todo tests for GH 16364 (array element lazily created at wrong index)

This commit adds some todo tests for GH 16364 that test the following
behavior:
* An array element that was previously uninitialized is created at the
  correct index when assigned from a subroutine's @_ alias which
  modifies the element's original array. The element is within the
  array.
* The same as the above but the element is outside of the array's
  range.
* An array element that was previously uninitialized is created at the
  correct index when assigned from a foreach loop's $_ alias which
  modifies the element's original array.

Author: 1-1sam

t/run/todo.t

@@ -137,6 +137,38 @@ TODO: {
     "undef:de567\nundef:de567", { eval $switches }, "");
 }
 
+TODO: {
+    local $::TODO = 'GH 16364';
+
+    my @arr;
+    my sub foo {
+        unshift @arr, 7;
+        $_[0] = 3;
+    }
+
+    @arr = ();
+    $arr[1] = 1;
+    foo($arr[0]);
+    is($arr[1], 3,
+       'Array element within array range created at correct index from subroutine @_ alias; GH 16364');
+
+    @arr = ();
+    $arr[1] = 1;
+    foo($arr[5]);
+    is($arr[6], 3,
+       'Array element outside array range created at correct index from subroutine @_ alias; GH 16364');
+
+    @arr = ();
+    $arr[1] = 1;
+    foreach (@arr) {
+        unshift @arr, 7;
+        $_ = 3;
+        last;
+    }
+    is($arr[1], 3, 'Array element created at correct index from foreach $_ alias; GH 16364');
+
+}
+
 TODO: {
     local $::TODO = 'GH 16865';
     fresh_perl('\(sort { 0 } 0, 0 .. "a")', { stderr => 'devnull' });