[Rust] Unused variable false positive in compound conditional statements

[tarolling]

Description of the false positive

When there is an if-let statement, and multiple conditions exist in the conditional check (either AND or OR as operators), CodeQL flags the original variable as unused if it is used in subsequent conditional statements.

Code samples or links to source code

There are many dismissed false positives linked to this merged PR: tarolling/seiri#57

A small example would be:

for result in builder.build() {
        match result {
            Ok(entry) => {
                if let Some(file_type) = entry.file_type()
                    && file_type.is_file()
                {
                    paths.push(entry.path().to_path_buf());
                }
            }
            Err(msg) => eprintln!("Error reading entry: {msg}"),
        }
    }

Here, file_type was flagged as a false positive, even though it is used in the following boolean statement file_type.is_file().

[hvitved]

Thanks for reporting this issue. I'll take a look.

[redsun82]

@tarolling Thanks for reporting this to us! if let ... && ... constructs was introduced in June with rust 1.88 (tracking issue) and we didn't yet manage to catch up with supporting it, but we will.

[hvitved]

Fix: #20203.