Move `#[do_not_recommend]` to the `#[diagnostic]` namespace

This commit moves the `#[do_not_recommend]` attribute to the
`#[diagnostic]` namespace. It still requires
`#![feature(do_not_recommend)]` to work.

2 files changed, 8 insertions, 2 deletions

diff --git a/compiler/rustc_trait_selection/src/solve/fulfill.rs b/compiler/rustc_trait_selection/src/solve/fulfill.rs
index 4933080451d..7291eb00e72 100644
--- a/compiler/rustc_trait_selection/src/solve/fulfill.rs
+++ b/compiler/rustc_trait_selection/src/solve/fulfill.rs
@@ -380,7 +380,10 @@ impl<'tcx> ProofTreeVisitor<'tcx> for BestObligation<'tcx> {
             source: CandidateSource::Impl(impl_def_id),
             result: _,
         } = candidate.kind()
-            && goal.infcx().tcx.has_attr(impl_def_id, sym::do_not_recommend)
+            && goal
+                .infcx()
+                .tcx
+                .has_attrs_with_path(impl_def_id, &[sym::diagnostic, sym::do_not_recommend])
         {
             return ControlFlow::Break(self.obligation.clone());
         }
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
index 20dfb5e6642..494fca0336c 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
@@ -1012,7 +1012,10 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         let mut base_cause = obligation.cause.code().clone();
         loop {
             if let ObligationCauseCode::ImplDerived(ref c) = base_cause {
-                if self.tcx.has_attr(c.impl_or_alias_def_id, sym::do_not_recommend) {
+                if self.tcx.has_attrs_with_path(
+                    c.impl_or_alias_def_id,
+                    &[sym::diagnostic, sym::do_not_recommend],
+                ) {
                     let code = (*c.derived.parent_code).clone();
                     obligation.cause.map_code(|_| code);
                     obligation.predicate = c.derived.parent_trait_pred.upcast(self.tcx);