Auto merge of #79349 - Nemo157:issue-79201, r=jyn514

Apply `doc(cfg)` from parent items while collecting trait impls

Because trait impls bypass the standard `clean` hierarchy they do not participate in the `propagate_doc_cfg` pass, so instead we need to pre-collect all possible `doc(cfg)` attributes that will apply to them when cleaning.

fixes #79201

2 files changed, 43 insertions, 1 deletions

diff --git a/src/test/rustdoc/doc-cfg.rs b/src/test/rustdoc/doc-cfg.rs
index f86541cd118..51a58378299 100644
--- a/src/test/rustdoc/doc-cfg.rs
+++ b/src/test/rustdoc/doc-cfg.rs
@@ -25,12 +25,13 @@ pub mod unix_only {
     // @has doc_cfg/unix_only/trait.ArmOnly.html \
     //  '//*[@id="main"]/*[@class="item-info"]/*[@class="stab portability"]' \
     //  'This is supported on Unix and ARM only.'
-    // @count - '//*[@class="stab portability"]' 2
+    // @count - '//*[@class="stab portability"]' 1
     #[doc(cfg(target_arch = "arm"))]
     pub trait ArmOnly {
         fn unix_and_arm_only_function();
     }
 
+    #[doc(cfg(target_arch = "arm"))]
     impl ArmOnly for super::Portable {
         fn unix_and_arm_only_function() {}
     }
diff --git a/src/test/rustdoc/issue-79201.rs b/src/test/rustdoc/issue-79201.rs
new file mode 100644
index 00000000000..f95d79cd493
--- /dev/null
+++ b/src/test/rustdoc/issue-79201.rs
@@ -0,0 +1,41 @@
+#![feature(doc_cfg)]
+
+// @has 'issue_79201/trait.Foo.html'
+// @count   - '//*[@class="stab portability"]' 6
+// @matches - '//*[@class="stab portability"]' 'crate feature foo-root'
+// @matches - '//*[@class="stab portability"]' 'crate feature foo-public-mod'
+// @matches - '//*[@class="stab portability"]' 'crate feature foo-private-mod'
+// @matches - '//*[@class="stab portability"]' 'crate feature foo-fn'
+// @matches - '//*[@class="stab portability"]' 'crate feature foo-method'
+
+pub trait Foo {}
+
+#[doc(cfg(feature = "foo-root"))]
+impl crate::Foo for usize {}
+
+#[doc(cfg(feature = "foo-public-mod"))]
+pub mod public {
+    impl crate::Foo for u8 {}
+}
+
+#[doc(cfg(feature = "foo-private-mod"))]
+mod private {
+    impl crate::Foo for u16 {}
+}
+
+#[doc(cfg(feature = "foo-const"))]
+const _: () = {
+    impl crate::Foo for u32 {}
+};
+
+#[doc(cfg(feature = "foo-fn"))]
+fn __() {
+    impl crate::Foo for u64 {}
+}
+
+#[doc(cfg(feature = "foo-method"))]
+impl dyn Foo {
+    fn __() {
+        impl crate::Foo for u128 {}
+    }
+}