(almost) Always use ObligationCtxt when dealing with canonical queries

compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs

@@ -5,14 +5,14 @@ use rustc_infer::infer::region_constraints::Constraint;
 use rustc_infer::infer::region_constraints::RegionConstraintData;
 use rustc_infer::infer::RegionVariableOrigin;
 use rustc_infer::infer::{InferCtxt, RegionResolutionError, SubregionOrigin, TyCtxtInferExt as _};
-use rustc_infer::traits::{Normalized, ObligationCause, TraitEngine, TraitEngineExt};
+use rustc_infer::traits::ObligationCause;
 use rustc_middle::ty::error::TypeError;
 use rustc_middle::ty::RegionVid;
 use rustc_middle::ty::UniverseIndex;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable};
 use rustc_span::Span;
 use rustc_trait_selection::traits::query::type_op;
-use rustc_trait_selection::traits::{SelectionContext, TraitEngineExt as _};
+use rustc_trait_selection::traits::ObligationCtxt;
 use rustc_traits::{type_op_ascribe_user_type_with_span, type_op_prove_predicate_with_cause};
 
 use std::fmt;
@@ -240,9 +240,9 @@ impl<'tcx> TypeOpInfo<'tcx> for PredicateQuery<'tcx> {
     ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
         let (ref infcx, key, _) =
             mbcx.infcx.tcx.infer_ctxt().build_with_canonical(cause.span, &self.canonical_query);
-        let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
-        type_op_prove_predicate_with_cause(infcx, &mut *fulfill_cx, key, cause);
-        try_extract_error_from_fulfill_cx(fulfill_cx, infcx, placeholder_region, error_region)
+        let ocx = ObligationCtxt::new(infcx);
+        type_op_prove_predicate_with_cause(&ocx, key, cause);
+        try_extract_error_from_fulfill_cx(&ocx, placeholder_region, error_region)
     }
 }
 
@@ -281,9 +281,7 @@ where
     ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
         let (ref infcx, key, _) =
             mbcx.infcx.tcx.infer_ctxt().build_with_canonical(cause.span, &self.canonical_query);
-        let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
-
-        let mut selcx = SelectionContext::new(infcx);
+        let ocx = ObligationCtxt::new(infcx);
 
         // FIXME(lqd): Unify and de-duplicate the following with the actual
         // `rustc_traits::type_op::type_op_normalize` query to allow the span we need in the
@@ -292,11 +290,9 @@ where
         // to normalize the `nll/relate_tys/impl-fn-ignore-binder-via-bottom.rs` test. Check
         // after #85499 lands to see if its fixes have erased this difference.
         let (param_env, value) = key.into_parts();
-        let Normalized { value: _, obligations } =
-            rustc_trait_selection::traits::normalize(&mut selcx, param_env, cause, value.value);
-        fulfill_cx.register_predicate_obligations(infcx, obligations);
+        let _ = ocx.normalize(cause, param_env, value.value);
 
-        try_extract_error_from_fulfill_cx(fulfill_cx, infcx, placeholder_region, error_region)
+        try_extract_error_from_fulfill_cx(&ocx, placeholder_region, error_region)
     }
 }
 
@@ -329,9 +325,9 @@ impl<'tcx> TypeOpInfo<'tcx> for AscribeUserTypeQuery<'tcx> {
     ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
         let (ref infcx, key, _) =
             mbcx.infcx.tcx.infer_ctxt().build_with_canonical(cause.span, &self.canonical_query);
-        let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
-        type_op_ascribe_user_type_with_span(infcx, &mut *fulfill_cx, key, Some(cause.span)).ok()?;
-        try_extract_error_from_fulfill_cx(fulfill_cx, infcx, placeholder_region, error_region)
+        let ocx = ObligationCtxt::new(infcx);
+        type_op_ascribe_user_type_with_span(&ocx, key, Some(cause.span)).ok()?;
+        try_extract_error_from_fulfill_cx(&ocx, placeholder_region, error_region)
     }
 }
 
@@ -372,25 +368,24 @@ impl<'tcx> TypeOpInfo<'tcx> for crate::type_check::InstantiateOpaqueType<'tcx> {
     }
 }
 
-#[instrument(skip(fulfill_cx, infcx), level = "debug")]
+#[instrument(skip(ocx), level = "debug")]
 fn try_extract_error_from_fulfill_cx<'tcx>(
-    mut fulfill_cx: Box<dyn TraitEngine<'tcx> + 'tcx>,
-    infcx: &InferCtxt<'tcx>,
+    ocx: &ObligationCtxt<'_, 'tcx>,
     placeholder_region: ty::Region<'tcx>,
     error_region: Option<ty::Region<'tcx>>,
 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
     // We generally shouldn't have errors here because the query was
     // already run, but there's no point using `delay_span_bug`
     // when we're going to emit an error here anyway.
-    let _errors = fulfill_cx.select_all_or_error(infcx);
-    let region_constraints = infcx.with_region_constraints(|r| r.clone());
+    let _errors = ocx.select_all_or_error();
+    let region_constraints = ocx.infcx.with_region_constraints(|r| r.clone());
     try_extract_error_from_region_constraints(
-        infcx,
+        ocx.infcx,
         placeholder_region,
         error_region,
         &region_constraints,
-        |vid| infcx.region_var_origin(vid),
-        |vid| infcx.universe_of_region(infcx.tcx.mk_region(ty::ReVar(vid))),
+        |vid| ocx.infcx.region_var_origin(vid),
+        |vid| ocx.infcx.universe_of_region(ocx.infcx.tcx.mk_region(ty::ReVar(vid))),
     )
 }
 

compiler/rustc_hir_analysis/src/check/compare_method.rs

@@ -290,23 +290,16 @@ fn compare_predicate_entailment<'tcx>(
     // type would be more appropriate. In other places we have a `Vec<Span>`
     // corresponding to their `Vec<Predicate>`, but we don't have that here.
     // Fixing this would improve the output of test `issue-83765.rs`.
-    let mut result = infcx
-        .at(&cause, param_env)
-        .sup(trait_fty, impl_fty)
-        .map(|infer_ok| ocx.register_infer_ok_obligations(infer_ok));
+    let mut result = ocx.sup(&cause, param_env, trait_fty, impl_fty);
 
     // HACK(RPITIT): #101614. When we are trying to infer the hidden types for
     // RPITITs, we need to equate the output tys instead of just subtyping. If
     // we just use `sup` above, we'll end up `&'static str <: _#1t`, which causes
     // us to infer `_#1t = #'_#2r str`, where `'_#2r` is unconstrained, which gets
     // fixed up to `ReEmpty`, and which is certainly not what we want.
     if trait_fty.has_infer_types() {
-        result = result.and_then(|()| {
-            infcx
-                .at(&cause, param_env)
-                .eq(trait_sig.output(), impl_sig.output())
-                .map(|infer_ok| ocx.register_infer_ok_obligations(infer_ok))
-        });
+        result =
+            result.and_then(|()| ocx.eq(&cause, param_env, trait_sig.output(), impl_sig.output()));
     }
 
     if let Err(terr) = result {
@@ -1389,10 +1382,7 @@ pub(crate) fn raw_compare_const_impl<'tcx>(
 
     debug!("compare_const_impl: trait_ty={:?}", trait_ty);
 
-    let err = infcx
-        .at(&cause, param_env)
-        .sup(trait_ty, impl_ty)
-        .map(|ok| ocx.register_infer_ok_obligations(ok));
+    let err = ocx.sup(&cause, param_env, trait_ty, impl_ty);
 
     if let Err(terr) = err {
         debug!(

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -1675,7 +1675,7 @@ fn receiver_is_valid<'tcx>(
 
     // `self: Self` is always valid.
     if can_eq_self(receiver_ty) {
-        if let Err(err) = wfcx.equate_types(&cause, wfcx.param_env, self_ty, receiver_ty) {
+        if let Err(err) = wfcx.eq(&cause, wfcx.param_env, self_ty, receiver_ty) {
             infcx.err_ctxt().report_mismatched_types(&cause, self_ty, receiver_ty, err).emit();
         }
         return true;
@@ -1705,9 +1705,7 @@ fn receiver_is_valid<'tcx>(
             if can_eq_self(potential_self_ty) {
                 wfcx.register_obligations(autoderef.into_obligations());
 
-                if let Err(err) =
-                    wfcx.equate_types(&cause, wfcx.param_env, self_ty, potential_self_ty)
-                {
+                if let Err(err) = wfcx.eq(&cause, wfcx.param_env, self_ty, potential_self_ty) {
                     infcx
                         .err_ctxt()
                         .report_mismatched_types(&cause, self_ty, potential_self_ty, err)

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

@@ -43,7 +43,7 @@ impl<'tcx> InferCtxt<'tcx> {
     ///
     /// This is only meant to be invoked as part of constructing an
     /// inference context at the start of a query (see
-    /// `InferCtxtBuilder::enter_with_canonical`). It basically
+    /// `InferCtxtBuilder::build_with_canonical`). It basically
     /// brings the canonical value "into scope" within your new infcx.
     ///
     /// At the end of processing, the substitution S (once

compiler/rustc_trait_selection/src/infer.rs

@@ -1,5 +1,5 @@
 use crate::traits::query::evaluate_obligation::InferCtxtExt as _;
-use crate::traits::{self, TraitEngine, TraitEngineExt};
+use crate::traits::{self, ObligationCtxt};
 
 use rustc_hir::def_id::DefId;
 use rustc_hir::lang_items::LangItem;
@@ -142,7 +142,7 @@ pub trait InferCtxtBuilderExt<'tcx> {
     fn enter_canonical_trait_query<K, R>(
         &mut self,
         canonical_key: &Canonical<'tcx, K>,
-        operation: impl FnOnce(&InferCtxt<'tcx>, &mut dyn TraitEngine<'tcx>, K) -> Fallible<R>,
+        operation: impl FnOnce(&ObligationCtxt<'_, 'tcx>, K) -> Fallible<R>,
     ) -> Fallible<CanonicalizedQueryResponse<'tcx, R>>
     where
         K: TypeFoldable<'tcx>,
@@ -170,17 +170,17 @@ impl<'tcx> InferCtxtBuilderExt<'tcx> for InferCtxtBuilder<'tcx> {
     fn enter_canonical_trait_query<K, R>(
         &mut self,
         canonical_key: &Canonical<'tcx, K>,
-        operation: impl FnOnce(&InferCtxt<'tcx>, &mut dyn TraitEngine<'tcx>, K) -> Fallible<R>,
+        operation: impl FnOnce(&ObligationCtxt<'_, 'tcx>, K) -> Fallible<R>,
     ) -> Fallible<CanonicalizedQueryResponse<'tcx, R>>
     where
         K: TypeFoldable<'tcx>,
         R: Debug + TypeFoldable<'tcx>,
         Canonical<'tcx, QueryResponse<'tcx, R>>: ArenaAllocatable<'tcx>,
     {
-        let (ref infcx, key, canonical_inference_vars) =
+        let (infcx, key, canonical_inference_vars) =
             self.build_with_canonical(DUMMY_SP, canonical_key);
-        let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
-        let value = operation(infcx, &mut *fulfill_cx, key)?;
-        infcx.make_canonicalized_query_response(canonical_inference_vars, value, &mut *fulfill_cx)
+        let ocx = ObligationCtxt::new(&infcx);
+        let value = operation(&ocx, key)?;
+        ocx.make_canonicalized_query_response(canonical_inference_vars, value)
     }
 }

compiler/rustc_trait_selection/src/traits/engine.rs

@@ -1,14 +1,21 @@
 use std::cell::RefCell;
+use std::fmt::Debug;
 
 use super::TraitEngine;
 use super::{ChalkFulfillmentContext, FulfillmentContext};
 use crate::infer::InferCtxtExt;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir::def_id::{DefId, LocalDefId};
+use rustc_infer::infer::at::ToTrace;
+use rustc_infer::infer::canonical::{
+    Canonical, CanonicalVarValues, CanonicalizedQueryResponse, QueryResponse,
+};
 use rustc_infer::infer::{InferCtxt, InferOk};
+use rustc_infer::traits::query::Fallible;
 use rustc_infer::traits::{
     FulfillmentError, Obligation, ObligationCause, PredicateObligation, TraitEngineExt as _,
 };
+use rustc_middle::arena::ArenaAllocatable;
 use rustc_middle::ty::error::TypeError;
 use rustc_middle::ty::ToPredicate;
 use rustc_middle::ty::TypeFoldable;
@@ -105,12 +112,12 @@ impl<'a, 'tcx> ObligationCtxt<'a, 'tcx> {
         self.register_infer_ok_obligations(infer_ok)
     }
 
-    pub fn equate_types(
+    pub fn eq<T: ToTrace<'tcx>>(
         &self,
         cause: &ObligationCause<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
-        expected: Ty<'tcx>,
-        actual: Ty<'tcx>,
+        expected: T,
+        actual: T,
     ) -> Result<(), TypeError<'tcx>> {
         match self.infcx.at(cause, param_env).eq(expected, actual) {
             Ok(InferOk { obligations, value: () }) => {
@@ -121,6 +128,22 @@ impl<'a, 'tcx> ObligationCtxt<'a, 'tcx> {
         }
     }
 
+    pub fn sup<T: ToTrace<'tcx>>(
+        &self,
+        cause: &ObligationCause<'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+        expected: T,
+        actual: T,
+    ) -> Result<(), TypeError<'tcx>> {
+        match self.infcx.at(cause, param_env).sup(expected, actual) {
+            Ok(InferOk { obligations, value: () }) => {
+                self.register_obligations(obligations);
+                Ok(())
+            }
+            Err(e) => Err(e),
+        }
+    }
+
     pub fn select_all_or_error(&self) -> Vec<FulfillmentError<'tcx>> {
         self.engine.borrow_mut().select_all_or_error(self.infcx)
     }
@@ -154,4 +177,20 @@ impl<'a, 'tcx> ObligationCtxt<'a, 'tcx> {
         }
         implied_bounds
     }
+
+    pub fn make_canonicalized_query_response<T>(
+        &self,
+        inference_vars: CanonicalVarValues<'tcx>,
+        answer: T,
+    ) -> Fallible<CanonicalizedQueryResponse<'tcx, T>>
+    where
+        T: Debug + TypeFoldable<'tcx>,
+        Canonical<'tcx, QueryResponse<'tcx, T>>: ArenaAllocatable<'tcx>,
+    {
+        self.infcx.make_canonicalized_query_response(
+            inference_vars,
+            answer,
+            &mut **self.engine.borrow_mut(),
+        )
+    }
 }

compiler/rustc_traits/src/implied_outlives_bounds.rs

@@ -28,9 +28,9 @@ fn implied_outlives_bounds<'tcx>(
     &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, Vec<OutlivesBound<'tcx>>>>,
     NoSolution,
 > {
-    tcx.infer_ctxt().enter_canonical_trait_query(&goal, |infcx, _fulfill_cx, key| {
+    tcx.infer_ctxt().enter_canonical_trait_query(&goal, |ocx, key| {
         let (param_env, ty) = key.into_parts();
-        compute_implied_outlives_bounds(&infcx, param_env, ty)
+        compute_implied_outlives_bounds(&ocx.infcx, param_env, ty)
     })
 }
 

compiler/rustc_traits/src/lib.rs

@@ -3,6 +3,7 @@
 
 #![deny(rustc::untranslatable_diagnostic)]
 #![deny(rustc::diagnostic_outside_of_impl)]
+#![feature(let_chains)]
 #![recursion_limit = "256"]
 
 #[macro_use]

compiler/rustc_traits/src/normalize_projection_ty.rs

@@ -1,6 +1,5 @@
 use rustc_infer::infer::canonical::{Canonical, QueryResponse};
 use rustc_infer::infer::TyCtxtInferExt;
-use rustc_infer::traits::TraitEngineExt as _;
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::{ParamEnvAnd, TyCtxt};
 use rustc_trait_selection::infer::InferCtxtBuilderExt;
@@ -23,8 +22,8 @@ fn normalize_projection_ty<'tcx>(
     tcx.sess.perf_stats.normalize_projection_ty.fetch_add(1, Ordering::Relaxed);
     tcx.infer_ctxt().enter_canonical_trait_query(
         &goal,
-        |infcx, fulfill_cx, ParamEnvAnd { param_env, value: goal }| {
-            let selcx = &mut SelectionContext::new(infcx);
+        |ocx, ParamEnvAnd { param_env, value: goal }| {
+            let selcx = &mut SelectionContext::new(ocx.infcx);
             let cause = ObligationCause::dummy();
             let mut obligations = vec![];
             let answer = traits::normalize_projection_type(
@@ -35,7 +34,7 @@ fn normalize_projection_ty<'tcx>(
                 0,
                 &mut obligations,
             );
-            fulfill_cx.register_predicate_obligations(infcx, obligations);
+            ocx.register_obligations(obligations);
             // FIXME(associated_const_equality): All users of normalize_projection_ty expected
             // a type, but there is the possibility it could've been a const now. Maybe change
             // it to a Term later?