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package typechecker
import java.lang.Math.min
import symtab.Flags._
import scala.reflect.runtime.ReflectionUtils
import scala.collection.mutable.ListBuffer
import scala.reflect.ClassTag
import scala.reflect.internal.util.Statistics
import scala.reflect.macros.util._
import scala.util.control.ControlThrowable
import scala.reflect.macros.runtime.{AbortMacroException, MacroRuntimes}
import scala.reflect.runtime.{universe => ru}
import scala.reflect.macros.compiler.DefaultMacroCompiler
import scala.runtime.ScalaRunTime
import Fingerprint._
* 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.BlackboxContext)
* (xs: c.Expr[List[T]])
* : c.Expr[T] = {
* ...
* }
* Then, if foo is called in[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))
trait Macros extends FastTrack with MacroRuntimes with Traces with Helpers {
self: Analyzer =>
import global._
import definitions._
import treeInfo.{isRepeatedParamType => _, _}
import MacrosStats._
def globalSettings = global.settings
protected def findMacroClassLoader(): ClassLoader = {
val classpath = global.classPath.asURLs
macroLogVerbose("macro classloader: initializing from -cp: %s".format(classpath))
ScalaClassLoader.fromURLs(classpath, self.getClass.getClassLoader)
/** `MacroImplBinding` and its companion module are responsible for
* serialization/deserialization of macro def -> impl bindings.
* The first officially released version of macros persisted these bindings across compilation runs
* using a neat trick. The right-hand side of a macro definition (which contains a reference to a macro impl)
* was typechecked and then put verbatim into an annotation on the macro definition.
* This solution is very simple, but unfortunately it's also lacking. If we use it, then
* signatures of macro defs become transitively dependent on scala-reflect.jar
* (because they refer to macro impls, and macro impls refer to scala.reflect.macros.BlackboxContext/WhiteboxContext defined in scala-reflect.jar).
* More details can be found in comments to
* Therefore we have to avoid putting macro impls into binding pickles and come up with our own serialization format.
* Situation is further complicated by the fact that it's not enough to just pickle macro impl's class name and method name,
* because macro expansion needs some knowledge about the shape of macro impl's signature (which we can't pickle).
* Hence we precompute necessary stuff (e.g. the layout of type parameters) when compiling macro defs.
/** 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.
case class MacroImplBinding(
// Is this macro impl a bundle (a trait extending BlackboxMacro or WhiteboxMacro) or a vanilla def?
val isBundle: Boolean,
// Is this macro impl blackbox (i.e. having BlackboxContext in its signature)?
val isBlackbox: Boolean,
// Java class name of the class that contains the macro implementation
// is used to load the corresponding object with Java reflection
className: String,
// method name of the macro implementation
// `className` and `methName` are all we need to reflectively invoke a macro implementation
// because macro implementations cannot be overloaded
methName: String,
// flattens the macro impl's parameter lists having symbols replaced with their fingerprints
// currently fingerprints are calculated solely from types of the symbols:
// * c.Expr[T] => LiftedTyped
// * c.Tree => LiftedUntyped
// * c.WeakTypeTag[T] => Tagged(index of the type parameter corresponding to that type tag)
// * everything else (e.g. scala.reflect.macros.BlackboxContext/WhiteboxContext) => Other
// f.ex. for: def impl[T: WeakTypeTag, U, V: WeakTypeTag](c: BlackboxContext)(x: c.Expr[T], y: c.Tree): (U, V) = ???
// `signature` will be equal to List(List(Other), List(LiftedTyped, LiftedUntyped), List(Tagged(0), Tagged(2)))
signature: List[List[Fingerprint]],
// type arguments part of a macro impl ref (the right-hand side of a macro definition)
// these trees don't refer to a macro impl, so we can pickle them as is
targs: List[Tree]) {
// Was this binding derived from a `def ... = macro ???` definition?
def is_??? = {
val Predef_??? = currentRun.runDefinitions.Predef_???
className == Predef_???.owner.javaClassName && methName == Predef_???.name.encoded
def isWhitebox = !isBlackbox
/** 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.BlackboxContext): c.Expr[Unit] = ???
* def foo: Unit = macro impl
* We will have the following annotation added on the macro definition `foo`:
* @scala.reflect.macros.internal.macroImpl(
* `macro`(
* "macroEngine" = <current macro engine>,
* "isBundle" = false,
* "isBlackbox" = true,
* "signature" = List(Other),
* "methodName" = "impl",
* "className" = "Macros$"))
def macroEngine = "v7.0 (implemented in Scala 2.11.0-M8)"
object MacroImplBinding {
def pickleAtom(obj: Any): Tree =
obj match {
case list: List[_] => Apply(Ident(ListModule), list map pickleAtom)
case s: String => Literal(Constant(s))
case d: Double => Literal(Constant(d))
case b: Boolean => Literal(Constant(b))
case f: Fingerprint => Literal(Constant(f.value))
def unpickleAtom(tree: Tree): Any =
tree match {
case Apply(list @ Ident(_), args) if list.symbol == ListModule => args map unpickleAtom
case Literal(Constant(s: String)) => s
case Literal(Constant(d: Double)) => d
case Literal(Constant(b: Boolean)) => b
case Literal(Constant(i: Int)) => Fingerprint(i)
def pickle(macroImplRef: Tree): Tree = {
val runDefinitions = currentRun.runDefinitions
import runDefinitions._
val MacroImplReference(isBundle, isBlackbox, owner, macroImpl, targs) = macroImplRef
// todo. refactor when fixing SI-5498
def className: String = {
def loop(sym: Symbol): String = sym match {
case sym if sym.isTopLevel =>
val suffix = if (sym.isModuleClass) "$" else ""
sym.fullName + suffix
case sym =>
val separator = if (sym.owner.isModuleClass) "" else "$"
loop(sym.owner) + separator + sym.javaSimpleName.toString
def signature: List[List[Fingerprint]] = {
def fingerprint(tpe: Type): Fingerprint = tpe.dealiasWiden match {
case TypeRef(_, RepeatedParamClass, underlying :: Nil) => fingerprint(underlying)
case ExprClassOf(_) => LiftedTyped
case TreeType() => LiftedUntyped
case _ => Other
val transformed = transformTypeTagEvidenceParams(macroImplRef, (param, tparam) => tparam)
mmap(transformed)(p => if (p.isTerm) fingerprint( else Tagged(p.paramPos))
val payload = List[(String, Any)](
"macroEngine" -> macroEngine,
"isBundle" -> isBundle,
"isBlackbox" -> isBlackbox,
"className" -> className,
"methodName" ->,
"signature" -> signature
// the shape of the nucleus is chosen arbitrarily. it doesn't carry any payload.
// it's only necessary as a stub `fun` for an Apply node that carries metadata in its `args`
// so don't try to find a program element named "macro" that corresponds to the nucleus
// I just named it "macro", because it's macro-related, but I could as well name it "foobar"
val nucleus = Ident(newTermName("macro"))
val wrapped = Apply(nucleus, payload map { case (k, v) => Assign(pickleAtom(k), pickleAtom(v)) })
val pickle = gen.mkTypeApply(wrapped, targs map (_.duplicate))
// assign NoType to all freshly created AST nodes
// otherwise pickler will choke on tree.tpe being null
// there's another gotcha
// if you don't assign a ConstantType to a constant
// then pickling will crash
new Transformer {
override def transform(tree: Tree) = {
tree match {
case Literal(const @ Constant(x)) if tree.tpe == null => tree setType ConstantType(const)
case _ if tree.tpe == null => tree setType NoType
case _ => ;
def unpickle(pickle: Tree): MacroImplBinding = {
val (wrapped, targs) =
pickle match {
case TypeApply(wrapped, targs) => (wrapped, targs)
case wrapped => (wrapped, Nil)
val Apply(_, pickledPayload) = wrapped
val payload ={ case Assign(k, v) => (unpickleAtom(k), unpickleAtom(v)) }.toMap
def fail(msg: String) = abort(s"bad macro impl binding: $msg")
def unpickle[T](field: String, clazz: Class[T]): T = {
def failField(msg: String) = fail(s"$field $msg")
if (!payload.contains(field)) failField("is supposed to be there")
val raw: Any = payload(field)
if (raw == null) failField(s"is not supposed to be null")
val expected =
val actual = raw.getClass
if (!expected.isAssignableFrom(actual)) failField(s"has wrong type: expected $expected, actual $actual")
val macroEngine = unpickle("macroEngine", classOf[String])
if (self.macroEngine != macroEngine) typer.TyperErrorGen.MacroIncompatibleEngineError(macroEngine)
val isBundle = unpickle("isBundle", classOf[Boolean])
val isBlackbox = unpickle("isBlackbox", classOf[Boolean])
val className = unpickle("className", classOf[String])
val methodName = unpickle("methodName", classOf[String])
val signature = unpickle("signature", classOf[List[List[Fingerprint]]])
MacroImplBinding(isBundle, isBlackbox, className, methodName, signature, targs)
def bindMacroImpl(macroDef: Symbol, macroImplRef: Tree): Unit = {
val pickle = MacroImplBinding.pickle(macroImplRef)
macroDef withAnnotation AnnotationInfo(MacroImplAnnotation.tpe, List(pickle), Nil)
def loadMacroImplBinding(macroDef: Symbol): Option[MacroImplBinding] =
macroDef.getAnnotation(MacroImplAnnotation) collect {
case AnnotationInfo(_, List(pickle), _) => MacroImplBinding.unpickle(pickle)
def isBlackbox(expandee: Tree): Boolean = isBlackbox(dissectApplied(expandee).core.symbol)
def isBlackbox(macroDef: Symbol): Boolean = {
val fastTrackBoxity = fastTrack.get(macroDef).map(_.isBlackbox)
val bindingBoxity = loadMacroImplBinding(macroDef).map(_.isBlackbox)
fastTrackBoxity orElse bindingBoxity getOrElse false
def computeMacroDefTypeFromMacroImplRef(macroDdef: DefDef, macroImplRef: Tree): Type = {
macroImplRef match {
case MacroImplReference(_, _, _, macroImpl, targs) =>
// Step I. Transform c.Expr[T] to T and everything else to Any
var runtimeType = decreaseMetalevel(
// Step II. Transform type parameters of a macro implementation into type arguments in a macro definition's body
runtimeType = runtimeType.substituteTypes(macroImpl.typeParams, targs map (_.tpe))
// Step III. Transform c.prefix.value.XXX to this.XXX and implParam.value.YYY to defParam.YYY
def unsigma(tpe: Type): Type =
transformTypeTagEvidenceParams(macroImplRef, (param, tparam) => NoSymbol) match {
case (implCtxParam :: Nil) :: implParamss =>
val implToDef = flatMap2(implParamss, macroDdef.vparamss)(map2(_, _)((_, _))).toMap
object UnsigmaTypeMap extends TypeMap {
def apply(tp: Type): Type = tp match {
case TypeRef(pre, sym, args) =>
val pre1 = pre match {
case SingleType(SingleType(SingleType(NoPrefix, c), prefix), value) if c == implCtxParam && prefix == MacroContextPrefix && value == ExprValue =>
case SingleType(SingleType(NoPrefix, implParam), value) if value == ExprValue =>
implToDef get implParam map (defParam => SingleType(NoPrefix, defParam.symbol)) getOrElse pre
case _ =>
val args1 = args map mapOver
TypeRef(pre1, sym, args1)
case _ =>
case _ =>
case _ =>
/** 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.
* @return Macro impl reference for the given macro definition if everything is okay.
* EmptyTree if an error occurs.
def typedMacroBody(typer: Typer, macroDdef: DefDef): Tree = pluginsTypedMacroBody(typer, macroDdef)
/** Default implementation of `typedMacroBody`.
* Can be overridden by analyzer plugins (see AnalyzerPlugins.pluginsTypedMacroBody for more details)
def standardTypedMacroBody(typer: Typer, macroDdef: DefDef): Tree = {
val macroDef = macroDdef.symbol
assert(macroDef.isMacro, macroDdef)
macroLogVerbose("typechecking macro def %s at %s".format(macroDef, macroDdef.pos))
if (fastTrack contains macroDef) {
macroLogVerbose("typecheck terminated unexpectedly: macro is fast track")
assert(!macroDdef.tpt.isEmpty, "fast track macros must provide result type")
} else {
def fail() = { if (macroDef != null) macroDef setFlag IS_ERROR; macroDdef setType ErrorType; EmptyTree }
def success(macroImplRef: Tree) = { bindMacroImpl(macroDef, macroImplRef); macroImplRef }
if (!typer.checkFeature(macroDdef.pos, currentRun.runDefinitions.MacrosFeature, immediate = true)) {
macroLogVerbose("typecheck terminated unexpectedly: language.experimental.macros feature is not enabled")
} else {
val macroDdef1: macroDdef.type = macroDdef
val typer1: typer.type = typer
val macroCompiler = new {
val global: =
val typer: = typer1.asInstanceOf[]
val macroDdef: = macroDdef1
} with DefaultMacroCompiler
val macroImplRef = macroCompiler.resolveMacroImpl
if (macroImplRef.isEmpty) fail() else success(macroImplRef)
def macroContext(typer: Typer, prefixTree: Tree, expandeeTree: Tree): MacroContext = {
new {
val universe: =
val callsiteTyper: universe.analyzer.Typer = typer.asInstanceOf[global.analyzer.Typer]
val expandee = universe.analyzer.macroExpanderAttachment(expandeeTree).original orElse duplicateAndKeepPositions(expandeeTree)
val macroRole = universe.analyzer.macroExpanderAttachment(expandeeTree).role
} with UnaffiliatedMacroContext {
val prefix = Expr[Nothing](prefixTree)(TypeTag.Nothing)
override def toString = "MacroContext(%s@%s +%d)".format(, expandee.pos, enclosingMacros.length - 1 /* exclude myself */)
/** Calculate the arguments to pass to a macro implementation when expanding the provided tree.
case class MacroArgs(c: MacroContext, others: List[Any])
def macroArgs(typer: Typer, expandee: Tree): MacroArgs = pluginsMacroArgs(typer, expandee)
/** Default implementation of `macroArgs`.
* Can be overridden by analyzer plugins (see AnalyzerPlugins.pluginsMacroArgs for more details)
def standardMacroArgs(typer: Typer, expandee: Tree): MacroArgs = {
val macroDef = expandee.symbol
val paramss = macroDef.paramss
val treeInfo.Applied(core, targs, argss) = expandee
val prefix = core match { case Select(qual, _) => qual; case _ => EmptyTree }
val context = expandee.attachments.get[MacroRuntimeAttachment].flatMap(_.macroContext).getOrElse(macroContext(typer, prefix, expandee))
|context: $context
|prefix: $prefix
|targs: $targs
|argss: $argss
|paramss: $paramss
import typer.TyperErrorGen._
val isNullaryArgsEmptyParams = argss.isEmpty && paramss == ListOfNil
if (paramss.length < argss.length) MacroTooManyArgumentListsError(expandee)
if (paramss.length > argss.length && !isNullaryArgsEmptyParams) MacroTooFewArgumentListsError(expandee)
val macroImplArgs: List[Any] =
if (fastTrack contains macroDef) {
// Take a dry run of the fast track implementation
if (fastTrack(macroDef) validate expandee) argss.flatten
else MacroTooFewArgumentListsError(expandee)
else {
def calculateMacroArgs(binding: MacroImplBinding) = {
val signature = if (binding.isBundle) binding.signature else binding.signature.tail
macroLogVerbose(s"binding: $binding")
// STEP I: prepare value arguments of the macro expansion
// wrap argss in c.Expr if necessary (i.e. if corresponding macro impl param is of type c.Expr[T])
// expand varargs (nb! varargs can apply to any parameter section, not necessarily to the last one)
val trees = map3(argss, paramss, signature)((args, defParams, implParams) => {
val isVarargs = isVarArgsList(defParams)
if (isVarargs) {
if (defParams.length > args.length + 1) MacroTooFewArgumentsError(expandee)
} else {
if (defParams.length < args.length) MacroTooManyArgumentsError(expandee)
if (defParams.length > args.length) MacroTooFewArgumentsError(expandee)
val wrappedArgs = mapWithIndex(args)((arg, j) => {
val fingerprint = implParams(min(j, implParams.length - 1))
fingerprint match {
case LiftedTyped => context.Expr[Nothing](arg.duplicate)(TypeTag.Nothing) // TODO: SI-5752
case LiftedUntyped => arg.duplicate
case _ => abort(s"unexpected fingerprint $fingerprint in $binding with paramss being $paramss " +
s"corresponding to arg $arg in $argss")
if (isVarargs) {
val (normal, varargs) = wrappedArgs splitAt (defParams.length - 1)
normal :+ varargs // pack all varargs into a single Seq argument (varargs Scala style)
} else wrappedArgs
macroLogVerbose(s"trees: $trees")
// STEP II: prepare type arguments of the macro expansion
// if paramss have typetag context bounds, add an arglist to argss if necessary and instantiate the corresponding evidences
// consider the following example:
// class D[T] {
// class C[U] {
// def foo[V] = macro[T, U, V]
// }
// }
// val outer1 = new D[Int]
// val outer2 = new outer1.C[String]
// then T and U need to be inferred from the lexical scope of the call using `asSeenFrom`
// whereas V won't be resolved by asSeenFrom and need to be loaded directly from `expandee` which needs to contain a TypeApply node
// also, macro implementation reference may contain a regular type as a type argument, then we pass it verbatim
val tags = signature.flatten collect { case f if f.isTag => f.paramPos } map (paramPos => {
val targ = binding.targs(paramPos).tpe.typeSymbol
val tpe = if (targ.isTypeParameterOrSkolem) {
if (targ.owner == macroDef) {
// doesn't work when macro def is compiled separately from its usages
// then targ is not a skolem and isn't equal to any of macroDef.typeParams
// val argPos = targ.deSkolemize.paramPos
val argPos = macroDef.typeParams.indexWhere( ==
} else
if (prefix == EmptyTree) macroDef.owner.tpe else prefix.tpe,
} else
macroLogVerbose(s"tags: $tags")
// if present, tags always come in a separate parameter/argument list
// that's because macro impls can't have implicit parameters other than c.WeakTypeTag[T]
(trees :+ tags).flatten
val binding = loadMacroImplBinding(macroDef).get
if (binding.is_???) Nil
else calculateMacroArgs(binding)
macroLogVerbose(s"macroImplArgs: $macroImplArgs")
MacroArgs(context, macroImplArgs)
/** Keeps track of macros in-flight.
* See more informations in comments to `openMacros` in `scala.reflect.macros.WhiteboxContext`.
var _openMacros = List[MacroContext]()
def openMacros = _openMacros
def pushMacroContext(c: MacroContext) = _openMacros ::= c
def popMacroContext() = _openMacros = _openMacros.tail
def enclosingMacroPosition = openMacros map (_.macroApplication.pos) find (_ ne NoPosition) getOrElse NoPosition
/** Describes the role that the macro expandee is performing.
type MacroRole =
final def APPLY_ROLE = MacroRole.Apply
final def UNAPPLY_ROLE = MacroRole.Unapply
/** Performs macro expansion:
* ========= Expandable trees =========
* 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>)
* ========= Macro expansion =========
* 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.
* @return
* 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
abstract class MacroExpander[Result: ClassTag](val role: MacroRole, val typer: Typer, val expandee: Tree) {
def allowExpandee(expandee: Tree): Boolean = true
def allowExpanded(expanded: Tree): Boolean = true
def allowedExpansions: String = "anything"
def allowResult(result: Result): Boolean = true
def onSuccess(expanded: Tree): Result
def onFallback(expanded: Tree): Result
def onSuppressed(expandee: Tree): Result = expandee match { case expandee: Result => expandee }
def onDelayed(expanded: Tree): Result = expanded match { case expanded: Result => expanded }
def onSkipped(expanded: Tree): Result = expanded match { case expanded: Result => expanded }
def onFailure(expanded: Tree): Result = { typer.infer.setError(expandee); expandee match { case expandee: Result => expandee } }
def apply(desugared: Tree): Result = {
if (isMacroExpansionSuppressed(desugared)) onSuppressed(expandee)
else expand(desugared)
protected def expand(desugared: Tree): Result = {
def showDetailed(tree: Tree) = showRaw(tree, printIds = true, printTypes = true)
def summary() = s"expander = $this, expandee = ${showDetailed(expandee)}, desugared = ${if (expandee == desugared) () else showDetailed(desugared)}"
if (macroDebugVerbose) println(s"macroExpand: ${summary()}")
assert(allowExpandee(expandee), summary())
linkExpandeeAndDesugared(expandee, desugared, role)
val start = if (Statistics.canEnable) Statistics.startTimer(macroExpandNanos) else null
if (Statistics.canEnable) Statistics.incCounter(macroExpandCount)
try {
withInfoLevel(nodePrinters.InfoLevel.Quiet) { // verbose printing might cause recursive macro expansions
if (expandee.symbol.isErroneous || (expandee exists (_.isErroneous))) {
val reason = if (expandee.symbol.isErroneous) "not found or incompatible macro implementation" else "erroneous arguments"
macroLogVerbose(s"cancelled macro expansion because of $reason: $expandee")
} else try {
val expanded = {
val runtime = macroRuntime(expandee)
if (runtime != null) macroExpandWithRuntime(typer, expandee, runtime)
else macroExpandWithoutRuntime(typer, expandee)
expanded match {
case Success(expanded) =>
if (allowExpanded(expanded)) {
// also see
val expanded1 = try onSuccess(duplicateAndKeepPositions(expanded)) finally popMacroContext()
if (!hasMacroExpansionAttachment(expanded1)) linkExpandeeAndExpanded(expandee, expanded1)
if (allowResult(expanded1)) expanded1 else onFailure(expanded)
} else {
typer.TyperErrorGen.MacroInvalidExpansionError(expandee,, allowedExpansions)
case Fallback(fallback) => onFallback(fallback)
case Delayed(delayed) => onDelayed(delayed)
case Skipped(skipped) => onSkipped(skipped)
case Failure(failure) => onFailure(failure)
} catch {
case typer.TyperErrorGen.MacroExpansionException => onFailure(expandee)
} finally {
if (Statistics.canEnable) Statistics.stopTimer(macroExpandNanos, start)
/** Expands a term macro used in apply role as `M(2)(3)` in `val x = M(2)(3)`.
* @param outerPt Expected type that comes from enclosing context (something that's traditionally called `pt`).
* @param innerPt Expected type that comes from the signature of a macro def, possibly wildcarded to help type inference.
class DefMacroExpander(typer: Typer, expandee: Tree, mode: Mode, outerPt: Type)
extends MacroExpander[Tree](APPLY_ROLE, typer, expandee) {
lazy val innerPt = {
val tp = if (isNullaryInvocation(expandee)) expandee.tpe.finalResultType else expandee.tpe
if (isBlackbox(expandee)) tp
else {
// approximation is necessary for whitebox macros to guide type inference
// read more in the comments for onDelayed below
val undetparams = tp collect { case tp if tp.typeSymbol.isTypeParameter => tp.typeSymbol }
override def onSuccess(expanded0: Tree) = {
// prematurely annotate the tree with a macro expansion attachment
// so that adapt called indirectly by typer.typed knows that it needs to apply the existential fixup
linkExpandeeAndExpanded(expandee, expanded0)
def typecheck(label: String, tree: Tree, pt: Type): Tree = {
if (tree.isErrorTyped) tree
else {
if (macroDebugVerbose) println(s"$label (against pt = $pt): $tree")
// `macroExpandApply` is called from `adapt`, where implicit conversions are disabled
// therefore we need to re-enable the conversions back temporarily
val result = typer.context.withImplicitsEnabled(typer.typed(tree, mode, pt))
if (result.isErrorTyped && macroDebugVerbose) println(s"$label has failed: ${typer.context.reportBuffer.errors}")
if (isBlackbox(expandee)) {
val expanded1 = atPos(enclosingMacroPosition.makeTransparent)(Typed(expanded0, TypeTree(innerPt)))
typecheck("blackbox typecheck", expanded1, outerPt)
} else {
val expanded1 = expanded0
val expanded2 = typecheck("whitebox typecheck #1", expanded1, outerPt)
typecheck("whitebox typecheck #2", expanded2, innerPt)
override def onDelayed(delayed: Tree) = {
// =========== THE SITUATION ===========
// If we've been delayed (i.e. bailed out of the expansion because of undetermined type params present in the expandee),
// then there are two possible situations we're in:
// 1) We're in POLYmode, when the typer tests the waters wrt type inference
// (e.g. as in typedArgToPoly in doTypedApply).
// 2) We're out of POLYmode, which means that the typer is out of tricks to infer our type
// (e.g. if we're an argument to a function call, then this means that no previous argument lists
// can determine our type variables for us).
// Situation #1 is okay for us, since there's no pressure. In POLYmode we're just verifying that
// there's nothing outrageously wrong with our undetermined type params (from what I understand!).
// Situation #2 requires measures to be taken. If we're in it, then noone's going to help us infer
// the undetermined type params. Therefore we need to do something ourselves or otherwise this
// expandee will forever remaing not expanded (see SI-5692). A traditional way out of this conundrum
// is to call `instantiate` and let the inferencer try to find the way out. It works for simple cases,
// but sometimes, if the inferencer lacks information, it will be forced to approximate.
// =========== THE PROBLEM ===========
// Consider the following example (thanks, Miles!):
// Iso represents an isomorphism between two datatypes:
// 1) An arbitrary one (e.g. a random case class)
// 2) A uniform representation for all datatypes (e.g. an HList)
// trait Iso[T, U] {
// def to(t : T) : U
// def from(u : U) : T
// }
// implicit def materializeIso[T, U]: Iso[T, U] = macro ???
// case class Foo(i: Int, s: String, b: Boolean)
// def foo[C, L](c: C)(implicit iso: Iso[C, L]): L =
// foo(Foo(23, "foo", true))
// In the snippet above, even though we know that there's a fundep going from T to U
// (in a sense that a datatype's uniform representation is unambiguously determined by the datatype,
// e.g. for Foo it will be Int :: String :: Boolean :: HNil), there's no way to convey this information
// to the typechecker. Therefore the typechecker will infer Nothing for L, which is hardly what we want.
// To give materializers a chance to say their word before vanilla inference kicks in,
// we infer as much as possible (e.g. in the example above even though L is hopeless, C still can be inferred to Foo)
// and then trigger macro expansion with the undetermined type parameters still there.
// Thanks to that the materializer can take a look at what's going on and react accordingly.
val shouldInstantiate = typer.context.undetparams.nonEmpty && !mode.inPolyMode
if (shouldInstantiate) {
if (isBlackbox(expandee)) typer.instantiatePossiblyExpectingUnit(delayed, mode, outerPt)
else {
forced += delayed
typer.infer.inferExprInstance(delayed, typer.context.extractUndetparams(), outerPt, keepNothings = false)
macroExpand(typer, delayed, mode, outerPt)
} else delayed
override def onFallback(fallback: Tree) = typer.typed(fallback, mode, outerPt)
/** Expands a term macro used in apply role as `M(2)(3)` in `val x = M(2)(3)`.
* @see DefMacroExpander
def macroExpand(typer: Typer, expandee: Tree, mode: Mode, pt: Type): Tree = pluginsMacroExpand(typer, expandee, mode, pt)
/** Default implementation of `macroExpand`.
* Can be overridden by analyzer plugins (see AnalyzerPlugins.pluginsMacroExpand for more details)
def standardMacroExpand(typer: Typer, expandee: Tree, mode: Mode, pt: Type): Tree = {
val expander = new DefMacroExpander(typer, expandee, mode, pt)
sealed abstract class MacroStatus(val result: Tree)
case class Success(expanded: Tree) extends MacroStatus(expanded)
case class Fallback(fallback: Tree) extends MacroStatus(fallback) { currentRun.seenMacroExpansionsFallingBack = true }
case class Delayed(delayed: Tree) extends MacroStatus(delayed)
case class Skipped(skipped: Tree) extends MacroStatus(skipped)
case class Failure(failure: Tree) extends MacroStatus(failure)
def Delay(expanded: Tree) = Delayed(expanded)
def Skip(expanded: Tree) = Skipped(expanded)
/** 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.
def macroExpandWithRuntime(typer: Typer, expandee: Tree, runtime: MacroRuntime): MacroStatus = {
val wasDelayed = isDelayed(expandee)
val undetparams = calculateUndetparams(expandee)
val nowDelayed = !typer.context.macrosEnabled || undetparams.nonEmpty
(wasDelayed, nowDelayed) match {
case (true, true) =>
case (true, false) =>
val expanded = macroExpandAll(typer, expandee)
if (expanded exists (_.isErroneous)) Failure(expandee)
else Skip(expanded)
case (false, true) =>
macroLogLite("macro expansion is delayed: %s".format(expandee))
delayed += expandee -> undetparams
expandee updateAttachment MacroRuntimeAttachment(delayed = true, typerContext = typer.context, macroContext = Some(macroArgs(typer, expandee).c))
case (false, false) =>
import typer.TyperErrorGen._
macroLogLite("performing macro expansion %s at %s".format(expandee, expandee.pos))
val args = macroArgs(typer, expandee)
try {
val numErrors = reporter.ERROR.count
def hasNewErrors = reporter.ERROR.count > numErrors
val expanded = { pushMacroContext(args.c); runtime(args) }
if (hasNewErrors) MacroGeneratedTypeError(expandee)
def validateResultingTree(expanded: Tree) = {
macroLogLite("" + expanded + "\n" + showRaw(expanded))
val freeSyms = expanded.freeTerms ++ expanded.freeTypes
freeSyms foreach (sym => MacroFreeSymbolError(expandee, sym))
// Macros might have spliced arguments with range positions into non-compliant
// locations, notably, under a tree without a range position. Or, they might
// splice a tree that `resetAttrs` has assigned NoPosition.
// Here, we just convert all positions in the tree to offset positions, and
// convert NoPositions to something sensible.
// Given that the IDE now sees the expandee (by using -Ymacro-expand:discard),
// this loss of position fidelity shouldn't cause any real problems.
// Alternatively, we could pursue a way to exclude macro expansions from position
// invariant checking, or find a way not to touch expansions that happen to validate.
// This would be useful for cases like:
// macro1 { macro2 { "foo" } }
// to allow `macro1` to see the range position of the "foo".
val expandedPos = enclosingMacroPosition.focus
def fixPosition(pos: Position) =
if (pos == NoPosition) expandedPos else pos.focus
expanded.foreach(t => t.pos = fixPosition(t.pos))
val result = atPos(enclosingMacroPosition.focus)(expanded)
expanded match {
case expanded: Expr[_] if expandee.symbol.isTermMacro => validateResultingTree(expanded.tree)
case expanded: Tree if expandee.symbol.isTermMacro => validateResultingTree(expanded)
case _ => MacroExpansionHasInvalidTypeError(expandee, expanded)
} catch {
case ex: Throwable =>
val realex = ReflectionUtils.unwrapThrowable(ex)
realex match {
case ex: AbortMacroException => MacroGeneratedAbort(expandee, ex)
case ex: ControlThrowable => throw ex
case ex: TypeError => MacroGeneratedTypeError(expandee, ex)
case _ => MacroGeneratedException(expandee, realex)
} finally {
/** 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.
def macroExpandWithoutRuntime(typer: Typer, expandee: Tree): MacroStatus = {
import typer.TyperErrorGen._
val fallbackSym = expandee.symbol.nextOverriddenSymbol orElse MacroImplementationNotFoundError(expandee)
macroLogLite(s"falling back to: $fallbackSym")
def mkFallbackTree(tree: Tree): Tree = {
tree match {
case Select(qual, name) => Select(qual, name) setPos tree.pos setSymbol fallbackSym
case Apply(fn, args) => Apply(mkFallbackTree(fn), args) setPos tree.pos
case TypeApply(fn, args) => TypeApply(mkFallbackTree(fn), args) setPos tree.pos
/** 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)
var hasPendingMacroExpansions = false
private val forced = perRunCaches.newWeakSet[Tree]
private val delayed = perRunCaches.newWeakMap[Tree, scala.collection.mutable.Set[Int]]()
private def isDelayed(expandee: Tree) = delayed contains expandee
private def calculateUndetparams(expandee: Tree): scala.collection.mutable.Set[Int] =
if (forced(expandee)) scala.collection.mutable.Set[Int]()
else delayed.getOrElse(expandee, {
val calculated = scala.collection.mutable.Set[Symbol]()
expandee foreach (sub => {
def traverse(sym: Symbol) = if (sym != null && (undetparams contains calculated += sym
if (sub.symbol != null) traverse(sub.symbol)
if (sub.tpe != null) sub.tpe foreach (sub => traverse(sub.typeSymbol))
macroLogVerbose("calculateUndetparams: %s".format(calculated))
calculated map (
private val undetparams = perRunCaches.newSet[Int]()
def notifyUndetparamsAdded(newUndets: List[Symbol]): Unit = {
undetparams ++= newUndets map (
if (macroDebugVerbose) newUndets foreach (sym => println("undetParam added: %s".format(sym)))
def notifyUndetparamsInferred(undetNoMore: List[Symbol], inferreds: List[Type]): Unit = {
undetparams --= undetNoMore map (
if (macroDebugVerbose) (undetNoMore zip inferreds) foreach { case (sym, tpe) => println("undetParam inferred: %s as %s".format(sym, tpe))}
if (!delayed.isEmpty)
delayed.toList foreach {
case (expandee, undetparams) if !undetparams.isEmpty =>
undetparams --= undetNoMore map (
if (undetparams.isEmpty) {
hasPendingMacroExpansions = true
macroLogVerbose(s"macro expansion is pending: $expandee")
case _ =>
// do nothing
/** Performs macro expansion on all subtrees of a given tree.
* Innermost macros are expanded first, outermost macros are expanded last.
* See the documentation for `macroExpand` for more information.
def macroExpandAll(typer: Typer, expandee: Tree): Tree =
new Transformer {
override def transform(tree: Tree) = super.transform(tree match {
// todo. expansion should work from the inside out
case tree if (delayed contains tree) && calculateUndetparams(tree).isEmpty && !tree.isErroneous =>
val context = tree.attachments.get[MacroRuntimeAttachment].get.typerContext
delayed -= tree
context.implicitsEnabled = typer.context.implicitsEnabled
context.enrichmentEnabled = typer.context.enrichmentEnabled
context.macrosEnabled = typer.context.macrosEnabled
macroExpand(newTyper(context), tree, EXPRmode, WildcardType)
case _ =>
object MacrosStats {
import scala.reflect.internal.TypesStats.typerNanos
val macroExpandCount = Statistics.newCounter ("#macro expansions", "typer")
val macroExpandNanos = Statistics.newSubTimer("time spent in macroExpand", typerNanos)
class Fingerprint private[Fingerprint](val value: Int) extends AnyVal {
def paramPos = { assert(isTag, this); value }
def isTag = value >= 0
override def toString = this match {
case Other => "Other"
case LiftedTyped => "Expr"
case LiftedUntyped => "Tree"
case _ => s"Tag($value)"
object Fingerprint {
def apply(value: Int) = new Fingerprint(value)
def Tagged(tparamPos: Int) = new Fingerprint(tparamPos)
val Other = new Fingerprint(-1)
val LiftedTyped = new Fingerprint(-2)
val LiftedUntyped = new Fingerprint(-3)
class MacroRole private[MacroRole](val name: String) extends AnyVal {
override def toString = name
object MacroRole {
val Apply = new MacroRole("apply")
val Unapply = new MacroRole("unapply")
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