#zig build-obj {
--name test -fno-emit-bin
-Mroot=test.zig
#}

#write test.zig {
const Opaque = opaque {};
const Untagged = @Union(.auto, null, &.{"foo"}, &.{Opaque}, &.{.{}});
export fn entry() usize {
    return @sizeOf(Untagged);
}
#}
#update
#check errors {
test.zig:2:49: error: cannot directly embed opaque type 'test.Opaque' in union
test.zig:2:49: note: opaque types have unknown size
test.zig:1:16: note: opaque declared here
#}
