wrong span for E0277

Code

pub fn f() {
    let _: Box<[str]>;
}

Current output

error[E0277]: the size for values of type `str` cannot be known at compilation time
 --> src/lib.rs:2:12
  |
2 |     let _: Box<[str]>;
  |            ^^^^^^^^^^ doesn't have a size known at compile-time
  |
  = help: the trait `Sized` is not implemented for `str`
  = note: slice and array elements must have `Sized` type

Desired output

error[E0277]: the size for values of type `str` cannot be known at compilation time
 --> src/lib.rs:2:12
  |
2 |     let _: Box<[str]>;
  |                 ^^^ doesn't have a size known at compile-time
  |
  = help: the trait `Sized` is not implemented for `str`
  = note: slice and array elements must have `Sized` type

Rationale and extra context

The type that "doesn't have a size known at compile time is "str". The size of a box is known (wither one or two pointers), it is therefore wrong to underline the Box part.

Other cases

Rust Version

1.89.0-nightly (2025-05-17 777d372772aa3b39ba72)

Anything else?

No response

Reproduce the diagnostic with the Rust snippet and the reported nightly version, comparing the current underline with the desired str span. Trace the compiler diagnostic span selection for E0277 and verify the result against the shown desired output; no source file or test is identified in the issue.