Empty match arms

[pickfire]

=> () should be => {} rust-lang/style-team#146

[pickfire]

I took my time trying to write this but I looked at the wrong line instead (is_empty_block). T_T

[laysauchoa]

@pickfire are you working on this? I would like to contribute. What should be done mainly here?

[pickfire]

@laysauchoa No, I tried checking this but I didn't spend much time on this issue. My guess is somewhere around https://github.com/rust-lang/rustfmt/blob/master/rustfmt-core/rustfmt-lib/src/matches.rs#L219 but I don't quite grasp the workflow of rustfmt yet, I don't quite know how to debug stuff here.

[ayazhafiz]

@laysauchoa take a look at matches#rewrite_match_body. It should be enough to check if the arm body is an empty block, which is resolved here:

rustfmt/rustfmt-core/rustfmt-lib/src/matches.rs

Lines 360 to 362 in 99edc88

	);
	let (is_block, is_empty_block) = if let ast::ExprKind::Block(ref block, _) = body.kind {
	(true, is_empty_block(context, block, Some(&body.attrs)))

And if so, rewrite the original arm body with (), maybe in the combine_orig_body closure which is one method responsible for formatting the rewritten arm body:

rustfmt/rustfmt-core/rustfmt-lib/src/matches.rs

Lines 370 to 377 in 99edc88

	let combine_orig_body = |body_str: &str| {
	let block_sep = match context.config.control_brace_style() {
	ControlBraceStyle::AlwaysNextLine if is_block => alt_block_sep,
	_ => " ",
	};
	Some(format!("{} =>{}{}{}", pats_str, block_sep, body_str, comma))
	};

Or something like that..