privacy: Do not mark items reachable farther than their nominal visibility

This commit reverts a change made in rust-lang#111425.
It was believed that this change was necessary for implementing type privacy lints, but rust-lang#111801 showed that it was not necessary.
Quite opposite, the revert fixes some issues.

Author: petrochenkov

compiler/rustc_lint/src/builtin.rs

@@ -665,9 +665,7 @@ declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS])
 
 impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
-        if !(cx.effective_visibilities.is_reachable(item.owner_id.def_id)
-            && cx.tcx.local_visibility(item.owner_id.def_id).is_public())
-        {
+        if !cx.effective_visibilities.is_reachable(item.owner_id.def_id) {
             return;
         }
         let (def, ty) = match item.kind {
@@ -786,9 +784,7 @@ impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
 
 impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
-        if !(cx.effective_visibilities.is_reachable(item.owner_id.def_id)
-            && cx.tcx.local_visibility(item.owner_id.def_id).is_public())
-        {
+        if !cx.effective_visibilities.is_reachable(item.owner_id.def_id) {
             return;
         }
 

compiler/rustc_middle/src/middle/privacy.rs

@@ -4,6 +4,7 @@
 use crate::ty::{TyCtxt, Visibility};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
+use rustc_hir::def::DefKind;
 use rustc_macros::HashStable;
 use rustc_query_system::ich::StableHashingContext;
 use rustc_span::def_id::{LocalDefId, CRATE_DEF_ID};
@@ -148,13 +149,12 @@ impl EffectiveVisibilities {
         };
     }
 
-    pub fn check_invariants(&self, tcx: TyCtxt<'_>, early: bool) {
+    pub fn check_invariants(&self, tcx: TyCtxt<'_>) {
         if !cfg!(debug_assertions) {
             return;
         }
         for (&def_id, ev) in &self.map {
             // More direct visibility levels can never go farther than less direct ones,
-            // neither of effective visibilities can go farther than nominal visibility,
             // and all effective visibilities are larger or equal than private visibility.
             let private_vis = Visibility::Restricted(tcx.parent_module_from_def_id(def_id));
             let span = tcx.def_span(def_id.to_def_id());
@@ -175,17 +175,20 @@ impl EffectiveVisibilities {
                     ev.reachable_through_impl_trait
                 );
             }
-            let nominal_vis = tcx.visibility(def_id);
-            // FIXME: `rustc_privacy` is not yet updated for the new logic and can set
-            // effective visibilities that are larger than the nominal one.
-            if !nominal_vis.is_at_least(ev.reachable_through_impl_trait, tcx) && early {
-                span_bug!(
-                    span,
-                    "{:?}: reachable_through_impl_trait {:?} > nominal {:?}",
-                    def_id,
-                    ev.reachable_through_impl_trait,
-                    nominal_vis
-                );
+            // All effective visibilities except `reachable_through_impl_trait` are limited to
+            // nominal visibility. For some items nominal visibility doesn't make sense so we
+            // don't check this condition for them.
+            if !matches!(tcx.def_kind(def_id), DefKind::Impl { .. }) {
+                let nominal_vis = tcx.visibility(def_id);
+                if !nominal_vis.is_at_least(ev.reachable, tcx) {
+                    span_bug!(
+                        span,
+                        "{:?}: reachable {:?} > nominal {:?}",
+                        def_id,
+                        ev.reachable,
+                        nominal_vis
+                    );
+                }
             }
         }
     }

compiler/rustc_privacy/src/lib.rs

@@ -894,7 +894,12 @@ impl<'tcx> DefIdVisitor<'tcx> for ReachEverythingInTheInterfaceVisitor<'_, 'tcx>
         _descr: &dyn fmt::Display,
     ) -> ControlFlow<Self::BreakTy> {
         if let Some(def_id) = def_id.as_local() {
-            self.ev.update_eff_vis(def_id, self.effective_vis, None, self.level);
+            // All effective visibilities except `reachable_through_impl_trait` are limited to
+            // nominal visibility. If any type or trait is leaked farther than that, it will
+            // produce type privacy errors on any use, so we don't consider it leaked.
+            let nominal_vis = (self.level != Level::ReachableThroughImplTrait)
+                .then(|| self.ev.tcx.local_visibility(def_id));
+            self.ev.update_eff_vis(def_id, self.effective_vis, nominal_vis, self.level);
         }
         ControlFlow::Continue(())
     }
@@ -1869,10 +1874,9 @@ impl SearchInterfaceForPrivateItemsVisitor<'_> {
             return false;
         };
 
-        // FIXME: `Level::Reachable` should be taken instead of `Level::Reexported`
-        let reexported_at_vis = *effective_vis.at_level(Level::Reexported);
+        let reachable_at_vis = *effective_vis.at_level(Level::Reachable);
 
-        if !vis.is_at_least(reexported_at_vis, self.tcx) {
+        if !vis.is_at_least(reachable_at_vis, self.tcx) {
             let lint = if self.in_primary_interface {
                 lint::builtin::PRIVATE_INTERFACES
             } else {
@@ -1889,7 +1893,7 @@ impl SearchInterfaceForPrivateItemsVisitor<'_> {
                         tcx: self.tcx,
                     })
                         .into(),
-                    item_vis_descr: &vis_to_string(self.item_def_id, reexported_at_vis, self.tcx),
+                    item_vis_descr: &vis_to_string(self.item_def_id, reachable_at_vis, self.tcx),
                     ty_span: vis_span,
                     ty_kind: kind,
                     ty_descr: descr.into(),
@@ -2278,7 +2282,7 @@ fn effective_visibilities(tcx: TyCtxt<'_>, (): ()) -> &EffectiveVisibilities {
         changed: false,
     };
 
-    visitor.effective_visibilities.check_invariants(tcx, true);
+    visitor.effective_visibilities.check_invariants(tcx);
     if visitor.impl_trait_pass {
         // Underlying types of `impl Trait`s are marked as reachable unconditionally,
         // so this pass doesn't need to be a part of the fixed point iteration below.
@@ -2295,7 +2299,7 @@ fn effective_visibilities(tcx: TyCtxt<'_>, (): ()) -> &EffectiveVisibilities {
             break;
         }
     }
-    visitor.effective_visibilities.check_invariants(tcx, false);
+    visitor.effective_visibilities.check_invariants(tcx);
 
     let mut check_visitor =
         TestReachabilityVisitor { tcx, effective_visibilities: &visitor.effective_visibilities };

library/core/src/iter/adapters/flatten.rs

@@ -310,7 +310,7 @@ where
 /// Real logic of both `Flatten` and `FlatMap` which simply delegate to
 /// this type.
 #[derive(Clone, Debug)]
-#[unstable(feature = "trusted_len", issue = "37572")]
+#[cfg_attr(bootstrap, unstable(feature = "trusted_len", issue = "37572"))]
 struct FlattenCompat<I, U> {
     iter: Fuse<I>,
     frontiter: Option<U>,
@@ -464,7 +464,7 @@ where
     }
 }
 
-#[unstable(feature = "trusted_len", issue = "37572")]
+#[cfg_attr(bootstrap, unstable(feature = "trusted_len", issue = "37572"))]
 impl<I, U> Iterator for FlattenCompat<I, U>
 where
     I: Iterator<Item: IntoIterator<IntoIter = U, Item = U::Item>>,
@@ -579,7 +579,7 @@ where
     }
 }
 
-#[unstable(feature = "trusted_len", issue = "37572")]
+#[cfg_attr(bootstrap, unstable(feature = "trusted_len", issue = "37572"))]
 impl<I, U> DoubleEndedIterator for FlattenCompat<I, U>
 where
     I: DoubleEndedIterator<Item: IntoIterator<IntoIter = U, Item = U::Item>>,
@@ -649,23 +649,23 @@ where
     }
 }
 
-#[unstable(feature = "trusted_len", issue = "37572")]
+#[cfg_attr(bootstrap, unstable(feature = "trusted_len", issue = "37572"))]
 unsafe impl<const N: usize, I, T> TrustedLen
     for FlattenCompat<I, <[T; N] as IntoIterator>::IntoIter>
 where
     I: TrustedLen<Item = [T; N]>,
 {
 }
 
-#[unstable(feature = "trusted_len", issue = "37572")]
+#[cfg_attr(bootstrap, unstable(feature = "trusted_len", issue = "37572"))]
 unsafe impl<'a, const N: usize, I, T> TrustedLen
     for FlattenCompat<I, <&'a [T; N] as IntoIterator>::IntoIter>
 where
     I: TrustedLen<Item = &'a [T; N]>,
 {
 }
 
-#[unstable(feature = "trusted_len", issue = "37572")]
+#[cfg_attr(bootstrap, unstable(feature = "trusted_len", issue = "37572"))]
 unsafe impl<'a, const N: usize, I, T> TrustedLen
     for FlattenCompat<I, <&'a mut [T; N] as IntoIterator>::IntoIter>
 where

tests/ui/privacy/effective_visibilities_full_priv.rs

@@ -6,7 +6,7 @@ struct SemiPriv;
 mod m {
     #[rustc_effective_visibility]
     struct Priv;
-    //~^ ERROR Direct: pub(self), Reexported: pub(self), Reachable: pub(crate), ReachableThroughImplTrait: pub(crate)
+    //~^ ERROR not in the table
     //~| ERROR not in the table
 
     #[rustc_effective_visibility]

tests/ui/privacy/effective_visibilities_full_priv.stderr

@@ -1,4 +1,4 @@
-error: Direct: pub(self), Reexported: pub(self), Reachable: pub(crate), ReachableThroughImplTrait: pub(crate)
+error: not in the table
   --> $DIR/effective_visibilities_full_priv.rs:8:5
    |
 LL |     struct Priv;