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/**
* Copyright (C) 2012 Typesafe Inc. <http://www.typesafe.com>
*/
package scala.async
import scala.language.experimental.macros
import scala.reflect.macros.Context
/*
* @author Philipp Haller
*/
object Async extends AsyncBase {
import scala.concurrent.Future
lazy val futureSystem = ScalaConcurrentFutureSystem
type FS = ScalaConcurrentFutureSystem.type
def async[T](body: T) = macro asyncImpl[T]
override def asyncImpl[T: c.WeakTypeTag](c: Context)(body: c.Expr[T]): c.Expr[Future[T]] = super.asyncImpl[T](c)(body)
}
object AsyncId extends AsyncBase {
lazy val futureSystem = IdentityFutureSystem
type FS = IdentityFutureSystem.type
def async[T](body: T) = macro asyncImpl[T]
override def asyncImpl[T: c.WeakTypeTag](c: Context)(body: c.Expr[T]): c.Expr[T] = super.asyncImpl[T](c)(body)
}
/**
* A base class for the `async` macro. Subclasses must provide:
*
* - Concrete types for a given future system
* - Tree manipulations to create and complete the equivalent of Future and Promise
* in that system.
* - The `async` macro declaration itself, and a forwarder for the macro implementation.
* (The latter is temporarily needed to workaround bug SI-6650 in the macro system)
*
* The default implementation, [[scala.async.Async]], binds the macro to `scala.concurrent._`.
*/
abstract class AsyncBase {
self =>
type FS <: FutureSystem
val futureSystem: FS
/**
* A call to `await` must be nested in an enclosing `async` block.
*
* A call to `await` does not block the current thread, rather it is a delimiter
* used by the enclosing `async` macro. Code following the `await`
* call is executed asynchronously, when the argument of `await` has been completed.
*
* @param awaitable the future from which a value is awaited.
* @tparam T the type of that value.
* @return the value.
*/
// TODO Replace with `@compileTimeOnly when this is implemented SI-6539
@deprecated("`await` must be enclosed in an `async` block", "0.1")
def await[T](awaitable: futureSystem.Fut[T]): T = ???
def asyncImpl[T: c.WeakTypeTag](c: Context)(body: c.Expr[T]): c.Expr[futureSystem.Fut[T]] = {
import c.universe._
import Flag._
val builder = new ExprBuilder[c.type, futureSystem.type](c, self.futureSystem)
val anaylzer = new AsyncAnalysis[c.type](c)
import builder.defn._
import builder.name
import builder.futureSystemOps
anaylzer.reportUnsupportedAwaits(body.tree)
// Transform to A-normal form:
// - no await calls in qualifiers or arguments,
// - if/match only used in statement position.
val anfTree: Block = {
val transform = new AnfTransform[c.type](c)
val unique = transform.uniqueNames(body.tree)
val stats1 :+ expr1 = transform.anf.transformToList(unique)
val block = Block(stats1, expr1)
c.typeCheck(block).asInstanceOf[Block]
}
// Analyze the block to find locals that will be accessed from multiple
// states of our generated state machine, e.g. a value assigned before
// an `await` and read afterwards.
val renameMap: Map[Symbol, TermName] = {
anaylzer.valDefsUsedInSubsequentStates(anfTree).map {
vd =>
(vd.symbol, builder.name.fresh(vd.name))
}.toMap
}
val startState = builder.stateAssigner.nextState()
val endState = Int.MaxValue
val asyncBlockBuilder = new builder.AsyncBlockBuilder(anfTree.stats, anfTree.expr, startState, endState, renameMap)
val handlerCases: List[CaseDef] = asyncBlockBuilder.mkCombinedHandlerCases[T]()
import asyncBlockBuilder.asyncStates
logDiagnostics(c)(anfTree, asyncStates.map(_.toString))
val initStates = asyncStates.init
val localVarTrees = asyncStates.flatMap(_.allVarDefs).toList
/*
lazy val onCompleteHandler = (tr: Try[Any]) => state match {
case 0 => {
x11 = tr.get.asInstanceOf[Double];
state = 1;
resume()
}
...
*/
val onCompleteHandler = {
val onCompleteHandlers = initStates.flatMap(_.mkOnCompleteHandler()).toList
Function(
List(ValDef(Modifiers(PARAM), name.tr, TypeTree(TryAnyType), EmptyTree)),
Match(Ident(name.state), onCompleteHandlers))
}
/*
def resume(): Unit = {
try {
state match {
case 0 => {
f11 = exprReturningFuture
f11.onComplete(onCompleteHandler)(context)
}
...
}
} catch {
case NonFatal(t) => result.failure(t)
}
}
*/
val resumeFunTree: c.Tree = DefDef(Modifiers(), name.resume, Nil, List(Nil), Ident(definitions.UnitClass),
Try(
Match(Ident(name.state), handlerCases),
List(
CaseDef(
Apply(Ident(NonFatalClass), List(Bind(name.tr, Ident(nme.WILDCARD)))),
EmptyTree,
Block(List({
val t = c.Expr[Throwable](Ident(name.tr))
futureSystemOps.completeProm[T](c.Expr[futureSystem.Prom[T]](Ident(name.result)), reify(scala.util.Failure(t.splice))).tree
}), c.literalUnit.tree))), EmptyTree))
val prom: Expr[futureSystem.Prom[T]] = reify {
// Create the empty promise
val result$async = futureSystemOps.createProm[T].splice
// Initialize the state
var state$async = 0
// Resolve the execution context
val execContext$async = futureSystemOps.execContext.splice
var onCompleteHandler$async: util.Try[Any] => Unit = null
// Spawn a future to:
futureSystemOps.future[Unit] {
c.Expr[Unit](Block(
// define vars for all intermediate results that are accessed from multiple states
localVarTrees :+
// define the resume() method
resumeFunTree :+
// assign onComplete function. (The var breaks the circular dependency with resume)`
Assign(Ident(name.onCompleteHandler), onCompleteHandler),
// and get things started by calling resume()
Apply(Ident(name.resume), Nil)))
}(c.Expr[futureSystem.ExecContext](Ident(name.execContext))).splice
// Return the promise from this reify block...
result$async
}
// ... and return its Future from the macro.
val result = futureSystemOps.promiseToFuture(prom)
AsyncUtils.vprintln(s"async state machine transform expands to:\n ${result.tree}")
result
}
def logDiagnostics(c: Context)(anfTree: c.Tree, states: Seq[String]) {
def location = try {
c.macroApplication.pos.source.path
} catch {
case _: UnsupportedOperationException =>
c.macroApplication.pos.toString
}
AsyncUtils.vprintln(s"In file '$location':")
AsyncUtils.vprintln(s"${c.macroApplication}")
AsyncUtils.vprintln(s"ANF transform expands to:\n $anfTree")
states foreach (s => AsyncUtils.vprintln(s))
}
}
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