Error message flips expected and actual types in E0271 note

[zzucch]

Code

use std::rc::Rc;

struct SomeOtherStruct<T> {
    data: Rc<T>,
}

struct SomeStruct<T> {
    data: Option<Rc<SomeOtherStruct<T>>>,
}

impl<T> SomeStruct<T> {
    pub fn iter(&self) -> impl Iterator<Item = Rc<T>> {
        SomeIterator {
            current: self.data.clone(),
        }
    }
}

struct SomeIterator<T> {
    current: Option<Rc<SomeOtherStruct<T>>>,
}

impl<T> Iterator for SomeIterator<T> {
    type Item = Rc<SomeOtherStruct<T>>;

    fn next(&mut self) -> Option<Self::Item> {
        unimplemented!()
    }
}

Current output

error[E0271]: expected `SomeIterator<T>` to be an iterator that yields `Rc<T>`, but it yields `Rc<SomeOtherStruct<T>>`
  --> src/lib.rs:12:27
   |
11 |   impl<T> SomeStruct<T> {
   |        - found this type parameter
12 |       pub fn iter(&self) -> impl Iterator<Item = Rc<T>> {
   |                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^ type mismatch resolving `<SomeIterator<T> as Iterator>::Item == Rc<T>`
13 | /         SomeIterator {
14 | |             current: self.data.clone(),
15 | |         }
   | |_________- return type was inferred to be `SomeIterator<T>` here
   |
note: expected this to be `Rc<SomeOtherStruct<T>>`
  --> src/lib.rs:24:17
   |
24 |     type Item = Rc<SomeOtherStruct<T>>;
   |                 ^^^^^^^^^^^^^^^^^^^^^^
   = note: expected struct `Rc<SomeOtherStruct<T>>`
              found struct `Rc<T>`

Desired output

error[E0271]: expected `SomeIterator<T>` to be an iterator that yields `Rc<T>`, but it yields `Rc<SomeOtherStruct<T>>`
  --> src/lib.rs:12:27
   |
11 |   impl<T> SomeStruct<T> {
   |        - found this type parameter
12 |       pub fn iter(&self) -> impl Iterator<Item = Rc<T>> {
   |                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^ type mismatch resolving `<SomeIterator<T> as Iterator>::Item == Rc<T>`
13 | /         SomeIterator {
14 | |             current: self.data.clone(),
15 | |         }
   | |_________- return type was inferred to be `SomeIterator<T>` here
   |
note: expected this to be `Rc<T>`
  --> src/lib.rs:24:17
   |
24 |     type Item = Rc<SomeOtherStruct<T>>;
   |                 ^^^^^^^^^^^^^^^^^^^^^^
   = note: expected struct `Rc<T>`
              found struct `Rc<SomeOtherStruct<T>>`

Rationale and extra context

The note section in error message for E0271 mixes up the expected and actual types. In the example, the error message incorrectly states that the iterator is expected to yield Rc<SomeOtherStruct> but actually yields Rc. It should state that the iterator is expected to yield Rc but actually yields Rc<SomeOtherStruct>.

The LSP highlighting for the error makes understanding the actual problem quite confusing

Other cases

No response

Rust Version

$ rustc --version --verbose
rustc 1.81.0 (eeb90cda1 2024-09-04) (built from a source tarball)
binary: rustc
commit-hash: eeb90cda1969383f56a2637cbd3037bdf598841c
commit-date: 2024-09-04
host: x86_64-unknown-linux-gnu
release: 1.81.0
LLVM version: 18.1.8

Anything else?

No response