Revert using withoutErased

not sure what I was doing there...

Author: natsukagami

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

@@ -659,14 +659,14 @@ class TypeErasure(sourceLanguage: SourceLanguage, semiEraseVCs: Boolean, isConst
       val formals = formals0.mapConserve(paramErasure)
       eraseResult(tp.resultType) match {
         case rt: MethodType =>
-          tp.withoutErased.derivedLambdaType(names ++ rt.paramNames, formals ++ rt.paramInfos, rt.resultType)
+          tp.derivedLambdaType(names ++ rt.paramNames, formals ++ rt.paramInfos, rt.resultType)
         case NoType =>
           // Can happen if we smuggle in a Nothing in the qualifier. Normally we prevent that
           // in Checking.checkMembersOK, but compiler-generated code can bypass this test.
           // See i15377.scala for a test case.
           NoType
         case rt =>
-          tp.withoutErased.derivedLambdaType(names, formals, rt)
+          tp.derivedLambdaType(names, formals, rt)
       }
     case tp: PolyType =>
       this(tp.resultType)

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

@@ -3924,15 +3924,6 @@ object Types {
       case c: ErasedMethodCompanion => c.isErased
       case _ => super.erasedParams
 
-    def withoutErased(using Context): MethodType =
-      val newCompanion = companion match {
-        case _: ErasedMethodType => MethodType
-        case _: ErasedContextualMethodType => ContextualMethodType
-        case _: ErasedImplicitMethodType => ImplicitMethodType
-        case c => return this
-      }
-      newCompanion(paramNames)(paramInfosExp, resultTypeExp)
-
     // Mark erased classes as erased parameters as well.
     def markErasedClasses(using Context): MethodType =
       val isErasedClass = paramInfos.map(_.isErasedClass)