Bring back convertNewArray into typer.

It's needed in order to create calls to newGenricArray
as it needs to infer the ClassTag.

Author: DarkDimius

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

@@ -560,7 +560,7 @@ trait Applications extends Compatibility { self: Typer =>
                 if (proto.argsAreTyped) new ApplyToTyped(tree, fun1, funRef, proto.typedArgs, pt)
                 else new ApplyToUntyped(tree, fun1, funRef, proto, pt)(argCtx(tree))
               val result = app.result
-              ConstFold(result)
+              convertNewArray(ConstFold(result))
             } { (failedVal, failedState) =>
               val fun2 = tryInsertImplicitOnQualifier(fun1, proto)
               if (fun1 eq fun2) {
@@ -636,6 +636,18 @@ trait Applications extends Compatibility { self: Typer =>
   def adaptTypeArg(tree: tpd.Tree, bound: Type)(implicit ctx: Context): tpd.Tree =
     tree.withType(tree.tpe.etaExpandIfHK(bound))
 
+  /** Rewrite `new Array[T](....)` trees to calls of newXYZArray methods.
+   *  It is performed during typer as creation of generic arrays needs a classTag.
+   *  we rely on implicit search to find one
+   */
+  def convertNewArray(tree: tpd.Tree)(implicit ctx: Context): tpd.Tree = tree match {
+    case Apply(TypeApply(tycon, targ :: Nil), args) if tycon.symbol == defn.ArrayConstructor =>
+      fullyDefinedType(tree.tpe, "array", tree.pos)
+      newArray(targ.tpe, tree.tpe, tree.pos, JavaSeqLiteral(args, TypeTree(defn.IntClass.typeRef)))
+    case _ =>
+      tree
+  }
+
   def typedUnApply(tree: untpd.Apply, selType: Type)(implicit ctx: Context): Tree = track("typedUnApply") {
     val Apply(qual, args) = tree
 

src/dotty/tools/dotc/typer/Typer.scala

@@ -1684,7 +1684,8 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
               case _ => Nil
             }
             if (typeArgs.isEmpty) typeArgs = constrained(poly, tree)._2
-              adaptInterpolated(tree.appliedToTypes(typeArgs), pt, original)
+            convertNewArray(
+              adaptInterpolated(tree.appliedToTypes(typeArgs), pt, original))
           }
         case wtp =>
           pt match {