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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
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
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Visibility
  1. Public
  2. All

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 TypingTransformer extends Global.Transformer
    Definition Classes
    TypingTransformers
  4. trait MatchMonadInterface extends AnyRef

    Interface with user-defined match monad? if there's a __match in scope, we use this as the match strategy, assuming it conforms to MatchStrategy as defined below:

    Interface with user-defined match monad? if there's a __match in scope, we use this as the match strategy, assuming it conforms to MatchStrategy as defined below:

    type Matcher[P[_], M[+_], A] = {
  def flatMap[B](f: P[A] => M[B]): M[B]
  def orElse[B >: A](alternative: => M[B]): M[B]
}

abstract class MatchStrategy[P[_], M[+_]] {
  // runs the matcher on the given input
  def runOrElse[T, U](in: P[T])(matcher: P[T] => M[U]): P[U]

  def zero: M[Nothing]
  def one[T](x: P[T]): M[T]
  def guard[T](cond: P[Boolean], then: => P[T]): M[T]
}

    P and M are derived from one's signature (def one[T](x: P[T]): M[T])

    if no __match is found, we assume the following implementation (and generate optimized code accordingly)

    object __match extends MatchStrategy[({type Id[x] = x})#Id, Option] {
  def zero = None
  def one[T](x: T) = Some(x)
  // NOTE: guard's return type must be of the shape M[T], where M is the monad in which the pattern match should be interpreted
  def guard[T](cond: Boolean, then: => T): Option[T] = if(cond) Some(then) else None
  def runOrElse[T, U](x: T)(f: T => Option[U]): U = f(x) getOrElse (throw new MatchError(x))
}
    Definition Classes
    Interface
  5. trait TypedSubstitution extends MatchMonadInterface
    Definition Classes
    Interface
  6. trait PropositionalLogic extends AnyRef
    Definition Classes
    Logic
  7. trait MatchAnalyzer extends MatchApproximator
    Definition Classes
    MatchAnalysis
  8. 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
  9. trait CodegenCore extends MatchMonadInterface
    Definition Classes
    MatchCodeGen
  10. trait OptimizedCodegen extends CodegenCore with TypedSubstitution with MatchMonadInterface
    Definition Classes
    MatchCodeGen
  11. trait PureCodegen extends CodegenCore with PureMatchMonadInterface
    Definition Classes
    MatchCodeGen
  12. trait PureMatchMonadInterface extends MatchMonadInterface
    Definition Classes
    MatchCodeGen
  13. trait CommonSubconditionElimination extends OptimizedCodegen with MatchApproximator
    Definition Classes
    MatchOptimization
  14. trait MatchOptimizer extends OptimizedCodegen with SwitchEmission with CommonSubconditionElimination
    Definition Classes
    MatchOptimization
  15. trait SwitchEmission extends TreeMakers with MatchMonadInterface
    Definition Classes
    MatchOptimization
  16. trait MatchTranslator extends PatternMatching.TreeMakers with PatternMatching.TreeMakerWarnings
    Definition Classes
    MatchTranslation
  17. final case class Suppression(suppressExhaustive: Boolean, suppressUnreachable: Boolean) extends Product with Serializable
    Definition Classes
    MatchTreeMaking
  18. trait TreeMakers extends TypedSubstitution with CodegenCore
    Definition Classes
    MatchTreeMaking
  19. trait TreeMakerWarnings extends AnyRef
    Definition Classes
    MatchWarnings
  20. class ExtractorAlignment extends ExtractorSubPatternAlignment
    Definition Classes
    PatternExpansion
  21. 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
  22. class MatchTransformer extends TypingTransformer
  23. class OptimizingMatchTranslator extends MatchTranslator with MatchOptimizer with MatchAnalyzer with Solver
  24. class PureMatchTranslator extends MatchTranslator with PureCodegen
  25. trait TreesAndTypesDomain extends PropositionalLogic with CheckableTreeAndTypeAnalysis
    Definition Classes
    ScalaLogic
  26. trait CNF extends PropositionalLogic
    Definition Classes
    Solving
  27. trait Solver extends CNF
    Definition Classes
    Solving
  28. 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 vpmName
    Definition Classes
    Interface
  4. object Suppression extends Serializable
    Definition Classes
    MatchTreeMaking
  5. final def !=(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  6. final def ##(): Int
    Definition Classes
    AnyRef → Any
  7. def +(other: String): String
    Implicit
    This member is added by an implicit conversion from PatternMatching to any2stringadd[PatternMatching] performed by method any2stringadd in scala.Predef.
    Definition Classes
    any2stringadd
  8. def ->[B](y: B): (PatternMatching, B)
    Implicit
    This member is added by an implicit conversion from PatternMatching to ArrowAssoc[PatternMatching] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc
    Annotations
    @inline()
  9. final def ==(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  10. final def afterOwnPhase[T](op: ⇒ T): T
    Definition Classes
    SubComponent
    Annotations
    @inline()
  11. def alignAcrossRows(xss: List[List[Any]], sep: String, lineSep: String = "\n"): String
    Definition Classes
    Logic
  12. final def asInstanceOf[T0]: T0
    Definition Classes
    Any
  13. final def beforeOwnPhase[T](op: ⇒ T): T
    Definition Classes
    SubComponent
    Annotations
    @inline()
  14. def binderTypeImpliedByPattern(pat: Global.Tree, pt: Global.Type, binder: Global.Symbol): 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.

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

    TODO: update spec as follows (deviation between **):

    A pattern binder x@p consists of a pattern variable x and a pattern p. The type of the variable x is the static type T **IMPLIED BY** the pattern p. This pattern matches any value v matched by the pattern p **Deleted: , provided the run-time type of v is also an instance of T, ** and it binds the variable name to that value.

    Addition: A pattern p _implies_ a type T if the pattern matches only values of the type T.

    Definition Classes
    TreeAndTypeAnalysis
  15. def clone(): AnyRef
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @native()
  16. final def dealiasWiden(tp: Global.Type): Global.Type
    Attributes
    protected
    Definition Classes
    Interface
  17. def enabled: Boolean

    Is this component enabled? Default is true.

    Is this component enabled? Default is true.

    Definition Classes
    SubComponent
  18. def ensuring(cond: (PatternMatching) ⇒ Boolean, msg: ⇒ Any): PatternMatching
    Implicit
    This member is added by an implicit conversion from PatternMatching to Ensuring[PatternMatching] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  19. def ensuring(cond: (PatternMatching) ⇒ Boolean): PatternMatching
    Implicit
    This member is added by an implicit conversion from PatternMatching to Ensuring[PatternMatching] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  20. def ensuring(cond: Boolean, msg: ⇒ Any): PatternMatching
    Implicit
    This member is added by an implicit conversion from PatternMatching to Ensuring[PatternMatching] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  21. def ensuring(cond: Boolean): PatternMatching
    Implicit
    This member is added by an implicit conversion from PatternMatching to Ensuring[PatternMatching] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  22. final def eq(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  23. def equals(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  24. def equivalentTree(a: Global.Tree, b: Global.Tree): Boolean
    Definition Classes
    TreeAndTypeAnalysis
  25. def finalize(): Unit
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] )
  26. def formatted(fmtstr: String): String
    Implicit
    This member is added by an implicit conversion from PatternMatching to StringFormat[PatternMatching] performed by method StringFormat in scala.Predef.
    Definition Classes
    StringFormat
    Annotations
    @inline()
  27. final def getClass(): Class[_]
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  28. final def hasStableSymbol(p: Global.Tree): Boolean
    Attributes
    protected
    Definition Classes
    Interface
  29. def hashCode(): Int

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

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

    Definition Classes
    SubComponent → AnyRef → Any
  30. 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
  31. def instanceOfTpImplies(tp: Global.Type, tpImplied: Global.Type): Boolean
    Definition Classes
    TreeAndTypeAnalysis
  32. 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
  33. final def isInstanceOf[T0]: Boolean
    Definition Classes
    Any
  34. final def mkFALSE: Global.Literal
    Attributes
    protected
    Definition Classes
    Interface
  35. final def mkTRUE: Global.Literal
    Attributes
    protected
    Definition Classes
    Interface
  36. final def ne(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  37. def newPhase(prev: nsc.Phase): StdPhase

    Create a new phase which applies transformer

    Create a new phase which applies transformer

    Definition Classes
    Transform → SubComponent
  38. def newTransformer(unit: Global.CompilationUnit): Global.Transformer

    The transformer factory

    The transformer factory

    Definition Classes
    PatternMatching → Transform
  39. final def notify(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  40. final def notifyAll(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  41. 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
  42. val phaseName: String

    The name of the phase

    The name of the phase

    Definition Classes
    PatternMatching → SubComponent
  43. 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
  44. 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
  45. def removeCPSFromPt(pt: Global.Type): Global.Type
    Definition Classes
    MatchCps
  46. val requires: List[String]

    Names of phases required by this component.

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

    Definition Classes
    SubComponent
  47. 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
  48. final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
    AnyRef
  49. 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
  50. def toString(): String
    Definition Classes
    AnyRef → Any
  51. def unapplyFormals(fun: Global.Tree, args: List[Global.Tree])(context: Context): List[Global.Type]
    Definition Classes
    PatternExpansion
  52. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  53. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  54. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @native()
  55. def →[B](y: B): (PatternMatching, B)
    Implicit
    This member is added by an implicit conversion from PatternMatching to ArrowAssoc[PatternMatching] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc

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 from PatternMatching to any2stringadd[PatternMatching]

Inherited by implicit conversion StringFormat from PatternMatching to StringFormat[PatternMatching]

Inherited by implicit conversion Ensuring from PatternMatching to Ensuring[PatternMatching]

Inherited by implicit conversion ArrowAssoc from PatternMatching to ArrowAssoc[PatternMatching]

Ungrouped