Scala Reflection Library 2.13.16 - scala.reflect.api.Internals.Importer
Keywords: Scala Reflection Library 2.13.16 scala.reflect.api.Internals.Importer

Scala Reflection Library2.13.16 < Back
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# Packages

-  package root
  Definition Classes
    root
-  package scala
  Definition Classes
    root
-  package reflect
  Definition Classes
    scala
-  package api

  EXPERIMENTAL

  EXPERIMENTAL

  The Scala Reflection API (located in scala-reflect.jar).

  In Scala 2.10.0, the Scala Reflection API and its implementation have an "experimental" status. This means that the API and the docs are not complete and can be changed in binary- and source-incompatible manner in 2.10.1. This also means that the implementation has some known issues.

  The following types are the backbone of the Scala Reflection API, and serve as a good starting point for information about Scala Reflection:

  - scala.reflect.api.Symbols
  - scala.reflect.api.Types
  - scala.reflect.api.Mirrors
  - scala.reflect.api.Universe

  For more information about Scala Reflection, see the Reflection Guide

  Definition Classes
    reflect
-  trait Internals extends AnyRef

  EXPERIMENTAL

  EXPERIMENTAL

  This trait assembles APIs occasionally necessary for performing low-level operations on reflection artifacts. See Internals#InternalApi for more information about nature, usefulness and compatibility guarantees of these APIs.

  Definition Classes
    api
- Compat
- CompatApi
- CompatToken
- FreeTermSymbol
- FreeTermSymbolApi
- FreeTypeSymbol
- FreeTypeSymbolApi
- Importer
- Internal
- InternalApi
- ReferenceToBoxed
- ReferenceToBoxedApi
- ReferenceToBoxedExtractor
- ReificationSupportApi

t

scala.reflect.api.Internals

# Importer

###

#### trait Importer extends AnyRef

This trait provides support for importers, a facility to migrate reflection artifacts between universes. Note: this trait should typically be used only rarely.

Reflection artifacts, such as Symbols and Types, are contained in Universes. Typically all processing happens within a single `Universe` (e.g. a compile-time macro `Universe` or a runtime reflection `Universe`), but sometimes there is a need to migrate artifacts from one `Universe` to another. For example, runtime compilation works by importing runtime reflection trees into a runtime compiler universe, compiling the importees and exporting the result back.

Reflection artifacts are firmly grounded in their `Universe`s, which is reflected by the fact that types of artifacts from different universes are not compatible. By using `Importer`s, however, they be imported from one universe into another. For example, to import `foo.bar.Baz` from the source `Universe` to the target `Universe`, an importer will first check whether the entire owner chain exists in the target `Universe`. If it does, then nothing else will be done. Otherwise, the importer will recreate the entire owner chain and will import the corresponding type signatures into the target `Universe`.

Since importers match `Symbol` tables of the source and the target `Universe`s using plain string names, it is programmer's responsibility to make sure that imports don't distort semantics, e.g., that `foo.bar.Baz` in the source `Universe` means the same that `foo.bar.Baz` does in the target `Universe`.

##### Example

Here's how one might implement a macro that performs compile-time evaluation of its argument by using a runtime compiler to compile and evaluate a tree that belongs to a compile-time compiler:

    def staticEval[T](x: T) = macro staticEval[T]

    def staticEval[T](c: scala.reflect.macros.blackbox.Context)(x: c.Expr[T]) = {
      // creates a runtime reflection universe to host runtime compilation
      import scala.reflect.runtime.{universe => ru}
      val mirror = ru.runtimeMirror(c.libraryClassLoader)
      import scala.tools.reflect.ToolBox
      val toolBox = mirror.mkToolBox()

      // runtime reflection universe and compile-time macro universe are different
      // therefore an importer is needed to bridge them
      // currently mkImporter requires a cast to correctly assign the path-dependent types
      val importer0 = ru.internal.mkImporter(c.universe)
      val importer = importer0.asInstanceOf[ru.internal.Importer { val from: c.universe.type }]

      // the created importer is used to turn a compiler tree into a runtime compiler tree
      // both compilers use the same classpath, so semantics remains intact
      val imported = importer.importTree(tree)

      // after the tree is imported, it can be evaluated as usual
      val tree = toolBox.untypecheck(imported.duplicate)
      val valueOfX = toolBox.eval(imported).asInstanceOf[T]
      ...
    }

Source
  Internals.scala

Linear Supertypes
AnyRef, Any
Type Hierarchy
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2. By Inheritance

Inherited

1. Importer
2. AnyRef
3. Any

Implicitly

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

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Visibility

1. Public
2. Protected

### Abstract Value Members

1.  abstract val from: Universe

   The source universe of reflection artifacts that will be processed.

   The source universe of reflection artifacts that will be processed. The target universe is universe that created this importer with `mkImporter`.

2.  abstract def importPosition(pos: Universe.Position): Universe.Position

   In the current universe, creates a position that corresponds to the provided position in the source universe.

3.  abstract def importSymbol(sym: Universe.Symbol): Universe.Symbol

   In the current universe, locates or creates a symbol that corresponds to the provided symbol in the source universe.

   In the current universe, locates or creates a symbol that corresponds to the provided symbol in the source universe. If necessary imports the owner chain, companions, type signature, annotations and attachments.

4.  abstract def importTree(tree: Universe.Tree): Universe.Tree

   In the current universe, creates a tree that corresponds to the provided tree in the source universe.

   In the current universe, creates a tree that corresponds to the provided tree in the source universe. If necessary imports the underlying symbols, types and attachments.

5.  abstract def importType(tpe: Universe.Type): Universe.Type

   In the current universe, locates or creates a type that corresponds to the provided type in the source universe.

   In the current universe, locates or creates a type that corresponds to the provided type in the source universe. If necessary imports the underlying symbols, annotations, scopes and trees.

6.  abstract val reverse: Universe.Importer { val from: Internals.this.type }

   An importer that works in reverse direction, namely: imports reflection artifacts from the current universe to the universe specified in `from`.

### Concrete 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 Universe.Importer toany2stringadd[Universe.Importer] performed by method any2stringadd in scala.Predef.
   Definition Classes
     any2stringadd
4.  def ->[B](y: B): (Universe.Importer, B)
   Implicit
     This member is added by an implicit conversion from Universe.Importer toArrowAssoc[Universe.Importer] 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[lang]
   Definition Classes
     AnyRef
   Annotations
     @throws(classOf[java.lang.CloneNotSupportedException]) @native()
8.  def ensuring(cond: (Universe.Importer) => Boolean, msg: => Any): Universe.Importer
   Implicit
     This member is added by an implicit conversion from Universe.Importer toEnsuring[Universe.Importer] performed by method Ensuring in scala.Predef.
   Definition Classes
     Ensuring
9.  def ensuring(cond: (Universe.Importer) => Boolean): Universe.Importer
   Implicit
     This member is added by an implicit conversion from Universe.Importer toEnsuring[Universe.Importer] performed by method Ensuring in scala.Predef.
   Definition Classes
     Ensuring
10.  def ensuring(cond: Boolean, msg: => Any): Universe.Importer
    Implicit
      This member is added by an implicit conversion from Universe.Importer toEnsuring[Universe.Importer] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
11.  def ensuring(cond: Boolean): Universe.Importer
    Implicit
      This member is added by an implicit conversion from Universe.Importer toEnsuring[Universe.Importer] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
12.  final def eq(arg0: AnyRef): Boolean
    Definition Classes
      AnyRef
13.  def equals(arg0: AnyRef): Boolean
    Definition Classes
      AnyRef → Any
14.  def finalize(): Unit
    Attributes
      protected[lang]
    Definition Classes
      AnyRef
    Annotations
      @throws(classOf[java.lang.Throwable])
15.  final def getClass(): Class[_ <: AnyRef]
    Definition Classes
      AnyRef → Any
    Annotations
      @native()
16.  def hashCode(): Int
    Definition Classes
      AnyRef → Any
    Annotations
      @native()
17.  final def isInstanceOf[T0]: Boolean
    Definition Classes
      Any
18.  final def ne(arg0: AnyRef): Boolean
    Definition Classes
      AnyRef
19.  final def notify(): Unit
    Definition Classes
      AnyRef
    Annotations
      @native()
20.  final def notifyAll(): Unit
    Definition Classes
      AnyRef
    Annotations
      @native()
21.  final def synchronized[T0](arg0: => T0): T0
    Definition Classes
      AnyRef
22.  def toString(): String
    Definition Classes
      AnyRef → Any
23.  final def wait(): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws(classOf[java.lang.InterruptedException])
24.  final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws(classOf[java.lang.InterruptedException])
25.  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 Universe.Importer toStringFormat[Universe.Importer] 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): (Universe.Importer, B)
   Implicit
     This member is added by an implicit conversion from Universe.Importer toArrowAssoc[Universe.Importer] 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 AnyRef

### Inherited from Any

### Inherited by implicit conversion any2stringadd fromUniverse.Importer to any2stringadd[Universe.Importer]

### Inherited by implicit conversion StringFormat fromUniverse.Importer to StringFormat[Universe.Importer]

### Inherited by implicit conversion Ensuring fromUniverse.Importer to Ensuring[Universe.Importer]

### Inherited by implicit conversion ArrowAssoc fromUniverse.Importer to ArrowAssoc[Universe.Importer]

### Ungrouped