Auto merge of rust-lang#126130 - compiler-errors:goal-relations, r=lcnr

Make `ObligationEmittingRelation`s emit `Goal` rather than `Obligation`

Helps avoid needing to uplift `Obligation` into the solver. We still can't get rid of `ObligationCause`, but we can keep it as an associated type for `InferCtxtLike` and just give it a `dummy` function.

There's some shuttling between `Goal` and `Obligation` that may be perf-sensitive... Let's see what rust-timer says.

r? lcnr

compiler/rustc_borrowck/src/type_check/relate_tys.rs

@@ -1,9 +1,10 @@
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::ErrorGuaranteed;
-use rustc_infer::infer::relate::{ObligationEmittingRelation, StructurallyRelateAliases};
+use rustc_infer::infer::relate::{PredicateEmittingRelation, StructurallyRelateAliases};
 use rustc_infer::infer::relate::{Relate, RelateResult, TypeRelation};
 use rustc_infer::infer::NllRegionVariableOrigin;
-use rustc_infer::traits::{Obligation, PredicateObligations};
+use rustc_infer::traits::solve::Goal;
+use rustc_infer::traits::Obligation;
 use rustc_middle::mir::ConstraintCategory;
 use rustc_middle::span_bug;
 use rustc_middle::traits::query::NoSolution;
@@ -153,9 +154,7 @@ impl<'me, 'bccx, 'tcx> NllTypeRelating<'me, 'bccx, 'tcx> {
                 "expected at least one opaque type in `relate_opaques`, got {a} and {b}."
             ),
         };
-        let cause = ObligationCause::dummy_with_span(self.span());
-        let obligations = infcx.handle_opaque_type(a, b, &cause, self.param_env())?.obligations;
-        self.register_obligations(obligations);
+        self.register_goals(infcx.handle_opaque_type(a, b, self.span(), self.param_env())?);
         Ok(())
     }
 
@@ -533,7 +532,7 @@ impl<'bccx, 'tcx> TypeRelation<TyCtxt<'tcx>> for NllTypeRelating<'_, 'bccx, 'tcx
     }
 }
 
-impl<'bccx, 'tcx> ObligationEmittingRelation<'tcx> for NllTypeRelating<'_, 'bccx, 'tcx> {
+impl<'bccx, 'tcx> PredicateEmittingRelation<'tcx> for NllTypeRelating<'_, 'bccx, 'tcx> {
     fn span(&self) -> Span {
         self.locations.span(self.type_checker.body)
     }
@@ -550,30 +549,40 @@ impl<'bccx, 'tcx> ObligationEmittingRelation<'tcx> for NllTypeRelating<'_, 'bccx
         &mut self,
         obligations: impl IntoIterator<Item: ty::Upcast<TyCtxt<'tcx>, ty::Predicate<'tcx>>>,
     ) {
-        self.register_obligations(
-            obligations
-                .into_iter()
-                .map(|to_pred| {
-                    Obligation::new(self.tcx(), ObligationCause::dummy(), self.param_env(), to_pred)
-                })
-                .collect(),
+        let tcx = self.tcx();
+        let param_env = self.param_env();
+        self.register_goals(
+            obligations.into_iter().map(|to_pred| Goal::new(tcx, param_env, to_pred)),
         );
     }
 
-    fn register_obligations(&mut self, obligations: PredicateObligations<'tcx>) {
+    fn register_goals(
+        &mut self,
+        obligations: impl IntoIterator<Item = Goal<'tcx, ty::Predicate<'tcx>>>,
+    ) {
         let _: Result<_, ErrorGuaranteed> = self.type_checker.fully_perform_op(
             self.locations,
             self.category,
             InstantiateOpaqueType {
-                obligations,
+                obligations: obligations
+                    .into_iter()
+                    .map(|goal| {
+                        Obligation::new(
+                            self.tcx(),
+                            ObligationCause::dummy_with_span(self.span()),
+                            goal.param_env,
+                            goal.predicate,
+                        )
+                    })
+                    .collect(),
                 // These fields are filled in during execution of the operation
                 base_universe: None,
                 region_constraints: None,
             },
         );
     }
 
-    fn register_type_relate_obligation(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) {
+    fn register_alias_relate_predicate(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) {
         self.register_predicates([ty::Binder::dummy(match self.ambient_variance {
             ty::Variance::Covariant => ty::PredicateKind::AliasRelate(
                 a.into(),

compiler/rustc_hir_typeck/src/coercion.rs

@@ -113,7 +113,7 @@ fn simple<'tcx>(kind: Adjust<'tcx>) -> impl FnOnce(Ty<'tcx>) -> Vec<Adjustment<'
 fn success<'tcx>(
     adj: Vec<Adjustment<'tcx>>,
     target: Ty<'tcx>,
-    obligations: traits::PredicateObligations<'tcx>,
+    obligations: Vec<traits::PredicateObligation<'tcx>>,
 ) -> CoerceResult<'tcx> {
     Ok(InferOk { value: (adj, target), obligations })
 }

compiler/rustc_infer/src/infer/at.rs

@@ -31,6 +31,8 @@ use crate::infer::relate::{Relate, StructurallyRelateAliases, TypeRelation};
 use rustc_middle::bug;
 use rustc_middle::ty::{Const, ImplSubject};
 
+use crate::traits::Obligation;
+
 /// Whether we should define opaque types or just treat them opaquely.
 ///
 /// Currently only used to prevent predicate matching from matching anything
@@ -119,10 +121,8 @@ impl<'a, 'tcx> At<'a, 'tcx> {
             self.param_env,
             define_opaque_types,
         );
-        fields
-            .sup()
-            .relate(expected, actual)
-            .map(|_| InferOk { value: (), obligations: fields.obligations })
+        fields.sup().relate(expected, actual)?;
+        Ok(InferOk { value: (), obligations: fields.into_obligations() })
     }
 
     /// Makes `expected <: actual`.
@@ -141,10 +141,8 @@ impl<'a, 'tcx> At<'a, 'tcx> {
             self.param_env,
             define_opaque_types,
         );
-        fields
-            .sub()
-            .relate(expected, actual)
-            .map(|_| InferOk { value: (), obligations: fields.obligations })
+        fields.sub().relate(expected, actual)?;
+        Ok(InferOk { value: (), obligations: fields.into_obligations() })
     }
 
     /// Makes `expected == actual`.
@@ -163,10 +161,22 @@ impl<'a, 'tcx> At<'a, 'tcx> {
             self.param_env,
             define_opaque_types,
         );
-        fields
-            .equate(StructurallyRelateAliases::No)
-            .relate(expected, actual)
-            .map(|_| InferOk { value: (), obligations: fields.obligations })
+        fields.equate(StructurallyRelateAliases::No).relate(expected, actual)?;
+        Ok(InferOk {
+            value: (),
+            obligations: fields
+                .goals
+                .into_iter()
+                .map(|goal| {
+                    Obligation::new(
+                        self.infcx.tcx,
+                        fields.trace.cause.clone(),
+                        goal.param_env,
+                        goal.predicate,
+                    )
+                })
+                .collect(),
+        })
     }
 
     /// Equates `expected` and `found` while structurally relating aliases.
@@ -187,10 +197,8 @@ impl<'a, 'tcx> At<'a, 'tcx> {
             self.param_env,
             DefineOpaqueTypes::Yes,
         );
-        fields
-            .equate(StructurallyRelateAliases::Yes)
-            .relate(expected, actual)
-            .map(|_| InferOk { value: (), obligations: fields.obligations })
+        fields.equate(StructurallyRelateAliases::Yes).relate(expected, actual)?;
+        Ok(InferOk { value: (), obligations: fields.into_obligations() })
     }
 
     pub fn relate<T>(
@@ -237,10 +245,8 @@ impl<'a, 'tcx> At<'a, 'tcx> {
             self.param_env,
             define_opaque_types,
         );
-        fields
-            .lub()
-            .relate(expected, actual)
-            .map(|value| InferOk { value, obligations: fields.obligations })
+        let value = fields.lub().relate(expected, actual)?;
+        Ok(InferOk { value, obligations: fields.into_obligations() })
     }
 
     /// Computes the greatest-lower-bound, or mutual subtype, of two
@@ -261,10 +267,8 @@ impl<'a, 'tcx> At<'a, 'tcx> {
             self.param_env,
             define_opaque_types,
         );
-        fields
-            .glb()
-            .relate(expected, actual)
-            .map(|value| InferOk { value, obligations: fields.obligations })
+        let value = fields.glb().relate(expected, actual)?;
+        Ok(InferOk { value, obligations: fields.into_obligations() })
     }
 }
 

compiler/rustc_infer/src/infer/mod.rs

@@ -1,17 +1,18 @@
 pub use at::DefineOpaqueTypes;
 pub use freshen::TypeFreshener;
 pub use lexical_region_resolve::RegionResolutionError;
+pub use relate::combine::CombineFields;
+pub use relate::combine::PredicateEmittingRelation;
+pub use relate::StructurallyRelateAliases;
 pub use rustc_macros::{TypeFoldable, TypeVisitable};
 pub use rustc_middle::ty::IntVarValue;
 pub use BoundRegionConversionTime::*;
 pub use RegionVariableOrigin::*;
 pub use SubregionOrigin::*;
 pub use ValuePairs::*;
 
-use crate::infer::relate::{CombineFields, RelateResult};
-use crate::traits::{
-    self, ObligationCause, ObligationInspector, PredicateObligations, TraitEngine,
-};
+use crate::infer::relate::RelateResult;
+use crate::traits::{self, ObligationCause, ObligationInspector, PredicateObligation, TraitEngine};
 use error_reporting::TypeErrCtxt;
 use free_regions::RegionRelations;
 use lexical_region_resolve::LexicalRegionResolutions;
@@ -68,7 +69,7 @@ pub mod type_variable;
 #[derive(Debug)]
 pub struct InferOk<'tcx, T> {
     pub value: T,
-    pub obligations: PredicateObligations<'tcx>,
+    pub obligations: Vec<PredicateObligation<'tcx>>,
 }
 pub type InferResult<'tcx, T> = Result<InferOk<'tcx, T>, TypeError<'tcx>>;
 
@@ -748,7 +749,7 @@ impl<'tcx, T> InferOk<'tcx, T> {
 }
 
 impl<'tcx> InferOk<'tcx, ()> {
-    pub fn into_obligations(self) -> PredicateObligations<'tcx> {
+    pub fn into_obligations(self) -> Vec<PredicateObligation<'tcx>> {
         self.obligations
     }
 }