needless nested match

[owenthewizard]

What it does

Warn on a nested match that can be merged.

Advantage

• Clarity
• Concise

Drawbacks

• Could be less readable in non-trivial cases (not Option/Result).

Example

match token {
    Ok(token) => match token {
        Token::A | Token::B => { ... }
    }
    Err(err) => {}
}

Could be written as:

match token {
    Ok(Token::A | Token::B) => { ... }
    Err(err) => {}
}

[y21]

This sounds like what the collapsible_match lint looks for. That lint should probably be extended to catch this