Eagerly detect coroutine recursion pre-mono when possible

3 files changed, 11 insertions, 81 deletions

diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index 6c534d58a7d..9ed56d7bde5 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -19,7 +19,7 @@ use rustc_middle::span_bug;
 use rustc_middle::ty::error::TypeErrorToStringExt;
 use rustc_middle::ty::fold::{BottomUpFolder, fold_regions};
 use rustc_middle::ty::layout::{LayoutError, MAX_SIMD_LANES};
-use rustc_middle::ty::util::{Discr, InspectCoroutineFields, IntTypeExt};
+use rustc_middle::ty::util::{Discr, IntTypeExt};
 use rustc_middle::ty::{
     AdtDef, GenericArgKind, RegionKind, TypeSuperVisitable, TypeVisitable, TypeVisitableExt,
 };
@@ -257,30 +257,9 @@ pub(super) fn check_opaque_for_cycles<'tcx>(
 
     // First, try to look at any opaque expansion cycles, considering coroutine fields
     // (even though these aren't necessarily true errors).
-    if tcx
-        .try_expand_impl_trait_type(def_id.to_def_id(), args, InspectCoroutineFields::Yes)
-        .is_err()
-    {
-        // Look for true opaque expansion cycles, but ignore coroutines.
-        // This will give us any true errors. Coroutines are only problematic
-        // if they cause layout computation errors.
-        if tcx
-            .try_expand_impl_trait_type(def_id.to_def_id(), args, InspectCoroutineFields::No)
-            .is_err()
-        {
-            let reported = opaque_type_cycle_error(tcx, def_id);
-            return Err(reported);
-        }
-
-        // And also look for cycle errors in the layout of coroutines.
-        if let Err(&LayoutError::Cycle(guar)) =
-            tcx.layout_of(
-                ty::TypingEnv::post_analysis(tcx, def_id.to_def_id())
-                    .as_query_input(Ty::new_opaque(tcx, def_id.to_def_id(), args)),
-            )
-        {
-            return Err(guar);
-        }
+    if tcx.try_expand_impl_trait_type(def_id.to_def_id(), args).is_err() {
+        let reported = opaque_type_cycle_error(tcx, def_id);
+        return Err(reported);
     }
 
     Ok(())
diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
index 8a121c5a865..9c5f30012e7 100644
--- a/compiler/rustc_interface/src/passes.rs
+++ b/compiler/rustc_interface/src/passes.rs
@@ -909,6 +909,11 @@ fn run_required_analyses(tcx: TyCtxt<'_>) {
                 tcx.ensure_ok().check_coroutine_obligations(
                     tcx.typeck_root_def_id(def_id.to_def_id()).expect_local(),
                 );
+                // Eagerly check the unsubstituted layout for cycles.
+                tcx.ensure_ok().layout_of(
+                    ty::TypingEnv::post_analysis(tcx, def_id.to_def_id())
+                        .as_query_input(tcx.type_of(def_id).instantiate_identity()),
+                );
             }
         });
     });
diff --git a/compiler/rustc_middle/src/ty/util.rs b/compiler/rustc_middle/src/ty/util.rs
index 318bd0c7ec0..6fd0fb9a0a4 100644
--- a/compiler/rustc_middle/src/ty/util.rs
+++ b/compiler/rustc_middle/src/ty/util.rs
@@ -777,7 +777,6 @@ impl<'tcx> TyCtxt<'tcx> {
         self,
         def_id: DefId,
         args: GenericArgsRef<'tcx>,
-        inspect_coroutine_fields: InspectCoroutineFields,
     ) -> Result<Ty<'tcx>, Ty<'tcx>> {
         let mut visitor = OpaqueTypeExpander {
             seen_opaque_tys: FxHashSet::default(),
@@ -786,9 +785,7 @@ impl<'tcx> TyCtxt<'tcx> {
             found_recursion: false,
             found_any_recursion: false,
             check_recursion: true,
-            expand_coroutines: true,
             tcx: self,
-            inspect_coroutine_fields,
         };
 
         let expanded_type = visitor.expand_opaque_ty(def_id, args).unwrap();
@@ -965,19 +962,11 @@ struct OpaqueTypeExpander<'tcx> {
     primary_def_id: Option<DefId>,
     found_recursion: bool,
     found_any_recursion: bool,
-    expand_coroutines: bool,
     /// Whether or not to check for recursive opaque types.
     /// This is `true` when we're explicitly checking for opaque type
     /// recursion, and 'false' otherwise to avoid unnecessary work.
     check_recursion: bool,
     tcx: TyCtxt<'tcx>,
-    inspect_coroutine_fields: InspectCoroutineFields,
-}
-
-#[derive(Copy, Clone, PartialEq, Eq, Debug)]
-pub enum InspectCoroutineFields {
-    No,
-    Yes,
 }
 
 impl<'tcx> OpaqueTypeExpander<'tcx> {
@@ -1009,41 +998,6 @@ impl<'tcx> OpaqueTypeExpander<'tcx> {
             None
         }
     }
-
-    fn expand_coroutine(&mut self, def_id: DefId, args: GenericArgsRef<'tcx>) -> Option<Ty<'tcx>> {
-        if self.found_any_recursion {
-            return None;
-        }
-        let args = args.fold_with(self);
-        if !self.check_recursion || self.seen_opaque_tys.insert(def_id) {
-            let expanded_ty = match self.expanded_cache.get(&(def_id, args)) {
-                Some(expanded_ty) => *expanded_ty,
-                None => {
-                    if matches!(self.inspect_coroutine_fields, InspectCoroutineFields::Yes) {
-                        for bty in self.tcx.bound_coroutine_hidden_types(def_id) {
-                            let hidden_ty = self.tcx.instantiate_bound_regions_with_erased(
-                                bty.instantiate(self.tcx, args),
-                            );
-                            self.fold_ty(hidden_ty);
-                        }
-                    }
-                    let expanded_ty = Ty::new_coroutine_witness(self.tcx, def_id, args);
-                    self.expanded_cache.insert((def_id, args), expanded_ty);
-                    expanded_ty
-                }
-            };
-            if self.check_recursion {
-                self.seen_opaque_tys.remove(&def_id);
-            }
-            Some(expanded_ty)
-        } else {
-            // If another opaque type that we contain is recursive, then it
-            // will report the error, so we don't have to.
-            self.found_any_recursion = true;
-            self.found_recursion = def_id == *self.primary_def_id.as_ref().unwrap();
-            None
-        }
-    }
 }
 
 impl<'tcx> TypeFolder<TyCtxt<'tcx>> for OpaqueTypeExpander<'tcx> {
@@ -1052,19 +1006,13 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for OpaqueTypeExpander<'tcx> {
     }
 
     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
-        let mut t = if let ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) = *t.kind() {
+        if let ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) = *t.kind() {
             self.expand_opaque_ty(def_id, args).unwrap_or(t)
-        } else if t.has_opaque_types() || t.has_coroutines() {
+        } else if t.has_opaque_types() {
             t.super_fold_with(self)
         } else {
             t
-        };
-        if self.expand_coroutines {
-            if let ty::CoroutineWitness(def_id, args) = *t.kind() {
-                t = self.expand_coroutine(def_id, args).unwrap_or(t);
-            }
         }
-        t
     }
 
     fn fold_predicate(&mut self, p: ty::Predicate<'tcx>) -> ty::Predicate<'tcx> {
@@ -1753,9 +1701,7 @@ pub fn reveal_opaque_types_in_bounds<'tcx>(
         found_recursion: false,
         found_any_recursion: false,
         check_recursion: false,
-        expand_coroutines: false,
         tcx,
-        inspect_coroutine_fields: InspectCoroutineFields::No,
     };
     val.fold_with(&mut visitor)
 }