I had to search for this, but managed to find the relevant mlugg@ comment[0] on the ZSF zulip:

> i had to change the bytes field from [*]align(@alignOf(T)) u8 to just [*]u8 (and cast the alignment back in the like one place that field is accessed). this wasn't necessary for MultiArrayList in and of itself, but it was necessary for embedding a MultiArrayList(T) inside of T without a dependency loop, like

    const T = struct {
        children: MultiArrayList(T),
    };
    // reproduced for completeness:
    fn MultiArrayList(comptime T: type) type {
        return struct {
            bytes: [*]align(@alignOf(T)) u8,
            // ...
        };
    }