privacy: Mark everything in a header of a reachable impl as reachable

src/test/ui/privacy/auxiliary/issue-57264-2.rs

@@ -0,0 +1,10 @@
+mod inner {
+    pub struct PubUnnameable;
+
+    impl PubUnnameable {
+        pub fn pub_method(self) {}
+    }
+}
+
+pub trait PubTraitWithSingleImplementor {}
+impl PubTraitWithSingleImplementor for Option<inner::PubUnnameable> {}

src/test/ui/privacy/issue-57264-1.rs

@@ -0,0 +1,8 @@
+// compile-pass
+// aux-build:issue-57264-1.rs
+
+extern crate issue_57264_1;
+
+fn main() {
+    issue_57264_1::Pub::pub_method();
+}

src/test/ui/privacy/issue-57264-2.rs

@@ -0,0 +1,10 @@
+// compile-pass
+// aux-build:issue-57264-2.rs
+
+extern crate issue_57264_2;
+
+fn infer<T: issue_57264_2::PubTraitWithSingleImplementor>(arg: T) -> T { arg }
+
+fn main() {
+    infer(None).unwrap().pub_method();
+}

src/test/ui/privacy/issue-57264.rs

@@ -1,8 +0,0 @@
-// compile-pass
-// aux-build:issue-57264.rs
-
-extern crate issue_57264;
-
-fn main() {
-    issue_57264::Pub::pub_method();
-}