Rust analyzer reports errors not reported by rustc

[DanielT]

Rust analyzer version: 0.3.2913 (Linux)
rustc version: 1.95.0

I have a program that causes rust-analyzer to report errors where rustc does not.

I've reduced my program to a short repro example:

// lib.rs
pub fn testcase(xml_str: &str) {
    let mut reader = quick_xml::Reader::from_str(xml_str);
    match reader.read_event().unwrap() {
        quick_xml::events::Event::GeneralRef(bytes_ref) => {
            match bytes_ref.as_ref() {
                b"amp" => {}
                b"lt" => {}
                b"apos" => {}
                _ => {}
            };
        }
        _ => {}
    }
}

# Cargo.toml
[package]
name = "ra-bug-repro"
edition = "2024"

[dependencies]
quick-xml = "0.40.1"
zip = "8.6.0"

Rust analyzer reports:

Line 7: expected &[u8; 3], found &'static [u8; 2]
Line 8: expected &[u8; 3], found &'static [u8; 4]

I made a particularly interesting discovery while reducing my code to the testcase: If the dependency on zip is removed in Cargo.toml then rust-analyzer no longer reports any errors. Just including this dependency, even unused, changes the behavior.

[ChayimFriedman2]

Adding extern crate zip; at the top makes rustc also report an error. So the problem is some AsRef impl in zip, and that rustc doesn't link the crate if it's unused and there is no extern crate for it while we do.

This is a bit of an edge case and while I'm not sure yet why we link the crate, we might decide to not fix this if it turns out too hard.

[DanielT]

Thanks for the quick response.

In that case I'll constrain the trait inference by changing my code:

...
let text: &[u8] = bytes_ref.as_ref()
match text {
...

As far as I'm concerned the matter is solved. I don't know if you want to keep this issue open to track down the crate linking edge case so I haven't closed it.