New lint: `manual_open_range_patterns`

What it does

Suggest using open range patterns instead of inclusive range patterns for integer types with upper bound equal to the maximum of that type.

Categories

• Kind: Style

Advantages

The suggested code is shorter and more readable. The shorter syntax doesn't require the MAX constant and so the variables type doesn't need to be repeated.

Drawbacks

None.

Explicitly including the upper bound gives no additional information. It just repeats the type and confirms that it has an upper bound. I expect this lint to be uncontroversial.

Example

match x as u32 {
      0 => println!("zero!"),
      1..=u32::MAX => println!("positive number!"),
}

Could be written as:

match x as u32 {
      0 => println!("zero!"),
      1.. => println!("positive number!"),
}

Configuration

MSRV 1.55

The issue names the proposed manual_open_range_patterns lint but provides no file, test, or entry point. Start by locating existing Clippy lint implementations for range patterns, then use the Rust examples and MSRV 1.55 as the behavioral baseline; done means the lint suggests open ranges for the described integer bounds and has coverage for that behavior.