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
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- MatchTreeMaking
- MatchCodeGen
- MatchTranslation
- Interface
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Type Members
-
abstract
class
StdPhase extends GlobalPhase
A standard phase template
A standard phase template
- Definition Classes
- SubComponent
-
class
Phase extends StdPhase
The phase defined by this transform
The phase defined by this transform
- Definition Classes
- Transform
-
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
-
abstract
class
TypingTransformer extends Global.Transformer
- Definition Classes
- TypingTransformers
-
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
-
trait
TypedSubstitution extends MatchMonadInterface
- Definition Classes
- Interface
-
trait
PropositionalLogic extends AnyRef
- Definition Classes
- Logic
-
trait
MatchAnalyzer extends MatchApproximator
- Definition Classes
- MatchAnalysis
-
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
-
trait
CodegenCore extends MatchMonadInterface
- Definition Classes
- MatchCodeGen
-
trait
OptimizedCodegen extends CodegenCore with TypedSubstitution with MatchMonadInterface
- Definition Classes
- MatchCodeGen
-
trait
PureCodegen extends CodegenCore with PureMatchMonadInterface
- Definition Classes
- MatchCodeGen
-
trait
PureMatchMonadInterface extends MatchMonadInterface
- Definition Classes
- MatchCodeGen
-
trait
CommonSubconditionElimination extends OptimizedCodegen with MatchApproximator
- Definition Classes
- MatchOptimization
-
trait
MatchOptimizer extends OptimizedCodegen with SwitchEmission with CommonSubconditionElimination
- Definition Classes
- MatchOptimization
-
trait
SwitchEmission extends TreeMakers with MatchMonadInterface
- Definition Classes
- MatchOptimization
-
trait
MatchTranslator extends PatternMatching.TreeMakers with PatternMatching.TreeMakerWarnings
- Definition Classes
- MatchTranslation
-
final
case class
Suppression(suppressExhaustive: Boolean, suppressUnreachable: Boolean) extends Product with Serializable
- Definition Classes
- MatchTreeMaking
-
trait
TreeMakers extends TypedSubstitution with CodegenCore
- Definition Classes
- MatchTreeMaking
-
trait
TreeMakerWarnings extends AnyRef
- Definition Classes
- MatchWarnings
-
class
ExtractorAlignment extends ExtractorSubPatternAlignment
- Definition Classes
- PatternExpansion
-
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
- class MatchTransformer extends TypingTransformer
- class OptimizingMatchTranslator extends MatchTranslator with MatchOptimizer with MatchAnalyzer with Solver
- class PureMatchTranslator extends MatchTranslator with PureCodegen
-
trait
TreesAndTypesDomain extends PropositionalLogic with CheckableTreeAndTypeAnalysis
- Definition Classes
- ScalaLogic
-
trait
CNF extends PropositionalLogic
- Definition Classes
- Solving
-
trait
Solver extends CNF
- Definition Classes
- Solving
-
trait
CheckableTreeAndTypeAnalysis extends AnyRef
- Definition Classes
- TreeAndTypeAnalysis
Abstract Value Members
-
abstract
val
global: Global
- Definition Classes
- PatternExpansion
-
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
-
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
-
object
CODE
- Definition Classes
- TreeDSL
-
object
debug
- Definition Classes
- Debugging
-
object
vpmName
- Definition Classes
- Interface
-
object
Suppression extends Serializable
- Definition Classes
- MatchTreeMaking
-
final
def
!=(arg0: Any): Boolean
- Definition Classes
- AnyRef → Any
-
final
def
##(): Int
- Definition Classes
- AnyRef → Any
-
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
-
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()
-
final
def
==(arg0: Any): Boolean
- Definition Classes
- AnyRef → Any
-
final
def
afterOwnPhase[T](op: ⇒ T): T
- Definition Classes
- SubComponent
- Annotations
- @inline()
-
def
alignAcrossRows(xss: List[List[Any]], sep: String, lineSep: String = "\n"): String
- Definition Classes
- Logic
-
final
def
asInstanceOf[T0]: T0
- Definition Classes
- Any
-
final
def
beforeOwnPhase[T](op: ⇒ T): T
- Definition Classes
- SubComponent
- Annotations
- @inline()
-
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 patternpat
(with expected typept
).Compute the type T implied for a value
v
matched by a patternpat
(with expected typept
).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 typeT
if the pattern matches only values of the typeT
.- Definition Classes
- TreeAndTypeAnalysis
-
def
clone(): AnyRef
- Attributes
- protected[lang]
- Definition Classes
- AnyRef
- Annotations
- @throws( ... ) @native()
-
final
def
dealiasWiden(tp: Global.Type): Global.Type
- Attributes
- protected
- Definition Classes
- Interface
-
def
enabled: Boolean
Is this component enabled? Default is true.
Is this component enabled? Default is true.
- Definition Classes
- SubComponent
-
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
-
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
-
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
-
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
-
final
def
eq(arg0: AnyRef): Boolean
- Definition Classes
- AnyRef
-
def
equals(arg0: Any): Boolean
- Definition Classes
- AnyRef → Any
-
def
equivalentTree(a: Global.Tree, b: Global.Tree): Boolean
- Definition Classes
- TreeAndTypeAnalysis
-
def
finalize(): Unit
- Attributes
- protected[lang]
- Definition Classes
- AnyRef
- Annotations
- @throws( classOf[java.lang.Throwable] )
-
final
def
getClass(): Class[_]
- Definition Classes
- AnyRef → Any
- Annotations
- @native()
-
final
def
hasStableSymbol(p: Global.Tree): Boolean
- Attributes
- protected
- Definition Classes
- Interface
-
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
-
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
-
def
instanceOfTpImplies(tp: Global.Type, tpImplied: Global.Type): Boolean
- Definition Classes
- TreeAndTypeAnalysis
-
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
-
final
def
isInstanceOf[T0]: Boolean
- Definition Classes
- Any
-
final
def
mkFALSE: Global.Literal
- Attributes
- protected
- Definition Classes
- Interface
-
final
def
mkTRUE: Global.Literal
- Attributes
- protected
- Definition Classes
- Interface
-
final
def
ne(arg0: AnyRef): Boolean
- Definition Classes
- AnyRef
-
def
newPhase(prev: nsc.Phase): StdPhase
Create a new phase which applies transformer
Create a new phase which applies transformer
- Definition Classes
- Transform → SubComponent
-
def
newRootLocalTyper(unit: Global.CompilationUnit): (analyzer)#Typer
- Attributes
- protected
- Definition Classes
- TypingTransformers
-
def
newTransformer(unit: Global.CompilationUnit): Global.Transformer
The transformer factory
The transformer factory
- Definition Classes
- PatternMatching → Transform
-
final
def
notify(): Unit
- Definition Classes
- AnyRef
- Annotations
- @native()
-
final
def
notifyAll(): Unit
- Definition Classes
- AnyRef
- Annotations
- @native()
-
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
-
val
phaseName: String
The name of the phase
The name of the phase
- Definition Classes
- PatternMatching → SubComponent
-
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
-
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
-
def
removeCPSFromPt(pt: Global.Type): Global.Type
- Definition Classes
- MatchCps
-
val
requires: List[String]
Names of phases required by this component.
Names of phases required by this component. Default is
Nil
.- Definition Classes
- SubComponent
-
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
-
final
def
synchronized[T0](arg0: ⇒ T0): T0
- Definition Classes
- AnyRef
-
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
-
def
toString(): String
- Definition Classes
- AnyRef → Any
-
def
unapplyFormals(fun: Global.Tree, args: List[Global.Tree])(context: Context): List[Global.Type]
- Definition Classes
- PatternExpansion
-
final
def
wait(): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
-
final
def
wait(arg0: Long, arg1: Int): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
-
final
def
wait(arg0: Long): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... ) @native()
-
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
Deprecated Value Members
-
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
- @deprecated @inline()
- Deprecated
(Since version 2.12.16) Use
formatString.format(value)
instead ofvalue.formatted(formatString)
, or use thef""
string interpolator. In Java 15 and later,formatted
resolves to the new method in String which has reversed parameters.
The Scala compiler and reflection APIs.