Dependency loop false positive with optional pointers

[Vexu]

const std = @import("std");

const S = struct {
    a: u32,
    b: Map,

    const Map = std.StringHashMap(?*S);
};
test "" {
    _ = S;
}

[andrewrk]

On the plus side, we're collecting some useful regression test cases for self-hosted

[andrewrk]

Previous issue for context: #4560

[Vexu]

It seems this has been broken since before 0.5.0 was released. I think I was hitting some other bug causing me to think this was a recent regression.