rustdoc: use shorter paths as preferred canonical paths

This is a solution to the `std::sync::poison` linking problem,
and, in general, makes intra-doc links shorter and clearer.

Author: notriddle

src/librustdoc/formats/cache.rs

@@ -305,6 +305,7 @@ impl DocFolder for CacheBuilder<'_, '_> {
             | clean::MacroItem(..)
             | clean::ProcMacroItem(..)
             | clean::VariantItem(..) => {
+                use rustc_data_structures::fx::IndexEntry as Entry;
                 if !self.cache.stripped_mod {
                     // Re-exported items mean that the same id can show up twice
                     // in the rustdoc ast that we're looking at. We know,
@@ -313,15 +314,15 @@ impl DocFolder for CacheBuilder<'_, '_> {
                     // paths map if there was already an entry present and we're
                     // not a public item.
                     let item_def_id = item.item_id.expect_def_id();
-                    if !self.cache.paths.contains_key(&item_def_id)
-                        || self
-                            .cache
-                            .effective_visibilities
-                            .is_directly_public(self.tcx, item_def_id)
-                    {
-                        self.cache
-                            .paths
-                            .insert(item_def_id, (self.cache.stack.clone(), item.type_()));
+                    match self.cache.paths.entry(item_def_id) {
+                        Entry::Vacant(entry) => {
+                            entry.insert((self.cache.stack.clone(), item.type_()));
+                        }
+                        Entry::Occupied(mut entry) => {
+                            if entry.get().0.len() > self.cache.stack.len() {
+                                entry.insert((self.cache.stack.clone(), item.type_()));
+                            }
+                        }
                     }
                 }
             }

tests/rustdoc/inline_local/parent-path-is-better.rs

@@ -0,0 +1,40 @@
+//! Test case for [134702]
+//!
+//! [134702]: https://github.com/rust-lang/rust/issues/134702
+#![crate_name = "foo"]
+
+pub mod inside1 {
+    pub use self::inner::Inside1;
+    mod inner {
+        pub struct Inside1;
+        impl Inside1 {
+            pub fn stuff(self) {}
+        }
+    }
+}
+
+pub mod inside2 {
+    pub use self::inner::Inside2;
+    mod inner {
+        pub struct Inside2;
+        impl Inside2 {
+            pub fn stuff(self) {}
+        }
+    }
+}
+
+pub mod nested {
+    //! [Inside1] [Inside2]
+    //@ has foo/nested/index.html '//a[@href="../struct.Inside1.html"]' 'Inside1'
+    //@ has foo/nested/index.html '//a[@href="../struct.Inside2.html"]' 'Inside2'
+    //! [Inside1::stuff] [Inside2::stuff]
+    //@ has foo/nested/index.html '//a[@href="../struct.Inside1.html#method.stuff"]' 'Inside1::stuff'
+    //@ has foo/nested/index.html '//a[@href="../struct.Inside2.html#method.stuff"]' 'Inside2::stuff'
+    use crate::inside1::Inside1;
+    use crate::inside2::Inside2;
+}
+
+#[doc(inline)]
+pub use inside1::Inside1;
+#[doc(inline)]
+pub use inside2::Inside2;