`cfg_eval` breaks type signature & completions

Using cfg_eval causes the type it's applied to to essentially not exist anymore in user-facing operations.
Neither type signature nor completions or any other LSP methods work for these types.

I've found this issue with both the core & cfg_eval crate implementations.

Adding cfg_eval to procMacro.ignored solves this issue, but can cause rust-analyzer to report errors that don't appear when compiling.

I'm guessing this is not strictly an issue with cfg_eval itself but a general issue with how proc macros are evaluated.
But since I haven't found a related issue so far & to help other people encountering issues with cfg_eval I've decided to create a new issue.

Here is a short example to reproduce the issue:

use serde::{Deserialize, Serialize};
use serde_with::{serde_as, DurationMilliSeconds};
use time::Duration;

#[cfg_eval]
#[serde_as]
#[derive(Serialize, Deserialize)]
pub struct Exercise {
    pub id: String,
    #[cfg_attr(feature = "serde", serde_as(as = "Option<DurationMilliSeconds<i64>>"))]
    pub duration: Option<Duration>,
}

fn test() {
    let exercise = Exercise {
        id: "an-id".to_string(),
        duration: Some(Duration::new(10, 0)),
    };
    let duration = exercise.duration;
}

rust-analyzer version: 1.72.0 (5680fa1 2023-08-23)

rustc version: 1.72.0 (5680fa18f 2023-08-23)

Reproduce the issue using the provided Rust example with cfg_eval, serde_as, and the Exercise type, then trace how proc macros are evaluated for user-facing operations. Verify whether type signatures and completions work without adding cfg_eval to procMacro.ignored, while ensuring the result does not introduce false errors compared with compilation.