Auto merge of rust-lang#122077 - oli-obk:eager_opaque_checks4, r=<try>

Pass list of defineable opaque types into canonical queries

This eliminates `DefiningAnchor::Bubble` for good and brings the old solver closer to the new one wrt cycles and nested obligations. At that point the difference between `DefiningAnchor::Bind([])` and `DefiningAnchor::Error` was academic. We only used the difference for some sanity checks, which actually had to be worked around in places, so I just removed `DefiningAnchor` entirely and just stored the list of opaques that may be defined.

fixes rust-lang#108498

* [ ] run crater

Author: bors

compiler/rustc_borrowck/src/consumers.rs

@@ -4,7 +4,6 @@ use rustc_hir::def_id::LocalDefId;
 use rustc_index::{IndexSlice, IndexVec};
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_middle::mir::{Body, Promoted};
-use rustc_middle::traits::DefiningAnchor;
 use rustc_middle::ty::TyCtxt;
 use std::rc::Rc;
 
@@ -106,7 +105,7 @@ pub fn get_body_with_borrowck_facts(
     options: ConsumerOptions,
 ) -> BodyWithBorrowckFacts<'_> {
     let (input_body, promoted) = tcx.mir_promoted(def);
-    let infcx = tcx.infer_ctxt().with_opaque_type_inference(DefiningAnchor::bind(tcx, def)).build();
+    let infcx = tcx.infer_ctxt().with_opaque_type_inference(def).build();
     let input_body: &Body<'_> = &input_body.borrow();
     let promoted: &IndexSlice<_, _> = &promoted.borrow();
     *super::do_mir_borrowck(&infcx, input_body, promoted, Some(options)).1.unwrap()

compiler/rustc_borrowck/src/lib.rs

@@ -32,7 +32,6 @@ use rustc_infer::infer::{
 use rustc_middle::mir::tcx::PlaceTy;
 use rustc_middle::mir::*;
 use rustc_middle::query::Providers;
-use rustc_middle::traits::DefiningAnchor;
 use rustc_middle::ty::{self, ParamEnv, RegionVid, TyCtxt};
 use rustc_session::lint::builtin::UNUSED_MUT;
 use rustc_span::{Span, Symbol};
@@ -126,7 +125,7 @@ fn mir_borrowck(tcx: TyCtxt<'_>, def: LocalDefId) -> &BorrowCheckResult<'_> {
         return tcx.arena.alloc(result);
     }
 
-    let infcx = tcx.infer_ctxt().with_opaque_type_inference(DefiningAnchor::bind(tcx, def)).build();
+    let infcx = tcx.infer_ctxt().with_opaque_type_inference(def).build();
     let promoted: &IndexSlice<_, _> = &promoted.borrow();
     let opt_closure_req = do_mir_borrowck(&infcx, input_body, promoted, None).0;
     debug!("mir_borrowck done");

compiler/rustc_borrowck/src/region_infer/opaque_types.rs

@@ -7,7 +7,6 @@ use rustc_infer::infer::InferCtxt;
 use rustc_infer::infer::TyCtxtInferExt as _;
 use rustc_infer::traits::{Obligation, ObligationCause};
 use rustc_macros::extension;
-use rustc_middle::traits::DefiningAnchor;
 use rustc_middle::ty::visit::TypeVisitableExt;
 use rustc_middle::ty::{self, OpaqueHiddenType, OpaqueTypeKey, Ty, TyCtxt, TypeFoldable};
 use rustc_middle::ty::{GenericArgKind, GenericArgs};
@@ -146,6 +145,17 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                 opaque_type_key,
                 universal_concrete_type,
             );
+
+            // Sometimes, when the hidden type is an inference variable, it can happen that
+            // the hidden type becomes the opaque type itself. In this case, this was an opaque
+            // usage of the opaque type and we can ignore it. This check is mirrored in typeck's
+            // writeback.
+            if let ty::Alias(ty::Opaque, alias_ty) = universal_concrete_type.ty.kind()
+                && alias_ty.def_id == opaque_type_key.def_id.to_def_id()
+                && alias_ty.args == opaque_type_key.args
+            {
+                continue;
+            }
             // Sometimes two opaque types are the same only after we remap the generic parameters
             // back to the opaque type definition. E.g. we may have `OpaqueType<X, Y>` mapped to `(X, Y)`
             // and `OpaqueType<Y, X>` mapped to `(Y, X)`, and those are the same, but we only know that
@@ -311,13 +321,13 @@ fn check_opaque_type_well_formed<'tcx>(
         parent_def_id = tcx.local_parent(parent_def_id);
     }
 
-    // FIXME(-Znext-solver): We probably should use `DefiningAnchor::Bind(&[])`
+    // FIXME(-Znext-solver): We probably should use `&[]` instead of
     // and prepopulate this `InferCtxt` with known opaque values, rather than
-    // using the `Bind` anchor here. For now it's fine.
+    // allowing opaque types to be defined and checking them after the fact.
     let infcx = tcx
         .infer_ctxt()
         .with_next_trait_solver(next_trait_solver)
-        .with_opaque_type_inference(DefiningAnchor::bind(tcx, parent_def_id))
+        .with_opaque_type_inference(parent_def_id)
         .build();
     let ocx = ObligationCtxt::new(&infcx);
     let identity_args = GenericArgs::identity_for_item(tcx, def_id);

compiler/rustc_hir_analysis/src/check/check.rs

@@ -13,7 +13,7 @@ use rustc_infer::infer::{RegionVariableOrigin, TyCtxtInferExt};
 use rustc_infer::traits::{Obligation, TraitEngineExt as _};
 use rustc_lint_defs::builtin::REPR_TRANSPARENT_EXTERNAL_PRIVATE_FIELDS;
 use rustc_middle::middle::stability::EvalResult;
-use rustc_middle::traits::{DefiningAnchor, ObligationCauseCode};
+use rustc_middle::traits::ObligationCauseCode;
 use rustc_middle::ty::fold::BottomUpFolder;
 use rustc_middle::ty::layout::{LayoutError, MAX_SIMD_LANES};
 use rustc_middle::ty::util::{Discr, InspectCoroutineFields, IntTypeExt};
@@ -345,10 +345,7 @@ fn check_opaque_meets_bounds<'tcx>(
     };
     let param_env = tcx.param_env(defining_use_anchor);
 
-    let infcx = tcx
-        .infer_ctxt()
-        .with_opaque_type_inference(DefiningAnchor::bind(tcx, defining_use_anchor))
-        .build();
+    let infcx = tcx.infer_ctxt().with_opaque_type_inference(defining_use_anchor).build();
     let ocx = ObligationCtxt::new(&infcx);
 
     let args = match *origin {
@@ -1558,7 +1555,7 @@ pub(super) fn check_coroutine_obligations(
         .ignoring_regions()
         // Bind opaque types to type checking root, as they should have been checked by borrowck,
         // but may show up in some cases, like when (root) obligations are stalled in the new solver.
-        .with_opaque_type_inference(DefiningAnchor::bind(tcx, typeck.hir_owner.def_id))
+        .with_opaque_type_inference(typeck.hir_owner.def_id)
         .build();
 
     let mut fulfillment_cx = <dyn TraitEngine<'_>>::new(&infcx);

compiler/rustc_hir_typeck/src/inherited.rs

@@ -5,7 +5,6 @@ use rustc_hir as hir;
 use rustc_hir::def_id::LocalDefId;
 use rustc_hir::HirIdMap;
 use rustc_infer::infer::{InferCtxt, InferOk, TyCtxtInferExt};
-use rustc_middle::traits::DefiningAnchor;
 use rustc_middle::ty::visit::TypeVisitableExt;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_span::def_id::LocalDefIdMap;
@@ -76,11 +75,7 @@ impl<'tcx> Inherited<'tcx> {
     pub fn new(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Self {
         let hir_owner = tcx.local_def_id_to_hir_id(def_id).owner;
 
-        let infcx = tcx
-            .infer_ctxt()
-            .ignoring_regions()
-            .with_opaque_type_inference(DefiningAnchor::bind(tcx, def_id))
-            .build();
+        let infcx = tcx.infer_ctxt().ignoring_regions().with_opaque_type_inference(def_id).build();
         let typeck_results = RefCell::new(ty::TypeckResults::new(hir_owner));
 
         Inherited {

compiler/rustc_infer/src/infer/at.rs

@@ -75,7 +75,7 @@ impl<'tcx> InferCtxt<'tcx> {
     pub fn fork_with_intercrate(&self, intercrate: bool) -> Self {
         Self {
             tcx: self.tcx,
-            defining_use_anchor: self.defining_use_anchor,
+            defining_opaque_types: self.defining_opaque_types,
             considering_regions: self.considering_regions,
             skip_leak_check: self.skip_leak_check,
             inner: self.inner.clone(),

compiler/rustc_infer/src/infer/canonical/canonicalizer.rs

@@ -45,6 +45,7 @@ impl<'tcx> InferCtxt<'tcx> {
         let param_env = self.tcx.canonical_param_env_cache.get_or_insert(
             self.tcx,
             param_env,
+            self.defining_opaque_types,
             query_state,
             |tcx, param_env, query_state| {
                 // FIXME(#118965): We don't canonicalize the static lifetimes that appear in the
@@ -540,6 +541,7 @@ impl<'cx, 'tcx> Canonicalizer<'cx, 'tcx> {
             max_universe: ty::UniverseIndex::ROOT,
             variables: List::empty(),
             value: (),
+            defining_opaque_types: infcx.map(|i| i.defining_opaque_types).unwrap_or_default(),
         };
         Canonicalizer::canonicalize_with_base(
             base,
@@ -609,7 +611,12 @@ impl<'cx, 'tcx> Canonicalizer<'cx, 'tcx> {
             .max()
             .unwrap_or(ty::UniverseIndex::ROOT);
 
-        Canonical { max_universe, variables: canonical_variables, value: (base.value, out_value) }
+        Canonical {
+            max_universe,
+            variables: canonical_variables,
+            value: (base.value, out_value),
+            defining_opaque_types: base.defining_opaque_types,
+        }
     }
 
     /// Creates a canonical variable replacing `kind` from the input,

compiler/rustc_infer/src/infer/mod.rs

@@ -34,7 +34,7 @@ use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKin
 use rustc_middle::infer::unify_key::{ConstVidKey, EffectVidKey};
 use rustc_middle::mir::interpret::{ErrorHandled, EvalToValTreeResult};
 use rustc_middle::mir::ConstraintCategory;
-use rustc_middle::traits::{select, DefiningAnchor};
+use rustc_middle::traits::select;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
 use rustc_middle::ty::fold::BoundVarReplacerDelegate;
 use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
@@ -234,18 +234,8 @@ impl<'tcx> InferCtxtInner<'tcx> {
 pub struct InferCtxt<'tcx> {
     pub tcx: TyCtxt<'tcx>,
 
-    /// The `DefId` of the item in whose context we are performing inference or typeck.
-    /// It is used to check whether an opaque type use is a defining use.
-    ///
-    /// If it is `DefiningAnchor::Bubble`, we can't resolve opaque types here and need to bubble up
-    /// the obligation. This frequently happens for
-    /// short lived InferCtxt within queries. The opaque type obligations are forwarded
-    /// to the outside until the end up in an `InferCtxt` for typeck or borrowck.
-    ///
-    /// Its default value is `DefiningAnchor::Bind(&[])`, which means no opaque types may be defined.
-    /// This way it is easier to catch errors that
-    /// might come up during inference or typeck.
-    pub defining_use_anchor: DefiningAnchor<'tcx>,
+    /// The `DefIds` of the opaque types that may have their hidden types constrained.
+    pub defining_opaque_types: &'tcx ty::List<LocalDefId>,
 
     /// Whether this inference context should care about region obligations in
     /// the root universe. Most notably, this is used during hir typeck as region
@@ -392,6 +382,10 @@ impl<'tcx> ty::InferCtxtLike for InferCtxt<'tcx> {
     fn probe_ct_var(&self, vid: ConstVid) -> Option<ty::Const<'tcx>> {
         self.probe_const_var(vid).ok()
     }
+
+    fn defining_opaque_types(&self) -> &'tcx ty::List<LocalDefId> {
+        self.defining_opaque_types
+    }
 }
 
 /// See the `error_reporting` module for more details.
@@ -606,7 +600,7 @@ impl fmt::Display for FixupError {
 /// Used to configure inference contexts before their creation.
 pub struct InferCtxtBuilder<'tcx> {
     tcx: TyCtxt<'tcx>,
-    defining_use_anchor: DefiningAnchor<'tcx>,
+    defining_opaque_types: &'tcx ty::List<LocalDefId>,
     considering_regions: bool,
     skip_leak_check: bool,
     /// Whether we are in coherence mode.
@@ -621,7 +615,7 @@ impl<'tcx> TyCtxt<'tcx> {
     fn infer_ctxt(self) -> InferCtxtBuilder<'tcx> {
         InferCtxtBuilder {
             tcx: self,
-            defining_use_anchor: DefiningAnchor::Bind(ty::List::empty()),
+            defining_opaque_types: ty::List::empty(),
             considering_regions: true,
             skip_leak_check: false,
             intercrate: false,
@@ -637,8 +631,16 @@ impl<'tcx> InferCtxtBuilder<'tcx> {
     /// It is only meant to be called in two places, for typeck
     /// (via `Inherited::build`) and for the inference context used
     /// in mir borrowck.
-    pub fn with_opaque_type_inference(mut self, defining_use_anchor: DefiningAnchor<'tcx>) -> Self {
-        self.defining_use_anchor = defining_use_anchor;
+    pub fn with_opaque_type_inference(mut self, defining_anchor: LocalDefId) -> Self {
+        self.defining_opaque_types = self.tcx.opaque_types_defined_by(defining_anchor);
+        self
+    }
+
+    pub fn with_defining_opaque_types(
+        mut self,
+        defining_opaque_types: &'tcx ty::List<LocalDefId>,
+    ) -> Self {
+        self.defining_opaque_types = defining_opaque_types;
         self
     }
 
@@ -670,30 +672,30 @@ impl<'tcx> InferCtxtBuilder<'tcx> {
     /// the bound values in `C` to their instantiated values in `V`
     /// (in other words, `S(C) = V`).
     pub fn build_with_canonical<T>(
-        &mut self,
+        self,
         span: Span,
         canonical: &Canonical<'tcx, T>,
     ) -> (InferCtxt<'tcx>, T, CanonicalVarValues<'tcx>)
     where
         T: TypeFoldable<TyCtxt<'tcx>>,
     {
-        let infcx = self.build();
+        let infcx = self.with_defining_opaque_types(canonical.defining_opaque_types).build();
         let (value, args) = infcx.instantiate_canonical_with_fresh_inference_vars(span, canonical);
         (infcx, value, args)
     }
 
     pub fn build(&mut self) -> InferCtxt<'tcx> {
         let InferCtxtBuilder {
             tcx,
-            defining_use_anchor,
+            defining_opaque_types,
             considering_regions,
             skip_leak_check,
             intercrate,
             next_trait_solver,
         } = *self;
         InferCtxt {
             tcx,
-            defining_use_anchor,
+            defining_opaque_types,
             considering_regions,
             skip_leak_check,
             inner: RefCell::new(InferCtxtInner::new()),

compiler/rustc_infer/src/infer/opaque_types/mod.rs

@@ -8,7 +8,7 @@ use hir::OpaqueTyOrigin;
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::sync::Lrc;
 use rustc_hir as hir;
-use rustc_middle::traits::{DefiningAnchor, ObligationCause};
+use rustc_middle::traits::ObligationCause;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
 use rustc_middle::ty::fold::BottomUpFolder;
 use rustc_middle::ty::GenericArgKind;
@@ -109,48 +109,44 @@ impl<'tcx> InferCtxt<'tcx> {
                         b,
                     ));
                 }
-                match self.defining_use_anchor {
-                    DefiningAnchor::Bind(_) => {
-                        // Check that this is `impl Trait` type is
-                        // declared by `parent_def_id` -- i.e., one whose
-                        // value we are inferring. At present, this is
-                        // always true during the first phase of
-                        // type-check, but not always true later on during
-                        // NLL. Once we support named opaque types more fully,
-                        // this same scenario will be able to arise during all phases.
-                        //
-                        // Here is an example using type alias `impl Trait`
-                        // that indicates the distinction we are checking for:
-                        //
-                        // ```rust
-                        // mod a {
-                        //   pub type Foo = impl Iterator;
-                        //   pub fn make_foo() -> Foo { .. }
-                        // }
-                        //
-                        // mod b {
-                        //   fn foo() -> a::Foo { a::make_foo() }
-                        // }
-                        // ```
-                        //
-                        // Here, the return type of `foo` references an
-                        // `Opaque` indeed, but not one whose value is
-                        // presently being inferred. You can get into a
-                        // similar situation with closure return types
-                        // today:
-                        //
-                        // ```rust
-                        // fn foo() -> impl Iterator { .. }
-                        // fn bar() {
-                        //     let x = || foo(); // returns the Opaque assoc with `foo`
-                        // }
-                        // ```
-                        if self.opaque_type_origin(def_id).is_none() {
-                            return None;
-                        }
-                    }
-                    DefiningAnchor::Bubble => {}
+                // Check that this is `impl Trait` type is
+                // declared by `parent_def_id` -- i.e., one whose
+                // value we are inferring. At present, this is
+                // always true during the first phase of
+                // type-check, but not always true later on during
+                // NLL. Once we support named opaque types more fully,
+                // this same scenario will be able to arise during all phases.
+                //
+                // Here is an example using type alias `impl Trait`
+                // that indicates the distinction we are checking for:
+                //
+                // ```rust
+                // mod a {
+                //   pub type Foo = impl Iterator;
+                //   pub fn make_foo() -> Foo { .. }
+                // }
+                //
+                // mod b {
+                //   fn foo() -> a::Foo { a::make_foo() }
+                // }
+                // ```
+                //
+                // Here, the return type of `foo` references an
+                // `Opaque` indeed, but not one whose value is
+                // presently being inferred. You can get into a
+                // similar situation with closure return types
+                // today:
+                //
+                // ```rust
+                // fn foo() -> impl Iterator { .. }
+                // fn bar() {
+                //     let x = || foo(); // returns the Opaque assoc with `foo`
+                // }
+                // ```
+                if self.opaque_type_origin(def_id).is_none() {
+                    return None;
                 }
+
                 if let ty::Alias(ty::Opaque, ty::AliasTy { def_id: b_def_id, .. }) = *b.kind() {
                     // We could accept this, but there are various ways to handle this situation, and we don't
                     // want to make a decision on it right now. Likely this case is so super rare anyway, that
@@ -375,14 +371,9 @@ impl<'tcx> InferCtxt<'tcx> {
     /// in its defining scope.
     #[instrument(skip(self), level = "trace", ret)]
     pub fn opaque_type_origin(&self, def_id: LocalDefId) -> Option<OpaqueTyOrigin> {
-        let defined_opaque_types = match self.defining_use_anchor {
-            DefiningAnchor::Bubble => return None,
-            DefiningAnchor::Bind(bind) => bind,
-        };
-
         let origin = self.tcx.opaque_type_origin(def_id);
 
-        defined_opaque_types.contains(&def_id).then_some(origin)
+        self.defining_opaque_types.contains(&def_id).then_some(origin)
     }
 }