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

Scala Compiler2.13.16 < Back


# 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

# PatternMatching

###

#### trait PatternMatching extends SubComponent with Transform with TypingTransformers with Debugging with Interface with MatchTranslation with MatchTreeMaking with MatchCodeGen with MatchCps with ScalaLogic with Solving with MatchAnalysis with MatchOptimization with MatchWarnings with PatternExpansion

Translate pattern matching.

Either into optimized if/then/else's, or virtualized as method calls (these methods form a zero-plus monad), similar in spirit to how for-comprehensions are compiled.

For each case, express all patterns as extractor calls, guards as 0-ary extractors, and sequence them using `flatMap` (lifting the body of the case into the monad using `one`).

Cases are combined into a pattern match using the `orElse` combinator (the implicit failure case is expressed using the monad's `zero`).

TODO:

- DCE (on irrefutable patterns)
- update spec and double check it's implemented correctly (see TODO's)

(longer-term) TODO:

- user-defined unapplyProd
- recover GADT typing by locally inserting implicit witnesses to type equalities derived from the current case, and considering these witnesses during subtyping (?)
- recover exhaustivity/unreachability of user-defined extractors by partitioning the types they match on using an HList or similar type-level structure

Source
  PatternMatching.scala

Linear Supertypes
PatternExpansion, MatchWarnings, MatchOptimization, MatchAnalysis, MatchApproximation, Solving, ScalaLogic, TreeAndTypeAnalysis, Logic, MatchCps, MatchTreeMaking, MatchCodeGen, MatchTranslation, Interface, TreeDSL, Debugging, TypingTransformers, Transform, SubComponent, AnyRef, Any
Known Subclasses
patmat
Type Hierarchy

Ordering

1. Alphabetic
2. By Inheritance

Inherited

1. PatternMatching
2. PatternExpansion
3. MatchWarnings
4. MatchOptimization
5. MatchAnalysis
6. MatchApproximation
7. Solving
8. ScalaLogic
9. TreeAndTypeAnalysis
10. Logic
11. MatchCps
12. MatchTreeMaking
13. MatchCodeGen
14. MatchTranslation
15. Interface
16. TreeDSL
17. Debugging
18. TypingTransformers
19. Transform
20. SubComponent
21. AnyRef
22. 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.  abstract class StdPhase extends GlobalPhase

   A standard phase template

   A standard phase template

   Definition Classes
     SubComponent
2.  class Phase extends StdPhase

   The phase defined by this transform

   The phase defined by this transform

   Definition Classes
     Transform
3.  abstract class ThicketTransformer extends TypingTransformer

   A base class for typing transformers that need to perform "thicket expansion".

   A base class for typing transformers that need to perform "thicket expansion". A thicket is the output of a transformation that is flattened into the enclosing block.

   Definition Classes
     TypingTransformers
4.  abstract class TypingTransformer extends Global.AstTransformer
   Definition Classes
     TypingTransformers
5.  trait MatchMonadInterface extends AnyRef
   Definition Classes
     Interface
6.  trait TypedSubstitution extends MatchMonadInterface
   Definition Classes
     Interface
7.  trait PropositionalLogic extends AnyRef
   Definition Classes
     Logic
8.  trait MatchAnalyzer extends MatchApproximator
   Definition Classes
     MatchAnalysis
9.  trait MatchApproximator extends TreeMakers with TreesAndTypesDomain

   Represent a match as a formula in propositional logic that encodes whether the match matches (abstractly: we only consider types)

   Represent a match as a formula in propositional logic that encodes whether the match matches (abstractly: we only consider types)

   Definition Classes
     MatchApproximation
10.  trait CodegenCore extends MatchMonadInterface
    Definition Classes
      MatchCodeGen
11.  trait OptimizedCodegen extends CodegenCore with TypedSubstitution with MatchMonadInterface
    Definition Classes
      MatchCodeGen
12.  trait CommonSubconditionElimination extends OptimizedCodegen with MatchApproximator
    Definition Classes
      MatchOptimization
13.  trait MatchOptimizer extends OptimizedCodegen with SwitchEmission with CommonSubconditionElimination
    Definition Classes
      MatchOptimization
14.  trait SwitchEmission extends TreeMakers with MatchMonadInterface
    Definition Classes
      MatchOptimization
15.  trait MatchTranslator extends PatternMatching.TreeMakers with PatternMatching.TreeMakerWarnings
    Definition Classes
      MatchTranslation
16.  final case class Suppression extends Product with Serializable
    Definition Classes
      MatchTreeMaking
17.  trait TreeMakers extends TypedSubstitution with CodegenCore
    Definition Classes
      MatchTreeMaking
18.  trait TreeMakerWarnings extends AnyRef
    Definition Classes
      MatchWarnings
19.  class ExtractorAlignment extends ExtractorSubPatternAlignment
    Definition Classes
      PatternExpansion
20.  trait ExtractorSubPatternAlignment extends AnyRef

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

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

    Definition Classes
      PatternExpansion
21.  class MatchTransformer extends TypingTransformer
22.  class OptimizingMatchTranslator extends MatchTranslator with MatchOptimizer with MatchAnalyzer with Solver
23.  trait TreesAndTypesDomain extends PropositionalLogic with CheckableTreeAndTypeAnalysis
    Definition Classes
      ScalaLogic
24.  trait CNF extends PropositionalLogic
    Definition Classes
      Solving
25.  trait Solver extends CNF
    Definition Classes
      Solving
26.  trait CheckableTreeAndTypeAnalysis extends AnyRef
    Definition Classes
      TreeAndTypeAnalysis

### Abstract Value Members

1.  abstract val global: Global
   Definition Classes
     PatternExpansion
2.  abstract val runsAfter: List[String]

   Names of phases that must run before this phase.

   Names of phases that must run before this phase.

   Definition Classes
     SubComponent
3.  abstract val runsRightAfter: Option[String]

   Name of the phase that this phase must follow immediately.

   Name of the phase that this phase must follow immediately.

   Definition Classes
     SubComponent

### Concrete Value Members

1.  object CODE
   Definition Classes
     TreeDSL
2.  object debug
   Definition Classes
     Debugging
3.  object Suppression extends java.io.Serializable
   Definition Classes
     MatchTreeMaking
4.  final def !=(arg0: Any): Boolean
   Definition Classes
     AnyRef → Any
5.  final def ##: Int
   Definition Classes
     AnyRef → Any
6.  def +(other: String): String
   Implicit
     This member is added by an implicit conversion from PatternMatching toany2stringadd[PatternMatching] performed by method any2stringadd in scala.Predef.
   Definition Classes
     any2stringadd
7.  def ->[B](y: B): (PatternMatching, B)
   Implicit
     This member is added by an implicit conversion from PatternMatching toArrowAssoc[PatternMatching] performed by method ArrowAssoc in scala.Predef.
   Definition Classes
     ArrowAssoc
   Annotations
     @inline()
8.  final def ==(arg0: Any): Boolean
   Definition Classes
     AnyRef → Any
9.  final def afterOwnPhase[T](op: => T): T
   Definition Classes
     SubComponent
   Annotations
     @inline()
10.  def alignAcrossRows(xss: List[List[Any]], sep: String, lineSep: String = "\n"): String
    Definition Classes
      Logic
11.  final def asInstanceOf[T0]: T0
    Definition Classes
      Any
12.  final def beforeOwnPhase[T](op: => T): T
    Definition Classes
      SubComponent
    Annotations
      @inline()
13.  def binderTypeImpliedByPattern(pat: Global.Tree, pt: Global.Type): Global.Type

    Compute the type T implied for a value `v` matched by a pattern `pat` (with expected type `pt`).

    Compute the type T implied for a value `v` matched by a pattern `pat` (with expected type `pt`).

    Usually, this is the pattern's type because pattern matching implies instance-of checks.

    However, Stable Identifier and Literal patterns are matched using `==`, which does not imply a type for the binder that binds the matched value. E.g., in `case x@Nil => x` , all we know about `x` is that it satisfies `Nil == x`, which could be anything. A type pattern with a literal type works the same as the corresponding literal pattern. A literal pattern with a Boolean or Unit pattern does enforce that the respective value (`true`, `false`, `()`) was matched, so in those cases, the pattern type is assumed.

    The other patterns imply type tests, so we can safely deduce that the binder has the pattern's type when the pattern matches. Concretely, a literal, type pattern, a case class (the constructor's result type) or extractor (the unapply's argument type) all imply type tests.

    See scala/bug#1503, scala/bug#5024: don't cast binders to types we're not sure they have

    Definition Classes
      TreeAndTypeAnalysis
14.  def clone(): AnyRef
    Attributes
      protected[lang]
    Definition Classes
      AnyRef
    Annotations
      @throws(classOf[java.lang.CloneNotSupportedException]) @native()
15.  def enabled: Boolean

    Is this component enabled? Default is true.

    Is this component enabled? Default is true.

    Definition Classes
      SubComponent
16.  def ensuring(cond: (PatternMatching) => Boolean, msg: => Any): PatternMatching
    Implicit
      This member is added by an implicit conversion from PatternMatching toEnsuring[PatternMatching] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
17.  def ensuring(cond: (PatternMatching) => Boolean): PatternMatching
    Implicit
      This member is added by an implicit conversion from PatternMatching toEnsuring[PatternMatching] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
18.  def ensuring(cond: Boolean, msg: => Any): PatternMatching
    Implicit
      This member is added by an implicit conversion from PatternMatching toEnsuring[PatternMatching] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
19.  def ensuring(cond: Boolean): PatternMatching
    Implicit
      This member is added by an implicit conversion from PatternMatching toEnsuring[PatternMatching] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
20.  final def eq(arg0: AnyRef): Boolean
    Definition Classes
      AnyRef
21.  def equals(other: Any): Boolean
    Definition Classes
      SubComponent → AnyRef → Any
22.  def equivalentTree(a: Global.Tree, b: Global.Tree): Boolean
    Definition Classes
      TreeAndTypeAnalysis
23.  def finalize(): Unit
    Attributes
      protected[lang]
    Definition Classes
      AnyRef
    Annotations
      @throws(classOf[java.lang.Throwable])
24.  final def getClass(): Class[_ <: AnyRef]
    Definition Classes
      AnyRef → Any
    Annotations
      @native()
25.  def hashCode(): Int

    SubComponents are added to a HashSet and two phases are the same if they have the same name.

    SubComponents are added to a HashSet and two phases are the same if they have the same name.

    Definition Classes
      SubComponent → AnyRef → Any
26.  val initial: Boolean

    True if this phase runs before all other phases.

    True if this phase runs before all other phases. Usually, `parser`.

    Definition Classes
      SubComponent
27.  def instanceOfTpImplies(tp: Global.Type, tpImplied: Global.Type): Boolean
    Definition Classes
      TreeAndTypeAnalysis
28.  val internal: Boolean

    True if this phase is not provided by a plug-in.

    True if this phase is not provided by a plug-in.

    Definition Classes
      SubComponent
29.  final def isInstanceOf[T0]: Boolean
    Definition Classes
      Any
30.  val javaClassesByUnit: HashMap[SourceFile, Set[Global.Symbol]]

    Symbols to force for determining children of sealed Java classes.

31.  final def ne(arg0: AnyRef): Boolean
    Definition Classes
      AnyRef
32.  def newPhase(prev: nsc.Phase): StdPhase

    Create a new phase which applies transformer

    Create a new phase which applies transformer

    Definition Classes
      Transform → SubComponent
33.  def newRootLocalTyper(unit: Global.CompilationUnit): (analyzer)#Typer
    Attributes
      protected
    Definition Classes
      TypingTransformers
34.  def newTransformer(unit: Global.CompilationUnit): Global.AstTransformer

    The transformer factory

    The transformer factory

    Definition Classes
      PatternMatching → Transform
35.  final def notify(): Unit
    Definition Classes
      AnyRef
    Annotations
      @native()
36.  final def notifyAll(): Unit
    Definition Classes
      AnyRef
    Annotations
      @native()
37.  def ownPhase: nsc.Phase

    The phase corresponding to this subcomponent in the current compiler run.

    The phase corresponding to this subcomponent in the current compiler run.

    Definition Classes
      SubComponent
38.  val phaseName: String

    The name of the phase

    The name of the phase

    Definition Classes
      PatternMatching → SubComponent
39.  def phaseNewFlags: Long

    New flags defined by the phase which are not valid before

    New flags defined by the phase which are not valid before

    Definition Classes
      SubComponent
40.  def phaseNextFlags: Long

    New flags defined by the phase which are not valid until immediately after it

    New flags defined by the phase which are not valid until immediately after it

    Definition Classes
      SubComponent
41.  def removeCPSFromPt(pt: Global.Type): Global.Type
    Definition Classes
      MatchCps
42.  val requires: List[String]

    Names of phases required by this component.

    Names of phases required by this component. Default is `Nil`.

    Definition Classes
      SubComponent
43.  val runsBefore: List[String]

    Names of phases that must run after this phase.

    Names of phases that must run after this phase. Default is `Nil`.

    Definition Classes
      SubComponent
44.  final def synchronized[T0](arg0: => T0): T0
    Definition Classes
      AnyRef
45.  val terminal: Boolean

    True if this phase runs after all other phases.

    True if this phase runs after all other phases. Usually, `terminal`.

    Definition Classes
      SubComponent
46.  def toString(): String
    Definition Classes
      AnyRef → Any
47.  def unapplyFormals(fun: Global.Tree, args: List[Global.Tree])(context: Context): List[Global.Type]
    Definition Classes
      PatternExpansion
48.  final def wait(): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws(classOf[java.lang.InterruptedException])
49.  final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws(classOf[java.lang.InterruptedException])
50.  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 PatternMatching toStringFormat[PatternMatching] 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): (PatternMatching, B)
   Implicit
     This member is added by an implicit conversion from PatternMatching toArrowAssoc[PatternMatching] 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 PatternExpansion

### Inherited from MatchWarnings

### Inherited from MatchOptimization

### Inherited from MatchAnalysis

### Inherited from MatchApproximation

### Inherited from Solving

### Inherited from ScalaLogic

### Inherited from TreeAndTypeAnalysis

### Inherited from Logic

### Inherited from MatchCps

### Inherited from MatchTreeMaking

### Inherited from MatchCodeGen

### Inherited from MatchTranslation

### Inherited from Interface

### Inherited from TreeDSL

### Inherited from Debugging

### Inherited from TypingTransformers

### Inherited from Transform

### Inherited from SubComponent

### Inherited from AnyRef

### Inherited from Any

### Inherited by implicit conversion any2stringadd fromPatternMatching to any2stringadd[PatternMatching]

### Inherited by implicit conversion StringFormat fromPatternMatching to StringFormat[PatternMatching]

### Inherited by implicit conversion Ensuring fromPatternMatching to Ensuring[PatternMatching]

### Inherited by implicit conversion ArrowAssoc fromPatternMatching to ArrowAssoc[PatternMatching]

### Ungrouped