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package scala.async
import scala.reflect.macros.Context
import collection.mutable
private[async] final case class AsyncAnalysis[C <: Context](override val c: C) extends TransformUtils(c) {
import c.universe._
/**
* Analyze the contents of an `async` block in order to:
* - Report unsupported `await` calls under nested templates, functions, by-name arguments.
*
* Must be called on the original tree, not on the ANF transformed tree.
*/
def reportUnsupportedAwaits(tree: Tree) {
new UnsupportedAwaitAnalyzer().traverse(tree)
}
/**
* Analyze the contents of an `async` block in order to:
* - Find which local `ValDef`-s need to be lifted to fields of the state machine, based
* on whether or not they are accessed only from a single state.
*
* Must be called on the ANF transformed tree.
*/
def valDefsUsedInSubsequentStates(tree: Tree): List[ValDef] = {
val analyzer = new AsyncDefinitionUseAnalyzer
analyzer.traverse(tree)
analyzer.valDefsToLift.toList
}
private class UnsupportedAwaitAnalyzer extends super.AsyncTraverser {
override def nestedClass(classDef: ClassDef) {
val kind = if (classDef.symbol.asClass.isTrait) "trait" else "class"
if (!reportUnsupportedAwait(classDef, s"nested $kind")) {
// do not allow local class definitions, because of SI-5467 (specific to case classes, though)
c.error(classDef.pos, s"Local class ${classDef.name.decoded} illegal within `async` block")
}
}
override def nestedModule(module: ModuleDef) {
if (!reportUnsupportedAwait(module, "nested object")) {
// local object definitions lead to spurious type errors (because of resetAllAttrs?)
c.error(module.pos, s"Local object ${module.name.decoded} illegal within `async` block")
}
}
override def byNameArgument(arg: Tree) {
reportUnsupportedAwait(arg, "by-name argument")
}
override def function(function: Function) {
reportUnsupportedAwait(function, "nested function")
}
override def traverse(tree: Tree) {
def containsAwait = tree exists isAwait
tree match {
case Try(_, _, _) if containsAwait =>
reportUnsupportedAwait(tree, "try/catch")
case _ =>
super.traverse(tree)
}
}
/**
* @return true, if the tree contained an unsupported await.
*/
private def reportUnsupportedAwait(tree: Tree, whyUnsupported: String): Boolean = {
val badAwaits: List[RefTree] = tree collect {
case rt: RefTree if isAwait(rt) => rt
}
badAwaits foreach {
tree =>
c.error(tree.pos, s"await must not be used under a $whyUnsupported.")
}
badAwaits.nonEmpty
}
}
private class AsyncDefinitionUseAnalyzer extends super.AsyncTraverser {
private var chunkId = 0
private def nextChunk() = chunkId += 1
private var valDefChunkId = Map[Symbol, (ValDef, Int)]()
val valDefsToLift: mutable.Set[ValDef] = collection.mutable.Set[ValDef]()
override def traverse(tree: Tree) = {
tree match {
case If(cond, thenp, elsep) if tree exists isAwait =>
traverseChunks(List(cond, thenp, elsep))
case Match(selector, cases) if tree exists isAwait =>
traverseChunks(selector :: cases)
case Apply(fun, args) if isAwait(fun) =>
super.traverse(tree)
nextChunk()
case vd: ValDef =>
super.traverse(tree)
valDefChunkId += (vd.symbol ->(vd, chunkId))
if (isAwait(vd.rhs)) valDefsToLift += vd
case as: Assign =>
if (isAwait(as.rhs)) {
assert(as.symbol != null, "internal error: null symbol for Assign tree:" + as)
// TODO test the orElse case, try to remove the restriction.
val (vd, defBlockId) = valDefChunkId.getOrElse(as.symbol, c.abort(as.pos, "await may only be assigned to a var/val defined in the async block. " + as.symbol))
valDefsToLift += vd
}
super.traverse(tree)
case rt: RefTree =>
valDefChunkId.get(rt.symbol) match {
case Some((vd, defChunkId)) if defChunkId != chunkId =>
valDefsToLift += vd
case _ =>
}
super.traverse(tree)
case _ => super.traverse(tree)
}
}
private def traverseChunks(trees: List[Tree]) {
trees.foreach {
t => traverse(t); nextChunk()
}
}
}
}
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