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Scala example source code file (Enclosures.scala)
The Enclosures.scala Scala example source codepackage scala package reflect package macros import scala.language.existentials // SI-6541 /** * <span class="badge badge-red" style="float: right;">EXPERIMENTAL</span> * * A slice of [[scala.reflect.macros.blackbox.Context the Scala macros context]] that exposes * enclosing trees (method, class, compilation unit and currently compiled macro application), * the enclosing position of the macro expansion, as well as macros and implicits * that are currently in-flight. * * Starting from Scala 2.11.0, the APIs to get the trees enclosing by the current macro application are deprecated, * and the reasons for that are two-fold. Firstly, we would like to move towards the philosophy of locally-expanded macros, * as it has proven to be important for understanding of code. Secondly, within the current architecture of scalac, * we are unable to have c.enclosingTree-style APIs working robustly. Required changes to the typechecker would greatly * exceed the effort that we would like to expend on this feature given the existence of more pressing concerns at the moment. * This is somewhat aligned with the overall evolution of macros during the 2.11 development cycle, where we played with * `c.introduceTopLevel` and `c.introduceMember`, but at the end of the day decided to reject them. * * If you're relying on the now deprecated APIs, consider using the new [[c.internal.enclosingOwner]] method that can be used to obtain * the names of enclosing definitions. Alternatively try reformulating your macros in terms of completely local expansion * and/or joining a discussion of a somewhat related potential language feature at [[https://groups.google.com/forum/#!topic/scala-debate/f4CLmYShX6Q]]. * We also welcome questions and suggestions on our mailing lists, where we would be happy to further discuss this matter. */ trait Enclosures { self: blackbox.Context => /** The tree that undergoes macro expansion. * Can be useful to get an offset or a range position of the entire tree being processed. */ def macroApplication: Tree /** Contexts that represent macros in-flight, including the current one. Very much like a stack trace, but for macros only. * Can be useful for interoperating with other macros and for imposing compiler-friendly limits on macro expansion. * * Is also priceless for emitting sane error messages for macros that are called by other macros on synthetic (i.e. position-less) trees. * In that dire case navigate the `enclosingMacros` stack, and it will most likely contain at least one macro with a position-ful macro application. * See `enclosingPosition` for a default implementation of this logic. * * Unlike `openMacros`, this is a val, which means that it gets initialized when the context is created * and always stays the same regardless of whatever happens during macro expansion. */ def enclosingMacros: List[blackbox.Context] /** Tries to guess a position for the enclosing application. * But that is simple, right? Just dereference `pos` of `macroApplication`? Not really. * If we're in a synthetic macro expansion (no positions), we must do our best to infer the position of something that triggerd this expansion. * Surprisingly, quite often we can do this by navigation the `enclosingMacros` stack. */ def enclosingPosition: Position /** Tree that corresponds to the enclosing method, or EmptyTree if not applicable. * @see [[scala.reflect.macros.Enclosures]] */ @deprecated("c.enclosingTree-style APIs are now deprecated; consult the scaladoc for more information", "2.11.0") def enclosingMethod: Tree /** Tree that corresponds to the enclosing class, or EmptyTree if not applicable. * @see [[scala.reflect.macros.Enclosures]] */ @deprecated("c.enclosingTree-style APIs are now deprecated; consult the scaladoc for more information", "2.11.0") def enclosingClass: Tree /** Tree that corresponds to the enclosing DefDef tree. * Throws `EnclosureException` if there's no such enclosing tree. * @see [[scala.reflect.macros.Enclosures]] */ @deprecated("c.enclosingTree-style APIs are now deprecated; consult the scaladoc for more information", "2.11.0") def enclosingDef: universe.DefDef /** Tree that corresponds to the enclosing Template tree. * Throws `EnclosureException` if there's no such enclosing tree. * @see [[scala.reflect.macros.Enclosures]] */ @deprecated("c.enclosingTree-style APIs are now deprecated; consult the scaladoc for more information", "2.11.0") def enclosingTemplate: universe.Template /** Tree that corresponds to the enclosing ImplDef tree (i.e. either ClassDef or ModuleDef). * Throws `EnclosureException` if there's no such enclosing tree. * @see [[scala.reflect.macros.Enclosures]] */ @deprecated("c.enclosingTree-style APIs are now deprecated; consult the scaladoc for more information", "2.11.0") def enclosingImpl: universe.ImplDef /** Tree that corresponds to the enclosing PackageDef tree. * Throws `EnclosureException` if there's no such enclosing tree. * @see [[scala.reflect.macros.Enclosures]] */ @deprecated("c.enclosingTree-style APIs are now deprecated; consult the scaladoc for more information", "2.11.0") def enclosingPackage: universe.PackageDef /** Compilation unit that contains this macro application. * @see [[scala.reflect.macros.Enclosures]] */ @deprecated("c.enclosingTree-style APIs are now deprecated; consult the scaladoc for more information", "2.11.0") def enclosingUnit: CompilationUnit /** Compilation run that contains this macro application. * @see [[scala.reflect.macros.Enclosures]] */ @deprecated("c.enclosingTree-style APIs are now deprecated; consult the scaladoc for more information", "2.11.0") def enclosingRun: Run /** Indicates than one of the enclosure methods failed to find a tree * of required type among enclosing trees. * @see [[scala.reflect.macros.Enclosures]] */ @deprecated("c.enclosingTree-style APIs are now deprecated; consult the scaladoc for more information", "2.11.0") case class EnclosureException(expected: Class[_], enclosingTrees: List[Tree]) extends Exception(s"Couldn't find a tree of type $expected among enclosing trees $enclosingTrees") } Other Scala source code examplesHere is a short list of links related to this Scala Enclosures.scala source code file: |
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