Don't check generic parameter's parent deprecation

Author: Avi-D-coder

src/librustc/middle/stability.rs

@@ -281,14 +281,21 @@ impl<'tcx> TyCtxt<'tcx> {
     /// If `id` is `Some(_)`, this function will also check if the item at `def_id` has been
     /// deprecated. If the item is indeed deprecated, we will emit a deprecation lint attached to
     /// `id`.
-    pub fn eval_stability(self, def_id: DefId, id: Option<HirId>, span: Span) -> EvalResult {
+    pub fn eval_stability(
+        self,
+        def_id: DefId,
+        id: Option<HirId>,
+        span: Span,
+        inherit_dep: bool,
+    ) -> EvalResult {
         // Deprecated attributes apply in-crate and cross-crate.
         if let Some(id) = id {
             if let Some(depr_entry) = self.lookup_deprecation_entry(def_id) {
                 let parent_def_id = self.hir().local_def_id(self.hir().get_parent_item(id));
-                let skip = self
-                    .lookup_deprecation_entry(parent_def_id)
-                    .map_or(false, |parent_depr| parent_depr.same_origin(&depr_entry));
+                let skip = !inherit_dep
+                    || self
+                        .lookup_deprecation_entry(parent_def_id)
+                        .map_or(false, |parent_depr| parent_depr.same_origin(&depr_entry));
 
                 if !skip {
                     let (message, lint) =
@@ -386,9 +393,26 @@ impl<'tcx> TyCtxt<'tcx> {
     /// Additionally, this function will also check if the item is deprecated. If so, and `id` is
     /// not `None`, a deprecated lint attached to `id` will be emitted.
     pub fn check_stability(self, def_id: DefId, id: Option<HirId>, span: Span) {
+        self.check_stability_internal(def_id, id, span, true)
+    }
+
+    /// Checks if an item is stable or error out.
+    ///
+    /// If the item defined by `def_id` is unstable and the corresponding `#![feature]` does not
+    /// exist, emits an error.
+    ///
+    /// Additionally when `inherit_dep` is `true`, this function will also check if the item is deprecated. If so, and `id` is
+    /// not `None`, a deprecated lint attached to `id` will be emitted.
+    pub fn check_stability_internal(
+        self,
+        def_id: DefId,
+        id: Option<HirId>,
+        span: Span,
+        inherit_dep: bool,
+    ) {
         let soft_handler =
             |lint, span, msg: &_| self.lint_hir(lint, id.unwrap_or(hir::CRATE_HIR_ID), span, msg);
-        match self.eval_stability(def_id, id, span) {
+        match self.eval_stability(def_id, id, span, inherit_dep) {
             EvalResult::Allow => {}
             EvalResult::Deny { feature, reason, issue, is_soft } => {
                 report_unstable(self.sess, feature, reason, issue, is_soft, span, soft_handler)

src/librustc_typeck/astconv.rs

@@ -699,7 +699,12 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 }
                 (GenericParamDefKind::Type { has_default, .. }, GenericArg::Type(ty)) => {
                     if *has_default {
-                        tcx.check_stability(param.def_id, Some(arg.id()), arg.span());
+                        tcx.check_stability_internal(
+                            param.def_id,
+                            Some(arg.id()),
+                            arg.span(),
+                            false,
+                        );
                     }
 
                     self.ast_ty_to_ty(&ty).into()

src/librustc_typeck/check/method/probe.rs

@@ -1252,7 +1252,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         if let Some(uc) = unstable_candidates {
             applicable_candidates.retain(|&(p, _)| {
                 if let stability::EvalResult::Deny { feature, .. } =
-                    self.tcx.eval_stability(p.item.def_id, None, self.span)
+                    self.tcx.eval_stability(p.item.def_id, None, self.span, false)
                 {
                     uc.push((p, feature));
                     return false;