Combining generic_const_exprs with `adt_const_params` talks about derefs that don't exist in the code

[oli-obk]

Combining this with adt_const_params can give weird errors:

#![feature(generic_const_exprs, adt_const_params)]

struct FieldElement<const N: &'static str> {
    n: [u64; num_limbs(N)],
}
const fn num_limbs(_: &str) -> usize {
    0
}

Error:

error: overly complex generic constant
 --> src/lib.rs:5:14
  |
5 |     n: [u64; num_limbs(N)],
  |              ^^^^^^^^^^-^
  |                        |
  |                        dereferencing is not supported in generic constants
  |
  = help: consider moving this anonymous constant into a `const` function
  = note: this operation may be supported in the future

https://play.rust-lang.org/?gist=a6a2aecfba83485968a81b8599b86cc5

(I hoped I can try and play with these to see if it would be possible to implement typed algebraic fields)

Originally posted by @elichai in #76560 (comment)

[oli-obk]

We probably need to skip reborrows by treating them as no-ops