Scala Reflection Library2.12.5 < Back
 

# Packages

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

  EXPERIMENTAL

  EXPERIMENTAL

  The base package for Scala macros.

  Macros are functions that are called by the compiler during compilation. Within these functions the programmer has access to compiler APIs. For example, it is possible to generate, analyze and typecheck code.

  See the Macros Guide on how to get started with Scala macros.

  Definition Classes
    reflect
-  package blackbox
  Definition Classes
    macros
-  package whitebox
  Definition Classes
    macros
- Context

p

scala.reflect.macros

# whitebox 

#### package whitebox

### Type Members

1.  trait Context extends blackbox.Context

   EXPERIMENTAL

   EXPERIMENTAL

   The whitebox Scala macros context.

   See the overview page for a description of how macros work. This documentation entry provides information on the API available to macro writers.

   A macro context wraps a compiler universe exposed in `universe` and having type scala.reflect.macros.Universe. This type is a refinement over the generic reflection API provided in scala.reflect.api.Universe. The extended Universe provides mutability for reflection artifacts (e.g. macros can change types of compiler trees, add annotation to symbols representing definitions, etc) and exposes some internal compiler functionality such as `Symbol.deSkolemize` or `Tree.attachments`.

   Another fundamental part of a macro context is `macroApplication`, which provides access to the tree undergoing macro expansion. Parts of this tree can be found in arguments of the corresponding macro implementations and in `prefix`, but `macroApplication` gives the full picture.

   Other than that, macro contexts provide facilities for typechecking, exploring the compiler's symbol table and enclosing trees and compilation units, evaluating trees, logging warnings/errors and much more. Refer to the documentation of top-level traits in this package to learn the details.

   If a macro def refers to a macro impl that uses `whitebox.Context`, then this macro def becomes a whitebox macro, gaining the ability to refine the type of its expansion beyond its official return type, which enables a number of important use cases. Blackbox macros, i.e. the ones defined with `blackbox.Context`, can't do that, so they are less powerful. However blackbox macros are also going to enjoy better support than whitebox macros, so choose wisely. See the Macros Guide for more information.

   See also

     `scala.reflect.macros.blackbox.Context`

### Ungrouped