only allow `ConstEquate` with `feature(gce)`

[rust.git] / compiler / rustc_trait_selection / src / traits / fulfill.rs

diff --git a/compiler/rustc_trait_selection/src/traits/fulfill.rs b/compiler/rustc_trait_selection/src/traits/fulfill.rs
index 6f3a9412dde7a80dbfc52075d51094e9620ccea7..19efc29762143adf4506618b16bf6fba8bb32513 100644 (file)
--- a/compiler/rustc_trait_selection/src/traits/fulfill.rs
+++ b/compiler/rustc_trait_selection/src/traits/fulfill.rs
@@ -102,7 +102,7 @@ pub fn new_in_snapshot() -> FulfillmentContext<'tcx> {
     }
 
     /// Attempts to select obligations using `selcx`.
-    fn select(&mut self, selcx: &mut SelectionContext<'a, 'tcx>) -> Vec<FulfillmentError<'tcx>> {
+    fn select(&mut self, selcx: SelectionContext<'a, 'tcx>) -> Vec<FulfillmentError<'tcx>> {
         let span = debug_span!("select", obligation_forest_size = ?self.predicates.len());
         let _enter = span.enter();
 
@@ -197,8 +197,8 @@ fn select_where_possible(
         &mut self,
         infcx: &InferCtxt<'_, 'tcx>,
     ) -> Vec<FulfillmentError<'tcx>> {
-        let mut selcx = SelectionContext::new(infcx);
-        self.select(&mut selcx)
+        let selcx = SelectionContext::new(infcx);
+        self.select(selcx)
     }
 
     fn pending_obligations(&self) -> Vec<PredicateObligation<'tcx>> {
@@ -210,8 +210,8 @@ fn relationships(&mut self) -> &mut FxHashMap<ty::TyVid, ty::FoundRelationships>
     }
 }
 
-struct FulfillProcessor<'a, 'b, 'tcx> {
-    selcx: &'a mut SelectionContext<'b, 'tcx>,
+struct FulfillProcessor<'a, 'tcx> {
+    selcx: SelectionContext<'a, 'tcx>,
 }
 
 fn mk_pending(os: Vec<PredicateObligation<'_>>) -> Vec<PendingPredicateObligation<'_>> {
@@ -220,7 +220,7 @@ fn mk_pending(os: Vec<PredicateObligation<'_>>) -> Vec<PendingPredicateObligatio
         .collect()
 }
 
-impl<'a, 'b, 'tcx> ObligationProcessor for FulfillProcessor<'a, 'b, 'tcx> {
+impl<'a, 'tcx> ObligationProcessor for FulfillProcessor<'a, 'tcx> {
     type Obligation = PendingPredicateObligation<'tcx>;
     type Error = FulfillmentErrorCode<'tcx>;
     type OUT = Outcome<Self::Obligation, Self::Error>;
@@ -291,7 +291,7 @@ fn process_obligation(
         if obligation.predicate.has_projections() {
             let mut obligations = Vec::new();
             let predicate = crate::traits::project::try_normalize_with_depth_to(
-                self.selcx,
+                &mut self.selcx,
                 obligation.param_env,
                 obligation.cause.clone(),
                 obligation.recursion_depth + 1,
@@ -495,19 +495,20 @@ fn process_obligation(
                 }
 
                 ty::PredicateKind::ConstEquate(c1, c2) => {
+                    assert!(
+                        self.selcx.tcx().features().generic_const_exprs,
+                        "`ConstEquate` without a feature gate: {c1:?} {c2:?}",
+                    );
                     debug!(?c1, ?c2, "equating consts");
-                    let tcx = self.selcx.tcx();
-                    if tcx.features().generic_const_exprs {
-                        // FIXME: we probably should only try to unify abstract constants
-                        // if the constants depend on generic parameters.
-                        //
-                        // Let's just see where this breaks :shrug:
-                        if let (ty::ConstKind::Unevaluated(a), ty::ConstKind::Unevaluated(b)) =
-                            (c1.kind(), c2.kind())
-                        {
-                            if infcx.try_unify_abstract_consts(a, b, obligation.param_env) {
-                                return ProcessResult::Changed(vec![]);
-                            }
+                    // FIXME: we probably should only try to unify abstract constants
+                    // if the constants depend on generic parameters.
+                    //
+                    // Let's just see where this breaks :shrug:
+                    if let (ty::ConstKind::Unevaluated(a), ty::ConstKind::Unevaluated(b)) =
+                        (c1.kind(), c2.kind())
+                    {
+                        if infcx.try_unify_abstract_consts(a, b, obligation.param_env) {
+                            return ProcessResult::Changed(vec![]);
                         }
                     }
 
@@ -608,7 +609,7 @@ fn process_backedge<'c, I>(
     }
 }
 
-impl<'a, 'b, 'tcx> FulfillProcessor<'a, 'b, 'tcx> {
+impl<'a, 'tcx> FulfillProcessor<'a, 'tcx> {
     #[instrument(level = "debug", skip(self, obligation, stalled_on))]
     fn process_trait_obligation(
         &mut self,
@@ -643,7 +644,7 @@ fn process_trait_obligation(
                 // information about the types in the trait.
                 stalled_on.clear();
                 stalled_on.extend(substs_infer_vars(
-                    self.selcx,
+                    &self.selcx,
                     trait_obligation.predicate.map_bound(|pred| pred.trait_ref.substs),
                 ));
 
@@ -695,12 +696,12 @@ fn process_projection_obligation(
             }
         }
 
-        match project::poly_project_and_unify_type(self.selcx, &project_obligation) {
+        match project::poly_project_and_unify_type(&mut self.selcx, &project_obligation) {
             ProjectAndUnifyResult::Holds(os) => ProcessResult::Changed(mk_pending(os)),
             ProjectAndUnifyResult::FailedNormalization => {
                 stalled_on.clear();
                 stalled_on.extend(substs_infer_vars(
-                    self.selcx,
+                    &self.selcx,
                     project_obligation.predicate.map_bound(|pred| pred.projection_ty.substs),
                 ));
                 ProcessResult::Unchanged
@@ -718,7 +719,7 @@ fn process_projection_obligation(
 
 /// Returns the set of inference variables contained in `substs`.
 fn substs_infer_vars<'a, 'tcx>(
-    selcx: &mut SelectionContext<'a, 'tcx>,
+    selcx: &SelectionContext<'a, 'tcx>,
     substs: ty::Binder<'tcx, SubstsRef<'tcx>>,
 ) -> impl Iterator<Item = TyOrConstInferVar<'tcx>> {
     selcx