Incorrect direction/place for "returning this value requires that `<variable>` is borrowed for `'static`" for E0597

Code

#[derive(Debug)]
pub struct Report(Vec<Box<dyn std::fmt::Debug>>);

fn main() -> Result<(), Report> {
    let string = "".to_string();
    let (_, b) = string
        .split(' ')
        .filter_map(|x| x.split_once(' '))
        .last()
        .unwrap();
    b.split_once(' ').ok_or_else(|| Report(vec![Box::new(b)]))?;
    Ok(())
}

Current output

error[E0597]: `string` does not live long enough
  --> test.rs:6:18
   |
5  |     let string = "".to_string();
   |         ------ binding `string` declared here
6  |     let (_, b) = string
   |                  ^^^^^^ borrowed value does not live long enough
7  |         .split(' ')
8  |         .filter_map(|x| x.split_once(' '))
   |                         ----------------- returning this value requires that `string` is borrowed for `'static`
...
13 | }
   | - `string` dropped here while still borrowed

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0597`.

Desired output

error[E0597]: `string` does not live long enough
  --> test.rs:6:18
   |
5  |     let string = "".to_string();
   |         ------ binding `string` declared here
6  |     let (_, b) = string
   |                  ^^^^^^ borrowed value does not live long enough
...
11 |     b.split_once(' ').ok_or_else(|| Report(vec![Box::new(b)]))?;
   |                                                          ^    - `string` dropped here while still borrowed
   |                                                          |
   |      returning this value requires that `string` is borrowed for `'static`

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0597`.

┌──────┐
│  OR  │
└──────┘

error[E0515]: cannot return value referencing local variable `string`
  --> test.rs:11:63
   |
6  |     let (_, b) = string
   |                  ------ `string` is borrowed here
...
11 |     b.split_once(' ').ok_or_else(|| Report(vec![Box::new(b)]))?;
   |                                                               ^ returns a value referencing data owned by the current function

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0515`.

Rationale and extra context

No response

Other cases

This error message look me quite a while to reproduce, so it seems to be pretty specific with the structure of `Option<Option<…>>`.

Changing `ok_or_else` to `ok_or` causes the same error.

Rust Version

rustc 1.77.0 (aedd173a2 2024-03-17)
binary: rustc
commit-hash: aedd173a2c086e558c2b66d3743b344f977621a7
commit-date: 2024-03-17
host: x86_64-unknown-linux-gnu
release: 1.77.0
LLVM version: 17.0.6

Anything else?

No response

Start by reproducing the supplied example with rustc 1.77.0 and compare the E0597 and E0515 diagnostics. Trace the compiler diagnostic code responsible for the borrow-checker span and message placement, then add a regression test for this nested Option case. Done means the diagnostic points to the returning expression as shown, or the alternative E0515 output is produced.