Auto merge of rust-lang#95337 - petrochenkov:doclink3, r=camelid

rustdoc: Fix resolution of `crate`-relative paths in doc links

Resolve `crate::foo` paths transparently to rustdoc, so their resolution no longer affects diagnostics and modules used for determining traits in scope.

The proper solution is to account for the current `module_id`/`parent_scope` in `fn resolve_crate_root`, but it's a slightly larger compiler changes. This PR moves the code closer to it, but keeps it rustdoc-specific.

Fixes rust-lang#78696
Fixes rust-lang#94924

Author: bors

compiler/rustc_resolve/src/lib.rs

@@ -3270,12 +3270,21 @@ impl<'a> Resolver<'a> {
         &mut self,
         path_str: &str,
         ns: Namespace,
-        module_id: DefId,
+        mut module_id: DefId,
     ) -> Option<Res> {
         let mut segments =
             Vec::from_iter(path_str.split("::").map(Ident::from_str).map(Segment::from_ident));
-        if path_str.starts_with("::") {
-            segments[0].ident.name = kw::PathRoot;
+        if let Some(segment) = segments.first_mut() {
+            if segment.ident.name == kw::Crate {
+                // FIXME: `resolve_path` always resolves `crate` to the current crate root, but
+                // rustdoc wants it to resolve to the `module_id`'s crate root. This trick of
+                // replacing `crate` with `self` and changing the current module should achieve
+                // the same effect.
+                segment.ident.name = kw::SelfLower;
+                module_id = module_id.krate.as_def_id();
+            } else if segment.ident.name == kw::Empty {
+                segment.ident.name = kw::PathRoot;
+            }
         }
 
         let module = self.expect_module(module_id);

src/librustdoc/passes/collect_intra_doc_links.rs

@@ -9,7 +9,7 @@ use rustc_hir::def::{
     Namespace::{self, *},
     PerNS,
 };
-use rustc_hir::def_id::{CrateNum, DefId, CRATE_DEF_ID};
+use rustc_hir::def_id::{DefId, CRATE_DEF_ID};
 use rustc_hir::Mutability;
 use rustc_middle::ty::{DefIdTree, Ty, TyCtxt};
 use rustc_middle::{bug, span_bug, ty};
@@ -1043,16 +1043,11 @@ impl<'a, 'tcx> DocVisitor for LinkCollector<'a, 'tcx> {
         // so we know which module it came from.
         for (parent_module, doc) in item.attrs.collapsed_doc_value_by_module_level() {
             debug!("combined_docs={}", doc);
-
-            let (krate, parent_node) = if let Some(id) = parent_module {
-                (id.krate, Some(id))
-            } else {
-                (item.def_id.krate(), parent_node)
-            };
             // NOTE: if there are links that start in one crate and end in another, this will not resolve them.
             // This is a degenerate case and it's not supported by rustdoc.
+            let parent_node = parent_module.or(parent_node);
             for md_link in markdown_links(&doc) {
-                let link = self.resolve_link(&item, &doc, parent_node, krate, md_link);
+                let link = self.resolve_link(&item, &doc, parent_node, md_link);
                 if let Some(link) = link {
                     self.cx.cache.intra_doc_links.entry(item.def_id).or_default().push(link);
                 }
@@ -1187,7 +1182,6 @@ impl LinkCollector<'_, '_> {
         item: &Item,
         dox: &str,
         parent_node: Option<DefId>,
-        krate: CrateNum,
         ori_link: MarkdownLink,
     ) -> Option<ItemLink> {
         trace!("considering link '{}'", ori_link.link);
@@ -1199,7 +1193,7 @@ impl LinkCollector<'_, '_> {
             link_range: ori_link.range.clone(),
         };
 
-        let PreprocessingInfo { path_str, disambiguator, extra_fragment, link_text } =
+        let PreprocessingInfo { ref path_str, disambiguator, extra_fragment, link_text } =
             match preprocess_link(&ori_link)? {
                 Ok(x) => x,
                 Err(err) => {
@@ -1221,7 +1215,6 @@ impl LinkCollector<'_, '_> {
                     return None;
                 }
             };
-        let mut path_str = &*path_str;
 
         let inner_docs = item.inner_docs(self.cx.tcx);
 
@@ -1239,7 +1232,7 @@ impl LinkCollector<'_, '_> {
         let base_node =
             if item.is_mod() && inner_docs { self.mod_ids.last().copied() } else { parent_node };
 
-        let Some(mut module_id) = base_node else {
+        let Some(module_id) = base_node else {
             // This is a bug.
             debug!("attempting to resolve item without parent module: {}", path_str);
             resolution_failure(
@@ -1252,26 +1245,6 @@ impl LinkCollector<'_, '_> {
             return None;
         };
 
-        let resolved_self;
-        let is_lone_crate = path_str == "crate";
-        if path_str.starts_with("crate::") || is_lone_crate {
-            use rustc_span::def_id::CRATE_DEF_INDEX;
-
-            // HACK(jynelson): rustc_resolve thinks that `crate` is the crate currently being documented.
-            // But rustdoc wants it to mean the crate this item was originally present in.
-            // To work around this, remove it and resolve relative to the crate root instead.
-            // HACK(jynelson)(2): If we just strip `crate::` then suddenly primitives become ambiguous
-            // (consider `crate::char`). Instead, change it to `self::`. This works because 'self' is now the crate root.
-            // FIXME(#78696): This doesn't always work.
-            if is_lone_crate {
-                path_str = "self";
-            } else {
-                resolved_self = format!("self::{}", &path_str["crate::".len()..]);
-                path_str = &resolved_self;
-            }
-            module_id = DefId { krate, index: CRATE_DEF_INDEX };
-        }
-
         let (mut res, fragment) = self.resolve_with_disambiguator_cached(
             ResolutionInfo {
                 item_id: item.def_id,

src/librustdoc/passes/collect_intra_doc_links/early.rs

@@ -32,11 +32,6 @@ crate fn early_resolve_intra_doc_links(
         all_trait_impls: Default::default(),
     };
 
-    // Because of the `crate::` prefix, any doc comment can reference
-    // the crate root's set of in-scope traits. This line makes sure
-    // it's available.
-    loader.add_traits_in_scope(CRATE_DEF_ID.to_def_id());
-
     // Overridden `visit_item` below doesn't apply to the crate root,
     // so we have to visit its attributes and reexports separately.
     loader.load_links_in_attrs(&krate.attrs);
@@ -105,9 +100,6 @@ impl IntraLinkCrateLoader<'_, '_> {
     /// having impls in them.
     fn add_foreign_traits_in_scope(&mut self) {
         for cnum in Vec::from_iter(self.resolver.cstore().crates_untracked()) {
-            // FIXME: Due to #78696 rustdoc can query traits in scope for any crate root.
-            self.add_traits_in_scope(cnum.as_def_id());
-
             let all_traits = Vec::from_iter(self.resolver.cstore().traits_in_crate_untracked(cnum));
             let all_trait_impls =
                 Vec::from_iter(self.resolver.cstore().trait_impls_in_crate_untracked(cnum));

src/test/rustdoc-ui/intra-doc/crate-nonexistent.rs

@@ -0,0 +1,5 @@
+#![deny(rustdoc::broken_intra_doc_links)]
+
+/// [crate::DoesNotExist]
+//~^ ERROR unresolved link to `crate::DoesNotExist`
+pub struct Item;

src/test/rustdoc-ui/intra-doc/crate-nonexistent.stderr

@@ -0,0 +1,14 @@
+error: unresolved link to `crate::DoesNotExist`
+  --> $DIR/crate-nonexistent.rs:3:6
+   |
+LL | /// [crate::DoesNotExist]
+   |      ^^^^^^^^^^^^^^^^^^^ no item named `DoesNotExist` in module `crate_nonexistent`
+   |
+note: the lint level is defined here
+  --> $DIR/crate-nonexistent.rs:1:9
+   |
+LL | #![deny(rustdoc::broken_intra_doc_links)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+

src/test/rustdoc/intra-doc/crate-relative-assoc.rs

@@ -0,0 +1,17 @@
+pub mod io {
+    pub trait Read {
+        fn read(&mut self);
+    }
+}
+
+pub mod bufreader {
+    // @has crate_relative_assoc/bufreader/index.html '//a/@href' 'struct.TcpStream.html#method.read'
+    //! [`crate::TcpStream::read`]
+    use crate::io::Read;
+}
+
+pub struct TcpStream;
+
+impl crate::io::Read for TcpStream {
+    fn read(&mut self) {}
+}