Pass list of defineable opaque types into canonical queries

Author: oli-obk

compiler/rustc_borrowck/src/region_infer/opaque_types.rs

@@ -146,6 +146,17 @@ 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

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_use_anchor,
             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_anchor: infcx.map(|i| i.defining_use_anchor).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_anchor: base.defining_anchor,
+        }
     }
 
     /// Creates a canonical variable replacing `kind` from the input,

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

@@ -22,6 +22,7 @@ use rustc_index::Idx;
 use rustc_index::IndexVec;
 use rustc_middle::arena::ArenaAllocatable;
 use rustc_middle::mir::ConstraintCategory;
+use rustc_middle::traits::DefiningAnchor;
 use rustc_middle::ty::fold::TypeFoldable;
 use rustc_middle::ty::{self, BoundVar, Ty, TyCtxt};
 use rustc_middle::ty::{GenericArg, GenericArgKind};
@@ -163,6 +164,9 @@ impl<'tcx> InferCtxt<'tcx> {
     }
 
     fn take_opaque_types_for_query_response(&self) -> Vec<(ty::OpaqueTypeKey<'tcx>, Ty<'tcx>)> {
+        if self.defining_use_anchor == DefiningAnchor::Error {
+            return vec![];
+        }
         self.take_opaque_types().into_iter().map(|(k, v)| (k, v.hidden_type.ty)).collect()
     }
 

compiler/rustc_infer/src/infer/mod.rs

@@ -242,13 +242,7 @@ 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.
+    /// The `DefIds` of the opaque types that may have their hidden types constrained.
     ///
     /// Its default value is `DefiningAnchor::Error`, this way it is easier to catch errors that
     /// might come up during inference or typeck.
@@ -399,6 +393,10 @@ 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_anchor(&self) -> DefiningAnchor<'tcx> {
+        self.defining_use_anchor
+    }
 }
 
 /// See the `error_reporting` module for more details.
@@ -677,14 +675,14 @@ 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_opaque_type_inference(canonical.defining_anchor).build();
         let (value, args) = infcx.instantiate_canonical_with_fresh_inference_vars(span, canonical);
         (infcx, value, args)
     }

compiler/rustc_infer/src/infer/opaque_types.rs

@@ -149,7 +149,6 @@ impl<'tcx> InferCtxt<'tcx> {
                             return None;
                         }
                     }
-                    DefiningAnchor::Bubble => {}
                     DefiningAnchor::Error => {
                         return None;
                     }
@@ -379,7 +378,7 @@ impl<'tcx> InferCtxt<'tcx> {
     #[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 | DefiningAnchor::Error => return None,
+            DefiningAnchor::Error => return None,
             DefiningAnchor::Bind(bind) => bind,
         };
 

compiler/rustc_middle/src/infer/canonical.rs

@@ -33,6 +33,7 @@ use std::ops::Index;
 
 use crate::infer::MemberConstraint;
 use crate::mir::ConstraintCategory;
+use crate::traits::DefiningAnchor;
 use crate::ty::GenericArg;
 use crate::ty::{self, BoundVar, List, Region, Ty, TyCtxt, TypeFlags, TypeVisitableExt};
 
@@ -153,11 +154,6 @@ pub struct QueryResponse<'tcx, R> {
     pub var_values: CanonicalVarValues<'tcx>,
     pub region_constraints: QueryRegionConstraints<'tcx>,
     pub certainty: Certainty,
-    /// List of opaque types which we tried to compare to another type.
-    /// Inside the query we don't know yet whether the opaque type actually
-    /// should get its hidden type inferred. So we bubble the opaque type
-    /// and the type it was compared against upwards and let the query caller
-    /// handle it.
     pub opaque_types: Vec<(ty::OpaqueTypeKey<'tcx>, Ty<'tcx>)>,
     pub value: R,
 }
@@ -316,6 +312,7 @@ impl<'tcx> CanonicalParamEnvCache<'tcx> {
         &self,
         tcx: TyCtxt<'tcx>,
         key: ty::ParamEnv<'tcx>,
+        defining_anchor: DefiningAnchor<'tcx>,
         state: &mut OriginalQueryValues<'tcx>,
         canonicalize_op: fn(
             TyCtxt<'tcx>,
@@ -330,6 +327,7 @@ impl<'tcx> CanonicalParamEnvCache<'tcx> {
                 max_universe: ty::UniverseIndex::ROOT,
                 variables: List::empty(),
                 value: key,
+                defining_anchor,
             };
         }
 
@@ -344,7 +342,8 @@ impl<'tcx> CanonicalParamEnvCache<'tcx> {
                 *canonical
             }
             Entry::Vacant(e) => {
-                let canonical = canonicalize_op(tcx, key, state);
+                let mut canonical = canonicalize_op(tcx, key, state);
+                canonical.defining_anchor = defining_anchor;
                 let OriginalQueryValues { var_values, universe_map } = state;
                 assert_eq!(universe_map.len(), 1);
                 e.insert((canonical, tcx.arena.alloc_slice(var_values)));

compiler/rustc_middle/src/query/plumbing.rs

@@ -340,10 +340,10 @@ macro_rules! define_callbacks {
                     <$($K)* as keys::Key>::CacheSelector as CacheSelector<'tcx, Erase<$V>>
                 >::Cache;
 
-                // Ensure that keys grow no larger than 64 bytes
+                // Ensure that keys grow no larger than 72 bytes
                 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
                 const _: () = {
-                    if mem::size_of::<Key<'static>>() > 64 {
+                    if mem::size_of::<Key<'static>>() > 72 {
                         panic!("{}", concat!(
                             "the query `",
                             stringify!($name),
@@ -354,10 +354,10 @@ macro_rules! define_callbacks {
                     }
                 };
 
-                // Ensure that values grow no larger than 64 bytes
+                // Ensure that values grow no larger than 72 bytes
                 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
                 const _: () = {
-                    if mem::size_of::<Value<'static>>() > 64 {
+                    if mem::size_of::<Value<'static>>() > 72 {
                         panic!("{}", concat!(
                             "the query `",
                             stringify!($name),

compiler/rustc_middle/src/traits/mod.rs

@@ -1001,21 +1001,15 @@ pub enum CodegenObligationError {
 /// opaques are replaced with inference vars eagerly in the old solver (e.g.
 /// in projection, and in the signature during function type-checking).
 #[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, HashStable, TypeFoldable, TypeVisitable)]
+#[derive(Default, TyEncodable, TyDecodable)]
 pub enum DefiningAnchor<'tcx> {
     /// Define opaques which are in-scope of the current item being analyzed.
     /// Also, eagerly replace these opaque types in `replace_opaque_types_with_inference_vars`.
     Bind(&'tcx ty::List<LocalDefId>),
-    /// In contexts where we don't currently know what opaques are allowed to be
-    /// defined, such as (old solver) canonical queries, we will simply allow
-    /// opaques to be defined, but "bubble" them up in the canonical response or
-    /// otherwise treat them to be handled later.
-    ///
-    /// We do not eagerly replace opaque types in `replace_opaque_types_with_inference_vars`,
-    /// which may affect what predicates pass and fail in the old trait solver.
-    Bubble,
     /// Do not allow any opaques to be defined. This is used to catch type mismatch
     /// errors when handling opaque types, and also should be used when we would
     /// otherwise reveal opaques (such as [`Reveal::All`] reveal mode).
+    #[default]
     Error,
 }
 

compiler/rustc_middle/src/traits/solve.rs

@@ -4,7 +4,7 @@ use rustc_span::def_id::DefId;
 
 use crate::infer::canonical::{CanonicalVarValues, QueryRegionConstraints};
 use crate::traits::query::NoSolution;
-use crate::traits::{Canonical, DefiningAnchor};
+use crate::traits::Canonical;
 use crate::ty::{
     self, FallibleTypeFolder, ToPredicate, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeVisitable,
     TypeVisitor,
@@ -114,7 +114,6 @@ impl MaybeCause {
 #[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, HashStable, TypeFoldable, TypeVisitable)]
 pub struct QueryInput<'tcx, T> {
     pub goal: Goal<'tcx, T>,
-    pub anchor: DefiningAnchor<'tcx>,
     pub predefined_opaques_in_body: PredefinedOpaques<'tcx>,
 }
 

compiler/rustc_middle/src/ty/context.rs

@@ -80,6 +80,7 @@ use std::ops::{Bound, Deref};
 #[allow(rustc::usage_of_ty_tykind)]
 impl<'tcx> Interner for TyCtxt<'tcx> {
     type DefId = DefId;
+    type DefiningAnchor = traits::DefiningAnchor<'tcx>;
     type AdtDef = ty::AdtDef<'tcx>;
     type GenericArgs = ty::GenericArgsRef<'tcx>;
     type GenericArg = ty::GenericArg<'tcx>;