fix: align erasure of Array[Nothing] and Array[Null] with Scala 2

[Cherry-picked c197afb]

Author: hamzaremmal

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

@@ -597,8 +597,8 @@ class TypeErasure(sourceLanguage: SourceLanguage, semiEraseVCs: Boolean, isConst
    *   will be returned.
    *
    *  In all other situations, |T| will be computed as follow:
-   *   - For a refined type scala.Array+[T]:
-   *      - if T is Nothing or Null, []Object
+   *   - For a refined type scala.Array[T]:
+   *      - {Scala 2} if T is Nothing or Null, []Object
    *      - otherwise, if T <: Object, []|T|
    *      - otherwise, if T is a type parameter coming from Java, []Object
    *      - otherwise, Object
@@ -781,10 +781,12 @@ class TypeErasure(sourceLanguage: SourceLanguage, semiEraseVCs: Boolean, isConst
     val defn.ArrayOf(elemtp) = tp: @unchecked
     if (isGenericArrayElement(elemtp, isScala2 = sourceLanguage.isScala2)) defn.ObjectType
     else
-      try
-        val eElem = erasureFn(sourceLanguage, semiEraseVCs = false, isConstructor, isSymbol, inSigName)(elemtp)
-        if eElem.isInstanceOf[WildcardType] then WildcardType
-        else JavaArrayType(eElem)
+      try 
+        if sourceLanguage.isScala2 && (elemtp.isNullType || elemtp.isNothingType) then
+          JavaArrayType(defn.ObjectType)
+        else erasureFn(sourceLanguage, semiEraseVCs = false, isConstructor, isSymbol, inSigName)(elemtp) match
+          case _: WildcardType => WildcardType
+          case elem => JavaArrayType(elem)
       catch case ex: Throwable =>
         handleRecursive("erase array type", tp.show, ex)
   }

sbt-test/scala2-compat/erasure/dottyApp/Api.scala

@@ -195,4 +195,10 @@ class Z {
   def objectARRAY_88(x: Array[Any]): Unit = {}
   def objectARRAY_89(x: Array[AnyRef]): Unit = {}
   def objectARRAY_90(x: Array[AnyVal]): Unit = {}
+
+  def objectARRAY_91(x: Array[Nothing]): Unit = {}
+  def objectARRAY_92(x: Array[Null]): Unit = {}
+  def objectARRAY_93(x: Array[_ <: Nothing]): Unit = {}
+  def objectARRAY_94(x: Array[_ <: Null]): Unit = {}
+
 }

sbt-test/scala2-compat/erasure/dottyApp/Main.scala

@@ -101,6 +101,10 @@ object Main {
     z.objectARRAY_88(dummy)
     z.objectARRAY_89(dummy)
     z.objectARRAY_90(dummy)
+    z.objectARRAY_91(dummy)
+    z.objectARRAY_92(dummy)
+    z.objectARRAY_93(dummy)
+    z.objectARRAY_94(dummy)
 
     val methods = classOf[scala2Lib.Z].getDeclaredMethods.toList ++ classOf[dottyApp.Z].getDeclaredMethods.toList
     methods.foreach { m =>

sbt-test/scala2-compat/erasure/scala2Lib/Api.scala

@@ -186,4 +186,10 @@ class Z {
   def objectARRAY_88(x: Array[Any]): Unit = {}
   def objectARRAY_89(x: Array[AnyRef]): Unit = {}
   def objectARRAY_90(x: Array[AnyVal]): Unit = {}
+
+  def objectARRAY_91(x: Array[Nothing]): Unit = {}
+  def objectARRAY_92(x: Array[Null]): Unit = {}
+  def objectARRAY_93(x: Array[_ <: Nothing]): Unit = {}
+  def objectARRAY_94(x: Array[_ <: Null]): Unit = {}
+
 }