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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Abstract Value Members
-
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
. -
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.
-
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.
-
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.
-
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.
-
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
-
final
def
!=(arg0: Any): Boolean
Test two objects for inequality.
Test two objects for inequality.
- returns
true
if !(this == that), false otherwise.
- Definition Classes
- AnyRef → Any
-
final
def
##(): Int
Equivalent to
x.hashCode
except for boxed numeric types andnull
.Equivalent to
x.hashCode
except for boxed numeric types andnull
. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. Fornull
returns a hashcode wherenull.hashCode
throws aNullPointerException
.- returns
a hash value consistent with ==
- Definition Classes
- AnyRef → Any
-
def
+(other: String): String
- Implicit
- 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
-
def
->[B](y: B): (Universe.Importer, B)
- Implicit
- 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()
-
final
def
==(arg0: Any): Boolean
The expression
x == that
is equivalent toif (x eq null) that eq null else x.equals(that)
.The expression
x == that
is equivalent toif (x eq null) that eq null else x.equals(that)
.- returns
true
if the receiver object is equivalent to the argument;false
otherwise.
- Definition Classes
- AnyRef → Any
-
final
def
asInstanceOf[T0]: T0
Cast the receiver object to be of type
T0
.Cast the receiver object to be of type
T0
.Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression
1.asInstanceOf[String]
will throw aClassCastException
at runtime, while the expressionList(1).asInstanceOf[List[String]]
will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.- returns
the receiver object.
- Definition Classes
- Any
- Exceptions thrown
ClassCastException
if the receiver object is not an instance of the erasure of typeT0
.
-
def
clone(): AnyRef
Create a copy of the receiver object.
Create a copy of the receiver object.
The default implementation of the
clone
method is platform dependent.- returns
a copy of the receiver object.
- Attributes
- protected[java.lang]
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
- Note
not specified by SLS as a member of AnyRef
-
def
ensuring(cond: (Universe.Importer) ⇒ Boolean, msg: ⇒ Any): Universe.Importer
- Implicit
- 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
-
def
ensuring(cond: (Universe.Importer) ⇒ Boolean): Universe.Importer
- Implicit
- 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
-
def
ensuring(cond: Boolean, msg: ⇒ Any): Universe.Importer
- Implicit
- 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
-
def
ensuring(cond: Boolean): Universe.Importer
- Implicit
- 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
-
final
def
eq(arg0: AnyRef): Boolean
Tests whether the argument (
that
) is a reference to the receiver object (this
).Tests whether the argument (
that
) is a reference to the receiver object (this
).The
eq
method implements an equivalence relation on non-null instances ofAnyRef
, and has three additional properties:- It is consistent: for any non-null instances
x
andy
of typeAnyRef
, multiple invocations ofx.eq(y)
consistently returnstrue
or consistently returnsfalse
. - For any non-null instance
x
of typeAnyRef
,x.eq(null)
andnull.eq(x)
returnsfalse
. null.eq(null)
returnstrue
.
When overriding the
equals
orhashCode
methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2
), they should be equal to each other (o1 == o2
) and they should hash to the same value (o1.hashCode == o2.hashCode
).- returns
true
if the argument is a reference to the receiver object;false
otherwise.
- Definition Classes
- AnyRef
- It is consistent: for any non-null instances
-
def
equals(arg0: Any): Boolean
The equality method for reference types.
-
def
finalize(): Unit
Called by the garbage collector on the receiver object when there are no more references to the object.
Called by the garbage collector on the receiver object when there are no more references to the object.
The details of when and if the
finalize
method is invoked, as well as the interaction betweenfinalize
and non-local returns and exceptions, are all platform dependent.- Attributes
- protected[java.lang]
- Definition Classes
- AnyRef
- Annotations
- @throws( classOf[java.lang.Throwable] )
- Note
not specified by SLS as a member of AnyRef
-
def
formatted(fmtstr: String): String
- Implicit
- 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()
-
final
def
getClass(): Class[_]
Returns the runtime class representation of the object.
Returns the runtime class representation of the object.
- returns
a class object corresponding to the runtime type of the receiver.
- Definition Classes
- AnyRef → Any
-
def
hashCode(): Int
The hashCode method for reference types.
-
final
def
isInstanceOf[T0]: Boolean
Test whether the dynamic type of the receiver object is
T0
.Test whether the dynamic type of the receiver object is
T0
.Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression
1.isInstanceOf[String]
will returnfalse
, while the expressionList(1).isInstanceOf[List[String]]
will returntrue
. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.- returns
true
if the receiver object is an instance of erasure of typeT0
;false
otherwise.
- Definition Classes
- Any
-
final
def
ne(arg0: AnyRef): Boolean
Equivalent to
!(this eq that)
.Equivalent to
!(this eq that)
.- returns
true
if the argument is not a reference to the receiver object;false
otherwise.
- Definition Classes
- AnyRef
-
final
def
notify(): Unit
Wakes up a single thread that is waiting on the receiver object's monitor.
Wakes up a single thread that is waiting on the receiver object's monitor.
- Definition Classes
- AnyRef
- Note
not specified by SLS as a member of AnyRef
-
final
def
notifyAll(): Unit
Wakes up all threads that are waiting on the receiver object's monitor.
Wakes up all threads that are waiting on the receiver object's monitor.
- Definition Classes
- AnyRef
- Note
not specified by SLS as a member of AnyRef
-
final
def
synchronized[T0](arg0: ⇒ T0): T0
- Definition Classes
- AnyRef
-
def
toString(): String
Creates a String representation of this object.
Creates a String representation of this object. The default representation is platform dependent. On the java platform it is the concatenation of the class name, "@", and the object's hashcode in hexadecimal.
- returns
a String representation of the object.
- Definition Classes
- AnyRef → Any
-
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( ... )
-
def
→[B](y: B): (Universe.Importer, B)
- Implicit
- 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