Review

Author: compiler-errors

compiler/rustc_next_trait_solver/src/solve/trait_goals.rs

@@ -208,20 +208,9 @@ where
             }
         }
 
-        // TODO:
-        if let ty::CoroutineWitness(def_id, _) = goal.predicate.self_ty().kind() {
-            match ecx.typing_mode() {
-                TypingMode::Analysis { stalled_generators, defining_opaque_types: _ } => {
-                    if def_id.as_local().is_some_and(|def_id| stalled_generators.contains(&def_id))
-                    {
-                        return ecx.forced_ambiguity(MaybeCause::Ambiguity);
-                    }
-                }
-                TypingMode::Coherence
-                | TypingMode::PostAnalysis
-                | TypingMode::Borrowck { defining_opaque_types: _ }
-                | TypingMode::PostBorrowckAnalysis { defined_opaque_types: _ } => {}
-            }
+        // We need to make sure to stall any coroutines we are inferring to avoid query cycles.
+        if let Some(cand) = ecx.try_stall_coroutine_witness(goal.predicate.self_ty()) {
+            return cand;
         }
 
         ecx.probe_and_evaluate_goal_for_constituent_tys(
@@ -275,20 +264,9 @@ where
             return Err(NoSolution);
         }
 
-        // TODO:
-        if let ty::CoroutineWitness(def_id, _) = goal.predicate.self_ty().kind() {
-            match ecx.typing_mode() {
-                TypingMode::Analysis { stalled_generators, defining_opaque_types: _ } => {
-                    if def_id.as_local().is_some_and(|def_id| stalled_generators.contains(&def_id))
-                    {
-                        return ecx.forced_ambiguity(MaybeCause::Ambiguity);
-                    }
-                }
-                TypingMode::Coherence
-                | TypingMode::PostAnalysis
-                | TypingMode::Borrowck { defining_opaque_types: _ }
-                | TypingMode::PostBorrowckAnalysis { defined_opaque_types: _ } => {}
-            }
+        // We need to make sure to stall any coroutines we are inferring to avoid query cycles.
+        if let Some(cand) = ecx.try_stall_coroutine_witness(goal.predicate.self_ty()) {
+            return cand;
         }
 
         ecx.probe_and_evaluate_goal_for_constituent_tys(
@@ -1400,4 +1378,26 @@ where
         let candidates = self.assemble_and_evaluate_candidates(goal, AssembleCandidatesFrom::All);
         self.merge_trait_candidates(goal, candidates)
     }
+
+    fn try_stall_coroutine_witness(
+        &mut self,
+        self_ty: I::Ty,
+    ) -> Option<Result<Candidate<I>, NoSolution>> {
+        if let ty::CoroutineWitness(def_id, _) = self_ty.kind() {
+            match self.typing_mode() {
+                TypingMode::Analysis { stalled_generators, defining_opaque_types: _ } => {
+                    if def_id.as_local().is_some_and(|def_id| stalled_generators.contains(&def_id))
+                    {
+                        return Some(self.forced_ambiguity(MaybeCause::Ambiguity));
+                    }
+                }
+                TypingMode::Coherence
+                | TypingMode::PostAnalysis
+                | TypingMode::Borrowck { defining_opaque_types: _ }
+                | TypingMode::PostBorrowckAnalysis { defined_opaque_types: _ } => {}
+            }
+        }
+
+        None
+    }
 }

compiler/rustc_trait_selection/src/solve/fulfill.rs

@@ -14,6 +14,7 @@ use rustc_middle::ty::{
 };
 use rustc_next_trait_solver::solve::{GenerateProofTree, HasChanged, SolverDelegateEvalExt as _};
 use rustc_span::Span;
+use rustc_type_ir::data_structures::DelayedSet;
 use tracing::instrument;
 
 use self::derive_errors::*;
@@ -236,7 +237,11 @@ where
                 infcx
                     .visit_proof_tree(
                         obl.as_goal(),
-                        &mut StalledOnCoroutines { stalled_generators, span: obl.cause.span },
+                        &mut StalledOnCoroutines {
+                            stalled_generators,
+                            span: obl.cause.span,
+                            cache: Default::default(),
+                        },
                     )
                     .is_break()
             })
@@ -247,7 +252,7 @@ where
 struct StalledOnCoroutines<'tcx> {
     stalled_generators: &'tcx ty::List<LocalDefId>,
     span: Span,
-    // TODO: Cache
+    cache: DelayedSet<Ty<'tcx>>,
 }
 
 impl<'tcx> inspect::ProofTreeVisitor<'tcx> for StalledOnCoroutines<'tcx> {
@@ -272,6 +277,10 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for StalledOnCoroutines<'tcx> {
     type Result = ControlFlow<()>;
 
     fn visit_ty(&mut self, ty: Ty<'tcx>) -> Self::Result {
+        if self.cache.insert(ty) {
+            return ControlFlow::Continue(());
+        }
+
         if let ty::CoroutineWitness(def_id, _) = *ty.kind()
             && def_id.as_local().is_some_and(|def_id| self.stalled_generators.contains(&def_id))
         {

compiler/rustc_trait_selection/src/solve/normalize.rs

@@ -60,7 +60,8 @@ where
 /// entered before passing `value` to the function. This is currently needed for
 /// `normalize_erasing_regions`, which skips binders as it walks through a type.
 ///
-/// TODO: doc
+/// This returns a set of stalled obligations if the typing mode of the underlying infcx
+/// has any stalled coroutine def ids.
 pub fn deeply_normalize_with_skipped_universes_and_ambiguous_goals<'tcx, T, E>(
     at: At<'_, 'tcx>,
     value: T,

compiler/rustc_ty_utils/src/lib.rs

@@ -32,6 +32,7 @@ mod needs_drop;
 mod opaque_types;
 mod representability;
 pub mod sig_types;
+mod stalled_generators;
 mod structural_match;
 mod ty;
 
@@ -50,4 +51,5 @@ pub fn provide(providers: &mut Providers) {
     ty::provide(providers);
     instance::provide(providers);
     structural_match::provide(providers);
+    stalled_generators::provide(providers);
 }

compiler/rustc_ty_utils/src/opaque_types.rs

@@ -1,7 +1,6 @@
 use rustc_data_structures::fx::FxHashSet;
-use rustc_hir as hir;
 use rustc_hir::def::DefKind;
-use rustc_hir::def_id::{DefId, LocalDefId};
+use rustc_hir::def_id::LocalDefId;
 use rustc_hir::intravisit;
 use rustc_hir::intravisit::Visitor;
 use rustc_middle::query::Providers;
@@ -356,51 +355,6 @@ fn opaque_types_defined_by<'tcx>(
     tcx.mk_local_def_ids(&collector.opaques)
 }
 
-// TODO: Move this out of `opaque_types`
-fn stalled_generators_within<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    item: LocalDefId,
-) -> &'tcx ty::List<LocalDefId> {
-    if !tcx.next_trait_solver_globally() {
-        return ty::List::empty();
-    }
-
-    let body = tcx.hir_body_owned_by(item);
-    let mut collector =
-        StalledGeneratorVisitor { tcx, root_def_id: item.to_def_id(), stalled_coroutines: vec![] };
-    collector.visit_body(body);
-    tcx.mk_local_def_ids(&collector.stalled_coroutines)
-}
-
-struct StalledGeneratorVisitor<'tcx> {
-    tcx: TyCtxt<'tcx>,
-    root_def_id: DefId,
-    stalled_coroutines: Vec<LocalDefId>,
-}
-
-impl<'tcx> Visitor<'tcx> for StalledGeneratorVisitor<'tcx> {
-    fn visit_nested_body(&mut self, id: hir::BodyId) {
-        if self.tcx.typeck_root_def_id(self.tcx.hir_body_owner_def_id(id).to_def_id())
-            == self.root_def_id
-        {
-            let body = self.tcx.hir_body(id);
-            self.visit_body(body);
-        }
-    }
-
-    fn visit_expr(&mut self, ex: &'tcx hir::Expr<'tcx>) {
-        if let hir::ExprKind::Closure(&hir::Closure {
-            def_id,
-            kind: hir::ClosureKind::Coroutine(_),
-            ..
-        }) = ex.kind
-        {
-            self.stalled_coroutines.push(def_id);
-        }
-        intravisit::walk_expr(self, ex);
-    }
-}
-
 pub(super) fn provide(providers: &mut Providers) {
-    *providers = Providers { opaque_types_defined_by, stalled_generators_within, ..*providers };
+    *providers = Providers { opaque_types_defined_by, ..*providers };
 }