Intra-doc links don't accept all macro delimiters

[LeSeulArtichaut]

Consider this code:

// This can be invoked with `foo!()`, `foo[]` or `foo{}`
#[macro_export] macro_rules! foo {
    () => {}
}

/// This is parsed as an intra-doc link: [foo!()]...
/// ...but those aren't: [foo![]] [foo!{}]
pub struct Foo;

I'm not sure if this is a deliberate decision or not. If it is, what's the rationale for not accepting [] and {}? cc @jyn514

[jyn514]

It isn't valid markdown syntax.

[jyn514]

Well, {} might be. But [] definitely is not.

[LeSeulArtichaut]

It isn't valid markdown syntax.

[foo![]](foo!) seems to work fine (it renders as foo![] and the link is correct). But maybe you're saying that we shouldn't accept [foo![]] because it wouldn't be valid markdown?

Well, {} might be.

Is it worth implementing?

[jyn514]

@LeSeulArtichaut hmm, it might be valid in that position, but it's not valid as a link reference:

See [foo![]].

[foo![]]: foo![]

But I guess there's no reason for rustdoc to explicitly reject it.

Is it worth implementing?

I would be ok with it, @Manishearth may have opinions.

[Manishearth]

I'm okay with it. I'm mostly wary about characters that are common in URLs, curly braces are not.

[LeSeulArtichaut]

Oh, the reason why [macro![]](macro!) works is because the rules for inline links are more relaxed:

Brackets are allowed in the link text only if (a) they are backslash-escaped or (b) they appear as a matched pair of brackets, with an open bracket [, a sequence of zero or more inlines, and a close bracket ].

vs

A link label begins with a left bracket ([) and ends with the first right bracket (]) that is not backslash-escaped. Unescaped square bracket characters are not allowed inside the opening and closing square brackets of link labels.

So instead do you think rustdoc should parse [macro!\[\]]?