E0499 message under-specifying regarding the nature of borrow conflict

Code

struct S {
    a: Vec<i32>,
    b: i32,
}

impl S {
    fn g(&mut self, x: &i32) -> i32 {
        self.b += 1;
        *x + self.b
    }

    fn f(&mut self) -> i32 {
        let x: &i32 = self.a.get_mut(0).unwrap();
        self.g(x)
    }
}

fn main() {}

Current output

error[E0499]: cannot borrow `*self` as mutable more than once at a time
  --> src/compiler_error_message_issue2.rs:14:9
   |
13 |         let x: &i32 = self.a.get_mut(0).unwrap();
   |                       ------ first mutable borrow occurs here
14 |         self.g(x)
   |         ^^^^   - first borrow later used here
   |         |
   |         second mutable borrow occurs here

Desired output

error[E0499]: cannot borrow `*self` as mutable when a part of it is already borrowed as mutable.
  --> src/compiler_error_message_issue2.rs:14:9
   |
13 |         let x: &i32 = self.a.get_mut(0).unwrap();
   |                       ------ mutable partial borrow of `self` first occurs here
14 |         self.g(x)
   |         ^^^^   - first borrow later used here
   |         |
   |         mutable borrow of `self` occurs here

Rationale and extra context

No response

Other cases

Rust Version

rustc --version --verbose
rustc 1.94.0 (4a4ef493e 2026-03-02)
binary: rustc
commit-hash: 4a4ef493e3a1488c6e321570238084b38948f6db
commit-date: 2026-03-02
host: x86_64-unknown-linux-gnu
release: 1.94.0

Anything else?

https://github.com/rust-lang/rust/issues/154275