Auto merge of #38689 - pnkfelix:dont-check-stability-on-private-items, r=nikomatsakis

Dont check stability for items that are not pub to universe.

Dont check stability for items that are not pub to universe.

In other words, skip it for private and even `pub(restricted)` items, because stability checks are only relevant to things visible in other crates.

Fix #38412.

1 files changed, 36 insertions, 1 deletions

diff --git a/src/librustc/middle/stability.rs b/src/librustc/middle/stability.rs
index f45e86f2f4b..e6c9d2c36d0 100644
--- a/src/librustc/middle/stability.rs
+++ b/src/librustc/middle/stability.rs
@@ -18,7 +18,7 @@ use hir::map as hir_map;
 use lint;
 use hir::def::Def;
 use hir::def_id::{CrateNum, CRATE_DEF_INDEX, DefId, DefIndex, LOCAL_CRATE};
-use ty::TyCtxt;
+use ty::{self, TyCtxt};
 use middle::privacy::AccessLevels;
 use syntax::symbol::Symbol;
 use syntax_pos::{Span, DUMMY_SP};
@@ -432,6 +432,36 @@ struct Checker<'a, 'tcx: 'a> {
 }
 
 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
+    // (See issue #38412)
+    fn skip_stability_check_due_to_privacy(self, def_id: DefId) -> bool {
+        let visibility = {
+            // Check if `def_id` is a trait method.
+            match self.sess.cstore.associated_item(def_id) {
+                Some(ty::AssociatedItem { container: ty::TraitContainer(trait_def_id), .. }) => {
+                    // Trait methods do not declare visibility (even
+                    // for visibility info in cstore). Use containing
+                    // trait instead, so methods of pub traits are
+                    // themselves considered pub.
+                    self.sess.cstore.visibility(trait_def_id)
+                }
+                _ => {
+                    // Otherwise, cstore info works directly.
+                    self.sess.cstore.visibility(def_id)
+                }
+            }
+        };
+
+        match visibility {
+            // must check stability for pub items.
+            ty::Visibility::Public => false,
+
+            // these are not visible outside crate; therefore
+            // stability markers are irrelevant, if even present.
+            ty::Visibility::Restricted(..) |
+            ty::Visibility::Invisible => true,
+        }
+    }
+
     pub fn check_stability(self, def_id: DefId, id: NodeId, span: Span) {
         if self.sess.codemap().span_allows_unstable(span) {
             debug!("stability: \
@@ -492,6 +522,11 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             self.stability.borrow_mut().used_features.insert(feature.clone(), level.clone());
         }
 
+        // Issue 38412: private items lack stability markers.
+        if self.skip_stability_check_due_to_privacy(def_id) {
+            return
+        }
+
         match stability {
             Some(&Stability { level: attr::Unstable {ref reason, issue}, ref feature, .. }) => {
                 if !self.stability.borrow().active_features.contains(feature) {