Add the return of default values when Nil is assigned

lib/Type/Nil.pod

@@ -17,7 +17,7 @@ container you assigned it into.
     $x.say;          #-> (Int)
 
 It is for this reason that assigning an untyped container as C<Nil> will result
-in an C<(Any)> object.
+in an L<(Any)> object.
 
     my $x = Nil;
     $x.say;          #-> (Any)
@@ -33,6 +33,14 @@ when said variable appears on the RHS, you can type the container as C<Nil>.
     my Str $s = $x;
     $s.say;          #-> (Str)
 
+There is an important exception to this transforms-into-type-object rule:
+assigning C<Nil> to a variable which has a default will restore that default.
+
+    my Int $x is default(42) = -1;
+    my $y = 1;
+    for $x,$y -> $val is rw { $val = $reset unless $val > 0 }
+    $x.say;          #-> 42
+
 =head1 Methods
 
 =head2 method gist