[perl #131290] is default() doesn't work on attributes

[Brad Gilbert via RT]

On Fri, 12 May 2017 03:04:46 -0700, elizabeth wrote:
> <lizmat>        m: class A { has Int $.a is default(42) }; dd A.new.a
> # expected to see 42 there, not Int, so feels like "is default" on
> attrs isn't implemented?

It does work if you add =Nil

    class A { has Int $.a is rw is default(42) = Nil };
    dd A.new.a; # 42
    $_ = A.new(:a(34));
    .a = Nil;
    dd .a; # 42