Only inspect user-written predicates for privacy concerns

compiler/rustc_ty_utils/src/sig_types.rs

@@ -13,6 +13,7 @@ pub trait SpannedTypeVisitor<'tcx> {
     fn visit(&mut self, span: Span, value: impl TypeVisitable<TyCtxt<'tcx>>) -> Self::Result;
 }
 
+#[instrument(level = "trace", skip(tcx, visitor))]
 pub fn walk_types<'tcx, V: SpannedTypeVisitor<'tcx>>(
     tcx: TyCtxt<'tcx>,
     item: LocalDefId,
@@ -36,7 +37,7 @@ pub fn walk_types<'tcx, V: SpannedTypeVisitor<'tcx>>(
             for (hir, ty) in hir_sig.inputs.iter().zip(ty_sig.inputs().iter()) {
                 try_visit!(visitor.visit(hir.span, ty.map_bound(|x| *x)));
             }
-            for (pred, span) in tcx.predicates_of(item).instantiate_identity(tcx) {
+            for (pred, span) in tcx.explicit_predicates_of(item).instantiate_identity(tcx) {
                 try_visit!(visitor.visit(span, pred));
             }
         }
@@ -54,7 +55,7 @@ pub fn walk_types<'tcx, V: SpannedTypeVisitor<'tcx>>(
                 // Associated types in traits don't necessarily have a type that we can visit
                 try_visit!(visitor.visit(ty.span, tcx.type_of(item).instantiate_identity()));
             }
-            for (pred, span) in tcx.predicates_of(item).instantiate_identity(tcx) {
+            for (pred, span) in tcx.explicit_predicates_of(item).instantiate_identity(tcx) {
                 try_visit!(visitor.visit(span, pred));
             }
         }
@@ -76,7 +77,7 @@ pub fn walk_types<'tcx, V: SpannedTypeVisitor<'tcx>>(
                 let ty = field.ty(tcx, args);
                 try_visit!(visitor.visit(span, ty));
             }
-            for (pred, span) in tcx.predicates_of(item).instantiate_identity(tcx) {
+            for (pred, span) in tcx.explicit_predicates_of(item).instantiate_identity(tcx) {
                 try_visit!(visitor.visit(span, pred));
             }
         }
@@ -95,12 +96,12 @@ pub fn walk_types<'tcx, V: SpannedTypeVisitor<'tcx>>(
                 _ => tcx.def_span(item),
             };
             try_visit!(visitor.visit(span, tcx.type_of(item).instantiate_identity()));
-            for (pred, span) in tcx.predicates_of(item).instantiate_identity(tcx) {
+            for (pred, span) in tcx.explicit_predicates_of(item).instantiate_identity(tcx) {
                 try_visit!(visitor.visit(span, pred));
             }
         }
         DefKind::TraitAlias | DefKind::Trait => {
-            for (pred, span) in tcx.predicates_of(item).instantiate_identity(tcx) {
+            for (pred, span) in tcx.explicit_predicates_of(item).instantiate_identity(tcx) {
                 try_visit!(visitor.visit(span, pred));
             }
         }

tests/ui/privacy/generic_struct_field_projection.rs

@@ -0,0 +1,38 @@
+//! To determine all the types that need to be private when looking at `Struct`, we
+//! used to invoke `predicates_of` to also look at types in `where` bounds.
+//! Unfortunately this also computes the inferred outlives bounds, which means for
+//! every field we check that if it is of type `&'a T` then `T: 'a` and if it is of
+//! struct type, we check that the struct satisfies its lifetime parameters by looking
+//! at its inferred outlives bounds. This means we end up with a `<Foo as Trait>::Assoc: 'a`
+//! in the outlives bounds of `Struct`. While this is trivially provable, privacy
+//! only sees `Foo` and `Trait` and determines that `Foo` is private and then errors.
+//! So now we invoke `explicit_predicates_of` to make sure we only care about user-written
+//! predicates.
+
+//@ check-pass
+
+mod baz {
+    struct Foo;
+
+    pub trait Trait {
+        type Assoc;
+    }
+
+    impl Trait for Foo {
+        type Assoc = ();
+    }
+
+    pub struct Bar<'a, T: Trait> {
+        source: &'a T::Assoc,
+    }
+
+    pub struct Baz<'a> {
+        mode: Bar<'a, Foo>,
+    }
+}
+
+pub struct Struct<'a> {
+    lexer: baz::Baz<'a>,
+}
+
+fn main() {}