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Scala.meta's quasiquotes for abstract syntax trees
package scala.meta
package internal
package quasiquotes
import scala.{Seq => _}
import scala.collection.immutable.Seq
import scala.runtime.ScalaRunTime
import scala.language.implicitConversions
import scala.language.experimental.macros
import scala.reflect.macros.whitebox.Context
import scala.collection.{immutable, mutable}
import org.scalameta.data._
import org.scalameta.adt.{Liftables => AdtLiftables, Reflection => AdtReflection}
import scala.meta.internal.ast.{Liftables => AstLiftables, Reflection => AstReflection}
import org.scalameta._
import org.scalameta.invariants._
import scala.meta.dialects // no underscore import
import scala.meta.classifiers._
import scala.meta.parsers._
import scala.meta.tokenizers._
import scala.meta.prettyprinters._
import scala.meta.internal.dialects.InstantiateDialect
import scala.meta.internal.{semantic => s}
import scala.meta.internal.ast.Quasi
import scala.meta.internal.ast.Helpers._
import scala.meta.internal.parsers.Messages
import scala.meta.internal.parsers.Absolutize._
import scala.meta.internal.tokens._
import scala.compat.Platform.EOL
// TODO: ideally, we would like to bootstrap these macros on top of scala.meta
// so that quasiquotes can be interpreted by any host, not just scalac
class ReificationMacros(val c: Context) extends AstReflection with AdtLiftables with AstLiftables with InstantiateDialect {
lazy val u: c.universe.type = c.universe
lazy val mirror: u.Mirror = c.mirror
import c.internal._
import decorators._
import c.universe.{Tree => _, Symbol => _, Type => _, Position => _, _}
import c.universe.{Tree => ReflectTree, Symbol => ReflectSymbol, Type => ReflectType, Position => ReflectPosition}
import scala.meta.{Tree => MetaTree, Type => MetaType, Dialect => Dialect}
import scala.meta.inputs.{Position => MetaPosition, _}
type MetaParser = (Input, Dialect) => MetaTree
val XtensionQuasiquoteTerm = "shadow scala.meta quasiquotes"
val XtensionParsersDialectApply = "shadow extension method conflict"
// NOTE: only Mode.Pattern really needs holes, and that's only because of Scala's limitations
// read a comment in liftUnquote for more information on that
case class Hole(name: TermName, arg: ReflectTree, var reifier: ReflectTree)
sealed trait Mode {
def isTerm: Boolean = this.isInstanceOf[Mode.Term]
def isPattern: Boolean = this.isInstanceOf[Mode.Pattern]
def multiline: Boolean
def holes: List[Hole]
}
object Mode {
case class Term(multiline: Boolean, holes: List[Hole]) extends Mode
case class Pattern(multiline: Boolean, holes: List[Hole], unapplySelector: ReflectTree) extends Mode
}
import definitions._
val SeqModule = c.mirror.staticModule("scala.collection.Seq")
val ScalaPackageObjectClass = c.mirror.staticModule("scala.package")
val ScalaList = ScalaPackageObjectClass.info.decl(TermName("List"))
val ScalaNil = ScalaPackageObjectClass.info.decl(TermName("Nil"))
val ScalaSeq = ScalaPackageObjectClass.info.decl(TermName("Seq"))
val ImmutableSeq = mirror.staticClass("scala.collection.immutable.Seq")
val InternalLift = c.mirror.staticModule("scala.meta.internal.quasiquotes.Lift")
val InternalUnlift = c.mirror.staticModule("scala.meta.internal.quasiquotes.Unlift")
val QuasiquotePrefix = c.freshName("quasiquote")
def apply(args: ReflectTree*)(dialect: ReflectTree): ReflectTree = expand(dialect)
def unapply(scrutinee: ReflectTree)(dialect: ReflectTree): ReflectTree = expand(dialect)
def expand(dialectTree: ReflectTree): ReflectTree = {
val (input, mode) = extractQuasiquotee()
val dialect = instantiateDialect(dialectTree, mode)
val parser = instantiateParser(c.macroApplication.symbol)
val skeleton = parseSkeleton(parser, input, dialect)
val hygienicSkeleton = hygienifySkeleton(skeleton)
reifySkeleton(hygienicSkeleton, mode)
}
private def extractQuasiquotee(): (Input, Mode) = {
val reflectInput = c.macroApplication.pos.source
val (parts, mode) = {
def isMultiline(firstPart: ReflectTree) = {
reflectInput.content(firstPart.pos.start - 2) == '"'
}
def mkHole(argi: (ReflectTree, Int)) = {
val (arg, i) = argi
val name = TermName(QuasiquotePrefix + "$hole$" + i)
Hole(name, arg, reifier = EmptyTree) // TODO: make reifier immutable somehow
}
try {
c.macroApplication match {
case q"$_($_.apply(..$parts)).$_.apply[..$_](..$args)($_)" =>
require(parts.length == args.length + 1)
val holes = args.zipWithIndex.map(mkHole)
(parts, Mode.Term(isMultiline(parts.head), holes))
case q"$_($_.apply(..$parts)).$_.unapply[..$_](${unapplySelector: Ident})($_)" =>
require(unapplySelector.name == TermName(""))
val args = c.internal.subpatterns(unapplySelector).get
require(parts.length == args.length + 1)
val holes = args.zipWithIndex.map(mkHole)
(parts, Mode.Pattern(isMultiline(parts.head), holes, unapplySelector))
}
} catch {
case ex: Exception =>
c.abort(c.macroApplication.pos, s"fatal error initializing quasiquote macro: ${showRaw(c.macroApplication)}")
}
}
val metaInput = {
val (firstPart, lastPart @ Literal(Constant(s_lastpart: String))) = (parts.head, parts.last)
val start = firstPart.pos.start // looks like we can trust this position to point to the character right after the opening quotes
val end = { // we have to infer this for ourselves, because there's no guarantee we run under -Yrangepos
var remaining = s_lastpart.length
var curr = lastPart.pos.start - 1
while (remaining > 0) {
curr += 1
if (reflectInput.content(curr) == '$') {
curr += 1
require(reflectInput.content(curr) == '$')
}
remaining -= 1
}
curr + 1
}
val result = {
if (reflectInput.file.file != null) Input.File(reflectInput.file.file)
else Input.String(new String(reflectInput.content)) // NOTE: can happen in REPL or in custom Global
}
Input.Slice(result, start, end)
}
(metaInput, mode)
}
private implicit def metaPositionToReflectPosition(pos: MetaPosition): ReflectPosition = {
// TODO: this is another instance of #383
c.macroApplication.pos.focus.withPoint(pos.start.absolutize.offset)
}
private def instantiateDialect(dialectTree: ReflectTree, mode: Mode): Dialect = {
val underlyingDialect = instantiateDialect(dialectTree)
if (mode.isTerm) dialects.QuasiquoteTerm(underlyingDialect, mode.multiline)
else dialects.QuasiquotePat(underlyingDialect, mode.multiline)
}
private def instantiateParser(interpolator: ReflectSymbol): MetaParser = {
val parserModule = interpolator.owner.owner.companion
val parsersModuleClass = Class.forName("scala.meta.quasiquotes.package$", true, this.getClass.getClassLoader)
val parsersModule = parsersModuleClass.getField("MODULE$").get(null)
val parserModuleGetter = parsersModule.getClass.getDeclaredMethod(parserModule.name.toString)
val parserModuleInstance = parserModuleGetter.invoke(parsersModule)
val parserMethod = parserModuleInstance.getClass.getDeclaredMethods().find(_.getName == "parse").head
(input: Input, dialect: Dialect) => {
try parserMethod.invoke(parserModuleInstance, input, dialect).asInstanceOf[MetaTree]
catch { case ex: java.lang.reflect.InvocationTargetException => throw ex.getTargetException }
}
}
private def parseSkeleton(parser: MetaParser, input: Input, dialect: Dialect): MetaTree = {
try {
parser(input, dialect)
} catch {
case TokenizeException(pos, message) => c.abort(pos, message)
case ParseException(pos, message) => c.abort(pos, message)
}
}
private def hygienifySkeleton(meta: MetaTree): MetaTree = {
// TODO: Implement this (https://github.com/scalameta/scalameta/issues/156)
// by setting Tree.env of appropriate trees (names, apply-like nodes) to appropriate values.
// So far, we don't have to set anything to anything,
// because Environment.None (the only possible value for environments at the moment) is the default.
meta
}
private def reifySkeleton(meta: MetaTree, mode: Mode): ReflectTree = {
val pendingQuasis = mutable.Stack[Quasi]()
implicit class XtensionRankedClazz(clazz: Class[_]) {
def unwrap: Class[_] = {
if (clazz.isArray) clazz.getComponentType.unwrap
else clazz
}
def wrap(rank: Int): Class[_] = {
if (rank == 0) clazz
else ScalaRunTime.arrayClass(clazz).wrap(rank - 1)
}
def toTpe: u.Type = {
if (clazz.isArray) {
appliedType(ImmutableSeq, clazz.getComponentType.toTpe)
} else {
def loop(owner: u.Symbol, parts: List[String]): u.Symbol = parts match {
case part :: Nil =>
if (clazz.getName.endsWith("$")) owner.info.decl(TermName(part))
else owner.info.decl(TypeName(part))
case part :: rest =>
loop(owner.info.decl(TermName(part)), rest)
case Nil =>
unreachable(debug(clazz))
}
val name = scala.reflect.NameTransformer.decode(clazz.getName)
val result = loop(mirror.RootPackage, name.stripSuffix("$").split(Array('.', '$')).toList)
if (result.isModule) result.asModule.info else result.asClass.toType
}
}
}
implicit class XtensionRankedTree(tree: u.Tree) {
def wrap(rank: Int): u.Tree = {
if (rank == 0) tree
else AppliedTypeTree(tq"$ImmutableSeq", List(tree.wrap(rank - 1)))
}
}
implicit class XtensionQuasiHole(quasi: Quasi) {
def hole: Hole = {
val pos = quasi.pos.absolutize
val maybeHole = mode.holes.find(h => pos.start.offset <= h.arg.pos.point && h.arg.pos.point <= pos.end.offset)
maybeHole.getOrElse(unreachable(debug(quasi, quasi.pos.absolutize, mode.holes, mode.holes.map(_.arg.pos))))
}
}
object Lifts {
def liftTree(tree: MetaTree): ReflectTree = {
Liftables.liftableSubTree(tree)
}
def liftOptionTree(maybeTree: Option[MetaTree]): ReflectTree = {
maybeTree match {
case Some(tree: Quasi) => liftQuasi(tree, optional = true)
case Some(otherTree) => q"_root_.scala.Some(${liftTree(otherTree)})"
case None => q"_root_.scala.None"
}
}
def liftTrees(trees: Seq[MetaTree]): ReflectTree = {
def loop(trees: List[MetaTree], acc: ReflectTree, prefix: List[MetaTree]): ReflectTree = trees match {
// TODO: instead of checking against 1, we should also take pendingQuasis into account
case (quasi: Quasi) +: rest if quasi.rank == 1 =>
if (acc.isEmpty) {
if (prefix.isEmpty) loop(rest, liftQuasi(quasi), Nil)
else loop(rest, prefix.foldRight(acc)((curr, acc) => {
// NOTE: We cannot do just q"${liftTree(curr)} +: ${liftQuasi(quasi)}"
// because that creates a synthetic temp variable that doesn't make any sense in a pattern.
// Neither can we do q"${liftQuasi(quasi)}.+:(${liftTree(curr)})",
// because that still wouldn't work in pattern mode.
// Finally, we can't do something like q"+:(${liftQuasi(quasi)}, (${liftTree(curr)}))",
// because would violate evaluation order guarantees that we must keep.
if (mode.isTerm) q"${liftTree(curr)} +: ${liftQuasi(quasi)}"
else pq"${liftTree(curr)} +: ${liftQuasi(quasi)}"
}), Nil)
} else {
require(prefix.isEmpty && debug(trees, acc, prefix))
if (mode.isTerm) loop(rest, q"$acc ++ ${liftQuasi(quasi)}", Nil)
else c.abort(quasi.pos, Messages.QuasiquoteAdjacentEllipsesInPattern(quasi.rank))
}
case other +: rest =>
if (acc.isEmpty) loop(rest, acc, prefix :+ other)
else {
require(prefix.isEmpty && debug(trees, acc, prefix))
if (mode.isTerm) loop(rest, q"$acc :+ ${liftTree(other)}", Nil)
else loop(rest, pq"$acc :+ ${liftTree(other)}", Nil)
}
case Nil =>
// NOTE: Luckily, at least this quasiquote works fine both in term and pattern modes
if (acc.isEmpty) q"_root_.scala.collection.immutable.Seq(..${prefix.map(liftTree)})"
else acc
}
loop(trees.toList, EmptyTree, Nil)
}
def liftOptionTrees(maybeTrees: Option[Seq[MetaTree]]): ReflectTree = {
maybeTrees match {
case Some(Seq(quasi: Quasi)) if quasi.rank == 0 =>
q"_root_.scala.Some(${liftTrees(Seq(quasi))})"
case Some(Seq(quasi: Quasi)) if quasi.rank > 0 =>
liftQuasi(quasi, optional = true)
case Some(otherTrees) =>
q"_root_.scala.Some(${liftTrees(otherTrees)})"
case None =>
q"_root_.scala.None"
}
}
def liftTreess(treess: Seq[Seq[MetaTree]]): ReflectTree = {
val tripleDotQuasis = treess.flatten.collect{ case quasi: Quasi if quasi.rank == 2 => quasi }
if (tripleDotQuasis.length == 0) {
Liftable.liftList[Seq[MetaTree]](Liftables.liftableSubTrees).apply(treess.toList)
} else if (tripleDotQuasis.length == 1) {
if (treess.flatten.length == 1) liftQuasi(tripleDotQuasis(0))
else c.abort(tripleDotQuasis(0).pos,
"implementation restriction: can't mix ...$ with anything else in parameter lists." + EOL +
"See https://github.com/scalameta/scalameta/issues/406 for details.")
} else {
c.abort(tripleDotQuasis(1).pos, Messages.QuasiquoteAdjacentEllipsesInPattern(2))
}
}
def liftQuasi(quasi: Quasi, optional: Boolean = false): ReflectTree = {
try {
pendingQuasis.push(quasi)
if (quasi.rank == 0) {
var inferredPt = quasi.pt.wrap(pendingQuasis.map(_.rank).sum).toTpe
if (optional) inferredPt = appliedType(typeOf[Option[_]], inferredPt)
val lifted = mode match {
case Mode.Term(_, _) =>
q"$InternalLift[$inferredPt](${quasi.hole.arg})"
case Mode.Pattern(_, _, _) =>
// TODO: Here, we would like to say q"$InternalUnlift[$inferredPt](${quasi.hole.arg})".
// Unfortunately, the way how patterns work prevents us from having it this easy:
// 1) unapplications can't have explicitly specified type arguments
// 2) pattern language is very limited and can't express what we want to express in Unlift
// Therefore, we're forced to take a two-step unquoting scheme: a) match everything in the corresponding hole,
// b) call Unlift.unapply as a normal method in the right-hand side part of the pattern matching clause.
val hole = quasi.hole
val inferredPt = hole.arg match {
case pq"_: $pt" => pt
case pq"$_: $pt" => pt
case _ =>
var inferredPt = tq"_root_.scala.meta.Tree".wrap(pendingQuasis.map(_.rank).sum)
if (optional) inferredPt = tq"_root_.scala.Option[$inferredPt]"
inferredPt
}
hole.reifier = atPos(quasi.pos)(q"$InternalUnlift.unapply[$inferredPt](${hole.name})") // TODO: make `reifier`a immutable somehow
pq"${hole.name}"
}
atPos(quasi.pos)(lifted)
} else {
quasi.tree match {
case quasi: Quasi if quasi.rank == 0 =>
// NOTE: Option[Seq[T]] exists only in one instance in our tree API: Template.stats.
// Unfortunately, there is a semantic difference between an empty template and a template
// without any stats, so we can't just replace it with Seq[T] and rely on tokens
// (because tokens may be lost, e.g. a TASTY roundtrip).
//
// Strictly speaking, we shouldn't be allowing ..$stats in Template.stats,
// because the pt is Option[Seq[T]], not a Seq[T], but given the fact that Template.stats
// is very common, I'm willing to bend the rules here and flatten Option[Seq[T]],
// capturing 0 trees if we have None and working as usual if we have Some.
//
// This is definitely loss of information, but if someone wants to discern Some and None,
// they are welcome to write $stats, which will correctly capture an Option.
// TODO: Well, they aren't welcome, because $stats will insert or capture just one stat.
// This is the same problem as with `q"new $x"`, where x is ambiguous between a template and a ctorcall.
if (optional) {
mode match {
case Mode.Term(_, _) =>
q"_root_.scala.Some(${liftQuasi(quasi)})"
case Mode.Pattern(_, holes, _) =>
val reified = liftQuasi(quasi)
val hole = holes.find(hole => reified.equalsStructure(pq"${hole.name}")).get
require(hole.reifier.nonEmpty)
val flattened = q"_root_.scala.meta.internal.quasiquotes.Flatten.unapply(${hole.name})"
val unlifted = (new Transformer {
override def transform(tree: ReflectTree): ReflectTree = tree match {
case Ident(name) if name == hole.name => Ident(TermName("tree"))
case tree => super.transform(tree)
}
}).transform(hole.reifier)
hole.reifier = atPos(quasi.pos)(q"$flattened.flatMap(tree => $unlifted)")
reified
}
} else {
liftQuasi(quasi)
}
case _ =>
c.abort(quasi.pos, "complex ellipses are not supported yet")
}
}
} finally {
pendingQuasis.pop()
}
}
}
object Liftables extends s.DenotationLiftables
with s.TypingLiftables
with s.EnvironmentLiftables {
// NOTE: we could write just `implicitly[Liftable[MetaTree]].apply(meta)`
// but that would bloat the code significantly with duplicated instances for denotations and sigmas
override lazy val u: c.universe.type = c.universe
implicit def liftableSubTree[T <: MetaTree]: Liftable[T] = Liftable((tree: T) => materializeAst[MetaTree].apply(tree))
implicit def liftableSubTrees[T <:MetaTree]: Liftable[Seq[T]] = Liftable((trees: Seq[T]) => Lifts.liftTrees(trees))
implicit def liftableSubTreess[T <: MetaTree]: Liftable[Seq[Seq[T]]] = Liftable((treess: Seq[Seq[T]]) => Lifts.liftTreess(treess))
implicit def liftableOptionSubTree[T <: MetaTree]: Liftable[Option[T]] = Liftable((x: Option[T]) => Lifts.liftOptionTree(x))
implicit def liftableOptionSubTrees[T <: MetaTree]: Liftable[Option[Seq[T]]] = Liftable((x: Option[Seq[T]]) => Lifts.liftOptionTrees(x))
}
mode match {
case Mode.Term(_, _) =>
val internalResult = Lifts.liftTree(meta)
if (sys.props("quasiquote.debug") != null) {
println(internalResult)
// println(showRaw(internalResult))
}
q"$InternalUnlift[${c.macroApplication.tpe}]($internalResult)"
case Mode.Pattern(_, holes, unapplySelector) =>
// inspired by https://github.com/densh/joyquote/blob/master/src/main/scala/JoyQuote.scala
val pattern = Lifts.liftTree(meta)
val (thenp, elsep) = {
if (holes.isEmpty) (q"true", q"false")
else {
val resultNames = holes.zipWithIndex.map({ case (_, i) => TermName(QuasiquotePrefix + "$result$" + i) })
val resultPatterns = resultNames.map(name => pq"_root_.scala.Some($name)")
val resultTerms = resultNames.map(name => q"$name")
val thenp = q"""
(..${holes.map(_.reifier)}) match {
case (..$resultPatterns) => _root_.scala.Some((..$resultTerms))
case _ => _root_.scala.None
}
"""
(thenp, q"_root_.scala.None")
}
}
val matchp = pattern match {
case Bind(_, Ident(termNames.WILDCARD)) => q"input match { case $pattern => $thenp }"
case _ => q"input match { case $pattern => $thenp; case _ => $elsep }"
}
val internalResult = q"new { def unapply(input: _root_.scala.meta.Tree) = $matchp }.unapply($unapplySelector)"
if (sys.props("quasiquote.debug") != null) {
println(internalResult)
// println(showRaw(internalResult))
}
internalResult // TODO: q"InternalLift[${unapplySelector.tpe}]($internalResult)"
}
}
}
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