Fix computation of moduleClass

Author: odersky

compiler/src/dotty/tools/dotc/fromtasty/ReadTastyTreesFromClasses.scala

@@ -33,7 +33,7 @@ class ReadTastyTreesFromClasses extends FrontEnd {
       }
 
       def alreadyLoaded(): None.type = {
-        ctx.warning("sclass $className cannot be unpickled because it is already loaded")
+        ctx.warning(s"sclass $className cannot be unpickled because it is already loaded")
         None
       }
 
@@ -66,7 +66,8 @@ class ReadTastyTreesFromClasses extends FrontEnd {
           clsd.infoOrCompleter match {
             case info: ClassfileLoader =>
               info.load(clsd) // sets cls.treeOrProvider and cls.moduleClass.treeProvider as a side-effect
-              compilationUnit(clsd.classSymbol).orElse(compilationUnit(clsd.moduleClass))
+              def moduleClass = clsd.owner.info.member(className.moduleClassName).symbol
+              compilationUnit(clsd.classSymbol).orElse(compilationUnit(moduleClass))
             case _ =>
               alreadyLoaded()
           }