Add the core logic in old and new solvers

2 files changed, 26 insertions, 0 deletions

diff --git a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs
index b42587618b5..ce9b794d40d 100644
--- a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs
@@ -22,6 +22,7 @@ use crate::delegate::SolverDelegate;
 use crate::placeholder::BoundVarReplacer;
 use crate::solve::inspect::{self, ProofTreeBuilder};
 use crate::solve::search_graph::SearchGraph;
+use crate::solve::ty::may_use_unstable_feature;
 use crate::solve::{
     CanonicalInput, Certainty, FIXPOINT_STEP_LIMIT, Goal, GoalEvaluation, GoalEvaluationKind,
     GoalSource, GoalStalledOn, HasChanged, NestedNormalizationGoals, NoSolution, QueryInput,
@@ -550,6 +551,9 @@ where
                 ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType(ct, ty)) => {
                     self.compute_const_arg_has_type_goal(Goal { param_env, predicate: (ct, ty) })
                 }
+                ty::PredicateKind::Clause(ty::ClauseKind::UnstableFeature(symbol)) => {
+                    self.compute_unstable_feature_goal(param_env, symbol)
+                }
                 ty::PredicateKind::Subtype(predicate) => {
                     self.compute_subtype_goal(Goal { param_env, predicate })
                 }
@@ -1177,6 +1181,14 @@ where
     ) -> T {
         BoundVarReplacer::replace_bound_vars(&**self.delegate, universes, t).0
     }
+
+    pub(super) fn may_use_unstable_feature(
+        &self,
+        param_env: I::ParamEnv,
+        symbol: I::Symbol,
+    ) -> bool {
+        may_use_unstable_feature(&**self.delegate, param_env, symbol)
+    }
 }
 
 /// Eagerly replace aliases with inference variables, emitting `AliasRelate`
diff --git a/compiler/rustc_next_trait_solver/src/solve/mod.rs b/compiler/rustc_next_trait_solver/src/solve/mod.rs
index e68ea22c7a2..5ea3f0d1061 100644
--- a/compiler/rustc_next_trait_solver/src/solve/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/mod.rs
@@ -148,6 +148,20 @@ where
         }
     }
 
+    fn compute_unstable_feature_goal(
+        &mut self,
+        param_env: <I as Interner>::ParamEnv,
+        symbol: <I as Interner>::Symbol,
+    ) -> QueryResult<I> {
+        if self.may_use_unstable_feature(param_env, symbol) {
+            self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
+        } else {
+            self.evaluate_added_goals_and_make_canonical_response(Certainty::Maybe(
+                MaybeCause::Ambiguity,
+            ))
+        }
+    }
+
     #[instrument(level = "trace", skip(self))]
     fn compute_const_evaluatable_goal(
         &mut self,