Rollup of 10 pull requests

compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs

@@ -155,13 +155,6 @@ fn add_hidden_type<'tcx>(
     }
 }
 
-fn get_hidden_type<'tcx>(
-    hidden_types: &DefinitionSiteHiddenTypes<'tcx>,
-    def_id: LocalDefId,
-) -> Option<EarlyBinder<'tcx, OpaqueHiddenType<'tcx>>> {
-    hidden_types.0.get(&def_id).map(|ty| EarlyBinder::bind(*ty))
-}
-
 #[derive(Debug)]
 struct DefiningUse<'tcx> {
     /// The opaque type using non NLL vars. This uses the actual
@@ -508,7 +501,8 @@ pub(crate) fn apply_definition_site_hidden_types<'tcx>(
     let tcx = infcx.tcx;
     let mut errors = Vec::new();
     for &(key, hidden_type) in opaque_types {
-        let Some(expected) = get_hidden_type(hidden_types, key.def_id) else {
+        let Some(expected) = hidden_types.0.get(&key.def_id).map(|ty| EarlyBinder::bind(*ty))
+        else {
             if !tcx.use_typing_mode_borrowck() {
                 if let ty::Alias(ty::Opaque, alias_ty) = hidden_type.ty.kind()
                     && alias_ty.def_id == key.def_id.to_def_id()

compiler/rustc_hir_typeck/src/lib.rs

@@ -219,6 +219,12 @@ fn typeck_with_inspect<'tcx>(
     // the future.
     fcx.check_repeat_exprs();
 
+    // We need to handle opaque types before emitting ambiguity errors as applying
+    // defining uses may guide type inference.
+    if fcx.next_trait_solver() {
+        fcx.try_handle_opaque_type_uses_next();
+    }
+
     fcx.type_inference_fallback();
 
     // Even though coercion casts provide type hints, we check casts after fallback for

compiler/rustc_hir_typeck/src/opaque_types.rs

@@ -22,35 +22,50 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
     /// inference variables.
     ///
     /// It then uses these defining uses to guide inference for all other uses.
+    ///
+    /// Unlike `handle_opaque_type_uses_next`, this does not report errors.
+    #[instrument(level = "debug", skip(self))]
+    pub(super) fn try_handle_opaque_type_uses_next(&mut self) {
+        // We clone the opaques instead of stealing them here as we still need
+        // to use them after fallback.
+        let opaque_types: Vec<_> = self.infcx.clone_opaque_types();
+
+        self.compute_definition_site_hidden_types(opaque_types, false);
+    }
+
+    /// This takes all the opaque type uses during HIR typeck. It first computes
+    /// the concrete hidden type by iterating over all defining uses.
+    ///
+    /// A use during HIR typeck is defining if all non-lifetime arguments are
+    /// unique generic parameters and the hidden type does not reference any
+    /// inference variables.
+    ///
+    /// It then uses these defining uses to guide inference for all other uses.
     #[instrument(level = "debug", skip(self))]
     pub(super) fn handle_opaque_type_uses_next(&mut self) {
         // We clone the opaques instead of stealing them here as they are still used for
         // normalization in the next generation trait solver.
-        let mut opaque_types: Vec<_> = self.infcx.clone_opaque_types();
+        let opaque_types: Vec<_> = self.infcx.clone_opaque_types();
         let num_entries = self.inner.borrow_mut().opaque_types().num_entries();
         let prev = self.checked_opaque_types_storage_entries.replace(Some(num_entries));
         debug_assert_eq!(prev, None);
-        for entry in &mut opaque_types {
-            *entry = self.resolve_vars_if_possible(*entry);
-        }
-        debug!(?opaque_types);
 
-        self.compute_definition_site_hidden_types(&opaque_types);
-        self.apply_definition_site_hidden_types(&opaque_types);
+        self.compute_definition_site_hidden_types(opaque_types, true);
     }
 }
 
+#[derive(Copy, Clone, Debug)]
 enum UsageKind<'tcx> {
     None,
     NonDefiningUse(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>),
     UnconstrainedHiddenType(OpaqueHiddenType<'tcx>),
-    HasDefiningUse,
+    HasDefiningUse(OpaqueHiddenType<'tcx>),
 }
 
 impl<'tcx> UsageKind<'tcx> {
     fn merge(&mut self, other: UsageKind<'tcx>) {
         match (&*self, &other) {
-            (UsageKind::HasDefiningUse, _) | (_, UsageKind::None) => unreachable!(),
+            (UsageKind::HasDefiningUse(_), _) | (_, UsageKind::None) => unreachable!(),
             (UsageKind::None, _) => *self = other,
             // When mergining non-defining uses, prefer earlier ones. This means
             // the error happens as early as possible.
@@ -64,7 +79,7 @@ impl<'tcx> UsageKind<'tcx> {
             // intended to be defining.
             (
                 UsageKind::NonDefiningUse(..) | UsageKind::UnconstrainedHiddenType(..),
-                UsageKind::UnconstrainedHiddenType(..) | UsageKind::HasDefiningUse,
+                UsageKind::UnconstrainedHiddenType(..) | UsageKind::HasDefiningUse(_),
             ) => *self = other,
         }
     }
@@ -73,8 +88,14 @@ impl<'tcx> UsageKind<'tcx> {
 impl<'tcx> FnCtxt<'_, 'tcx> {
     fn compute_definition_site_hidden_types(
         &mut self,
-        opaque_types: &[(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)],
+        mut opaque_types: Vec<(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)>,
+        error_on_missing_defining_use: bool,
     ) {
+        for entry in opaque_types.iter_mut() {
+            *entry = self.resolve_vars_if_possible(*entry);
+        }
+        debug!(?opaque_types);
+
         let tcx = self.tcx;
         let TypingMode::Analysis { defining_opaque_types_and_generators } = self.typing_mode()
         else {
@@ -88,19 +109,47 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
                 _ => unreachable!("not opaque or generator: {def_id:?}"),
             }
 
+            // We do actually need to check this the second pass (we can't just
+            // store this), because we can go from `UnconstrainedHiddenType` to
+            // `HasDefiningUse` (because of fallback)
             let mut usage_kind = UsageKind::None;
-            for &(opaque_type_key, hidden_type) in opaque_types {
+            for &(opaque_type_key, hidden_type) in &opaque_types {
                 if opaque_type_key.def_id != def_id {
                     continue;
                 }
 
                 usage_kind.merge(self.consider_opaque_type_use(opaque_type_key, hidden_type));
-                if let UsageKind::HasDefiningUse = usage_kind {
+
+                if let UsageKind::HasDefiningUse(..) = usage_kind {
                     break;
                 }
             }
 
+            if let UsageKind::HasDefiningUse(ty) = usage_kind {
+                for &(opaque_type_key, hidden_type) in &opaque_types {
+                    if opaque_type_key.def_id != def_id {
+                        continue;
+                    }
+
+                    let expected = EarlyBinder::bind(ty.ty).instantiate(tcx, opaque_type_key.args);
+                    self.demand_eqtype(hidden_type.span, expected, hidden_type.ty);
+                }
+
+                // Being explicit here: it may be possible that we in a
+                // previous call to this function we did an insert, but this
+                // should be just fine, since they all get equated anyways and
+                // we shouldn't ever go from `HasDefiningUse` to anyway else.
+                let _ = self.typeck_results.borrow_mut().hidden_types.insert(def_id, ty);
+            }
+
+            // If we're in `fn try_handle_opaque_type_uses_next` then do not
+            // report any errors.
+            if !error_on_missing_defining_use {
+                continue;
+            }
+
             let guar = match usage_kind {
+                UsageKind::HasDefiningUse(_) => continue,
                 UsageKind::None => {
                     if let Some(guar) = self.tainted_by_errors() {
                         guar
@@ -137,7 +186,6 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
                             .emit()
                     }
                 }
-                UsageKind::HasDefiningUse => continue,
             };
 
             self.typeck_results
@@ -148,8 +196,9 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
         }
     }
 
+    #[tracing::instrument(skip(self), ret)]
     fn consider_opaque_type_use(
-        &mut self,
+        &self,
         opaque_type_key: OpaqueTypeKey<'tcx>,
         hidden_type: OpaqueHiddenType<'tcx>,
     ) -> UsageKind<'tcx> {
@@ -161,11 +210,7 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
         ) {
             match err {
                 NonDefiningUseReason::Tainted(guar) => {
-                    self.typeck_results.borrow_mut().hidden_types.insert(
-                        opaque_type_key.def_id,
-                        OpaqueHiddenType::new_error(self.tcx, guar),
-                    );
-                    return UsageKind::HasDefiningUse;
+                    return UsageKind::HasDefiningUse(OpaqueHiddenType::new_error(self.tcx, guar));
                 }
                 _ => return UsageKind::NonDefiningUse(opaque_type_key, hidden_type),
             };
@@ -193,27 +238,7 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
             self.tcx,
             DefiningScopeKind::HirTypeck,
         );
-
-        let prev = self
-            .typeck_results
-            .borrow_mut()
-            .hidden_types
-            .insert(opaque_type_key.def_id, hidden_type);
-        assert!(prev.is_none());
-        UsageKind::HasDefiningUse
-    }
-
-    fn apply_definition_site_hidden_types(
-        &mut self,
-        opaque_types: &[(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)],
-    ) {
-        let tcx = self.tcx;
-        for &(key, hidden_type) in opaque_types {
-            let expected = *self.typeck_results.borrow_mut().hidden_types.get(&key.def_id).unwrap();
-
-            let expected = EarlyBinder::bind(expected.ty).instantiate(tcx, key.args);
-            self.demand_eqtype(hidden_type.span, expected, hidden_type.ty);
-        }
+        UsageKind::HasDefiningUse(hidden_type)
     }
 
     /// We may in theory add further uses of an opaque after cloning the opaque

compiler/rustc_next_trait_solver/src/solve/search_graph.rs

@@ -99,19 +99,23 @@ where
         response_no_constraints(cx, input, Certainty::overflow(false))
     }
 
-    fn is_ambiguous_result(result: QueryResult<I>) -> bool {
-        result.is_ok_and(|response| {
-            has_no_inference_or_external_constraints(response)
+    fn is_ambiguous_result(result: QueryResult<I>) -> Option<Certainty> {
+        result.ok().and_then(|response| {
+            if has_no_inference_or_external_constraints(response)
                 && matches!(response.value.certainty, Certainty::Maybe { .. })
+            {
+                Some(response.value.certainty)
+            } else {
+                None
+            }
         })
     }
 
     fn propagate_ambiguity(
         cx: I,
         for_input: CanonicalInput<I>,
-        from_result: QueryResult<I>,
+        certainty: Certainty,
     ) -> QueryResult<I> {
-        let certainty = from_result.unwrap().value.certainty;
         response_no_constraints(cx, for_input, certainty)
     }
 

compiler/rustc_type_ir/src/interner.rs

@@ -11,7 +11,7 @@ use crate::inherent::*;
 use crate::ir_print::IrPrint;
 use crate::lang_items::{SolverAdtLangItem, SolverLangItem, SolverTraitLangItem};
 use crate::relate::Relate;
-use crate::solve::{CanonicalInput, ExternalConstraintsData, QueryResult, inspect};
+use crate::solve::{CanonicalInput, Certainty, ExternalConstraintsData, QueryResult, inspect};
 use crate::visit::{Flags, TypeVisitable};
 use crate::{self as ty, CanonicalParamEnvCacheEntry, search_graph};
 
@@ -550,6 +550,7 @@ impl<T, R, E> CollectAndApply<T, R> for Result<T, E> {
 impl<I: Interner> search_graph::Cx for I {
     type Input = CanonicalInput<I>;
     type Result = QueryResult<I>;
+    type AmbiguityInfo = Certainty;
 
     type DepNodeIndex = I::DepNodeIndex;
     type Tracked<T: Debug + Clone> = I::Tracked<T>;

compiler/rustc_type_ir/src/search_graph/mod.rs

@@ -40,6 +40,7 @@ pub use global_cache::GlobalCache;
 pub trait Cx: Copy {
     type Input: Debug + Eq + Hash + Copy;
     type Result: Debug + Eq + Hash + Copy;
+    type AmbiguityInfo: Debug + Eq + Hash + Copy;
 
     type DepNodeIndex;
     type Tracked<T: Debug + Clone>: Debug;
@@ -96,11 +97,13 @@ pub trait Delegate: Sized {
         input: <Self::Cx as Cx>::Input,
     ) -> <Self::Cx as Cx>::Result;
 
-    fn is_ambiguous_result(result: <Self::Cx as Cx>::Result) -> bool;
+    fn is_ambiguous_result(
+        result: <Self::Cx as Cx>::Result,
+    ) -> Option<<Self::Cx as Cx>::AmbiguityInfo>;
     fn propagate_ambiguity(
         cx: Self::Cx,
         for_input: <Self::Cx as Cx>::Input,
-        from_result: <Self::Cx as Cx>::Result,
+        ambiguity_info: <Self::Cx as Cx>::AmbiguityInfo,
     ) -> <Self::Cx as Cx>::Result;
 
     fn compute_goal(
@@ -913,9 +916,9 @@ impl<D: Delegate<Cx = X>, X: Cx> SearchGraph<D> {
 /// heads from the stack. This may not necessarily mean that we've actually
 /// reached a fixpoint for that cycle head, which impacts the way we rebase
 /// provisional cache entries.
-enum RebaseReason {
+enum RebaseReason<X: Cx> {
     NoCycleUsages,
-    Ambiguity,
+    Ambiguity(X::AmbiguityInfo),
     Overflow,
     /// We've actually reached a fixpoint.
     ///
@@ -951,7 +954,7 @@ impl<D: Delegate<Cx = X>, X: Cx> SearchGraph<D, X> {
         &mut self,
         cx: X,
         stack_entry: &StackEntry<X>,
-        rebase_reason: RebaseReason,
+        rebase_reason: RebaseReason<X>,
     ) {
         let popped_head_index = self.stack.next_index();
         #[allow(rustc::potential_query_instability)]
@@ -969,10 +972,6 @@ impl<D: Delegate<Cx = X>, X: Cx> SearchGraph<D, X> {
                     return true;
                 };
 
-                let Some(new_highest_head_index) = heads.opt_highest_cycle_head_index() else {
-                    return false;
-                };
-
                 // We're rebasing an entry `e` over a head `p`. This head
                 // has a number of own heads `h` it depends on.
                 //
@@ -1033,8 +1032,8 @@ impl<D: Delegate<Cx = X>, X: Cx> SearchGraph<D, X> {
                         // is not actually equal to the final provisional result. We
                         // need to discard the provisional cache entry in this case.
                         RebaseReason::NoCycleUsages => return false,
-                        RebaseReason::Ambiguity => {
-                            *result = D::propagate_ambiguity(cx, input, *result);
+                        RebaseReason::Ambiguity(info) => {
+                            *result = D::propagate_ambiguity(cx, input, info);
                         }
                         RebaseReason::Overflow => *result = D::fixpoint_overflow_result(cx, input),
                         RebaseReason::ReachedFixpoint(None) => {}
@@ -1046,6 +1045,10 @@ impl<D: Delegate<Cx = X>, X: Cx> SearchGraph<D, X> {
                     };
                 }
 
+                let Some(new_highest_head_index) = heads.opt_highest_cycle_head_index() else {
+                    return false;
+                };
+
                 // We now care about the path from the next highest cycle head to the
                 // provisional cache entry.
                 *path_from_head = path_from_head.extend(Self::cycle_path_kind(
@@ -1268,6 +1271,7 @@ impl<D: Delegate<Cx = X>, X: Cx> SearchGraph<D, X> {
     }
 
     /// Whether we've reached a fixpoint when evaluating a cycle head.
+    #[instrument(level = "trace", skip(self, stack_entry), ret)]
     fn reached_fixpoint(
         &mut self,
         stack_entry: &StackEntry<X>,
@@ -1355,8 +1359,12 @@ impl<D: Delegate<Cx = X>, X: Cx> SearchGraph<D, X> {
             // As we only get to this branch if we haven't yet reached a fixpoint,
             // we also taint all provisional cache entries which depend on the
             // current goal.
-            if D::is_ambiguous_result(result) {
-                self.rebase_provisional_cache_entries(cx, &stack_entry, RebaseReason::Ambiguity);
+            if let Some(info) = D::is_ambiguous_result(result) {
+                self.rebase_provisional_cache_entries(
+                    cx,
+                    &stack_entry,
+                    RebaseReason::Ambiguity(info),
+                );
                 return EvaluationResult::finalize(stack_entry, encountered_overflow, result);
             };