Merge pull request scala#4637 from retronym/ticket/9401

SI-9401 Avoid SOE with array + missing classtag

Author: lrytz

src/compiler/scala/tools/nsc/typechecker/Typers.scala

@@ -4577,7 +4577,7 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
           typed1(atPos(tree.pos)(Block(stats, Apply(expr, args) setPos tree.pos.makeTransparent)), mode, pt)
         case Apply(fun, args) =>
           normalTypedApply(tree, fun, args) match {
-            case ArrayInstantiation(tree1)                                           => typed(tree1, mode, pt)
+            case ArrayInstantiation(tree1)                                           => if (tree1.isErrorTyped) tree1 else typed(tree1, mode, pt)
             case Apply(Select(fun, nme.apply), _) if treeInfo.isSuperConstrCall(fun) => TooManyArgumentListsForConstructor(tree) //SI-5696
             case tree1                                                               => tree1
           }

test/files/neg/t9401.check

@@ -0,0 +1,4 @@
+t9401.scala:3: error: cannot find class tag for element type T
+  gencastarray = new Array[T](0)
+                 ^
+one error found

test/files/neg/t9401.scala

@@ -0,0 +1,4 @@
+class Resetting[T] {
+  var gencastarray: Any = null
+  gencastarray = new Array[T](0)
+}