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)