Make the compiler suggest actual paths instead of visible paths if the visible paths are through any doc hidden path.

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -25,6 +25,7 @@ use rustc_middle::bug;
 use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams, simplify_type};
 use rustc_middle::ty::print::{
     PrintTraitRefExt as _, with_crate_prefix, with_forced_trimmed_paths,
+    with_no_visible_paths_if_doc_hidden,
 };
 use rustc_middle::ty::{self, GenericArgKind, IsSuggestable, Ty, TyCtxt, TypeVisitableExt};
 use rustc_span::def_id::DefIdSet;
@@ -3328,15 +3329,19 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let path_strings = candidates.iter().map(|trait_did| {
                 format!(
                     "{prefix}{}{postfix}\n",
-                    with_crate_prefix!(self.tcx.def_path_str(*trait_did)),
+                    with_no_visible_paths_if_doc_hidden!(with_crate_prefix!(
+                        self.tcx.def_path_str(*trait_did)
+                    )),
                 )
             });
 
             let glob_path_strings = globs.iter().map(|trait_did| {
                 let parent_did = parent_map.get(trait_did).unwrap();
                 format!(
                     "{prefix}{}::*{postfix} // trait {}\n",
-                    with_crate_prefix!(self.tcx.def_path_str(*parent_did)),
+                    with_no_visible_paths_if_doc_hidden!(with_crate_prefix!(
+                        self.tcx.def_path_str(*parent_did)
+                    )),
                     self.tcx.item_name(*trait_did),
                 )
             });

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -63,6 +63,7 @@ thread_local! {
     static FORCE_TRIMMED_PATH: Cell<bool> = const { Cell::new(false) };
     static REDUCED_QUERIES: Cell<bool> = const { Cell::new(false) };
     static NO_VISIBLE_PATH: Cell<bool> = const { Cell::new(false) };
+    static NO_VISIBLE_PATH_IF_DOC_HIDDEN: Cell<bool> = const { Cell::new(false) };
     static RTN_MODE: Cell<RtnMode> = const { Cell::new(RtnMode::ForDiagnostic) };
 }
 
@@ -134,6 +135,8 @@ define_helper!(
     /// Prevent selection of visible paths. `Display` impl of DefId will prefer
     /// visible (public) reexports of types as paths.
     fn with_no_visible_paths(NoVisibleGuard, NO_VISIBLE_PATH);
+    /// Prevent selection of visible paths if the paths are through a doc hidden path.
+    fn with_no_visible_paths_if_doc_hidden(NoVisibleIfDocHiddenGuard, NO_VISIBLE_PATH_IF_DOC_HIDDEN);
 );
 
 #[must_use]
@@ -569,6 +572,10 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
             return Ok(false);
         };
 
+        if self.tcx().is_doc_hidden(visible_parent) && with_no_visible_paths_if_doc_hidden() {
+            return Ok(false);
+        }
+
         let actual_parent = self.tcx().opt_parent(def_id);
         debug!(
             "try_print_visible_def_path: visible_parent={:?} actual_parent={:?}",

tests/ui/typeck/auxiliary/suggest-trait-reexported-as-not-doc-visible-a.rs

@@ -0,0 +1,5 @@
+//@ edition: 2021
+
+pub trait Foo {
+    fn foo();
+}

tests/ui/typeck/auxiliary/suggest-trait-reexported-as-not-doc-visible-b.rs

@@ -0,0 +1,14 @@
+// ignore-tidy-linelength
+//@ edition: 2021
+//@ aux-crate:suggest_trait_reexported_as_not_doc_visible_a=suggest-trait-reexported-as-not-doc-visible-a.rs
+
+pub struct Bar;
+
+impl __DocHidden::Foo for Bar {
+    fn foo() {}
+}
+
+#[doc(hidden)]
+pub mod __DocHidden {
+    pub use suggest_trait_reexported_as_not_doc_visible_a::Foo;
+}

tests/ui/typeck/suggest-trait-reexported-as-not-doc-visible.rs

@@ -0,0 +1,11 @@
+// ignore-tidy-linelength
+//@ edition: 2021
+//@ aux-crate:suggest_trait_reexported_as_not_doc_visible_a=suggest-trait-reexported-as-not-doc-visible-a.rs
+//@ aux-crate:suggest_trait_reexported_as_not_doc_visible_b=suggest-trait-reexported-as-not-doc-visible-b.rs
+
+use suggest_trait_reexported_as_not_doc_visible_b::Bar;
+
+fn main() {
+    Bar::foo();
+    //~^ ERROR: no function or associated item named `foo` found for struct `Bar` in the current scope [E0599]
+}

tests/ui/typeck/suggest-trait-reexported-as-not-doc-visible.stderr

@@ -0,0 +1,15 @@
+error[E0599]: no function or associated item named `foo` found for struct `Bar` in the current scope
+  --> $DIR/suggest-trait-reexported-as-not-doc-visible.rs:9:10
+   |
+LL |     Bar::foo();
+   |          ^^^ function or associated item not found in `Bar`
+   |
+   = help: items from traits can only be used if the trait is in scope
+help: trait `Foo` which provides `foo` is implemented but not in scope; perhaps you want to import it
+   |
+LL + use suggest_trait_reexported_as_not_doc_visible_a::Foo;
+   |
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0599`.