handle reservation impls, track impl source

compiler/rustc_trait_selection/src/solve/assembly/mod.rs

@@ -110,7 +110,7 @@ pub(super) trait GoalKind<'tcx>:
         ecx: &mut EvalCtxt<'_, 'tcx>,
         goal: Goal<'tcx, Self>,
         impl_def_id: DefId,
-    ) -> QueryResult<'tcx>;
+    ) -> Result<Candidate<'tcx>, NoSolution>;
 
     /// If the predicate contained an error, we want to avoid emitting unnecessary trait
     /// errors but still want to emit errors for other trait goals. We have some special
@@ -400,8 +400,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
             if let Some(impls_for_type) = trait_impls.non_blanket_impls().get(&simp) {
                 for &impl_def_id in impls_for_type {
                     match G::consider_impl_candidate(self, goal, impl_def_id) {
-                        Ok(result) => candidates
-                            .push(Candidate { source: CandidateSource::Impl(impl_def_id), result }),
+                        Ok(candidate) => candidates.push(candidate),
                         Err(NoSolution) => (),
                     }
                 }
@@ -519,8 +518,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         let trait_impls = tcx.trait_impls_of(goal.predicate.trait_def_id(tcx));
         for &impl_def_id in trait_impls.blanket_impls() {
             match G::consider_impl_candidate(self, goal, impl_def_id) {
-                Ok(result) => candidates
-                    .push(Candidate { source: CandidateSource::Impl(impl_def_id), result }),
+                Ok(candidate) => candidates.push(candidate),
                 Err(NoSolution) => (),
             }
         }

compiler/rustc_trait_selection/src/solve/eval_ctxt/probe.rs

@@ -1,5 +1,10 @@
+use crate::solve::assembly::Candidate;
+
 use super::EvalCtxt;
-use rustc_middle::traits::solve::{inspect, CandidateSource, QueryResult};
+use rustc_middle::traits::{
+    query::NoSolution,
+    solve::{inspect, CandidateSource, QueryResult},
+};
 use std::marker::PhantomData;
 
 pub(in crate::solve) struct ProbeCtxt<'me, 'a, 'tcx, F, T> {
@@ -36,6 +41,23 @@ where
     }
 }
 
+pub(in crate::solve) struct TraitProbeCtxt<'me, 'a, 'tcx, F> {
+    cx: ProbeCtxt<'me, 'a, 'tcx, F, QueryResult<'tcx>>,
+    source: CandidateSource,
+}
+
+impl<'tcx, F> TraitProbeCtxt<'_, '_, 'tcx, F>
+where
+    F: FnOnce(&QueryResult<'tcx>) -> inspect::ProbeKind<'tcx>,
+{
+    pub(in crate::solve) fn enter(
+        self,
+        f: impl FnOnce(&mut EvalCtxt<'_, 'tcx>) -> QueryResult<'tcx>,
+    ) -> Result<Candidate<'tcx>, NoSolution> {
+        self.cx.enter(|ecx| f(ecx)).map(|result| Candidate { source: self.source, result })
+    }
+}
+
 impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
     /// `probe_kind` is only called when proof tree building is enabled so it can be
     /// as expensive as necessary to output the desired information.
@@ -69,20 +91,18 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
     pub(in crate::solve) fn probe_trait_candidate(
         &mut self,
         source: CandidateSource,
-    ) -> ProbeCtxt<
-        '_,
-        'a,
-        'tcx,
-        impl FnOnce(&QueryResult<'tcx>) -> inspect::ProbeKind<'tcx>,
-        QueryResult<'tcx>,
-    > {
-        ProbeCtxt {
-            ecx: self,
-            probe_kind: move |result: &QueryResult<'tcx>| inspect::ProbeKind::TraitCandidate {
-                source,
-                result: *result,
+    ) -> TraitProbeCtxt<'_, 'a, 'tcx, impl FnOnce(&QueryResult<'tcx>) -> inspect::ProbeKind<'tcx>>
+    {
+        TraitProbeCtxt {
+            cx: ProbeCtxt {
+                ecx: self,
+                probe_kind: move |result: &QueryResult<'tcx>| inspect::ProbeKind::TraitCandidate {
+                    source,
+                    result: *result,
+                },
+                _result: PhantomData,
             },
-            _result: PhantomData,
+            source,
         }
     }
 }

compiler/rustc_trait_selection/src/solve/project_goals/mod.rs

@@ -1,6 +1,6 @@
 use crate::traits::{check_args_compatible, specialization_graph};
 
-use super::assembly::{self, structural_traits};
+use super::assembly::{self, structural_traits, Candidate};
 use super::EvalCtxt;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::DefId;
@@ -154,7 +154,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
         ecx: &mut EvalCtxt<'_, 'tcx>,
         goal: Goal<'tcx, ProjectionPredicate<'tcx>>,
         impl_def_id: DefId,
-    ) -> QueryResult<'tcx> {
+    ) -> Result<Candidate<'tcx>, NoSolution> {
         let tcx = ecx.tcx();
 
         let goal_trait_ref = goal.predicate.projection_ty.trait_ref(tcx);

compiler/rustc_trait_selection/src/solve/trait_goals.rs

@@ -1,12 +1,14 @@
 //! Dealing with trait goals, i.e. `T: Trait<'a, U>`.
 
-use super::assembly::{self, structural_traits};
+use super::assembly::{self, structural_traits, Candidate};
 use super::{EvalCtxt, SolverMode};
 use rustc_hir::def_id::DefId;
 use rustc_hir::{LangItem, Movability};
 use rustc_infer::traits::query::NoSolution;
 use rustc_middle::traits::solve::inspect::ProbeKind;
-use rustc_middle::traits::solve::{CanonicalResponse, Certainty, Goal, QueryResult};
+use rustc_middle::traits::solve::{
+    CandidateSource, CanonicalResponse, Certainty, Goal, QueryResult,
+};
 use rustc_middle::traits::{BuiltinImplSource, Reveal};
 use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams, TreatProjections};
 use rustc_middle::ty::{self, ToPredicate, Ty, TyCtxt};
@@ -38,7 +40,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
         ecx: &mut EvalCtxt<'_, 'tcx>,
         goal: Goal<'tcx, TraitPredicate<'tcx>>,
         impl_def_id: DefId,
-    ) -> QueryResult<'tcx> {
+    ) -> Result<Candidate<'tcx>, NoSolution> {
         let tcx = ecx.tcx();
 
         let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
@@ -63,7 +65,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
             },
         };
 
-        ecx.probe_misc_candidate("impl").enter(|ecx| {
+        ecx.probe_trait_candidate(CandidateSource::Impl(impl_def_id)).enter(|ecx| {
             let impl_args = ecx.fresh_args_for_item(impl_def_id);
             let impl_trait_ref = impl_trait_ref.instantiate(tcx, impl_args);