Scala Compiler2.12.2-20170504-135222-21d12e9 < 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
-  abstract class Fields extends SubComponent with InfoTransform with TreeDSL with TypingTransformers with AccessorSynthesis

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

  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...)

  Definition Classes
    transform
- AccessorTreeSynthesis
- BitmapInfo
- CODE
- CheckInitAccessorSymbolSynth
- CheckedAccessorSymbolSynth
- CheckedAccessorTreeSynthesis
- FieldMemoization
- FieldsTransformer
- Phase
- StdPhase
- TypingTransformer

c

scala.tools.nsc.transform.Fields

# FieldMemoization 

###

#### class FieldMemoization extends AnyRef

Source
  Fields.scala

Linear Supertypes
AnyRef, Any
Type Hierarchy
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Ordering

1. Alphabetic
2. By Inheritance

Inherited

1. FieldMemoization
2. AnyRef
3. Any

Implicitly

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

1. Hide All
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Visibility

1. Public
2. All

### Instance Constructors

1.  new FieldMemoization(accessorOrField: Global.Symbol, site: Global.Symbol)

### 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 FieldMemoization to any2stringadd[FieldMemoization] performed by method any2stringadd in scala.Predef.
   Definition Classes
     any2stringadd
4.  def ->[B](y: B): (FieldMemoization, B)
   Implicit
     This member is added by an implicit conversion from FieldMemoization to ArrowAssoc[FieldMemoization] 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[java.lang]
   Definition Classes
     AnyRef
   Annotations
     @throws( ... )
8.  val constantTyped: Boolean
9.  def ensuring(cond: (FieldMemoization) ⇒ Boolean, msg: ⇒ Any): FieldMemoization
   Implicit
     This member is added by an implicit conversion from FieldMemoization to Ensuring[FieldMemoization] performed by method Ensuring in scala.Predef.
   Definition Classes
     Ensuring
10.  def ensuring(cond: (FieldMemoization) ⇒ Boolean): FieldMemoization
    Implicit
      This member is added by an implicit conversion from FieldMemoization to Ensuring[FieldMemoization] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
11.  def ensuring(cond: Boolean, msg: ⇒ Any): FieldMemoization
    Implicit
      This member is added by an implicit conversion from FieldMemoization to Ensuring[FieldMemoization] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
12.  def ensuring(cond: Boolean): FieldMemoization
    Implicit
      This member is added by an implicit conversion from FieldMemoization to Ensuring[FieldMemoization] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
13.  final def eq(arg0: AnyRef): Boolean
    Definition Classes
      AnyRef
14.  def equals(arg0: Any): Boolean
    Definition Classes
      AnyRef → Any
15.  def finalize(): Unit
    Attributes
      protected[java.lang]
    Definition Classes
      AnyRef
    Annotations
      @throws( classOf[java.lang.Throwable] )
16.  def formatted(fmtstr: String): String
    Implicit
      This member is added by an implicit conversion from FieldMemoization to StringFormat[FieldMemoization] performed by method StringFormat in scala.Predef.
    Definition Classes
      StringFormat
    Annotations
      @inline()
17.  final def getClass(): Class[_]
    Definition Classes
      AnyRef → Any
18.  def hashCode(): Int
    Definition Classes
      AnyRef → Any
19.  final def isInstanceOf[T0]: Boolean
    Definition Classes
      Any
20.  final def ne(arg0: AnyRef): Boolean
    Definition Classes
      AnyRef
21.  final def notify(): Unit
    Definition Classes
      AnyRef
22.  final def notifyAll(): Unit
    Definition Classes
      AnyRef
23.  final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
      AnyRef
24.  def toString(): String
    Definition Classes
      AnyRef → Any
25.  val tp: Global.Type
26.  final def wait(): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws( ... )
27.  final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws( ... )
28.  final def wait(arg0: Long): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws( ... )
29.  def →[B](y: B): (FieldMemoization, B)
    Implicit
      This member is added by an implicit conversion from FieldMemoization to ArrowAssoc[FieldMemoization] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
      ArrowAssoc

### Inherited from AnyRef

### Inherited from Any

### Inherited by implicit conversion any2stringadd from FieldMemoization to any2stringadd[FieldMemoization]

### Inherited by implicit conversion StringFormat from FieldMemoization to StringFormat[FieldMemoization]

### Inherited by implicit conversion Ensuring from FieldMemoization to Ensuring[FieldMemoization]

### Inherited by implicit conversion ArrowAssoc from FieldMemoization to ArrowAssoc[FieldMemoization]

### Ungrouped