`cfg_accessible` is not processed before derive macros

[theemathas]

I tried this code:

#![feature(cfg_accessible)]

#[derive(Clone)]
#[cfg_accessible(std::nonexistent)]
struct Thing;

I expected the code to compile. Instead, I got the following error:

error[E0412]: cannot find type `Thing` in this scope
 --> src/lib.rs:3:10
  |
3 | #[derive(Clone)]
  |          ^^^^^ not found in this scope

error[E0425]: cannot find value `Thing` in this scope
 --> src/lib.rs:3:10
  |
3 | #[derive(Clone)]
  |          ^^^^^ not found in this scope

Some errors have detailed explanations: E0412, E0425.
For more information about an error, try `rustc --explain E0412`.

Note that similar code using cfg instead of cfg_accessible compiles fine:

#![feature(cfg_accessible)]

#[derive(Clone)]
#[cfg(false)]
struct Thing;

From my testing, it seems that #[cfg] is processed before derive macros see the input. However, it is not processed before attribute macros see the input. However, cfg_accessible is treated as an attribute macros, and is processed from top-to-bottom along with other normal derive macros and attribute macros.

Meta

Reproducible on the playground with version 1.93.0-nightly (2025-11-04 f15a7f38580ddbdc1a23)

[petrochenkov]

cfg_accessible is a regular procedural macro attribute, so it's expanded in left-to-right order.
cfg and cfg_attr are special exceptions, that are not expanded in LTR order, for historical reasons rather than by design, ideally the'd work in LTR order too.
So I think this works as expected.