Cycle detected when deriving PartialEq, Eq for type with non-primitive const param.

[CDirkx]

The following code used to compile on nightly:

#![feature(const_generics)]

#[derive(PartialEq, Eq)]
struct Inner;

#[derive(PartialEq, Eq)]
struct Outer<const I: Inner>;

but now results in

error[E0391]: cycle detected when computing type of `Outer::I`
   --> src\lib.rs:7:20
    |
7   | struct Outer<const I: Inner>;
    |                    ^
    |
    = note: ...which requires computing whether `Inner` implements `PartialStructuralEq` and `StructuralEq`...
    = note: ...which requires evaluating trait selection obligation `Inner: std::marker::StructuralPartialEq`...
note: ...which requires trait impls of `std::marker::StructuralPartialEq`...
   --> .../src/rust\library\core\src\marker.rs:152:1
    |
152 | pub trait StructuralPartialEq {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires computing type of `<impl at src\lib.rs:6:10: 6:19>`...
   --> src\lib.rs:6:10
    |
6   | #[derive(PartialEq, Eq)]
    |          ^^^^^^^^^
    = note: ...which again requires computing type of `Outer::I`, completing the cycle
note: cycle used when computing type of `<impl at src\lib.rs:6:21: 6:23>`
   --> src\lib.rs:6:21
    |
6   | #[derive(PartialEq, Eq)]
    |                     ^^
    = note: this error originates in a derive macro (in Nightly builds, run with -Z macro-backtrace for more info)

The same is true for any non-primitive const param, i.e.:

#[derive(PartialEq, Eq)]
struct Outer<const I: Option<usize>>;