Do not use the name of a symbol when not needed.

[Cherry-picked cb1d50f]

Author: noti0na1

compiler/src/dotty/tools/dotc/core/Scopes.scala

@@ -164,15 +164,15 @@ object Scopes {
      */
     final def filteredScope(
         keep: Symbol => Boolean,
-        rename: (Symbol, Name) => Name = (_, name) => name)(using Context): Scope =
+        rename: Symbol => Name | Null = _ => null)(using Context): Scope =
       var result: MutableScope | Null = null
       for sym <- iterator do
         def drop() =
           if result == null then result = cloneScope
           result.nn.unlink(sym)
         if keep(sym) then
-          val newName = rename(sym, sym.name)
-          if newName != sym.name then
+          val newName = rename(sym)
+          if newName != null then
             drop()
             result.nn.enter(newName, sym)
         else

compiler/src/dotty/tools/dotc/core/TypeErasure.scala

@@ -727,10 +727,10 @@ class TypeErasure(sourceLanguage: SourceLanguage, semiEraseVCs: Boolean, isConst
             }
           val erasedDecls = decls.filteredScope(
               keep = sym => !sym.isType || sym.isClass,
-              rename = (sym, name) =>
+              rename = sym =>
                 if sym.lastKnownDenotation.unforcedAnnotation(defn.TargetNameAnnot).isDefined
                 then sym.targetName
-                else name
+                else null
             )
           val selfType1 = if cls.is(Module) then cls.sourceModule.termRef else NoType
           tp.derivedClassInfo(NoPrefix, erasedParents, erasedDecls, selfType1)