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/Scala 2.13 Reflection

Trait scala.reflect.macros.Typers

trait Typers extends AnyRef

EXPERIMENTAL

A slice of the Scala macros context that partially exposes the type checker to macro writers.

Self Type
blackbox.Context
Source
Typers.scala
Linear Supertypes
AnyRef, Any
Known Subclasses
Context, Context

Type Members

type TypecheckException = macros.TypecheckException

See also

scala.reflect.macros.TypecheckException

abstract type TypecheckMode

Represents mode of operations of the typechecker underlying c.typecheck calls. Is necessary since the shape of the typechecked tree alone is not enough to guess how it should be typechecked. Can be TERMmode (typecheck as a term), TYPEmode (typecheck as a type) or PATTERNmode (typecheck as a pattern).

Abstract Value Members

abstract val PATTERNmode: blackbox.Context.TypecheckMode

abstract val TERMmode: blackbox.Context.TypecheckMode

Indicates that an argument to c.typecheck should be typechecked as a term. This is the default typechecking mode in Scala 2.11 and the only one supported in Scala 2.10.

abstract val TYPEmode: blackbox.Context.TypecheckMode

abstract def inferImplicitValue(pt: blackbox.Context.Type, silent: Boolean = true, withMacrosDisabled: Boolean = false, pos: blackbox.Context.Position = enclosingPosition): blackbox.Context.Tree

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.

Exceptions thrown

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

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.

Exceptions thrown

abstract def openMacros: List[blackbox.Context]

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.

abstract def typecheck(tree: blackbox.Context.Tree, mode: blackbox.Context.TypecheckMode = TERMmode, pt: blackbox.Context.Type = universe.WildcardType, silent: Boolean = false, withImplicitViewsDisabled: Boolean = false, withMacrosDisabled: Boolean = false): blackbox.Context.Tree

Typechecks the provided tree against the expected type pt in the macro callsite context under typechecking mode specified in mode with TERMmode being default. This populates symbols and types of the tree and possibly transforms it to reflect certain desugarings.

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

Exceptions thrown

abstract def untypecheck(tree: blackbox.Context.Tree): blackbox.Context.Tree

In the current implementation of Scala's reflection API, untyped trees (also known as parser trees or unattributed trees) are observationally different from typed trees (also known as typer trees, typechecked trees or attributed trees),

Usually, if some compiler API takes a tree, then both untyped and typed trees will do. However in some cases, only untyped or only typed trees are appropriate. For example, eval only accepts untyped trees and one can only splice typed trees inside typed trees. Therefore in the current reflection API, there is a need in functions that go back and forth between untyped and typed trees. For this we have typecheck and untypecheck.

Note that untypecheck is currently afflicted by https://github.com/scala/bug/issues/5464, which makes it sometimes corrupt trees so that they don't make sense anymore. Unfortunately, there's no workaround for that. We plan to fix this issue soon, but for now please keep it in mind.

See also

http://stackoverflow.com/questions/20936509/scala-macros-what-is-the-difference-between-typed-aka-typechecked-an-untyped

abstract def resetLocalAttrs(tree: blackbox.Context.Tree): blackbox.Context.Tree

Recursively resets locally defined symbols and types in a given tree. WARNING: Don't use this API, go for untypecheck instead.

Annotations
@deprecated
Deprecated

(Since version 2.11.0) use c.untypecheck instead

Concrete Value Members

final def !=(arg0: Any): Boolean

Definition Classes
AnyRef → Any

final def ##(): Int

Definition Classes
AnyRef → Any

def +(other: String): String

Implicit
This member is added by an implicit conversion from Typers toany2stringadd[Typers] performed by method any2stringadd in scala.Predef.
Definition Classes
any2stringadd

def ->[B](y: B): (Typers, B)

Implicit
This member is added by an implicit conversion from Typers toArrowAssoc[Typers] performed by method ArrowAssoc in scala.Predef.
Definition Classes
ArrowAssoc
Annotations
@inline()

final def ==(arg0: Any): Boolean

Definition Classes
AnyRef → Any

val TypecheckException: macros.TypecheckException.type

See also

scala.reflect.macros.TypecheckException

final def asInstanceOf[T0]: T0

Definition Classes
Any

def clone(): AnyRef

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

def ensuring(cond: (Typers) => Boolean, msg: => Any): Typers

Implicit
This member is added by an implicit conversion from Typers toEnsuring[Typers] performed by method Ensuring in scala.Predef.
Definition Classes
Ensuring

def ensuring(cond: (Typers) => Boolean): Typers

Implicit
This member is added by an implicit conversion from Typers toEnsuring[Typers] performed by method Ensuring in scala.Predef.
Definition Classes
Ensuring

def ensuring(cond: Boolean, msg: => Any): Typers

Implicit
This member is added by an implicit conversion from Typers toEnsuring[Typers] performed by method Ensuring in scala.Predef.
Definition Classes
Ensuring

def ensuring(cond: Boolean): Typers

Implicit
This member is added by an implicit conversion from Typers toEnsuring[Typers] performed by method Ensuring in scala.Predef.
Definition Classes
Ensuring

final def eq(arg0: AnyRef): Boolean

Definition Classes
AnyRef

def equals(arg0: AnyRef): Boolean

Definition Classes
AnyRef → Any

def finalize(): Unit

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

def formatted(fmtstr: String): String

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

final def getClass(): Class[_ <: AnyRef]

Definition Classes
AnyRef → Any
Annotations
@native()

def hashCode(): Int

Definition Classes
AnyRef → Any
Annotations
@native()

final def isInstanceOf[T0]: Boolean

Definition Classes
Any

final def ne(arg0: AnyRef): Boolean

Definition Classes
AnyRef

final def notify(): Unit

Definition Classes
AnyRef
Annotations
@native()

final def notifyAll(): Unit

Definition Classes
AnyRef
Annotations
@native()

final def synchronized[T0](arg0: => T0): T0

Definition Classes
AnyRef

def toString(): String

Definition Classes
AnyRef → Any

final def wait(): Unit

Definition Classes
AnyRef
Annotations
@throws(classOf[java.lang.InterruptedException])

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

Definition Classes
AnyRef
Annotations
@throws(classOf[java.lang.InterruptedException])

final def wait(arg0: Long): Unit

Definition Classes
AnyRef
Annotations
@throws(classOf[java.lang.InterruptedException]) @native()

© 2002-2019 EPFL, with contributions from Lightbend.
Licensed under the Apache License, Version 2.0.
https://www.scala-lang.org/api/2.13.0/scala-reflect/scala/reflect/macros/Typers.html