Optimization for Scala2 symbol unpickling

Author: odersky

compiler/src/dotty/tools/dotc/core/unpickleScala2/Scala2Unpickler.scala

@@ -431,7 +431,11 @@ class Scala2Unpickler(bytes: Array[Byte], classRoot: ClassDenotation, moduleClas
       owner.setFlag(DefaultParameterized)
     }
 
-    name = name.adjustIfModuleClass(flags)
+    var mangledName = name
+    if (flags is (ModuleClass, butNot = Package)) {
+      name = name.moduleClassName
+      mangledName = mangledName ++ "$"
+    }
     if (flags is Method) {
       name =
         if (name == nme.TRAIT_CONSTRUCTOR) nme.CONSTRUCTOR
@@ -446,8 +450,7 @@ class Scala2Unpickler(bytes: Array[Byte], classRoot: ClassDenotation, moduleClas
       flags = flags &~ Scala2SuperAccessor
     }
 
-    val mname = name.mangled
-    def nameMatches(rootName: Name) = mname == rootName.mangled
+    def nameMatches(rootName: Name) = mangledName == rootName.mangled
     def isClassRoot = nameMatches(classRoot.name) && (owner == classRoot.owner) && !(flags is ModuleClass)
     def isModuleClassRoot = nameMatches(moduleClassRoot.name) && (owner == moduleClassRoot.owner) && (flags is Module)
     def isModuleRoot = nameMatches(moduleClassRoot.name.sourceModuleName) && (owner == moduleClassRoot.owner) && (flags is Module)