ignore deprecation for items deprecated by the same attribute

Whenever a node whould be reported as deprecated:

- check if the parent item is also deprecated

- if it is and both were deprecated by the same attribute

- skip the deprecation warning

fixes #35128
closes #16490

src/librustc/middle/stability.rs

@@ -386,7 +386,7 @@ struct Checker<'a, 'tcx: 'a> {
 
 impl<'a, 'tcx> Checker<'a, 'tcx> {
     fn check(&mut self, id: DefId, span: Span,
-             stab: &Option<&Stability>, _depr: &Option<Deprecation>) {
+             stab: &Option<&Stability>, _depr: &Option<DeprecationEntry>) {
         if !is_staged_api(self.tcx, id) {
             return;
         }
@@ -511,7 +511,7 @@ pub fn check_item<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                             warn_about_defns: bool,
                             cb: &mut FnMut(DefId, Span,
                                            &Option<&Stability>,
-                                           &Option<Deprecation>)) {
+                                           &Option<DeprecationEntry>)) {
     match item.node {
         hir::ItemExternCrate(_) => {
             // compiler-generated `extern crate` items have a dummy span.
@@ -550,7 +550,7 @@ pub fn check_item<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 pub fn check_expr<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, e: &hir::Expr,
                             cb: &mut FnMut(DefId, Span,
                                            &Option<&Stability>,
-                                           &Option<Deprecation>)) {
+                                           &Option<DeprecationEntry>)) {
     let span;
     let id = match e.node {
         hir::ExprMethodCall(i, _, _) => {
@@ -614,7 +614,7 @@ pub fn check_path<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                             path: &hir::Path, id: ast::NodeId,
                             cb: &mut FnMut(DefId, Span,
                                            &Option<&Stability>,
-                                           &Option<Deprecation>)) {
+                                           &Option<DeprecationEntry>)) {
     // Paths in import prefixes may have no resolution.
     match tcx.expect_def_or_none(id) {
         Some(Def::PrimTy(..)) => {}
@@ -630,7 +630,7 @@ pub fn check_path_list_item<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                       item: &hir::PathListItem,
                                       cb: &mut FnMut(DefId, Span,
                                                      &Option<&Stability>,
-                                                     &Option<Deprecation>)) {
+                                                     &Option<DeprecationEntry>)) {
     match tcx.expect_def(item.node.id()) {
         Def::PrimTy(..) => {}
         def => {
@@ -642,7 +642,7 @@ pub fn check_path_list_item<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 pub fn check_pat<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, pat: &hir::Pat,
                            cb: &mut FnMut(DefId, Span,
                                           &Option<&Stability>,
-                                          &Option<Deprecation>)) {
+                                          &Option<DeprecationEntry>)) {
     debug!("check_pat(pat = {:?})", pat);
     if is_internal(tcx, pat.span) { return; }
 
@@ -673,7 +673,7 @@ fn maybe_do_stability_check<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                       id: DefId, span: Span,
                                       cb: &mut FnMut(DefId, Span,
                                                      &Option<&Stability>,
-                                                     &Option<Deprecation>)) {
+                                                     &Option<DeprecationEntry>)) {
     if is_internal(tcx, span) {
         debug!("maybe_do_stability_check: \
                 skipping span={:?} since it is internal", span);
@@ -682,7 +682,7 @@ fn maybe_do_stability_check<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     let (stability, deprecation) = if is_staged_api(tcx, id) {
         (tcx.lookup_stability(id), None)
     } else {
-        (None, tcx.lookup_deprecation(id))
+        (None, tcx.lookup_deprecation_entry(id))
     };
     debug!("maybe_do_stability_check: \
             inspecting id={:?} span={:?} of stability={:?}", id, span, stability);

src/librustc_lint/builtin.rs

@@ -583,13 +583,20 @@ impl Deprecated {
     }
 
     fn lint(&self, cx: &LateContext, _id: DefId, span: Span,
-            stability: &Option<&attr::Stability>, deprecation: &Option<attr::Deprecation>) {
+            stability: &Option<&attr::Stability>,
+            deprecation: &Option<stability::DeprecationEntry>) {
         // Deprecated attributes apply in-crate and cross-crate.
         if let Some(&attr::Stability{rustc_depr: Some(attr::RustcDeprecation{ref reason, ..}), ..})
                 = *stability {
             output(cx, DEPRECATED, span, Some(&reason))
-        } else if let Some(attr::Deprecation{ref note, ..}) = *deprecation {
-            output(cx, DEPRECATED, span, note.as_ref().map(|x| &**x))
+        } else if let Some(ref depr_entry) = *deprecation {
+            if let Some(parent_depr) = cx.tcx.lookup_deprecation_entry(self.parent_def(cx)) {
+                if parent_depr.same_origin(depr_entry) {
+                    return;
+                }
+            }
+
+            output(cx, DEPRECATED, span, depr_entry.attr.note.as_ref().map(|x| &**x))
         }
 
         fn output(cx: &LateContext, lint: &'static Lint, span: Span, note: Option<&str>) {