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package magnolia
import scala.reflect._, macros._
import macrocompat.bundle
import scala.util.Try
import scala.collection.immutable.ListMap
object GlobalMutableState {
private[magnolia] var state: ListMap[AnyRef, AnyRef] = ListMap()
private[magnolia] def push(key: AnyRef, value: AnyRef): Unit = {
state += ((key, value))
}
private[magnolia] def pop(): Unit = {
state = state.init
}
private[magnolia] def has(c: whitebox.Context)(key: AnyRef): Option[c.universe.Tree] =
state.get(key).asInstanceOf[Option[c.universe.Tree]]
private[magnolia] var searchType: AnyRef = null
}
@bundle
class Macros(val context: whitebox.Context) extends GenericMacro(context) {
protected def classBody(context: whitebox.Context)(genericType: context.Type, implementation: context.Tree): context.Tree = {
import context.universe._
q"""def extract(src: _root_.magnolia.Thing): $genericType = $implementation"""
}
protected def dereferenceValue(context: whitebox.Context)(value: context.Tree, elem: String): context.Tree = {
import context.universe._
q"$value.access($elem)"
}
protected def callDelegateMethod(context: whitebox.Context)(value: context.Tree, argument: context.Tree): context.Tree = {
import context.universe._
q"$value.extract($argument)"
}
protected def coproductReduction(context: whitebox.Context)(left: context.Tree, right: context.Tree): context.Tree = {
import context.universe._
q"$left.orElse($right)"
}
}
abstract class GenericMacro(whiteboxContext: whitebox.Context) {
val c = whiteboxContext
def getImplicit(genericType: c.universe.Type,
typeConstructor: c.universe.Type,
myName: c.universe.TermName,
count: Int): c.Tree = {
import c.universe._
println(s"getImplicit($genericType, $count)")
val result = GlobalMutableState.has(c)(genericType).map { nm => q"$nm" }.orElse {
val searchType = appliedType(typeConstructor, genericType)
if(GlobalMutableState.has(c)(genericType).isEmpty) {
scala.util.Try {
GlobalMutableState.searchType = genericType
c.inferImplicitValue(searchType, false, false)
}.toOption.orElse {
println("Recursing")
directInferImplicit(genericType, typeConstructor, count + 1)
}
} else {
directInferImplicit(genericType, typeConstructor, count + 1)
}
}.getOrElse {
println("Failed 2.")
c.abort(c.enclosingPosition, "Could not find extractor for type "+genericType)
}
result
}
def directInferImplicit(genericType: c.universe.Type,
typeConstructor: c.universe.Type,
count: Int): Option[c.Tree] = {
import c.universe._
println(s"directInferImplicit($genericType, $count)")
val myName: TermName = TermName(c.freshName(genericType.typeSymbol.name.encodedName.toString.toLowerCase+"Extractor"))
val typeSymbol = genericType.typeSymbol
val classType = if(typeSymbol.isClass) Some(typeSymbol.asClass) else None
val isCaseClass = classType.map(_.isCaseClass).getOrElse(false)
val isSealedTrait = classType.map(_.isSealed).getOrElse(false)
val isAnyVal = genericType <:< typeOf[AnyVal]
val resultType = appliedType(typeConstructor, genericType)
val construct = if(isCaseClass) {
val implicits = genericType.decls.collect {
case m: MethodSymbol if m.isCaseAccessor => m.asMethod
}.map { param =>
val returnType = param.returnType
GlobalMutableState.push(genericType, myName)
val imp = getImplicit(returnType, typeConstructor, myName, count)
GlobalMutableState.pop()
val dereferenced = dereferenceValue(c)(q"src", param.name.toString)
callDelegateMethod(c)(imp, dereferenced)
}
Some(q"new $genericType(..$implicits)")
} else if(isSealedTrait) {
val subtypes = classType.get.knownDirectSubclasses.to[List]
Some(subtypes.map(_.asType.toType).map { searchType =>
GlobalMutableState.push(genericType, myName)
val res = getImplicit(searchType, typeConstructor, myName, count)
GlobalMutableState.pop()
res
}.reduce(coproductReduction(c))).map { imp =>
callDelegateMethod(c)(imp, q"src")
}
} else None
val result = construct.map { const =>
val methodImplementation = classBody(c)(genericType, const)
q"""{
def $myName: $resultType = new $resultType {
$methodImplementation
}
$myName
}"""
}
result
}
protected def classBody(c: whitebox.Context)(genericType: c.Type, implementation: c.Tree): c.Tree
protected def coproductReduction(c: whitebox.Context)(left: c.Tree, right: c.Tree): c.Tree
protected def dereferenceValue(c: whitebox.Context)(value: c.Tree, elem: String): c.Tree
protected def callDelegateMethod(c: whitebox.Context)(value: c.Tree, argument: c.Tree): c.Tree
def generic[T: c.WeakTypeTag, Tc: c.WeakTypeTag]: c.Tree = {
import c.universe._
val genericType: Type = weakTypeOf[T]
val reentrant = genericType == GlobalMutableState.searchType
if(reentrant) {
println("Reentrant.")
???
}
val typeConstructor: Type = weakTypeOf[Tc].typeConstructor
val result = directInferImplicit(genericType, typeConstructor, 0)
println(result)
try result.map { tree => c.typecheck(tree) } catch {
case e: Exception =>
println(result)
println("Failed to typecheck because: "+e)
}
result.getOrElse {
println("Count not infer extractor...")
c.abort(c.enclosingPosition, "Could not infer extractor. Sorry.")
}
}
}
|
