generator layout

struct-enum.zig

return struct {
    suspended: ?anyframe = null,
    out: ?Out = null,
    state: enum {
        pending,
        consumed,
        complete,
    } = .complete,
};

union.zig

return union {
    .pending = struct { suspended: anyframe, out = Out },
    .consumed = struct { suspended: anyframe },
    .complete = void,
};