rustdoc: remove macro redirects

[nrc]

PR #35234 changed macro URLs to remove the !. It left redirects in so as not to break existing URLs. At some point, we should remove these redirects so as not to accumulate too much cruft. Obviously this will require some message before we do so.

See FIXME in render.rs

[ollie27]

Personally I don't see much reason to ever remove the redirects. For example I would expect https://doc.rust-lang.org/std/macro.assert!.html to continue to work basically forever,

[Mark-Simulacrum]

Nominating for discussion. It's been almost two years; I think we should consider this issue again.

[QuietMisdreavus]

@rust-lang/rustdoc, what do you think?

I personally don't see the harm in keeping it. Do we have crates with many more macros than the standard library, where having these redirect pages is a problem? I'm with @ollie27, keeping the link alive is more important to me than removing these small files from the output.

[GuillaumeGomez]

I don't know why it'd cause issues so ok for me.

[QuietMisdreavus]

Based on the rousing discussion here, I think the consensus can be described as "it's okay to keep them around". Before i close this issue, though, we should remove the FIXME that it refers to:

rust/src/librustdoc/html/render.rs

Lines 1969 to 1978 in 12ed235

	// If the item is a macro, redirect from the old macro URL (with !)
	// to the new one (without).
	// FIXME(#35705) remove this redirect.
	if item_type == ItemType::Macro {
	let redir_name = format!("{}.{}!.html", item_type, name);
	let redir_dst = self.dst.join(redir_name);
	let redirect_out = try_err!(File::create(&redir_dst), &redir_dst);
	let mut redirect_out = BufWriter::new(redirect_out);
	try_err!(layout::redirect(&mut redirect_out, file_name), &redir_dst);
	}

Just to keep things neat.

[QuietMisdreavus]

A PR to remove that comment is live at #52510.