Scala Compiler 2.13.16 - scala.tools.nsc.transform.Fields
Keywords: Scala Compiler 2.13.16 scala.tools.nsc.transform.Fields

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 async
  Definition Classes
    transform
-  package patmat
  Definition Classes
    transform
- AccessorSynthesis
- CleanUp
- Constructors
- Delambdafy
- Erasure
- ExplicitOuter
- ExtensionMethods
- Fields
- Flatten
- InfoTransform
- LambdaLift
- Mixin
- OverridingPairs
- PostErasure
- SampleTransform
- SpecializeTypes
- Statics
- TailCalls
- Transform
- TypeAdaptingTransformer
- TypingTransformers
- UnCurry

c

scala.tools.nsc.transform

# Fields

###

#### abstract class Fields extends SubComponent with InfoTransform with TreeDSL with TypingTransformers with AccessorSynthesis

Synthesize accessors, fields (and bitmaps) for (lazy) vals and modules.

During Namers, a `ValDef` that is `lazy`, deferred and/or defined in a trait carries its getter's symbol. The underlying field symbol does not exist until this phase.

For `val`s defined in classes, we still emit a field immediately. TODO: uniformly assign getter symbol to all `ValDef`s, stop using `accessed`.

This phase synthesizes accessors, fields and bitmaps (for lazy or init-checked vals under -Xcheckinit) in the first (closest in the subclassing lattice) subclass (not a trait) of a trait.

For lazy vals and modules, we emit accessors that using double-checked locking (DCL) to balance thread safety and performance. For both lazy vals and modules, the a compute method contains the DCL's slow path.

Local lazy vals do not receive bitmaps, but use a Lazy*Holder that has the volatile init bit and the computed value. See `mkLazyLocalDef`.

Constructors will move the rhs to an assignment in the template body. Those statements then move to the template into the constructor, which means it will initialize the fields defined in this template (and execute the corresponding side effects). We need to maintain the connection between getter and rhs until after specialization so that it can duplicate vals.

A ModuleDef is desugared to a ClassDef, an accessor (which reuses the module's term symbol) and a module var (unless the module is static and does not implement a member of a supertype, or we're in a trait).

For subclasses of traits that define modules, a module var is mixed in, as well as the required module accessors.

Phase ordering:

- Runs after uncurry to deal with classes that implement SAM traits with ValDefs.
- Runs before erasure (to get bridges), and thus before lambdalift/flatten, so that nested functions/definitions must be considered.
- Lambdalift introduces new paramaccessors for captured vals, but runs too late in the pipeline, so mixins still synthesizes implementations for these accessors when a local trait that captures is subclassed.

In the future, would like to get closer to dotty, which lifts a val's RHS (a similar thing is done for template-level statements) to a method `$_initialize_$1$x` instead of a block, which is used in the constructor to initialize the val. This makes for a nice unification of strict and lazy vals, in that the RHS is lifted to a method for both, with the corresponding compute method called at the appropriate time.)

This only reduces the required number of methods per field declaration in traits, if we encode the name (and place in initialisation order) of the field in the name of its initializing method, to allow separate compilation. (The name mangling must include ordering, and thus complicate incremental compilation: ideally, we'd avoid renumbering unchanged methods, but that would result in different bytecode between clean recompiles and incremental ones).

In the even longer term (Scala 3?), I agree with @DarkDimius that it would make sense to hide the difference between strict and lazy vals. All vals are lazy, but the memoization overhead is removed when we statically know they are forced during initialization. We could still expose the low-level field semantics through `private[this] val`s.

In any case, the current behavior of overriding vals is pretty surprising. An overridden val's side-effect is still performed. The only change due to overriding is that its value is never written to the field (the overridden val's value is, of course, stored in the field in addition to its side-effect being performed).

TODO: Java 9 support for vals defined in traits. They are currently emitted as final, but the write (putfield) to the val does not occur syntactically within the <init> method (it's done by the trait setter, which is called from the trait's mixin constructor, which is called from the subclass's constructor...)

Source
  Fields.scala

Linear Supertypes
AccessorSynthesis, TypingTransformers, TreeDSL, InfoTransform, Transform, SubComponent, AnyRef, Any
Known Subclasses
fields
Type Hierarchy

Ordering

1. Alphabetic
2. By Inheritance

Inherited

1. Fields
2. AccessorSynthesis
3. TypingTransformers
4. TreeDSL
5. InfoTransform
6. Transform
7. SubComponent
8. AnyRef
9. 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

### Instance Constructors

1.  new Fields()

### Type Members

1.  abstract class StdPhase extends GlobalPhase

   A standard phase template

   A standard phase template

   Definition Classes
     SubComponent
2.  trait AccessorTreeSynthesis extends AnyRef
   Definition Classes
     AccessorSynthesis
3.  case class BitmapInfo(symbol: Global.Symbol, mask: Global.Literal) extends Product with Serializable
   Definition Classes
     AccessorSynthesis
4.  class CheckedAccessorSymbolSynth extends AnyRef
   Definition Classes
     AccessorSynthesis
5.  trait CheckedAccessorTreeSynthesis extends AccessorTreeSynthesis
   Definition Classes
     AccessorSynthesis
6.  class FieldMemoization extends AnyRef
7.  class FieldsTransformer extends TypingTransformer with CheckedAccessorTreeSynthesis
8.  final type InfoPhase = Phase
   Definition Classes
     InfoTransform
   Annotations
     @nowarn()
9.  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
10.  abstract class TypingTransformer extends Global.AstTransformer
    Definition Classes
      TypingTransformers

### Deprecated Type Members

1.  class Phase extends InfoTransform.Phase
   Definition Classes
     InfoTransform
   Annotations
     @nowarn() @deprecated
   Deprecated

     (Since version 2.13.4) use InfoPhase instead

### Abstract Value Members

1.  abstract val global: Global
   Definition Classes
     TypingTransformers
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.  final def !=(arg0: Any): Boolean
   Definition Classes
     AnyRef → Any
3.  final def ##: Int
   Definition Classes
     AnyRef → Any
4.  def +(other: String): String
   Implicit
     This member is added by an implicit conversion from Fields toany2stringadd[Fields] performed by method any2stringadd in scala.Predef.
   Definition Classes
     any2stringadd
5.  def ->[B](y: B): (Fields, B)
   Implicit
     This member is added by an implicit conversion from Fields toArrowAssoc[Fields] performed by method ArrowAssoc in scala.Predef.
   Definition Classes
     ArrowAssoc
   Annotations
     @inline()
6.  final def ==(arg0: Any): Boolean
   Definition Classes
     AnyRef → Any
7.  val EmptyThicket: Global.EmptyTree.type
   Definition Classes
     AccessorSynthesis
8.  final val TRAIT_SETTER_FLAGS: 576460752303947793L
9.  def Thicket(trees: List[Global.Tree]): Global.TermTree with java.io.Serializable
   Definition Classes
     AccessorSynthesis
10.  final def afterOwnPhase[T](op: => T): T
    Definition Classes
      SubComponent
    Annotations
      @inline()
11.  final def asInstanceOf[T0]: T0
    Definition Classes
      Any
12.  final def beforeOwnPhase[T](op: => T): T
    Definition Classes
      SubComponent
    Annotations
      @inline()
13.  def castHack(tree: Global.Tree, pt: Global.Type): Global.Tree
14.  def changesBaseClasses: Boolean
    Attributes
      protected
    Definition Classes
      InfoTransform
15.  def checkAndClear(flag: Long)(sym: Global.Symbol): Boolean
16.  def checkAndClearNeedsTrees(setter: Global.Symbol): Boolean
17.  def checkAndClearOverriddenTraitSetter(setter: Global.Symbol): Boolean
18.  def checkedAccessorSymbolSynth(clz: Global.Symbol): CheckedAccessorSymbolSynth
    Definition Classes
      AccessorSynthesis
19.  def clone(): AnyRef
    Attributes
      protected[lang]
    Definition Classes
      AnyRef
    Annotations
      @throws(classOf[java.lang.CloneNotSupportedException]) @native()
20.  def dropFieldAnnotationsFromGetter(sym: Global.Symbol): Unit
21.  def enabled: Boolean

    Is this component enabled? Default is true.

    Is this component enabled? Default is true.

    Definition Classes
      SubComponent
22.  def ensuring(cond: (Fields) => Boolean, msg: => Any): Fields
    Implicit
      This member is added by an implicit conversion from Fields toEnsuring[Fields] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
23.  def ensuring(cond: (Fields) => Boolean): Fields
    Implicit
      This member is added by an implicit conversion from Fields toEnsuring[Fields] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
24.  def ensuring(cond: Boolean, msg: => Any): Fields
    Implicit
      This member is added by an implicit conversion from Fields toEnsuring[Fields] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
25.  def ensuring(cond: Boolean): Fields
    Implicit
      This member is added by an implicit conversion from Fields toEnsuring[Fields] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
26.  final def eq(arg0: AnyRef): Boolean
    Definition Classes
      AnyRef
27.  def equals(other: Any): Boolean
    Definition Classes
      SubComponent → AnyRef → Any
28.  def explodeThicket(tree: Global.Tree): List[Global.Tree]
    Definition Classes
      AccessorSynthesis
29.  def fieldMemoizationIn(accessorOrField: Global.Symbol, site: Global.Symbol): FieldMemoization
30.  def fieldTypeOfAccessorIn(accessor: Global.Symbol, pre: Global.Type): Global.Type
31.  def finalize(): Unit
    Attributes
      protected[lang]
    Definition Classes
      AnyRef
    Annotations
      @throws(classOf[java.lang.Throwable])
32.  final def getClass(): Class[_ <: AnyRef]
    Definition Classes
      AnyRef → Any
    Annotations
      @native()
33.  def getterTreeAnnotationsTargetFieldAndGetter(owner: Global.Symbol, mods: Global.Modifiers): Boolean
34.  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
35.  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
36.  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
37.  final def isInstanceOf[T0]: Boolean
    Definition Classes
      Any
38.  def keepsTypeParams: Boolean
    Attributes
      protected
    Definition Classes
      InfoTransform
39.  def lazyVarOf(sym: Global.Symbol): Global.Symbol
40.  def matchingAccessor(pre: Global.Type, member: Global.Symbol, clazz: Global.Symbol): Global.Symbol
41.  def mustExplodeThicket(tree: Global.Tree): Boolean
    Definition Classes
      AccessorSynthesis
42.  final def ne(arg0: AnyRef): Boolean
    Definition Classes
      AnyRef
43.  def newPhase(prev: nsc.Phase): StdPhase

    Create a new phase which applies transformer

    Create a new phase which applies transformer

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

    The transformer factory

    The transformer factory

    Attributes
      protected
    Definition Classes
      Fields → Transform
46.  def nonStaticModuleToMethod(module: Global.Symbol): Unit
47.  final def notDeferredOrSynthImpl(sym: Global.Symbol): Boolean
    Annotations
      @inline()
48.  final def notify(): Unit
    Definition Classes
      AnyRef
    Annotations
      @native()
49.  final def notifyAll(): Unit
    Definition Classes
      AnyRef
    Annotations
      @native()
50.  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
51.  val phaseName: String

    the following two members override abstract members in Transform

    the following two members override abstract members in Transform

    Definition Classes
      Fields → SubComponent
52.  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
      Fields → SubComponent
53.  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
54.  val requires: List[String]

    Names of phases required by this component.

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

    Definition Classes
      SubComponent
55.  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
56.  def symbolAnnotationsTargetFieldAndGetter(sym: Global.Symbol): Boolean
57.  final def synchronized[T0](arg0: => T0): T0
    Definition Classes
      AnyRef
58.  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
59.  def toString(): String
    Definition Classes
      AnyRef → Any
60.  def transformInfo(sym: Global.Symbol, tp: Global.Type): Global.Type
    Definition Classes
      Fields → InfoTransform
61.  final def wait(): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws(classOf[java.lang.InterruptedException])
62.  final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws(classOf[java.lang.InterruptedException])
63.  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 Fields toStringFormat[Fields] 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): (Fields, B)
   Implicit
     This member is added by an implicit conversion from Fields toArrowAssoc[Fields] 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 AccessorSynthesis

### Inherited from TypingTransformers

### Inherited from TreeDSL

### Inherited from InfoTransform

### Inherited from Transform

### Inherited from SubComponent

### Inherited from AnyRef

### Inherited from Any

### Inherited by implicit conversion any2stringadd fromFields to any2stringadd[Fields]

### Inherited by implicit conversion StringFormat fromFields to StringFormat[Fields]

### Inherited by implicit conversion Ensuring fromFields to Ensuring[Fields]

### Inherited by implicit conversion ArrowAssoc fromFields to ArrowAssoc[Fields]

### Ungrouped