Odd formatting of type def with many generics

I'm seeing this behavior in rustfmt 1.6.0-nightly (c469197b 2023-08-22):

// Before (correct in stable)
type AAAAAAAAAAAAA: BBBBBBBBBBBBBBB<
    CCCCCCCCCCCCCCCCC,
    DDDDDDDDDDDDDDDDD,
    EEEEEEEEEEEEEEEEE,
    FFFFFFFFFFFFFFFFF,
    GGGGGGGGGGGGGGGGG,
    HHHHHHHHHHHHHHHHH,
    IIIIIIIIIIIIIIIII,
>;

// After (hopefully not correct)
type AAAAAAAAAAAAA: BBBBBBBBBBBBBBB<
        CCCCCCCCCCCCCCCCC,
        DDDDDDDDDDDDDDDDD,
        EEEEEEEEEEEEEEEEE,
        FFFFFFFFFFFFFFFFF,
        GGGGGGGGGGGGGGGGG,
        HHHHHHHHHHHHHHHHH,
        IIIIIIIIIIIIIIIII,
    >;

It's completely unclear to me what the expected behavior is at this point, but judging by https://github.com/rust-lang/rustfmt/issues/5577 (specifically this: https://github.com/rust-lang/rustfmt/issues/5577#issuecomment-1407489330), this is not what you want.