Lint for trailing comma in macro parameters

[KershawChang]

What it does

This proposed lint would detect and warn about unnecessary trailing commas in macro parameters. While a trailing comma in macro parameters is not an error in Rust, it can be superfluous and might not align with some coding style preferences.

Advantage

• Improved Readability: Removing unnecessary trailing commas can make the code clearer and easier to read.
• Consistency: Enforcing this style can help maintain a consistent coding standard across the codebase.

Drawbacks

No response

Example

println!("Hello, world!", );

Could be written as:

println!("Hello, world!");

[Alexendoo]

Related: rust-lang/rustfmt#3065

[pacak]

Not every macro behaves the same way with respect to trailing commas FWIW. Macros bundled with rustc tend to accept them, but treats them as optional. Macros created by user might require it to function.