clippy::option-if-let-else generates invalid Rust code when the if-let-else block allows for better type coercion

Summary

The lint is triggered, but the provided code doesn't compile. I'm not particularly familiar with compilers, so this may actually be a shortcoming of the rust compiler in the case of Option::map_or_else, but I figured it was better to start here.

Lint Name

clippy::option-if-let-else

Reproducer

I tried this code:

use std::io::Error;
use std::pin::Pin;

use futures::Stream;

fn main() {
    let result = Ok::<_, Error>(tokio_stream::once(Ok(())));

    let stream: Pin<Box<dyn Stream<Item = Result<(), Error>>>> = if let Ok(stream) = result {
        Box::pin(stream)
    } else {
        Box::pin(tokio_stream::pending())
    };
}

I saw this happen:
This code compiles, as expected, but clippy provides the following alternative:

I tried this code:

use std::io::Error;
use std::pin::Pin;

use futures::Stream;

fn main() {
    let result = Ok::<_, Error>(tokio_stream::once(Ok(())));

    let stream: Pin<Box<dyn Stream<Item = Result<(), Error>>>> = result.map_or_else(
        |_| Box::pin(tokio_stream::pending::<Result<(), Error>>()),
        |stream| Box::pin(stream),
    );
}

I saw this happen:

error[E0308]: mismatched types
   --> src/main.rs:11:27
    |
11  |         |stream| Box::pin(stream),
    |                  -------- ^^^^^^ expected `Pending<Result<(), Error>>`, found `Once<Result<(), _>>`
    |                  |
    |                  arguments to this function are incorrect
    |
    = note: expected struct `tokio_stream::Pending<Result<(), std::io::Error>>`
               found struct `tokio_stream::Once<Result<(), _>>`
note: associated function defined here
   --> /home/jeremy/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/alloc/src/boxed.rs:326:12
    |
326 |     pub fn pin(x: T) -> Pin<Box<T>> {
    |            ^^^

For more information about this error, try `rustc --explain E0308`.
error: could not compile `temp` (bin "temp") due to 1 previous error

I expected to see this happen:
MaybeIncorrect clippy lints should generate valid Rust code.

Version

rustc 1.81.0-nightly (cc8da78a0 2024-07-04)
binary: rustc
commit-hash: cc8da78a036dc3c15c35a97651b02af9a6d30c1e
commit-date: 2024-07-04
host: x86_64-unknown-linux-gnu
release: 1.81.0-nightly
LLVM version: 18.1.7

Additional Labels

@rustbot label +I-suggestion-causes-error

Start by reproducing the supplied Rust example with clippy::option-if-let-else and inspect the lint implementation that generates the map_or_else suggestion. Compare the suggested code with the original coercion behavior; done means the lint no longer emits code that fails to compile, with a regression test covering this case.