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

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

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### 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 information
     This member is added by an implicit conversion from Universe.Importer to any2stringadd[Universe.Importer] performed by method any2stringadd in scala.Predef.
   Definition Classes
     any2stringadd

4. #### def ->[B](y: B): (Universe.Importer, B)

   Implicit information
     This member is added by an implicit conversion from Universe.Importer to ArrowAssoc[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[java.lang]
   Definition Classes
     AnyRef
   Annotations
     @throws( ... )

8. #### def ensuring(cond: (Universe.Importer) ⇒ Boolean, msg: ⇒ Any): Universe.Importer

   Implicit information
     This member is added by an implicit conversion from Universe.Importer to Ensuring[Universe.Importer] performed by method Ensuring in scala.Predef.
   Definition Classes
     Ensuring

9. #### def ensuring(cond: (Universe.Importer) ⇒ Boolean): Universe.Importer

   Implicit information
     This member is added by an implicit conversion from Universe.Importer to Ensuring[Universe.Importer] performed by method Ensuring in scala.Predef.
   Definition Classes
     Ensuring

10. #### def ensuring(cond: Boolean, msg: ⇒ Any): Universe.Importer

    Implicit information
      This member is added by an implicit conversion from Universe.Importer to Ensuring[Universe.Importer] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring

11. #### def ensuring(cond: Boolean): Universe.Importer

    Implicit information
      This member is added by an implicit conversion from Universe.Importer to Ensuring[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: Any): Boolean

    Definition Classes
      AnyRef → Any

14. #### def finalize(): Unit

    Attributes
      protected[java.lang]
    Definition Classes
      AnyRef
    Annotations
      @throws( classOf[java.lang.Throwable] )

15. #### def formatted(fmtstr: String): String

    Implicit information
      This member is added by an implicit conversion from Universe.Importer to StringFormat[Universe.Importer] performed by method StringFormat in scala.Predef.
    Definition Classes
      StringFormat
    Annotations
      @inline()

16. #### final def getClass(): Class[_]

    Definition Classes
      AnyRef → Any

17. #### def hashCode(): Int

    Definition Classes
      AnyRef → Any

18. #### final def isInstanceOf[T0]: Boolean

    Definition Classes
      Any

19. #### final def ne(arg0: AnyRef): Boolean

    Definition Classes
      AnyRef

20. #### final def notify(): Unit

    Definition Classes
      AnyRef

21. #### final def notifyAll(): Unit

    Definition Classes
      AnyRef

22. #### final def synchronized[T0](arg0: ⇒ T0): T0

    Definition Classes
      AnyRef

23. #### def toString(): String

    Definition Classes
      AnyRef → Any

24. #### final def wait(): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

25. #### final def wait(arg0: Long, arg1: Int): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

26. #### final def wait(arg0: Long): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

27. #### def →[B](y: B): (Universe.Importer, B)

    Implicit information
      This member is added by an implicit conversion from Universe.Importer to ArrowAssoc[Universe.Importer] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
      ArrowAssoc

### Inherited from AnyRef

### Inherited from Any

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

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

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

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

### Ungrouped