Expands a term macro used in apply role as M(2)(3)
in val x = M(2)(3)
.
Calculate the arguments to pass to a macro implementation when expanding the provided tree.
Performs macro expansion:
Performs macro expansion:
A term of one of the following shapes:
Ident(<term macro>) Select(<any qualifier>, <term macro>) TypeApply(<any of the above>, <targs>) Apply(...Apply(<any of the above>, <args1>)...<argsN>)
First of all macroExpandXXX
:
1) If necessary desugars the expandee
to fit into the default expansion scheme
that is understood by macroExpandWithRuntime
/ macroExpandWithoutRuntime
Then macroExpandWithRuntime
:
2) Checks whether the expansion needs to be delayed
3) Loads macro implementation using macroMirror
4) Synthesizes invocation arguments for the macro implementation
5) Checks that the result is a tree or an expr bound to this universe
Finally macroExpandXXX
:
6) Validates the expansion against the white list of supported tree shapes
7) Typechecks the result as required by the circumstances of the macro application
If -Ymacro-debug-lite is enabled, you will get basic notifications about macro expansion along with macro expansions logged in the form that can be copy/pasted verbatim into REPL.
If -Ymacro-debug-verbose is enabled, you will get detailed log of how exactly this function performs class loading and method resolution in order to load the macro implementation. The log will also include other non-trivial steps of macro expansion.
the expansion result if the expansion has been successful, the fallback tree if the expansion has been unsuccessful, but there is a fallback, the expandee unchanged if the expansion has been delayed, the expandee fully expanded if the expansion has been delayed before and has been expanded now, the expandee with an error marker set if the expansion has been cancelled due malformed arguments or implementation the expandee with an error marker set if there has been an error
Represents all the information that a macro definition needs to know about its implementation.
Represents all the information that a macro definition needs to know about its implementation. Includes a path to load the implementation via Java reflection, and various accounting information necessary when composing an argument list for the reflective invocation.
Abstracts away resolution of macro runtimes.
Abstracts away resolution of macro runtimes.
Keeps track of macros in-flight.
Keeps track of macros in-flight.
See more informations in comments to openMacros
in scala.reflect.macros.whitebox.Context
.
Decreases metalevel of the type, i.e.
Decreases metalevel of the type, i.e. transforms: * c.Expr[T] to T * Nothing to Nothing * Anything else to NoType
Metalevels.scala for more information and examples about metalevels
Macro classloader that is used to resolve and run macro implementations.
Macro classloader that is used to resolve and run macro implementations. Loads classes from from -cp (aka the library classpath). Is also capable of detecting REPL and reusing its classloader.
When -Xmacro-jit is enabled, we sometimes fallback to on-the-fly compilation of macro implementations, which compiles implementations into a virtual directory (very much like REPL does) and then conjures a classloader mapped to that virtual directory.
Without any restrictions on macro expansion, macro applications will expand at will, and when type inference is involved, expansions will end up using yet uninferred type params.
Without any restrictions on macro expansion, macro applications will expand at will, and when type inference is involved, expansions will end up using yet uninferred type params.
For some macros this might be ok (thanks to TreeTypeSubstituter that replaces the occurrences of undetparams with their inferred values), but in general case this won't work. E.g. for reification simple substitution is not enough - we actually need to re-reify inferred types.
Luckily, there exists a very simple way to fix the problem: delay macro expansion until everything is inferred. Here are the exact rules. Macro application gets delayed if any of its subtrees contain: 1) type vars (tpe.isInstanceOf[TypeVar]) // [Eugene] this check is disabled right now, because TypeVars seem to be created from undetparams anyways 2) undetparams (sym.isTypeParameter && !sym.isSkolem)
Increases metalevel of the type, i.e.
Increases metalevel of the type, i.e. transforms: * T to c.Expr[T]
Metalevels.scala for more information and examples about metalevels
Macro def -> macro impl bindings are serialized into a macroImpl
annotation
with synthetic content that carries the payload described in MacroImplBinding
.
Macro def -> macro impl bindings are serialized into a macroImpl
annotation
with synthetic content that carries the payload described in MacroImplBinding
.
For example, for a pair of macro definition and macro implementation: def impl(c: scala.reflect.macros.blackbox.Context): c.Expr[Unit] = ??? def foo: Unit = macro impl
We will have the following annotation added on the macro definition foo
:
Expands a term macro used in apply role as M(2)(3)
in val x = M(2)(3)
.
Expands a term macro used in apply role as M(2)(3)
in val x = M(2)(3)
.
DefMacroExpander
Performs macro expansion on all subtrees of a given tree.
Performs macro expansion on all subtrees of a given tree.
Innermost macros are expanded first, outermost macros are expanded last.
See the documentation for macroExpand
for more information.
Expands a macro when a runtime (i.e.
Expands a macro when a runtime (i.e. the macro implementation) can be successfully loaded Meant for internal use within the macro infrastructure, don't use it elsewhere.
Expands a macro when a runtime (i.e.
Expands a macro when a runtime (i.e. the macro implementation) cannot be loaded Meant for internal use within the macro infrastructure, don't use it elsewhere.
Produces a function that can be used to invoke macro implementation for a given macro definition: 1) Looks up macro implementation symbol in this universe.
Produces a function that can be used to invoke macro implementation for a given macro definition: 1) Looks up macro implementation symbol in this universe. 2) Loads its enclosing class from the macro classloader. 3) Loads the companion of that enclosing class from the macro classloader. 4) Resolves macro implementation within the loaded companion.
Requested runtime if macro implementation can be loaded successfully from either of the mirrors,
null
otherwise.
Default implementation of isBlackbox
.
Default implementation of isBlackbox
.
Can be overridden by analyzer plugins (see AnalyzerPlugins.pluginsIsBlackbox for more details)
Default implementation of macroArgs
.
Default implementation of macroArgs
.
Can be overridden by analyzer plugins (see AnalyzerPlugins.pluginsMacroArgs for more details)
Default implementation of macroExpand
.
Default implementation of macroExpand
.
Can be overridden by analyzer plugins (see AnalyzerPlugins.pluginsMacroExpand for more details)
Default implementation of typedMacroBody
.
Default implementation of typedMacroBody
.
Can be overridden by analyzer plugins (see AnalyzerPlugins.pluginsTypedMacroBody for more details)
Transforms parameters lists of a macro impl.
Transforms parameters lists of a macro impl.
The transform
function is invoked only for WeakTypeTag evidence parameters.
The transformer takes two arguments: a value parameter from the parameter list and a type parameter that is witnesses by the value parameter.
If the transformer returns a NoSymbol, the value parameter is not included from the result. If the transformer returns something else, this something else is included in the result instead of the value parameter.
Despite of being highly esoteric, this function significantly simplifies signature analysis. For example, it can be used to strip macroImpl.paramss from the evidences (necessary when checking def <-> impl correspondence) or to streamline creation of the list of macro arguments.
Verifies that the body of a macro def typechecks to a reference to a static public non-overloaded method or a top-level macro bundle, and that that method is signature-wise compatible with the given macro definition.
Verifies that the body of a macro def typechecks to a reference to a static public non-overloaded method or a top-level macro bundle, and that that method is signature-wise compatible with the given macro definition.
Macro impl reference for the given macro definition if everything is okay. EmptyTree if an error occurs.
Transforms c.Expr[T] types into c.Tree and leaves the rest unchanged.
Transforms c.Expr[T] types into c.Tree and leaves the rest unchanged.
Code to deal with macros, namely with: * Compilation of macro definitions * Expansion of macro applications
Say we have in a class C:
def foo[T](xs: List[T]): T = macro fooBar
Then fooBar needs to point to a static method of the following form:
def fooBar[T: c.WeakTypeTag] // type tag annotation is optional (c: scala.reflect.macros.blackbox.Context) (xs: c.Expr[List[T]]) : c.Expr[T] = { ... }
Then, if foo is called in qual.foo[Int](elems), where qual: D, the macro application is expanded to a reflective invocation of fooBar with parameters:
(simpleMacroContext{ type PrefixType = D; val prefix = qual }) (Expr(elems)) (TypeTag(Int))