Rollup merge of rust-lang#136073 - compiler-errors:recursive-coro-always, r=oli-obk

Always compute coroutine layout for eagerly emitting recursive layout errors

Detect recursive coroutine layouts even if we don't detect opaque type recursion in the new solver. This is for two reasons:
1. It helps us detect (bad) recursive async function calls in the new solver, which due to its approach to normalization causes us to not detect this via a recursive RPIT (since the opaques are more eagerly revealed in the opaque body).
    * Fixes rust-lang/trait-system-refactor-initiative#137.
2. It helps us detect (bad) recursive async functions behind AFITs. See the AFIT test that changed for the old solver too.
3. It also greatly simplifies the recursive impl trait check, since I can remove some jankness around how it handles coroutines.

Author: matthiaskrgr

Diff for: 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 for: 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().layout_of(
+                    ty::TypingEnv::post_analysis(tcx, def_id.to_def_id())
+                        .as_query_input(tcx.type_of(def_id).instantiate_identity()),
+                );
             }
         });
     });

Diff for: 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)
 }

Diff for: tests/ui/async-await/in-trait/indirect-recursion-issue-112047.rs

@@ -1,8 +1,5 @@
 //@ edition: 2021
 
-// Test doesn't fail until monomorphization time, unfortunately.
-//@ build-fail
-
 fn main() {
     let _ = async {
         A.first().await.second().await;

Diff for: tests/ui/async-await/in-trait/indirect-recursion-issue-112047.stderr

@@ -1,5 +1,5 @@
 error[E0733]: recursion in an async fn requires boxing
-  --> $DIR/indirect-recursion-issue-112047.rs:34:5
+  --> $DIR/indirect-recursion-issue-112047.rs:31:5
    |
 LL |     async fn second(self) {
    |     ^^^^^^^^^^^^^^^^^^^^^

Diff for: tests/ui/force-inlining/deny-async.rs

@@ -1,6 +1,6 @@
-//@ check-fail
 //@ compile-flags: --crate-type=lib
 //@ edition: 2021
+
 #![allow(internal_features)]
 #![feature(rustc_attrs)]
 
@@ -20,5 +20,7 @@ pub fn callee_justified() {
 
 async fn async_caller() {
     callee();
+    //~^ ERROR `callee` could not be inlined
     callee_justified();
+    //~^ ERROR `callee_justified` could not be inlined
 }

Diff for: tests/ui/force-inlining/deny-async.stderr

@@ -20,5 +20,22 @@ LL | pub fn callee_justified() {
    |
    = note: incompatible due to: #[rustc_no_mir_inline]
 
-error: aborting due to 2 previous errors
+error: `callee` could not be inlined into `async_caller::{closure#0}` but is required to be inlined
+  --> $DIR/deny-async.rs:22:5
+   |
+LL |     callee();
+   |     ^^^^^^^^ ...`callee` called here
+   |
+   = note: could not be inlined due to: #[rustc_no_mir_inline]
+
+error: `callee_justified` could not be inlined into `async_caller::{closure#0}` but is required to be inlined
+  --> $DIR/deny-async.rs:24:5
+   |
+LL |     callee_justified();
+   |     ^^^^^^^^^^^^^^^^^^ ...`callee_justified` called here
+   |
+   = note: could not be inlined due to: #[rustc_no_mir_inline]
+   = note: `callee_justified` is required to be inlined to: the test requires it
+
+error: aborting due to 4 previous errors
 

Diff for: tests/ui/impl-trait/recursive-coroutine-indirect.current.stderr

@@ -1,5 +1,5 @@
 error[E0733]: recursion in a coroutine requires boxing
-  --> $DIR/recursive-coroutine-indirect.rs:11:18
+  --> $DIR/recursive-coroutine-indirect.rs:8:18
    |
 LL |     #[coroutine] move || {
    |                  ^^^^^^^

Diff for: tests/ui/impl-trait/recursive-coroutine-indirect.next.stderr

@@ -1,5 +1,5 @@
 error[E0733]: recursion in a coroutine requires boxing
-  --> $DIR/recursive-coroutine-indirect.rs:11:18
+  --> $DIR/recursive-coroutine-indirect.rs:8:18
    |
 LL |     #[coroutine] move || {
    |                  ^^^^^^^

Diff for: tests/ui/impl-trait/recursive-coroutine-indirect.rs

@@ -2,9 +2,6 @@
 //@ ignore-compare-mode-next-solver (explicit revisions)
 //@[next] compile-flags: -Znext-solver
 
-//@[next] build-fail
-// Deeply normalizing writeback results of opaques makes this into a post-mono error :(
-
 #![feature(coroutines)]
 #![allow(unconditional_recursion)]
 fn coroutine_hold() -> impl Sized {

Diff for: tests/ui/type-alias-impl-trait/indirect-recursion-issue-112047.rs

@@ -1,5 +1,4 @@
 //@ edition: 2021
-//@ build-fail
 
 #![feature(impl_trait_in_assoc_type)]
 

Diff for: tests/ui/type-alias-impl-trait/indirect-recursion-issue-112047.stderr

@@ -1,11 +1,11 @@
 error[E0733]: recursion in an async block requires boxing
-  --> $DIR/indirect-recursion-issue-112047.rs:22:9
+  --> $DIR/indirect-recursion-issue-112047.rs:21:9
    |
 LL |         async move { recur(self).await; }
    |         ^^^^^^^^^^   ----------------- recursive call here
    |
 note: which leads to this async fn
-  --> $DIR/indirect-recursion-issue-112047.rs:14:1
+  --> $DIR/indirect-recursion-issue-112047.rs:13:1
    |
 LL | async fn recur(t: impl Recur) {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^