cleans up initialization of runtime reflection

At first I just tried to remove syntheticCoreClasses from missingHook
and put them into the initializer of freshly created mirrors in order to
reduce the non-determinism in mutations of the global symbol table.

And then it didn't work, crashing on me claiming that AnyRef is missing.
Apparently we still need AnyRefClass in missingHook, just because it's
impossible to initialize (i.e. unpickle) ScalaPackageClass without it.

And then it still didn't work, whining about multiple overloaded defs
of some synthetic symbols. That was really tricky, but I figured it out
as well by initializing ScalaPackageClass first before forcing any
synthetic symbols (see the details in comments).

And then it worked, but stopped working half a year later when
Jason and I came to revisit this old pull request. The final twist
was pre-initializing ObjectClass, because it's a dependency of AnyRefClass,
which is a critical dependency of ScalaPackageClass (full information
can be found in comments).

1 files changed, 9 insertions, 22 deletions

diff --git a/src/reflect/scala/reflect/runtime/JavaMirrors.scala b/src/reflect/scala/reflect/runtime/JavaMirrors.scala
index 2cdacde900..487da2eb4b 100644
--- a/src/reflect/scala/reflect/runtime/JavaMirrors.scala
+++ b/src/reflect/scala/reflect/runtime/JavaMirrors.scala
@@ -44,16 +44,6 @@ private[reflect] trait JavaMirrors extends internal.SymbolTable with api.JavaUni
 
   trait JavaClassCompleter extends FlagAssigningCompleter
 
-  def init() = {
-    definitions.AnyValClass // force it.
-
-    // establish root association to avoid cyclic dependency errors later
-    rootMirror.classToScala(classOf[java.lang.Object]).initialize
-
-    // println("initializing definitions")
-    definitions.init()
-  }
-
   def runtimeMirror(cl: ClassLoader): Mirror = mirrors get cl match {
     case Some(WeakReference(m)) => m
     case _ => createMirror(rootMirror.RootClass, cl)
@@ -1280,11 +1270,6 @@ private[reflect] trait JavaMirrors extends internal.SymbolTable with api.JavaUni
     case _ => abort(s"${sym}.enclosingRootClass = ${sym.enclosingRootClass}, which is not a RootSymbol")
   }
 
-  private lazy val syntheticCoreClasses: Map[(String, Name), Symbol] = {
-    def mapEntry(sym: Symbol): ((String, Name), Symbol) = (sym.owner.fullName, sym.name) -> sym
-    Map() ++ (definitions.syntheticCoreClasses map mapEntry)
-  }
-
   /** 1. If `owner` is a package class (but not the empty package) and `name` is a term name, make a new package
    *  <owner>.<name>, otherwise return NoSymbol.
    *  Exception: If owner is root and a java class with given name exists, create symbol in empty package instead
@@ -1301,13 +1286,15 @@ private[reflect] trait JavaMirrors extends internal.SymbolTable with api.JavaUni
       if (name.isTermName && !owner.isEmptyPackageClass)
         return mirror.makeScalaPackage(
           if (owner.isRootSymbol) name.toString else owner.fullName+"."+name)
-      syntheticCoreClasses get ((owner.fullName, name)) foreach { tsym =>
-        // synthetic core classes are only present in root mirrors
-        // because Definitions.scala, which initializes and enters them, only affects rootMirror
-        // therefore we need to enter them manually for non-root mirrors
-        if (mirror ne thisUniverse.rootMirror) owner.info.decls enter tsym
-        return tsym
-      }
+      if (name == tpnme.AnyRef && owner.owner.isRoot && owner.name == tpnme.scala_)
+        // when we synthesize the scala.AnyRef symbol, we need to add it to the scope of the scala package
+        // the problem is that adding to the scope implies doing something like `owner.info.decls enter anyRef`
+        // which entails running a completer for the scala package
+        // which will try to unpickle the stuff in scala/package.class
+        // which will transitively load scala.AnyRef
+        // which doesn't exist yet, because it hasn't been added to the scope yet
+        // this missing hook ties the knot without introducing synchronization problems like before
+        return definitions.AnyRefClass
     }
     info("*** missing: "+name+"/"+name.isTermName+"/"+owner+"/"+owner.hasPackageFlag+"/"+owner.info.decls.getClass)
     super.missingHook(owner, name)