fix: correctly require a ClassTag when building a multidimensional Array

Author: hamzaremmal

compiler/src/dotty/tools/dotc/typer/Applications.scala

@@ -1433,7 +1433,7 @@ trait Applications extends Compatibility {
           .select(defn.newGenericArrayMethod).withSpan(tree.span)
           .appliedToTypeTrees(targs).appliedToTermArgs(args)
 
-      if (TypeErasure.isGeneric(targ.tpe))
+      if TypeErasure.isGeneric(targ.tpe) || targ.tpe.derivesFrom(defn.ArrayClass) then
         newGenericArrayCall
       else tree
     case _ =>

tests/run/i23901/MyArray_1.scala

@@ -0,0 +1,4 @@
+import scala.reflect.ClassTag
+
+object MyArray:
+  def empty[T: ClassTag]: Array[Array[T]] = new Array[Array[T]](0)

tests/run/i23901/Test_2.scala

@@ -0,0 +1,3 @@
+@main def Test =
+  val arr: Array[Array[String]] = MyArray.empty[String]
+  assert(arr.length == 0)