Duplicate bounds behave differently depending on their order for const_trait_impl

[fee1-dead]

I tried this code:

const fn equals_self<T: PartialEq + ~const PartialEq>(t: &T) -> bool {
    *t == *t
}

I expected to see this happen: It should be the same as

const fn equals_self<T: ~const PartialEq + PartialEq>(t: &T) -> bool {
    *t == *t
}

Instead, this happened: It errors for the former but does not error for the second example.

@rustbot label F-const_trait_impl

See https://github.com/rust-lang/rust/pull/88328/files#r697229693

[fee1-dead]

Another example:

#![feature(const_fn_trait_bound)]
#![feature(const_trait_impl)]

trait A: PartialEq {}

const fn equals_self<T: A + ~const PartialEq>(t: &T) -> bool {
    *t == *t
}

play