Const generics causes monomorphization to compare constants by identity instead of structurally. This means that two different references to equal data will compare as unequal.

The root problem is in

I tried this code:

#![feature(const_generics)]

pub fn function_with_bytes<const BYTES: &'static [u8; 4]>() -> &'static [u8] {
    BYTES
}

pub fn main() {
    assert_eq!(function_with_bytes::<b"AAAA">(), &[0x41, 0x41, 0x41, 0x41]);
    assert_eq!(function_with_bytes::<{&[0x41, 0x41, 0x41, 0x41]}>(), b"AAAA");
}

I expected to see this happen: successful compilation just as if the type were &'static [u8]

Instead, this happened:

error: symbol `_ZN10playground19function_with_bytes17h85b0fd4613beba85E` is already defined
 --> src/main.rs:3:1
  |
3 | / pub fn function_with_bytes<const BYTES: &'static [u8; 4]>() -> &'static [u8] {
4 | |     BYTES
5 | | }
  | |_^

cc @varkor

cc @rust-lang/wg-const-eval It's a footgun that ConstKind and especially ConstValue can be compared for equality. Technically a ConstKind::Unevaluated is value/structurally equal to any other ConstKind. We may need that Eq impl for query return value hashing though, not sure.