scala.reflect.macros

Context

trait Context extends Aliases with Enclosures with Names with Reifiers with FrontEnds with Infrastructure with Typers with Parsers with Evals with ExprUtils with Synthetics

EXPERIMENTAL

The 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.

Source
Context.scala
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Type Members

  1. type CompilationUnit = Universe.CompilationUnit

    The type of compilation units.

    The type of compilation units.

    Definition Classes
    Aliases
  2. case class EnclosureException(expected: Class[_], enclosingTrees: List[Context.Tree]) extends Exception with Product with Serializable

    Indicates than one of the enclosure methods failed to find a tree of required type among enclosing trees.

  3. type Expr[+T] = Universe.Expr[T]

    Expr wraps an abstract syntax tree and tags it with its type.

    Expr wraps an abstract syntax tree and tags it with its type.

    Definition Classes
    Aliases
  4. abstract type MacroRole

    The semantic role that macroApplication plays in the code.

    The semantic role that macroApplication plays in the code.

    Definition Classes
    Enclosures
  5. type Modifiers = Universe.Modifiers

    The type of tree modifiers.

    The type of tree modifiers.

    Definition Classes
    Aliases
  6. type Name = Universe.Name

    The abstract type of names.

    The abstract type of names.

    Definition Classes
    Aliases
  7. trait PackageSpec[T] extends AnyRef

    A factory which can create a package def from a prototype and a list of declarations.

  8. type Position = Universe.Position

    Defines a universe-specific notion of positions.

    Defines a universe-specific notion of positions.

    Definition Classes
    Aliases
  9. abstract type PrefixType

    The type of the prefix tree from which the macro is selected.

    The type of the prefix tree from which the macro is selected. See the documentation entry for prefix for an example.

  10. type Run = Universe.Run

    The type of compilation runs.

    The type of compilation runs.

    Definition Classes
    Aliases
  11. type Scope = Universe.Scope

    The base type of all scopes.

    The base type of all scopes.

    Definition Classes
    Aliases
  12. type Symbol = Universe.Symbol

    The type of symbols representing declarations.

    The type of symbols representing declarations.

    Definition Classes
    Aliases
  13. type TermName = Universe.TermName

    The abstract type of names representing terms.

    The abstract type of names representing terms.

    Definition Classes
    Aliases
  14. type Tree = Universe.Tree

    The type of Scala abstract syntax trees.

    The type of Scala abstract syntax trees.

    Definition Classes
    Aliases
  15. type Type = Universe.Type

    The type of Scala types, and also Scala type signatures.

    The type of Scala types, and also Scala type signatures. (No difference is internally made between the two).

    Definition Classes
    Aliases
  16. type TypeName = Universe.TypeName

    The abstract type of names representing types.

    The abstract type of names representing types.

    Definition Classes
    Aliases
  17. type TypeTag[T] = Universe.TypeTag[T]

    The type of type tags.

    The type of type tags.

    Definition Classes
    Aliases
  18. type WeakTypeTag[T] = Universe.WeakTypeTag[T]

    The type of weak type tags.

    The type of weak type tags.

    Definition Classes
    Aliases

Abstract Value Members

  1. abstract def APPLY_ROLE: MacroRole

    The role that represents an application of a term macro, e.

    The role that represents an application of a term macro, e.g. M(2)(3) in val x = M(2)(3) or M(a, b) in x match { case x @ M(a, b) => }.

    Definition Classes
    Enclosures
  2. abstract def Expr[T](tree: Tree)(implicit arg0: WeakTypeTag[T]): Expr[T]

    A shorthand to create an expr.

    A shorthand to create an expr.

    Unlike the conventional expr factory, which requires a scala.reflect.api.TreeCreator, this one accepts a regular tree, but the resulting exprs are unable of being migrated to other universes/mirrors (the functionality normally not needed for macros, since there is only one compile-time universe and only one compile-time mirror).

    Definition Classes
    Aliases
  3. abstract def TypeTag[T](tpe: Type): TypeTag[T]

    A shorthand to create a type tag.

    A shorthand to create a type tag.

    Unlike the conventional type tag factory, which requires a scala.reflect.api.TypeCreator, this one accepts a regular type, but the resulting type tags are unable of being migrated to other universes/mirrors (the functionality normally not needed for macros, since there is only one compile-time universe and only one compile-time mirror).

    Definition Classes
    Aliases
  4. abstract def WeakTypeTag[T](tpe: Type): WeakTypeTag[T]

    A shorthand to create a weak type tag.

    A shorthand to create a weak type tag.

    Unlike the conventional type tag factory, which requires a scala.reflect.api.TypeCreator, this one accepts a regular type, but the resulting type tags are unable of being migrated to other universes/mirrors (the functionality normally not needed for macros, since there is only one compile-time universe and only one compile-time mirror).

    Definition Classes
    Aliases
  5. abstract def abort(pos: Position, msg: String): Nothing

    Abruptly terminates current macro expansion leaving a note about what happened.

    Abruptly terminates current macro expansion leaving a note about what happened. Use enclosingPosition if you're in doubt what position to pass to pos.

    Definition Classes
    FrontEnds
  6. abstract def classPath: List[URL]

    Exposes current classpath.

    Exposes current classpath.

    Definition Classes
    Infrastructure
  7. abstract def compilerSettings: List[String]

    Exposes current compiler settings as a list of options.

    Exposes current compiler settings as a list of options. Use scalac -help, scalac -X and scalac -Y to learn about currently supported options.

    Definition Classes
    Infrastructure
  8. abstract def echo(pos: Position, msg: String): Unit

    For sending a message which should not be labeled as a warning/error, but also shouldn't require -verbose to be visible.

    For sending a message which should not be labeled as a warning/error, but also shouldn't require -verbose to be visible. Use enclosingPosition if you're in doubt what position to pass to pos.

    Definition Classes
    FrontEnds
  9. abstract def enclosingDef: Universe.DefDef

    Tree that corresponds to the enclosing DefDef tree.

    Tree that corresponds to the enclosing DefDef tree. Throws EnclosureException if there's no such enclosing tree.

    Definition Classes
    Enclosures
  10. abstract def enclosingImpl: Universe.ImplDef

    Tree that corresponds to the enclosing ImplDef tree (i.

    Tree that corresponds to the enclosing ImplDef tree (i.e. either ClassDef or ModuleDef). Throws EnclosureException if there's no such enclosing tree.

    Definition Classes
    Enclosures
  11. abstract def enclosingImplicits: List[(Type, Tree)]

    Types along with corresponding trees for which implicit arguments are currently searched.

    Types along with corresponding trees for which implicit arguments are currently searched. Can be useful to get information about an application with an implicit parameter that is materialized during current macro expansion.

    Unlike openImplicits, 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.

    Definition Classes
    Enclosures
  12. abstract def enclosingMacros: List[Context]

    Contexts that represent macros in-flight, including the current one.

    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.

    Definition Classes
    Enclosures
  13. abstract def enclosingPackage: Universe.PackageDef

    Tree that corresponds to the enclosing PackageDef tree.

    Tree that corresponds to the enclosing PackageDef tree. Throws EnclosureException if there's no such enclosing tree.

    Definition Classes
    Enclosures
  14. abstract def enclosingPosition: Position

    Tries to guess a position for the enclosing application.

    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.

    Definition Classes
    Enclosures
  15. abstract def enclosingRun: Run

    Compilation run that contains this macro application.

    Compilation run that contains this macro application.

    Definition Classes
    Enclosures
  16. abstract def enclosingTemplate: Universe.Template

    Tree that corresponds to the enclosing Template tree.

    Tree that corresponds to the enclosing Template tree. Throws EnclosureException if there's no such enclosing tree.

    Definition Classes
    Enclosures
  17. abstract def enclosingUnit: CompilationUnit

    Compilation unit that contains this macro application.

    Compilation unit that contains this macro application.

    Definition Classes
    Enclosures
  18. abstract def error(pos: Position, msg: String): Unit

    Emits a compilation error.

    Emits a compilation error. Use enclosingPosition if you're in doubt what position to pass to pos.

    Definition Classes
    FrontEnds
  19. abstract def eval[T](expr: Expr[T]): T

    Takes a typed wrapper for a tree of type T and evaluates it to a value of type T.

    Takes a typed wrapper for a tree of type T and evaluates it to a value of type T.

    Can be used to perform compile-time computations on macro arguments to the extent permitted by the shape of the arguments.

    Known issues: because of https://issues.scala-lang.org/browse/SI-5748 trees being evaluated first need to undergo resetAllAttrs. Resetting symbols and types mutates the tree in place, therefore the conventional approach is to duplicate the tree first.

    scala> def impl(c: Context)(x: c.Expr[String]) = {
         | val x1 = c.Expr[String](c.resetAllAttrs(x.tree.duplicate))
         | println(s"compile-time value is: ${c.eval(x1)}")
         | x
         | }
    impl: (c: Context)(x: c.Expr[String])c.Expr[String]
    
    scala> def test(x: String) = macro impl
    test: (x: String)String
    
    scala> test("x")
    compile-time value is: x
    res0: String = x
    
    scala> test("x" + "y")
    compile-time value is: xy
    res1: String = xy
    
    scala> val x = "x"
    x: String = x
    
    scala> test(x + "y")
    compile-time value is: xy
    res2: String = xy
    
    scala> { val x = "x"; test(x + "y") }
    error: exception during macro expansion:
    scala.tools.reflect.ToolBoxError: reflective compilation failed

    Note that in the last case evaluation has failed, because the argument of a macro refers to a runtime value x, which is unknown at compile time.

    Definition Classes
    Evals
  20. abstract def freshName[NameType <: Name](name: NameType): NameType

    Creates a unique name having a given name as a prefix and having the same flavor (term name or type name) as the given name.

    Creates a unique name having a given name as a prefix and having the same flavor (term name or type name) as the given name.

    Definition Classes
    Names
  21. abstract def freshName(name: String): String

    Creates a unique string having a given prefix.

    Creates a unique string having a given prefix.

    Definition Classes
    Names
  22. abstract def freshName(): String

    Creates a unique string.

    Creates a unique string.

    Definition Classes
    Names
  23. abstract def hasErrors: Boolean

    Does the compilation session have any errors?

    Does the compilation session have any errors?

    Definition Classes
    FrontEnds
  24. abstract def hasWarnings: Boolean

    Does the compilation session have any warnings?

    Does the compilation session have any warnings?

    Definition Classes
    FrontEnds
  25. abstract def inferImplicitValue(pt: Type, silent: Boolean = true, withMacrosDisabled: Boolean = false, pos: Position = enclosingPosition): Tree

    Infers an implicit value of the expected type pt in the macro callsite context.

    Infers an implicit value of the expected type pt in the macro callsite context. Optional pos parameter provides a position that will be associated with the implicit search.

    If silent is false, TypecheckException will be thrown in case of an inference error. If silent is true, the typecheck is silent and will return EmptyTree if an error occurs. Such errors don't vanish and can be inspected by turning on -Xlog-implicits. Unlike in typeCheck, silent is true by default.

    Definition Classes
    Typers
    Exceptions thrown
    [[scala.reflect.macros.TypecheckException]]

  26. abstract def inferImplicitView(tree: Tree, from: Type, to: Type, silent: Boolean = true, withMacrosDisabled: Boolean = false, pos: Position = enclosingPosition): Tree

    Infers an implicit view from the provided tree tree of the type from to the type to in the macro callsite context.

    Infers an implicit view from the provided tree tree of the type from to the type to in the macro callsite context. Optional pos parameter provides a position that will be associated with the implicit search.

    If silent is false, TypecheckException will be thrown in case of an inference error. If silent is true, the typecheck is silent and will return EmptyTree if an error occurs. Such errors don't vanish and can be inspected by turning on -Xlog-implicits. Unlike in typeCheck, silent is true by default.

    Definition Classes
    Typers
    Exceptions thrown
    [[scala.reflect.macros.TypecheckException]]

  27. abstract def info(pos: Position, msg: String, force: Boolean): Unit

    Emits an informational message, suppressed unless -verbose or force=true.

    Emits an informational message, suppressed unless -verbose or force=true. Use enclosingPosition if you're in doubt what position to pass to pos.

    Definition Classes
    FrontEnds
  28. abstract def introduceTopLevel[T](packagePrototype: T, definitions: Universe.ImplDef*)(implicit arg0: PackageSpec[T]): List[Universe.RefTree]

    Adds a list of top-level definitions to the compiler's symbol table.

    Adds a list of top-level definitions to the compiler's symbol table. _TOP_LEVEL Allowed definitions include classes (represented by ClassDef trees), traits (represented by ClassDef trees having the TRAIT flag set in mods) and objects (represented by ModuleDef trees).

    The definitions are put into the package with a prototype provided in packagePrototype. Supported prototypes are (see PackageSpec for more details): * Strings and names representing a fully-qualified name of the package * Trees that can work as package ids * Package or package class symbols

    Typical value for a package prototype is a fully-qualified name in a string. For example, to generate a class available at foo.bar.Test, call this method as follows:

    introduceTopLevel("foo.bar", ClassDef(<mods>, TypeName("Test"), <tparams>, <template>))

    It is possible to add definitions to the empty package by using nme.EMPTY_PACKAGE_NAME.toString, but that's not recommended, since such definitions cannot be seen from outside the empty package.

    Only the multi-parameter overload of this method can be used to introduce companions. If companions are introduced by two different calls, then they will be put into different virtual files, and scalac will show an error about companions being defined in different files. By the way, this also means that there's currently no way to define a companion for an existing class or module_TOP_LEVEL.

    Returns a list of fully-qualified references to the introduced definitions.

    Definition Classes
    Synthetics
  29. abstract def introduceTopLevel[T](packagePrototype: T, definition: Universe.ImplDef)(implicit arg0: PackageSpec[T]): Universe.RefTree

    Adds a top-level definition to the compiler's symbol table.

    Adds a top-level definition to the compiler's symbol table. _TOP_LEVEL Allowed definitions include classes (represented by ClassDef trees), traits (represented by ClassDef trees having the TRAIT flag set in mods) and objects (represented by ModuleDef trees).

    The definitions are put into the package with a prototype provided in packagePrototype. Supported prototypes are (see PackageSpec for more details): * Strings and names representing a fully-qualified name of the package * Trees that can work as package ids * Package or package class symbols

    Typical value for a package prototype is a fully-qualified name in a string. For example, to generate a class available at foo.bar.Test, call this method as follows:

    introduceTopLevel("foo.bar", ClassDef(<mods>, TypeName("Test"), <tparams>, <template>))

    It is possible to add definitions to the empty package by using nme.EMPTY_PACKAGE_NAME.toString, but that's not recommended, since such definitions cannot be seen from outside the empty package.

    Only the multi-parameter overload of this method can be used to introduce companions. If companions are introduced by two different calls, then they will be put into different virtual files, and scalac will show an error about companions being defined in different files. By the way, this also means that there's currently no way to define a companion for an existing class or module_TOP_LEVEL.

    Returns a fully-qualified reference to the introduced definition.

    Definition Classes
    Synthetics
  30. abstract def literal(x: Char): Expr[Char]

    Shorthand for Literal(Constant(x: Char)) in the underlying universe.

    Shorthand for Literal(Constant(x: Char)) in the underlying universe.

    Definition Classes
    ExprUtils
  31. abstract def literal(x: String): Expr[String]

    Shorthand for Literal(Constant(x: String)) in the underlying universe.

    Shorthand for Literal(Constant(x: String)) in the underlying universe.

    Definition Classes
    ExprUtils
  32. abstract def literal(x: Double): Expr[Double]

    Shorthand for Literal(Constant(x: Double)) in the underlying universe.

    Shorthand for Literal(Constant(x: Double)) in the underlying universe.

    Definition Classes
    ExprUtils
  33. abstract def literal(x: Float): Expr[Float]

    Shorthand for Literal(Constant(x: Float)) in the underlying universe.

    Shorthand for Literal(Constant(x: Float)) in the underlying universe.

    Definition Classes
    ExprUtils
  34. abstract def literal(x: Long): Expr[Long]

    Shorthand for Literal(Constant(x: Long)) in the underlying universe.

    Shorthand for Literal(Constant(x: Long)) in the underlying universe.

    Definition Classes
    ExprUtils
  35. abstract def literal(x: Int): Expr[Int]

    Shorthand for Literal(Constant(x: Int)) in the underlying universe.

    Shorthand for Literal(Constant(x: Int)) in the underlying universe.

    Definition Classes
    ExprUtils
  36. abstract def literal(x: Short): Expr[Short]

    Shorthand for Literal(Constant(x: Short)) in the underlying universe.

    Shorthand for Literal(Constant(x: Short)) in the underlying universe.

    Definition Classes
    ExprUtils
  37. abstract def literal(x: Byte): Expr[Byte]

    Shorthand for Literal(Constant(x: Byte)) in the underlying universe.

    Shorthand for Literal(Constant(x: Byte)) in the underlying universe.

    Definition Classes
    ExprUtils
  38. abstract def literal(x: Boolean): Expr[Boolean]

    Shorthand for Literal(Constant(x: Boolean)) in the underlying universe.

    Shorthand for Literal(Constant(x: Boolean)) in the underlying universe.

    Definition Classes
    ExprUtils
  39. abstract def literalFalse: Expr[Boolean]

    Shorthand for Literal(Constant(false)) in the underlying universe.

    Shorthand for Literal(Constant(false)) in the underlying universe.

    Definition Classes
    ExprUtils
  40. abstract def literalNull: Expr[Null]

    Shorthand for Literal(Constant(null)) in the underlying universe.

    Shorthand for Literal(Constant(null)) in the underlying universe.

    Definition Classes
    ExprUtils
  41. abstract def literalTrue: Expr[Boolean]

    Shorthand for Literal(Constant(true)) in the underlying universe.

    Shorthand for Literal(Constant(true)) in the underlying universe.

    Definition Classes
    ExprUtils
  42. abstract def literalUnit: Expr[Unit]

    Shorthand for Literal(Constant(())) in the underlying universe.

    Shorthand for Literal(Constant(())) in the underlying universe.

    Definition Classes
    ExprUtils
  43. abstract def macroApplication: Tree

    The tree that undergoes macro expansion.

    The tree that undergoes macro expansion. Can be useful to get an offset or a range position of the entire tree being processed.

    Definition Classes
    Enclosures
  44. abstract def macroRole: MacroRole

    The semantic role that macroApplication plays in the code.

    The semantic role that macroApplication plays in the code.

    Definition Classes
    Enclosures
  45. abstract val mirror: Universe.Mirror

    The mirror of the compile-time universe.

  46. abstract def mkPackageDef(sym: Symbol, stats: List[Tree]): Universe.PackageDef

    Attributes
    protected
    Definition Classes
    Synthetics
  47. abstract def mkPackageDef(tree: Universe.RefTree, stats: List[Tree]): Universe.PackageDef

    Attributes
    protected
    Definition Classes
    Synthetics
  48. abstract def mkPackageDef(name: TermName, stats: List[Tree]): Universe.PackageDef

    Attributes
    protected
    Definition Classes
    Synthetics
  49. abstract def mkPackageDef(name: String, stats: List[Tree]): Universe.PackageDef

    Attributes
    protected
    Definition Classes
    Synthetics
  50. abstract def openImplicits: List[(Type, Tree)]

    Types along with corresponding trees for which implicit arguments are currently searched.

    Types along with corresponding trees for which implicit arguments are currently searched. Can be useful to get information about an application with an implicit parameter that is materialized during current macro expansion.

    Unlike enclosingImplicits, this is a def, which means that it gets recalculated on every invocation, so it might change depending on what is going on during macro expansion.

    Definition Classes
    Typers
  51. abstract def openMacros: List[Context]

    Contexts that represent macros in-flight, including the current one.

    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 openMacros 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 enclosingMacros, this is a def, which means that it gets recalculated on every invocation, so it might change depending on what is going on during macro expansion.

    Definition Classes
    Typers
  52. abstract def parse(code: String): Tree

    Parses a string with a Scala expression into an abstract syntax tree.

    Parses a string with a Scala expression into an abstract syntax tree. Only works for expressions, i.e. parsing a package declaration will fail.

    Definition Classes
    Parsers
    Exceptions thrown
    [[scala.reflect.macros.ParseException]]

  53. abstract val prefix: Expr[PrefixType]

    The prefix tree from which the macro is selected.

    The prefix tree from which the macro is selected.

    For example, for a macro filter defined as an instance method on a collection Coll, prefix represents an equivalent of this for normal instance methods:

    scala> class Coll[T] {
         | def filter(p: T => Boolean): Coll[T] = macro M.filter[T]
         | }; object M {
         | def filter[T](c: Context { type PrefixType = Coll[T] })
         |              (p: c.Expr[T => Boolean]): c.Expr[Coll[T]] =
         |   {
         |     println(c.prefix.tree)
         |     c.prefix
         |   }
         | }
    defined class Coll
    defined module Macros
    
    scala> new Coll[Int]().filter(_ % 2 == 0)
    new Coll[Int]()
    res0: Coll[Int] = ...
    
    scala> val x = new Coll[String]()
    x: Coll[String] = ...
    
    scala> x.filter(_ != "")
    $line11.$read.$iw.$iw.$iw.$iw.$iw.$iw.$iw.$iw.$iw.$iw.$iw.$iw.x
    res1 @ 35563b4b: x.type = ...

    Note how the value of prefix changes depending on the qualifier of the macro call (i.e. the expression that is at the left-hand side of the dot).

    Another noteworthy thing about the snippet above is the Context { type PrefixType = Coll[T] } type that is used to stress that the macro implementation works with prefixes of type Coll[T].

  54. abstract def reifyEnclosingRuntimeClass: Tree

    Given a type, generate a tree that when compiled and executed produces the runtime class of the enclosing class or module.

    Given a type, generate a tree that when compiled and executed produces the runtime class of the enclosing class or module. Returns EmptyTree if there does not exist an enclosing class or module.

    Definition Classes
    Reifiers
  55. abstract def reifyRuntimeClass(tpe: Type, concrete: Boolean = true): Tree

    Given a type, generate a tree that when compiled and executed produces the runtime class of the original type.

    Given a type, generate a tree that when compiled and executed produces the runtime class of the original type. If concrete is true, then this function will bail on types, who refer to abstract types (like ClassTag does).

    Definition Classes
    Reifiers
  56. abstract def reifyTree(universe: Tree, mirror: Tree, tree: Tree): Tree

    Given a tree, generate a tree that when compiled and executed produces the original tree.

    Given a tree, generate a tree that when compiled and executed produces the original tree. For more information and examples see the documentation for Universe.reify.

    The produced tree will be bound to the specified universe and mirror. Possible values for universe include universe.treeBuild.mkRuntimeUniverseRef. Possible values for mirror include EmptyTree (in that case the reifier will automatically pick an appropriate mirror).

    This function is deeply connected to Universe.reify, a macro that reifies arbitrary expressions into runtime trees. They do very similar things (Universe.reify calls Context.reifyTree to implement itself), but they operate on different metalevels (see below).

    Let's study the differences between Context.reifyTree and Universe.reify on an example of using them inside a fooMacro macro:

    * Since reify itself is a macro, it will be executed when fooMacro is being compiled (metalevel -1) and will produce a tree that when evaluated during macro expansion of fooMacro (metalevel 0) will recreate the input tree.

    This provides a facility analogous to quasi-quoting. Writing "reify{ expr }" will generate an AST that represents expr. Afterwards this AST (or its parts) can be used to construct the return value of fooMacro.

    * reifyTree is evaluated during macro expansion (metalevel 0) and will produce a tree that when evaluated during the runtime of the program (metalevel 1) will recreate the input tree.

    This provides a way to retain certain trees from macro expansion time to be inspected later, in the runtime. For example, DSL authors may find it useful to capture DSL snippets into ASTs that are then processed at runtime in a domain-specific way.

    Also note the difference between universes of the runtime trees produced by two reifies:

    * The result of compiling and running the result of reify will be bound to the Universe that called reify. This is possible because it's a macro, so it can generate whatever code it wishes.

    * The result of compiling and running the result of reifyTree will be the prefix that needs to be passed explicitly. This happens because the Universe of the evaluated result is from a different metalevel than the Context the called reify.

    Typical usage of this function is to retain some of the trees received/created by a macro into the form that can be inspected (via pattern matching) or compiled/run (by a reflective ToolBox) during the runtime.

    Definition Classes
    Reifiers
  57. abstract def reifyType(universe: Tree, mirror: Tree, tpe: Type, concrete: Boolean = false): Tree

    Given a type, generate a tree that when compiled and executed produces the original type.

    Given a type, generate a tree that when compiled and executed produces the original type. The produced tree will be bound to the specified universe and mirror. For more information and examples see the documentation for Context.reifyTree and Universe.reify.

    Definition Classes
    Reifiers
  58. abstract def resetAllAttrs(tree: Tree): Tree

    Recursively resets symbols and types in a given tree.

    Recursively resets symbols and types in a given tree.

    Note that this does not revert the tree to its pre-typer shape. For more info, read up https://issues.scala-lang.org/browse/SI-5464.

    Definition Classes
    Typers
  59. abstract def resetLocalAttrs(tree: Tree): Tree

    Recursively resets locally defined symbols and types in a given tree.

    Recursively resets locally defined symbols and types in a given tree.

    Note that this does not revert the tree to its pre-typer shape. For more info, read up https://issues.scala-lang.org/browse/SI-5464.

    Definition Classes
    Typers
  60. abstract def settings: List[String]

    Exposes macro-specific settings as a list of strings.

    Exposes macro-specific settings as a list of strings. These settings are passed to the compiler via the "-Xmacro-settings:setting1,setting2...,settingN" command-line option.

    Definition Classes
    Infrastructure
  61. abstract def topLevelDef(name: Name): Tree

    Looks up a top-level definition tree with a given fully-qualified name (term name for modules, type name for classes).

    Looks up a top-level definition tree with a given fully-qualified name (term name for modules, type name for classes). _TREE Top-level tree is a tree that represents a non-inner class or object in one of the currently compiled source files. Note that top-level isn't equivalent to scala.reflect.api.Symbols#SymbolApi.isStatic, because static also embraces definitions nested in static objects _TREE. If such a tree does not exist, returns EmptyTree.

    Definition Classes
    Synthetics
  62. abstract def topLevelRef(name: Name): Tree

    Returns a reference to a top-level definition tree with a given fully-qualified name (term name for modules, type name for classes).

    Returns a reference to a top-level definition tree with a given fully-qualified name (term name for modules, type name for classes). _TREE Top-level tree is a tree that represents a non-inner class or object in one of the currently compiled source files. Note that top-level isn't equivalent to scala.reflect.api.Symbols#SymbolApi.isStatic, because static also embraces definitions nested in static objects _TREE. If such a tree does not exist, returns EmptyTree.

    Definition Classes
    Synthetics
  63. abstract def typeCheck(tree: Tree, pt: Type = WildcardType, silent: Boolean = false, withImplicitViewsDisabled: Boolean = false, withMacrosDisabled: Boolean = false): Tree

    Typechecks the provided tree against the expected type pt in the macro callsite context.

    Typechecks the provided tree against the expected type pt in the macro callsite context.

    If silent is false, TypecheckException will be thrown in case of a typecheck error. If silent is true, the typecheck is silent and will return EmptyTree if an error occurs. Such errors don't vanish and can be inspected by turning on -Ymacro-debug-verbose. Unlike in inferImplicitValue and inferImplicitView, silent is false by default.

    Typechecking can be steered with the following optional parameters: withImplicitViewsDisabled recursively prohibits implicit views (though, implicit vals will still be looked up and filled in), default value is false withMacrosDisabled recursively prohibits macro expansions and macro-based implicits, default value is false

    Definition Classes
    Typers
    Exceptions thrown
    [[scala.reflect.macros.TypecheckException]]

  64. abstract val universe: Universe

    The compile-time universe.

  65. abstract def unreifyTree(tree: Tree): Tree

    Undoes reification of a tree.

    Undoes reification of a tree.

    This reversion doesn't simply restore the original tree (that would lose the context of reification), but does something more involved that conforms to the following laws:

    1) unreifyTree(reifyTree(tree)) != tree // unreified tree is tree + saved context // in current implementation, the result of unreify is opaque // i.e. there's no possibility to inspect underlying tree/context

    2) reifyTree(unreifyTree(reifyTree(tree))) == reifyTree(tree) // the result of reifying a tree in its original context equals to // the result of reifying a tree along with its saved context

    3) compileAndEval(unreifyTree(reifyTree(tree))) ~ compileAndEval(tree) // at runtime original and unreified trees are behaviorally equivalent

    Definition Classes
    Reifiers
  66. abstract def warning(pos: Position, msg: String): Unit

    Emits a warning.

    Emits a warning. Use enclosingPosition if you're in doubt what position to pass to pos.

    Definition Classes
    FrontEnds
  67. abstract def enclosingClass: Tree

    Tree that corresponds to the enclosing class, or EmptyTree if not applicable.

    Tree that corresponds to the enclosing class, or EmptyTree if not applicable.

    Definition Classes
    Enclosures
    Annotations
    @deprecated
    Deprecated

    (Since version 2.10.1) Use enclosingImpl instead, but be wary of changes in semantics

  68. abstract def enclosingMethod: Tree

    Tree that corresponds to the enclosing method, or EmptyTree if not applicable.

    Tree that corresponds to the enclosing method, or EmptyTree if not applicable.

    Definition Classes
    Enclosures
    Annotations
    @deprecated
    Deprecated

    (Since version 2.10.1) Use enclosingDef instead, but be wary of changes in semantics

  69. abstract def fresh[NameType <: Name](name: NameType): NameType

    Creates a unique name having a given name as a prefix and having the same flavor (term name or type name) as the given name.

    Creates a unique name having a given name as a prefix and having the same flavor (term name or type name) as the given name.

    Definition Classes
    Names
    Annotations
    @deprecated
    Deprecated

    (Since version 2.11.0) Use freshName instead

  70. abstract def fresh(name: String): String

    Creates a unique string having a given prefix.

    Creates a unique string having a given prefix.

    Definition Classes
    Names
    Annotations
    @deprecated
    Deprecated

    (Since version 2.11.0) Use freshName instead

  71. abstract def fresh(): String

    Creates a unique string.

    Creates a unique string.

    Definition Classes
    Names
    Annotations
    @deprecated
    Deprecated

    (Since version 2.11.0) Use freshName instead

Concrete Value Members

  1. final def !=(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef
  2. final def !=(arg0: Any): Boolean

    Definition Classes
    Any
  3. final def ##(): Int

    Definition Classes
    AnyRef → Any
  4. def +(other: String): String

    Implicit information
    This member is added by an implicit conversion from Context to StringAdd[Context] performed by method StringAdd in scala.Predef.
    Definition Classes
    StringAdd
  5. def ->[B](y: B): (Context, B)

    Implicit information
    This member is added by an implicit conversion from Context to ArrowAssoc[Context] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc
    Annotations
    @inline()
  6. final def ==(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef
  7. final def ==(arg0: Any): Boolean

    Definition Classes
    Any
  8. val Expr: Universe.Expr.type

    Constructor/Extractor for Expr.

    Constructor/Extractor for Expr.

    Definition Classes
    Aliases
  9. object PackageSpec

    Hosts supported package specs.

  10. val TypeTag: Universe.TypeTag.type

    Constructor/Extractor for TypeTag.

    Constructor/Extractor for TypeTag.

    Definition Classes
    Aliases
  11. val WeakTypeTag: Universe.WeakTypeTag.type

    Constructor/Extractor for WeakTypeTag.

    Constructor/Extractor for WeakTypeTag.

    Definition Classes
    Aliases
  12. final def asInstanceOf[T0]: T0

    Definition Classes
    Any
  13. def clone(): AnyRef

    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws()
  14. def ensuring(cond: (Context) ⇒ Boolean, msg: ⇒ Any): Context

    Implicit information
    This member is added by an implicit conversion from Context to Ensuring[Context] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  15. def ensuring(cond: (Context) ⇒ Boolean): Context

    Implicit information
    This member is added by an implicit conversion from Context to Ensuring[Context] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  16. def ensuring(cond: Boolean, msg: ⇒ Any): Context

    Implicit information
    This member is added by an implicit conversion from Context to Ensuring[Context] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  17. def ensuring(cond: Boolean): Context

    Implicit information
    This member is added by an implicit conversion from Context to Ensuring[Context] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  18. final def eq(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef
  19. def equals(arg0: Any): Boolean

    Definition Classes
    AnyRef → Any
  20. def finalize(): Unit

    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws()
  21. def formatted(fmtstr: String): String

    Returns string formatted according to given format string.

    Returns string formatted according to given format string. Format strings are as for String.format (@see java.lang.String.format).

    Implicit information
    This member is added by an implicit conversion from Context to StringFormat[Context] performed by method StringFormat in scala.Predef.
    Definition Classes
    StringFormat
    Annotations
    @inline()
  22. final def getClass(): Class[_]

    Definition Classes
    AnyRef → Any
  23. def hashCode(): Int

    Definition Classes
    AnyRef → Any
  24. final def isInstanceOf[T0]: Boolean

    Definition Classes
    Any
  25. final def ne(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef
  26. final def notify(): Unit

    Definition Classes
    AnyRef
  27. final def notifyAll(): Unit

    Definition Classes
    AnyRef
  28. final def synchronized[T0](arg0: ⇒ T0): T0

    Definition Classes
    AnyRef
  29. def toString(): String

    Definition Classes
    AnyRef → Any
  30. def typeOf[T](implicit ttag: TypeTag[T]): Type

    Shortcut for implicitly[TypeTag[T]].tpe

    Shortcut for implicitly[TypeTag[T]].tpe

    Definition Classes
    Aliases
  31. def typeTag[T](implicit ttag: TypeTag[T]): TypeTag[T]

    Shortcut for implicitly[TypeTag[T]]

    Shortcut for implicitly[TypeTag[T]]

    Definition Classes
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  32. final def wait(): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws()
  33. final def wait(arg0: Long, arg1: Int): Unit

    Definition Classes
    AnyRef
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    @throws()
  34. final def wait(arg0: Long): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws()
  35. def weakTypeOf[T](implicit attag: WeakTypeTag[T]): Type

    Shortcut for implicitly[WeakTypeTag[T]].tpe

    Shortcut for implicitly[WeakTypeTag[T]].tpe

    Definition Classes
    Aliases
  36. def weakTypeTag[T](implicit attag: WeakTypeTag[T]): WeakTypeTag[T]

    Shortcut for implicitly[WeakTypeTag[T]]

    Shortcut for implicitly[WeakTypeTag[T]]

    Definition Classes
    Aliases
  37. def [B](y: B): (Context, B)

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

Inherited from Synthetics

Inherited from ExprUtils

Inherited from Evals

Inherited from Parsers

Inherited from Typers

Inherited from Infrastructure

Inherited from FrontEnds

Inherited from Reifiers

Inherited from Names

Inherited from Enclosures

Inherited from Aliases

Inherited from AnyRef

Inherited from Any

Inherited by implicit conversion StringAdd from Context to StringAdd[Context]

Inherited by implicit conversion StringFormat from Context to StringFormat[Context]

Inherited by implicit conversion Ensuring from Context to Ensuring[Context]

Inherited by implicit conversion ArrowAssoc from Context to ArrowAssoc[Context]

Ungrouped