New lint suggestion: Lint against `Some(self)` in `Error::source`

What it does

This lint prevents the incorrect usage of returning Some(self) in Error::source.

Advantage

• Avoid an infinite loop for consumers of Error::source that wants to visit all the error sources.

Drawbacks

No response

Example

impl Error for MyError {
    fn source(&self) -> Option<&(dyn Error + 'static)> {
        Some(self)
    }
}

Could be written correctly as:

impl Error for MyError {}

No implementation files or tests are named in the issue. Start by locating Clippy's existing lint implementations and tests for Rust error handling, then compare their structure with the Error::source example. Done means the incorrect Some(self) pattern is diagnosed by a lint and covered by tests without affecting valid implementations.