scala.reflect.macros.TypecheckException
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).
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.
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.
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.
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.
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
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.
Recursively resets locally defined symbols and types in a given tree. WARNING: Don't use this API, go for untypecheck instead.
(Since version 2.11.0) use c.untypecheck
instead
scala.reflect.macros.TypecheckException
© 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
EXPERIMENTAL
A slice of the Scala macros context that partially exposes the type checker to macro writers.