Incorrect explanation for upvar move in FnMut closure

[digama0]

Given the following code (playground):

fn use_mut(_: impl FnMut()) {}
fn main() {
    let mut upvar = Some(String::new());
    use_mut(move || {
        || {
            || {
                upvar.take();
                if let Some(_s) = upvar {}
            };
        };
    });
}

The current output is:

error[E0507]: cannot move out of `upvar`, a captured variable in an `FnMut` closure
  --> src/main.rs:5:9
   |
3  |       let mut upvar = Some(String::new());
   |           --------- captured outer variable
4  |       use_mut(move || {
   |  _____________-
5  | |         || {
   | |         ^^ move out of `upvar` occurs here
6  | |             || {
7  | |                 upvar.take();
   | |                 -----
   | |                 |
   | |                 variable moved due to use in closure
   | |                 move occurs because `upvar` has type `Option<String>`, which does not implement the `Copy` trait
...  |
10 | |         };
11 | |     });
   | |_____- captured by this `FnMut` closure

The error is correct, but the diagnostic points to upvar.take() as the reason why the value is moved, while the real culprit is the match expression if let Some(_s) = upvar {}, which is not indicated.

Occurs in 1.63.0 stable and 1.65.0-nightly (2022-08-16 86c6ebee8fa0a5ad1e18).