Rustdoc doesn't warn if links to associated items are ambiguous if primitives are involved

[jyn514]

Rustdoc should give an error if the base res is ambiguous, but it doesn't:

$ cat primitive-ambiguous.rs 
//! [usize::MAX]

mod usize {
  const MAX: usize = 1;
}
$ rustdoc primitive-ambiguous.rs
$

This was originally discovered through the special case

//! [usize::MAX]

#[doc(primitive = "usize")]
mod usize {}

which I think should continue working, rustdoc shouldn't give an ambiguity error if the module has doc(primitive) on it.

Originally posted by @jyn514 in #83849 (comment)

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HEAD is 2616ab1

[jyn514]

Oof I just realized this is a lot harder than I expected. For the case where usize is a module, usize::MAX resolves normally with resolve_path, before the hacky string splitting for resolve_associated_item. So to support prim@usize::MAX I need to do the string splitting before resolve_path ever runs, and call resolve_primitive_associated_item instead.

@Manishearth btw do you want that prim@usize::MAX syntax to work? Or should it just not be possible to disambiguate the two? It does seem weird for the disambiguator to refer to the root res usize instead of MAX, that's inconsistent with how it works eveywhere else.

[Manishearth]

@Manishearth btw do you want that prim@usize::MAX syntax to work? Or should it just not be possible to disambiguate the two? It does seem weird for the disambiguator to refer to the root res usize instead of MAX, that's inconsistent with how it works eveywhere else.

Hmm, this sounds like a pretty big complication; unsure if we should.

We can just special case the primitives and do both lookups.

[jyn514]

We can just special case the primitives and do both lookups.

Sorry, I don't follow - what should happen if it's ambiguous (both resolve)?

[jyn514]

I would also be ok with saying "don't name modules after primitives" and closing this as WONTFIX, that seems confusing anyway.

[Manishearth]

I mean, don't name modules after primitives such that the names clash. Fine with wontfixing