementArity is...

- zero: A perfect match between extractor and the fixed patterns. If there is a star pattern it will match any sequence.
- positive: There are more patterns than products. There will have to be a sequence which can populate at least `elementArity` patterns.
- negative: There are more products than patterns: compile time error.

Source
  PatternExpansion.scala

Linear Supertypes
AnyRef, Any
Known Subclasses
patmat, PatternMatching
Type Hierarchy

Ordering

1. Alphabetic
2. By Inheritance

Inherited

1. PatternExpansion
2. AnyRef
3. Any

Implicitly

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

1. Hide All
2. Show All

Visibility

1. Public
2. Protected

### Type Members

1.  class ExtractorAlignment extends ExtractorSubPatternAlignment
2.  trait ExtractorSubPatternAlignment extends AnyRef

   The arities we can derive looking only at the subpatterns (the args of the unapply node)

### Abstract Value Members

1.  abstract val global: Global

### Concrete 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
     This member is added by an implicit conversion from PatternExpansion toany2stringadd[PatternExpansion] performed by method any2stringadd in scala.Predef.
   Definition Classes
     any2stringadd
4.  def ->[B](y: B): (PatternExpansion, B)
   Implicit
     This member is added by an implicit conversion from PatternExpansion toArrowAssoc[PatternExpansion] 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[lang]
   Definition Classes
     AnyRef
   Annotations
     @throws(classOf[java.lang.CloneNotSupportedException]) @native()
8.  def ensuring(cond: (PatternExpansion) => Boolean, msg: => Any): PatternExpansion
   Implicit
     This member is added by an implicit conversion from PatternExpansion toEnsuring[PatternExpansion] performed by method Ensuring in scala.Predef.
   Definition Classes
     Ensuring
9.  def ensuring(cond: (PatternExpansion) => Boolean): PatternExpansion
   Implicit
     This member is added by an implicit conversion from PatternExpansion toEnsuring[PatternExpansion] performed by method Ensuring in scala.Predef.
   Definition Classes
     Ensuring
10.  def ensuring(cond: Boolean, msg: => Any): PatternExpansion
    Implicit
      This member is added by an implicit conversion from PatternExpansion toEnsuring[PatternExpansion] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
11.  def ensuring(cond: Boolean): PatternExpansion
    Implicit
      This member is added by an implicit conversion from PatternExpansion toEnsuring[PatternExpansion] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
12.  final def eq(arg0: AnyRef): Boolean
    Definition Classes
      AnyRef
13.  def equals(arg0: AnyRef): Boolean
    Definition Classes
      AnyRef → Any
14.  def finalize(): Unit
    Attributes
      protected[lang]
    Definition Classes
      AnyRef
    Annotations
      @throws(classOf[java.lang.Throwable])
15.  final def getClass(): Class[_ <: AnyRef]
    Definition Classes
      AnyRef → Any
    Annotations
      @native()
16.  def hashCode(): Int
    Definition Classes
      AnyRef → Any
    Annotations
      @native()
17.  final def isInstanceOf[T0]: Boolean
    Definition Classes
      Any
18.  final def ne(arg0: AnyRef): Boolean
    Definition Classes
      AnyRef
19.  final def notify(): Unit
    Definition Classes
      AnyRef
    Annotations
      @native()
20.  final def notifyAll(): Unit
    Definition Classes
      AnyRef
    Annotations
      @native()
21.  final def synchronized[T0](arg0: => T0): T0
    Definition Classes
      AnyRef
22.  def toString(): String
    Definition Classes
      AnyRef → Any
23.  def unapplyFormals(fun: Global.Tree, args: List[Global.Tree])(context: Context): List[Global.Type]
24.  final def wait(): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws(classOf[java.lang.InterruptedException])
25.  final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws(classOf[java.lang.InterruptedException])
26.  final def wait(arg0: Long): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws(classOf[java.lang.InterruptedException]) @native()

### Deprecated Value Members

1.  def formatted(fmtstr: String): String
   Implicit
     This member is added by an implicit conversion from PatternExpansion toStringFormat[PatternExpansion] performed by method StringFormat in scala.Predef.
   Definition Classes
     StringFormat
   Annotations
     @deprecated @inline()
   Deprecated

     (Since version 2.12.16) Use `formatString.format(value)` instead of `value.formatted(formatString)`, or use the `f""` string interpolator. In Java 15 and later, `formatted` resolves to the new method in String which has reversed parameters.

2.  def →[B](y: B): (PatternExpansion, B)
   Implicit
     This member is added by an implicit conversion from PatternExpansion toArrowAssoc[PatternExpansion] performed by method ArrowAssoc in scala.Predef.
   Definition Classes
     ArrowAssoc
   Annotations
     @deprecated
   Deprecated

     (Since version 2.13.0) Use `->` instead. If you still wish to display it as one character, consider using a font with programming ligatures such as Fira Code.

### Inherited from AnyRef

### Inherited from Any

### Inherited by implicit conversion any2stringadd fromPatternExpansion to any2stringadd[PatternExpansion]

### Inherited by implicit conversion StringFormat fromPatternExpansion to StringFormat[PatternExpansion]

### Inherited by implicit conversion Ensuring fromPatternExpansion to Ensuring[PatternExpansion]

### Inherited by implicit conversion ArrowAssoc fromPatternExpansion to ArrowAssoc[PatternExpansion]

### Ungrouped