1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
|
/*
* 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._
val builder = ExprBuilder[c.type, futureSystem.type](c, self.futureSystem)
val anaylzer = AsyncAnalysis[c.type](c)
val utils = TransformUtils[c.type](c)
import utils.{name, defn}
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 anf = AnfTransform[c.type](c)
val stats1 :+ expr1 = anf(body.tree)
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, name.fresh(vd.name))
}.toMap
}
val asyncBlock: builder.AsyncBlock = builder.build(anfTree, renameMap)
import asyncBlock.asyncStates
logDiagnostics(c)(anfTree, asyncStates.map(_.toString))
val localVarTrees = anfTree.collect {
case vd@ValDef(_, _, tpt, _) if renameMap contains vd.symbol =>
utils.mkVarDefTree(tpt.tpe, renameMap(vd.symbol))
}
val onCompleteHandler = asyncBlock.onCompleteHandler
val resumeFunTree = asyncBlock.resumeFunTree[T]
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))
}
}
|
