Move macro classloader cache to top level object.

Author: retronym

src/compiler/scala/reflect/macros/runtime/MacroRuntimes.scala

@@ -60,10 +60,14 @@ trait MacroRuntimes extends JavaReflectionRuntimes {
    *  a classloader mapped to that virtual directory.
    */
   private lazy val defaultMacroClassloaderCache = {
-    def attemptClose(loader: ClassLoader): Unit = loader match {
-      case u: URLClassLoader => debuglog("Closing macro runtime classloader"); u.close()
-      case afcl: AbstractFileClassLoader => attemptClose(afcl.getParent)
-      case _ => ???
+    def attemptClose(loader: ClassLoader): Unit = {
+      if (!scala.tools.nsc.typechecker.Macros.macroClassLoadersCache.owns(loader)) {
+        loader match {
+          case u: URLClassLoader => debuglog("Closing macro runtime classloader"); u.close()
+          case afcl: AbstractFileClassLoader => attemptClose(afcl.getParent)
+          case _ => ???
+        }
+      }
     }
     perRunCaches.newGeneric(findMacroClassLoader, attemptClose _)
   }

src/compiler/scala/tools/nsc/classpath/ZipAndJarFileLookupFactory.scala

@@ -190,6 +190,7 @@ final class FileBasedCache[T] {
   import java.nio.file.Path
   private case class Stamp(lastModified: FileTime, fileKey: Object)
   private val cache = collection.mutable.Map.empty[Seq[Path], (Seq[Stamp], T)]
+  def owns(t: T): Boolean = cache.valuesIterator.exists(_._2.asInstanceOf[AnyRef] eq t.asInstanceOf[AnyRef])
 
   def getOrCreate(paths: Seq[Path], create: () => T): T = cache.synchronized {
     val stamps = paths.map { path =>

src/compiler/scala/tools/nsc/typechecker/Macros.scala

@@ -67,9 +67,6 @@ trait Macros extends MacroRuntimes with Traces with Helpers {
 
   def globalSettings = global.settings
 
-  private final val macroClassLoadersCache =
-    new scala.tools.nsc.classpath.FileBasedCache[ScalaClassLoader]()
-
   /** Obtains a `ClassLoader` instance used for macro expansion.
    *
    *  By default a new `ScalaClassLoader` is created using the classpath
@@ -109,7 +106,7 @@ trait Macros extends MacroRuntimes with Traces with Helpers {
           macroLogVerbose(s"macro classloader: caching is disabled because the following paths are not supported: ${nonJarZips.mkString(",")}.")
           newLoader()
         } else {
-          macroClassLoadersCache.getOrCreate(locations.map(_.jfile.toPath()), newLoader)
+          Macros.macroClassLoadersCache.getOrCreate(locations.map(_.jfile.toPath()), newLoader)
         }
       }
     }
@@ -944,6 +941,12 @@ trait Macros extends MacroRuntimes with Traces with Helpers {
     }.transform(expandee)
 }
 
+object Macros {
+  final val macroClassLoadersCache =
+    new scala.tools.nsc.classpath.FileBasedCache[ScalaClassLoader]()
+
+}
+
 trait MacrosStats {
   self: TypesStats with Statistics =>
   val macroExpandCount    = newCounter ("#macro expansions", "typer")