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An asynchronous programming facility for Scala that offers a direct API for working with Futures.
The newest version!
/*
* Copyright (C) 2012 Typesafe Inc.
*/
package scala.async.internal
import scala.tools.nsc.Global
import scala.Predef._
private[async] trait AnfTransform {
self: AsyncMacro =>
import global._
import reflect.internal.Flags._
def anfTransform(tree: Tree): Block = {
// Must prepend the () for issue #31.
val block = callSiteTyper.typedPos(tree.pos)(Block(List(Literal(Constant(()))), tree)).setType(tree.tpe)
new SelectiveAnfTransform().transform(block)
}
sealed abstract class AnfMode
case object Anf extends AnfMode
case object Linearizing extends AnfMode
final class SelectiveAnfTransform extends MacroTypingTransformer {
var mode: AnfMode = Anf
def blockToList(tree: Tree): List[Tree] = tree match {
case Block(stats, expr) => stats :+ expr
case t => t :: Nil
}
def listToBlock(trees: List[Tree]): Block = trees match {
case trees @ (init :+ last) =>
val pos = trees.map(_.pos).reduceLeft(_ union _)
Block(init, last).setType(last.tpe).setPos(pos)
}
override def transform(tree: Tree): Block = {
def anfLinearize: Block = {
val trees: List[Tree] = mode match {
case Anf => anf._transformToList(tree)
case Linearizing => linearize._transformToList(tree)
}
listToBlock(trees)
}
tree match {
case _: ValDef | _: DefDef | _: Function | _: ClassDef | _: TypeDef =>
atOwner(tree.symbol)(anfLinearize)
case _: ModuleDef =>
atOwner(tree.symbol.moduleClass orElse tree.symbol)(anfLinearize)
case _ =>
anfLinearize
}
}
private object linearize {
def transformToList(tree: Tree): List[Tree] = {
mode = Linearizing; blockToList(transform(tree))
}
def transformToBlock(tree: Tree): Block = listToBlock(transformToList(tree))
def _transformToList(tree: Tree): List[Tree] = trace(tree) {
val stats :+ expr = anf.transformToList(tree)
def statsExprUnit =
stats :+ expr :+ localTyper.typedPos(expr.pos)(Literal(Constant(())))
expr match {
case Apply(fun, args) if isAwait(fun) =>
val valDef = defineVal(name.await, expr, tree.pos)
stats :+ valDef :+ gen.mkAttributedStableRef(valDef.symbol).setType(tree.tpe).setPos(tree.pos)
case If(cond, thenp, elsep) =>
// if type of if-else is Unit don't introduce assignment,
// but add Unit value to bring it into form expected by async transform
if (expr.tpe =:= definitions.UnitTpe) {
statsExprUnit
} else {
val varDef = defineVar(name.ifRes, expr.tpe, tree.pos)
def branchWithAssign(orig: Tree) = localTyper.typedPos(orig.pos) {
def cast(t: Tree) = mkAttributedCastPreservingAnnotations(t, varDef.symbol.tpe)
orig match {
case Block(thenStats, thenExpr) => Block(thenStats, Assign(Ident(varDef.symbol), cast(thenExpr)))
case _ => Assign(Ident(varDef.symbol), cast(orig))
}
}
val ifWithAssign = treeCopy.If(tree, cond, branchWithAssign(thenp), branchWithAssign(elsep)).setType(definitions.UnitTpe)
stats :+ varDef :+ ifWithAssign :+ gen.mkAttributedStableRef(varDef.symbol).setType(tree.tpe).setPos(tree.pos)
}
case LabelDef(name, params, rhs) =>
statsExprUnit
case Match(scrut, cases) =>
// if type of match is Unit don't introduce assignment,
// but add Unit value to bring it into form expected by async transform
if (expr.tpe =:= definitions.UnitTpe) {
statsExprUnit
}
else {
val varDef = defineVar(name.matchRes, expr.tpe, tree.pos)
def typedAssign(lhs: Tree) =
localTyper.typedPos(lhs.pos)(Assign(Ident(varDef.symbol), mkAttributedCastPreservingAnnotations(lhs, varDef.symbol.tpe)))
val casesWithAssign = cases map {
case cd@CaseDef(pat, guard, body) =>
val newBody = body match {
case b@Block(caseStats, caseExpr) => treeCopy.Block(b, caseStats, typedAssign(caseExpr)).setType(definitions.UnitTpe)
case _ => typedAssign(body)
}
treeCopy.CaseDef(cd, pat, guard, newBody).setType(definitions.UnitTpe)
}
val matchWithAssign = treeCopy.Match(tree, scrut, casesWithAssign).setType(definitions.UnitTpe)
require(matchWithAssign.tpe != null, matchWithAssign)
stats :+ varDef :+ matchWithAssign :+ gen.mkAttributedStableRef(varDef.symbol).setPos(tree.pos).setType(tree.tpe)
}
case _ =>
stats :+ expr
}
}
private def defineVar(prefix: String, tp: Type, pos: Position): ValDef = {
val sym = currOwner.newTermSymbol(name.fresh(prefix), pos, MUTABLE | SYNTHETIC).setInfo(uncheckedBounds(tp))
ValDef(sym, gen.mkZero(uncheckedBounds(tp))).setType(NoType).setPos(pos)
}
}
private object trace {
private var indent = -1
private def indentString = " " * indent
def apply[T](args: Any)(t: => T): T = {
def prefix = mode.toString.toLowerCase
indent += 1
def oneLine(s: Any) = s.toString.replaceAll("""\n""", "\\\\n").take(127)
try {
AsyncUtils.trace(s"${indentString}$prefix(${oneLine(args)})")
val result = t
AsyncUtils.trace(s"${indentString}= ${oneLine(result)}")
result
} finally {
indent -= 1
}
}
}
private def defineVal(prefix: String, lhs: Tree, pos: Position): ValDef = {
val sym = currOwner.newTermSymbol(name.fresh(prefix), pos, SYNTHETIC).setInfo(uncheckedBounds(lhs.tpe))
changeOwner(lhs, currentOwner, sym)
ValDef(sym, changeOwner(lhs, currentOwner, sym)).setType(NoType).setPos(pos)
}
private object anf {
def transformToList(tree: Tree): List[Tree] = {
mode = Anf; blockToList(transform(tree))
}
def _transformToList(tree: Tree): List[Tree] = trace(tree) {
val containsAwait = tree exists isAwait
if (!containsAwait) {
tree match {
case Block(stats, expr) =>
// avoids nested block in `while(await(false)) ...`.
// TODO I think `containsAwait` really should return true if the code contains a label jump to an enclosing
// while/doWhile and there is an await *anywhere* inside that construct.
stats :+ expr
case _ => List(tree)
}
} else tree match {
case Select(qual, sel) =>
val stats :+ expr = linearize.transformToList(qual)
stats :+ treeCopy.Select(tree, expr, sel)
case Throw(expr) =>
val stats :+ expr1 = linearize.transformToList(expr)
stats :+ treeCopy.Throw(tree, expr1)
case Typed(expr, tpt) =>
val stats :+ expr1 = linearize.transformToList(expr)
stats :+ treeCopy.Typed(tree, expr1, tpt)
case treeInfo.Applied(fun, targs, argss) if argss.nonEmpty =>
// we can assume that no await call appears in a by-name argument position,
// this has already been checked.
val funStats :+ simpleFun = linearize.transformToList(fun)
val (argStatss, argExprss): (List[List[List[Tree]]], List[List[Tree]]) =
mapArgumentss[List[Tree]](fun, argss) {
case Arg(expr, byName, _) if byName /*|| isPure(expr) TODO */ => (Nil, expr)
case Arg(expr, _, argName) =>
linearize.transformToList(expr) match {
case stats :+ expr1 =>
val valDef = defineVal(argName, expr1, expr1.pos)
require(valDef.tpe != null, valDef)
val stats1 = stats :+ valDef
(stats1, atPos(tree.pos.makeTransparent)(gen.stabilize(gen.mkAttributedIdent(valDef.symbol))))
}
}
def copyApplied(tree: Tree, depth: Int): Tree = {
tree match {
case TypeApply(_, targs) => treeCopy.TypeApply(tree, simpleFun, targs)
case _ if depth == 0 => simpleFun
case Apply(fun, args) =>
val newTypedArgs = map2(args.map(_.pos), argExprss(depth - 1))((pos, arg) => localTyper.typedPos(pos)(arg))
treeCopy.Apply(tree, copyApplied(fun, depth - 1), newTypedArgs)
}
}
/** The depth of the nested applies: e.g. Apply(Apply(Apply(_, _), _), _)
* has depth 3. Continues through type applications (without counting them.)
*/
def applyDepth: Int = {
def loop(tree: Tree): Int = tree match {
case Apply(fn, _) => 1 + loop(fn)
case TypeApply(fn, _) => loop(fn)
case AppliedTypeTree(fn, _) => loop(fn)
case _ => 0
}
loop(tree)
}
val typedNewApply = copyApplied(tree, applyDepth)
funStats ++ argStatss.flatten.flatten :+ typedNewApply
case Block(stats, expr) =>
(stats :+ expr).flatMap(linearize.transformToList)
case ValDef(mods, name, tpt, rhs) =>
if (rhs exists isAwait) {
val stats :+ expr = atOwner(currOwner.owner)(linearize.transformToList(rhs))
stats.foreach(changeOwner(_, currOwner, currOwner.owner))
stats :+ treeCopy.ValDef(tree, mods, name, tpt, expr)
} else List(tree)
case Assign(lhs, rhs) =>
val stats :+ expr = linearize.transformToList(rhs)
stats :+ treeCopy.Assign(tree, lhs, expr)
case If(cond, thenp, elsep) =>
val condStats :+ condExpr = linearize.transformToList(cond)
val thenBlock = linearize.transformToBlock(thenp)
val elseBlock = linearize.transformToBlock(elsep)
condStats :+ treeCopy.If(tree, condExpr, thenBlock, elseBlock)
case Match(scrut, cases) =>
val scrutStats :+ scrutExpr = linearize.transformToList(scrut)
val caseDefs = cases map {
case CaseDef(pat, guard, body) =>
// extract local variables for all names bound in `pat`, and rewrite `body`
// to refer to these.
// TODO we can move this into ExprBuilder once we get rid of `AsyncDefinitionUseAnalyzer`.
val block = linearize.transformToBlock(body)
val (valDefs, mappings) = (pat collect {
case b@Bind(name, _) =>
val vd = defineVal(name.toTermName + AnfTransform.this.name.bindSuffix, gen.mkAttributedStableRef(b.symbol).setPos(b.pos), b.pos)
(vd, (b.symbol, vd.symbol))
}).unzip
val (from, to) = mappings.unzip
val b@Block(stats1, expr1) = block.substituteSymbols(from, to).asInstanceOf[Block]
val newBlock = treeCopy.Block(b, valDefs ++ stats1, expr1)
treeCopy.CaseDef(tree, pat, guard, newBlock)
}
scrutStats :+ treeCopy.Match(tree, scrutExpr, caseDefs)
case LabelDef(name, params, rhs) =>
List(LabelDef(name, params, Block(linearize.transformToList(rhs), Literal(Constant(())))).setSymbol(tree.symbol))
case TypeApply(fun, targs) =>
val funStats :+ simpleFun = linearize.transformToList(fun)
funStats :+ treeCopy.TypeApply(tree, simpleFun, targs)
case _ =>
List(tree)
}
}
}
}
}
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