Intern external constraints in new solver

compiler/rustc_middle/src/arena.rs

@@ -112,6 +112,7 @@ macro_rules! arena_types {
 
             [decode] trait_impl_trait_tys: rustc_data_structures::fx::FxHashMap<rustc_hir::def_id::DefId, rustc_middle::ty::Ty<'tcx>>,
             [] bit_set_u32: rustc_index::bit_set::BitSet<u32>,
+            [] external_constraints: rustc_middle::traits::solve::ExternalConstraintsData<'tcx>,
         ]);
     )
 }

compiler/rustc_middle/src/traits/mod.rs

@@ -5,6 +5,7 @@
 mod chalk;
 pub mod query;
 pub mod select;
+pub mod solve;
 pub mod specialization_graph;
 mod structural_impls;
 pub mod util;

compiler/rustc_middle/src/traits/solve.rs

@@ -0,0 +1,55 @@
+use std::ops::ControlFlow;
+
+use rustc_data_structures::intern::Interned;
+
+use crate::ty::{FallibleTypeFolder, Ty, TypeFoldable, TypeFolder, TypeVisitable, TypeVisitor};
+
+#[derive(Debug, PartialEq, Eq, Copy, Clone, Hash)]
+pub struct ExternalConstraints<'tcx>(pub(crate) Interned<'tcx, ExternalConstraintsData<'tcx>>);
+
+impl<'tcx> std::ops::Deref for ExternalConstraints<'tcx> {
+    type Target = ExternalConstraintsData<'tcx>;
+
+    fn deref(&self) -> &Self::Target {
+        &*self.0
+    }
+}
+
+/// Additional constraints returned on success.
+#[derive(Debug, PartialEq, Eq, Clone, Hash, Default)]
+pub struct ExternalConstraintsData<'tcx> {
+    // FIXME: implement this.
+    pub regions: (),
+    pub opaque_types: Vec<(Ty<'tcx>, Ty<'tcx>)>,
+}
+
+impl<'tcx> TypeFoldable<'tcx> for ExternalConstraints<'tcx> {
+    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
+        Ok(FallibleTypeFolder::tcx(folder).intern_external_constraints(ExternalConstraintsData {
+            regions: (),
+            opaque_types: self
+                .opaque_types
+                .iter()
+                .map(|opaque| opaque.try_fold_with(folder))
+                .collect::<Result<_, F::Error>>()?,
+        }))
+    }
+
+    fn fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
+        TypeFolder::tcx(folder).intern_external_constraints(ExternalConstraintsData {
+            regions: (),
+            opaque_types: self.opaque_types.iter().map(|opaque| opaque.fold_with(folder)).collect(),
+        })
+    }
+}
+
+impl<'tcx> TypeVisitable<'tcx> for ExternalConstraints<'tcx> {
+    fn visit_with<V: TypeVisitor<'tcx>>(
+        &self,
+        visitor: &mut V,
+    ) -> std::ops::ControlFlow<V::BreakTy> {
+        self.regions.visit_with(visitor)?;
+        self.opaque_types.visit_with(visitor)?;
+        ControlFlow::Continue(())
+    }
+}

compiler/rustc_middle/src/ty/context.rs

@@ -17,6 +17,7 @@ use crate::mir::{
 };
 use crate::thir::Thir;
 use crate::traits;
+use crate::traits::solve::{ExternalConstraints, ExternalConstraintsData};
 use crate::ty::query::{self, TyCtxtAt};
 use crate::ty::{
     self, AdtDef, AdtDefData, AdtKind, Binder, Const, ConstData, DefIdTree, FloatTy, FloatVar,
@@ -148,6 +149,7 @@ pub struct CtxtInterners<'tcx> {
     bound_variable_kinds: InternedSet<'tcx, List<ty::BoundVariableKind>>,
     layout: InternedSet<'tcx, LayoutS<VariantIdx>>,
     adt_def: InternedSet<'tcx, AdtDefData>,
+    external_constraints: InternedSet<'tcx, ExternalConstraintsData<'tcx>>,
 }
 
 impl<'tcx> CtxtInterners<'tcx> {
@@ -169,6 +171,7 @@ impl<'tcx> CtxtInterners<'tcx> {
             bound_variable_kinds: Default::default(),
             layout: Default::default(),
             adt_def: Default::default(),
+            external_constraints: Default::default(),
         }
     }
 
@@ -1449,6 +1452,7 @@ direct_interners! {
     const_allocation: intern_const_alloc(Allocation): ConstAllocation -> ConstAllocation<'tcx>,
     layout: intern_layout(LayoutS<VariantIdx>): Layout -> Layout<'tcx>,
     adt_def: intern_adt_def(AdtDefData): AdtDef -> AdtDef<'tcx>,
+    external_constraints: intern_external_constraints(ExternalConstraintsData<'tcx>): ExternalConstraints -> ExternalConstraints<'tcx>,
 }
 
 macro_rules! slice_interners {

compiler/rustc_trait_selection/src/solve/mod.rs

@@ -24,7 +24,8 @@ use rustc_infer::infer::{InferCtxt, InferOk, TyCtxtInferExt};
 use rustc_infer::traits::query::NoSolution;
 use rustc_infer::traits::Obligation;
 use rustc_middle::infer::canonical::Certainty as OldCertainty;
-use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_middle::traits::solve::{ExternalConstraints, ExternalConstraintsData};
+use rustc_middle::ty::{self, TyCtxt};
 use rustc_middle::ty::{
     CoercePredicate, RegionOutlivesPredicate, SubtypePredicate, ToPredicate, TypeOutlivesPredicate,
 };
@@ -72,8 +73,7 @@ impl<'tcx, P> From<Obligation<'tcx, P>> for Goal<'tcx, P> {
         Goal { param_env: obligation.param_env, predicate: obligation.predicate }
     }
 }
-
-#[derive(Debug, PartialEq, Eq, Clone, Hash, TypeFoldable, TypeVisitable)]
+#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, TypeFoldable, TypeVisitable)]
 pub struct Response<'tcx> {
     pub var_values: CanonicalVarValues<'tcx>,
     /// Additional constraints returned by this query.
@@ -121,14 +121,6 @@ pub enum MaybeCause {
     Overflow,
 }
 
-/// Additional constraints returned on success.
-#[derive(Debug, PartialEq, Eq, Clone, Hash, TypeFoldable, TypeVisitable, Default)]
-pub struct ExternalConstraints<'tcx> {
-    // FIXME: implement this.
-    regions: (),
-    opaque_types: Vec<(Ty<'tcx>, Ty<'tcx>)>,
-}
-
 type CanonicalGoal<'tcx, T = ty::Predicate<'tcx>> = Canonical<'tcx, Goal<'tcx, T>>;
 type CanonicalResponse<'tcx> = Canonical<'tcx, Response<'tcx>>;
 /// The result of evaluating a canonical query.
@@ -218,15 +210,14 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
                 EvalCtxt { infcx, var_values, search_graph, in_projection_eq_hack: false };
             let result = ecx.compute_goal(goal);
 
-            // FIXME: `Response` should be `Copy`
-            if search_graph.try_finalize_goal(tcx, canonical_goal, result.clone()) {
+            if search_graph.try_finalize_goal(tcx, canonical_goal, result) {
                 return result;
             }
         }
     }
 
     fn make_canonical_response(&self, certainty: Certainty) -> QueryResult<'tcx> {
-        let external_constraints = take_external_constraints(self.infcx)?;
+        let external_constraints = compute_external_query_constraints(self.infcx)?;
 
         Ok(self.infcx.canonicalize_response(Response {
             var_values: self.var_values,
@@ -461,18 +452,18 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
 }
 
 #[instrument(level = "debug", skip(infcx), ret)]
-fn take_external_constraints<'tcx>(
+fn compute_external_query_constraints<'tcx>(
     infcx: &InferCtxt<'tcx>,
 ) -> Result<ExternalConstraints<'tcx>, NoSolution> {
     let region_obligations = infcx.take_registered_region_obligations();
     let opaque_types = infcx.take_opaque_types_for_query_response();
-    Ok(ExternalConstraints {
+    Ok(infcx.tcx.intern_external_constraints(ExternalConstraintsData {
         // FIXME: Now that's definitely wrong :)
         //
         // Should also do the leak check here I think
         regions: drop(region_obligations),
         opaque_types,
-    })
+    }))
 }
 
 fn instantiate_canonical_query_response<'tcx>(
@@ -492,7 +483,10 @@ fn instantiate_canonical_query_response<'tcx>(
                     Certainty::Yes => OldCertainty::Proven,
                     Certainty::Maybe(_) => OldCertainty::Ambiguous,
                 },
-                opaque_types: resp.external_constraints.opaque_types,
+                // FIXME: This to_owned makes me sad, but we should eventually impl
+                // `instantiate_query_response_and_region_obligations` separately
+                // instead of piggybacking off of the old implementation.
+                opaque_types: resp.external_constraints.opaque_types.to_owned(),
                 value: resp.certainty,
             }),
         ) else { bug!(); };
@@ -510,7 +504,10 @@ pub(super) fn response_no_constraints<'tcx>(
         variables: goal.variables,
         value: Response {
             var_values: CanonicalVarValues::make_identity(tcx, goal.variables),
-            external_constraints: Default::default(),
+            // FIXME: maybe we should store the "no response" version in tcx, like
+            // we do for tcx.types and stuff.
+            external_constraints: tcx
+                .intern_external_constraints(ExternalConstraintsData::default()),
             certainty,
         },
     })

compiler/rustc_trait_selection/src/solve/search_graph/cache.rs

@@ -95,8 +95,7 @@ impl<'tcx> ProvisionalCache<'tcx> {
     }
 
     pub(super) fn provisional_result(&self, entry_index: EntryIndex) -> QueryResult<'tcx> {
-        // FIXME: Responses should probably be `Copy` as well
-        self.entries[entry_index].response.clone()
+        self.entries[entry_index].response
     }
 }
 

triagebot.toml

@@ -250,7 +250,8 @@ new_pr = true
 
 [autolabel."WG-trait-system-refactor"]
 trigger_files = [
-    "compiler/rustc_trait_selection/src/solve"
+    "compiler/rustc_trait_selection/src/solve",
+    "compiler/rustc_middle/src/traits/solve.rs"
 ]
 
 [notify-zulip."I-prioritize"]