Reach the body of functions returning impl Trait but don't treat it as public

src/librustc_privacy/lib.rs

@@ -433,10 +433,6 @@ impl<'b, 'a, 'tcx> ReachEverythingInTheInterfaceVisitor<'b, 'a, 'tcx> {
 
     fn ty(&mut self) -> &mut Self {
         let ty = self.ev.tcx.type_of(self.item_def_id);
-        self.walk_ty(ty)
-    }
-
-    fn walk_ty(&mut self, ty: Ty<'tcx>) -> &mut Self {
         ty.visit_with(self);
         if let ty::TyFnDef(def_id, _) = ty.sty {
             if def_id == self.item_def_id {
@@ -1568,7 +1564,7 @@ impl<'a, 'tcx> Visitor<'tcx> for PrivateItemsInPublicInterfacesVisitor<'a, 'tcx>
                 // where `X` is the `impl Iterator<Item=T>` itself,
                 // stored in `predicates_of`, not in the `Ty` itself.
 
-                self.check(item.id, self.inner_visibility).predicates();
+                self.check(item.id, item_visibility).predicates();
             }
             // Subitems of these items have inherited publicity
             hir::ItemConst(..) | hir::ItemStatic(..) | hir::ItemFn(..) |

src/test/run-pass/impl-trait/auxiliary/xcrate.rs

@@ -17,6 +17,10 @@ fn some_internal_fn() -> u32 {
     1
 }
 
+fn other_internal_fn() -> u32 {
+    1
+}
+
 // See #40839
 pub fn return_closure_accessing_internal_fn() -> impl Fn() -> u32 {
     || {
@@ -25,5 +29,5 @@ pub fn return_closure_accessing_internal_fn() -> impl Fn() -> u32 {
 }
 
 pub fn return_internal_fn() -> impl Fn() -> u32 {
-    some_internal_fn
+    other_internal_fn
 }

src/test/ui/impl-trait/issue-52128.rs

@@ -0,0 +1,35 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// compile-pass
+
+#![deny(warnings)]
+
+use std::collections::BTreeMap;
+
+pub struct RangeMap {
+    map: BTreeMap<Range, u8>,
+}
+
+#[derive(Eq, PartialEq, Ord, PartialOrd)]
+struct Range;
+
+impl RangeMap {
+    fn iter_with_range<'a>(&'a self) -> impl Iterator<Item = (&'a Range, &'a u8)> + 'a {
+        self.map.range(Range..Range)
+    }
+
+    pub fn iter<'a>(&'a self) -> impl Iterator<Item = &'a u8> + 'a {
+        self.iter_with_range().map(|(_, data)| data)
+    }
+
+}
+
+fn main() {}