Rollup merge of #128912 - compiler-errors:do-not-recommend-impl, r=lcnr

Store `do_not_recommend`-ness in impl header

Alternative to #128674

It's less flexible, but also less invasive. Hopefully it's also performant. I'd recommend we think separately about the design for how to gate arbitrary diagnostic attributes moving forward.

compiler/rustc_trait_selection/src/solve/fulfill.rs

@@ -13,7 +13,6 @@ use rustc_middle::bug;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_next_trait_solver::solve::{GenerateProofTree, SolverDelegateEvalExt as _};
-use rustc_span::symbol::sym;
 
 use super::delegate::SolverDelegate;
 use super::inspect::{self, ProofTreeInferCtxtExt, ProofTreeVisitor};
@@ -440,10 +439,7 @@ impl<'tcx> ProofTreeVisitor<'tcx> for BestObligation<'tcx> {
             source: CandidateSource::Impl(impl_def_id),
             result: _,
         } = candidate.kind()
-            && goal
-                .infcx()
-                .tcx
-                .has_attrs_with_path(impl_def_id, &[sym::diagnostic, sym::do_not_recommend])
+            && goal.infcx().tcx.do_not_recommend_impl(impl_def_id)
         {
             return ControlFlow::Break(self.obligation.clone());
         }