fix intra-doc links on nested use and extern crate items

[lukas-code]

This PR fixes two rustdoc ICEs that happen if there are any intra-doc links on nested use or extern crate items, for example:

/// Re-export [`fmt`] and [`io`].
pub use std::{fmt, io}; // "nested" use = use with braces

/// Re-export [`std`].
pub extern crate std;

Nested use items were incorrectly considered private and therefore didn't have their intra-doc links resolved. I fixed this by always resolving intra-doc links for nested use items that are declared pub.

During AST->HIR lowering, nested use items are desugared like this:

pub use std::{}; // "list stem"
pub use std::fmt;
pub use std::io;

Each of these HIR nodes has it's own effective visibility and the list stem is always considered private.
To check the effective visibility of an AST node, the AST node is mapped to a HIR node with Resolver::local_def_id, which returns the (private) list stem for nested use items.

For extern crate, there was a hack in rustdoc that stored the DefId of the crate itself in the cleaned item, instead of the DefId of the extern crate item. This made rustdoc look at the resolved links of the extern crate's crate root instead of the extern crate item. I've removed this hack and instead translate the DefId in the appropriate places.

As as side effect of fixing extern crate, i've turned

#[doc(masked)]
extern crate self as _;

into a no-op instead of hiding all trait impls. Proper verification for doc(masked) is included as a bonus.

fixes #113896

[rustbot]

r? @davidtwco

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[GuillaumeGomez]

Looks good to me, thanks!

Might be worth to have @petrochenkov take a look as well.

[petrochenkov]

r=me after fixing the articles.
@rustbot author

[petrochenkov]

@bors r=GuillaumeGomez,petrochenkov

[bors]

📌 Commit 637ea3f has been approved by GuillaumeGomez,petrochenkov

It is now in the queue for this repository.

[bors]

⌛ Testing commit 637ea3f with merge beef07f...

[bors]

☀️ Test successful - checks-actions
Approved by: GuillaumeGomez,petrochenkov
Pushing beef07f to master...

[rust-timer]

Finished benchmarking commit (beef07f): comparison URL.

Overall result: ❌✅ regressions and improvements - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	1.0%	[1.0%, 1.0%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.3%	[-0.3%, -0.2%]	2
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.4%	[-2.4%, -2.4%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.4%	[-2.4%, -2.4%]	1

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 652.747s -> 650.991s (-0.27%)