rustdoc shows associated type in supertrait bound twice when both Deref and DerefMut have a `Target` bound

[RalfJung]

This is visible here:

pub trait AllocBytes: Clone + Debug + Eq + PartialEq + Hash + Deref<Target = [u8], Target = [u8]> + DerefMut {

Compared to the actual sources, the Target = [u8] is duplicated at Deref but missing at DerefMut.

pub trait AllocBytes:
    Clone + fmt::Debug + Eq + PartialEq + Hash + Deref<Target = [u8]> + DerefMut<Target = [u8]>

(On DerefMut the constraint is redundant, that is likely what is throwing rustdoc off.)

Cc @rust-lang/rustdoc

[fmease]

I've been aware of flaws like this for a long time (your issue is an instance of the more general #113015) and I generally know how to fix this but work has stalled (e.g. this tangentially related PR #116735) because the way data is represented in rustdoc (rustdoc::clean::types) makes this unnecessarily hard to implement (if not impossible) with respect to correctness and performance. If I were to work with rustc data types directly (cc #76382), it would be a piece of cake.

[fmease]

I really want to fix issues like this though, let me take another look.

[RalfJung]

Thanks!

Closing in favor of #113015 then.