/* comment */ inside trait generics gets duplicated

[xhalo32]

trait Test</* comment */ T> {}

Gets reformatted as

trait Test</* comment */ T> /* comment */ T> {}

Whereas no changes were expected.

Playground:
https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=88c36ba8a83e2c01030bbbf95327be6a

Setting version = Two has no effect.

λ rustfmt --version
rustfmt 1.4.38-stable (7737e0b 2022-04-04)

[calebcartwright]

Thank you for the report! This feels like a bug with duplicative/overlapping comment recovery that's probably using the wrong span. The bug doesn't occur if there's a where clause present, so I suspect the problem is somewhere around here:

rustfmt/src/items.rs

Lines 1084 to 1104 in 79515f1

	} else {
	let item_snippet = context.snippet(item.span);
	if let Some(lo) = item_snippet.find('/') {
	// 1 = `{`
	let comment_hi = body_lo - BytePos(1);
	let comment_lo = item.span.lo() + BytePos(lo as u32);
	if comment_lo < comment_hi {
	match recover_missing_comment_in_span(
	mk_sp(comment_lo, comment_hi),
	Shape::indented(offset, context.config),
	context,
	last_line_width(&result),
	) {
	Some(ref missing_comment) if !missing_comment.is_empty() => {
	result.push_str(missing_comment);
	}
	_ => (),
	}
	}
	}
	}

For anyone interested in taking a look, we should probably reduce the area that's being scanned for comments there to something less than the entire span of the item (most likely simply from the end of the where clause's span to the start of the body span)