# Pastebin Xb8uUGSF
raku -MJSON::Class -e '

class TestObject does JSON::Class {
    has Str $.string;
}

constant TestObjects = (Array[TestObject] but JSON::Class);


class Bla does JSON::Class {
    has TestObjects %.aaa;
}



my $json = q<{"aaa": [{ "string" : "one" }, { "string" : "two" }]}>;


say Bla.from-json: $json



'
Type check failed in assignment to %!aaa; expected Array[TestObject]+{JSON::Class} but got Array ([TestObject.new(stri...)
  in sub _unmarshal at /Users/fernando/.rakubrew/versions/moar-2020.11/share/perl6/site/sources/BD58585C8BB103CC821AB89EFD8D30DA4FB8FDF9 (JSON::Unmarshal) line 112
  in sub unmarshal at /Users/fernando/.rakubrew/versions/moar-2020.11/share/perl6/site/sources/BD58585C8BB103CC821AB89EFD8D30DA4FB8FDF9 (JSON::Unmarshal) line 158
  in method from-json at /Users/fernando/.rakubrew/versions/moar-2020.11/share/perl6/site/sources/C0029D661A8CA443DB83A67FE58F3E10D590C1A0 (JSON::Class) line 91
  in block <unit> at -e line 19