rust-lang
diff --git a/‎compiler/rustc_middle/src/traits/mod.rs
+7-1 b/‎compiler/rustc_middle/src/traits/mod.rs
+7-1
diff --git a/‎compiler/rustc_middle/src/traits/query.rs
+1-1 b/‎compiler/rustc_middle/src/traits/query.rs
+1-1
diff --git a/‎compiler/rustc_middle/src/traits/solve.rs
+11-9 b/‎compiler/rustc_middle/src/traits/solve.rs
+11-9
diff --git a/‎compiler/rustc_middle/src/traits/solve/inspect.rs
+79 b/‎compiler/rustc_middle/src/traits/solve/inspect.rs
+79
diff --git a/‎compiler/rustc_middle/src/traits/solve/inspect/format.rs
+131 b/‎compiler/rustc_middle/src/traits/solve/inspect/format.rs
+131
diff --git a/‎compiler/rustc_session/src/options.rs
+2 b/‎compiler/rustc_session/src/options.rs
+2
@@ -981,7 +981,7 @@ pub enum CodegenObligationError {
     FulfillmentError,
 }
 
-#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, TypeFoldable, TypeVisitable)]
+#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, HashStable, TypeFoldable, TypeVisitable)]
 pub enum DefiningAnchor {
     /// `DefId` of the item.
     Bind(LocalDefId),
@@ -991,3 +991,9 @@ pub enum DefiningAnchor {
     /// Used to catch type mismatch errors when handling opaque types.
     Error,
 }
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, HashStable)]
+pub enum IsNormalizesToHack {
+    Yes,
+    No,
+}
@@ -92,7 +92,7 @@ pub type CanonicalTypeOpProvePredicateGoal<'tcx> =
 pub type CanonicalTypeOpNormalizeGoal<'tcx, T> =
     Canonical<'tcx, ty::ParamEnvAnd<'tcx, type_op::Normalize<T>>>;
 
-#[derive(Copy, Clone, Debug, HashStable, PartialEq, Eq)]
+#[derive(Copy, Clone, Debug, Hash, HashStable, PartialEq, Eq)]
 pub struct NoSolution;
 
 impl<'tcx> From<TypeError<'tcx>> for NoSolution {
 
@@ -11,14 +11,16 @@ use crate::ty::{
     TypeVisitor,
 };
 
+pub mod inspect;
+
 pub type EvaluationCache<'tcx> = Cache<CanonicalInput<'tcx>, QueryResult<'tcx>>;
 
 /// A goal is a statement, i.e. `predicate`, we want to prove
 /// given some assumptions, i.e. `param_env`.
 ///
 /// Most of the time the `param_env` contains the `where`-bounds of the function
 /// we're currently typechecking while the `predicate` is some trait bound.
-#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, TypeFoldable, TypeVisitable)]
+#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, HashStable, TypeFoldable, TypeVisitable)]
 pub struct Goal<'tcx, P> {
     pub predicate: P,
     pub param_env: ty::ParamEnv<'tcx>,
@@ -39,15 +41,15 @@ impl<'tcx, P> Goal<'tcx, P> {
     }
 }
 
-#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, TypeFoldable, TypeVisitable)]
+#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, HashStable, TypeFoldable, TypeVisitable)]
 pub struct Response<'tcx> {
     pub certainty: Certainty,
     pub var_values: CanonicalVarValues<'tcx>,
     /// Additional constraints returned by this query.
     pub external_constraints: ExternalConstraints<'tcx>,
 }
 
-#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, TypeFoldable, TypeVisitable)]
+#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, HashStable, TypeFoldable, TypeVisitable)]
 pub enum Certainty {
     Yes,
     Maybe(MaybeCause),
@@ -86,7 +88,7 @@ impl Certainty {
 }
 
 /// Why we failed to evaluate a goal.
-#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, TypeFoldable, TypeVisitable)]
+#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, HashStable, TypeFoldable, TypeVisitable)]
 pub enum MaybeCause {
     /// We failed due to ambiguity. This ambiguity can either
     /// be a true ambiguity, i.e. there are multiple different answers,
@@ -96,20 +98,20 @@ pub enum MaybeCause {
     Overflow,
 }
 
-#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, TypeFoldable, TypeVisitable)]
+#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, HashStable, TypeFoldable, TypeVisitable)]
 pub struct QueryInput<'tcx, T> {
     pub goal: Goal<'tcx, T>,
     pub anchor: DefiningAnchor,
     pub predefined_opaques_in_body: PredefinedOpaques<'tcx>,
 }
 
 /// Additional constraints returned on success.
-#[derive(Debug, PartialEq, Eq, Clone, Hash, Default)]
+#[derive(Debug, PartialEq, Eq, Clone, Hash, HashStable, Default)]
 pub struct PredefinedOpaquesData<'tcx> {
     pub opaque_types: Vec<(ty::OpaqueTypeKey<'tcx>, Ty<'tcx>)>,
 }
 
-#[derive(Debug, PartialEq, Eq, Copy, Clone, Hash)]
+#[derive(Debug, PartialEq, Eq, Copy, Clone, Hash, HashStable)]
 pub struct PredefinedOpaques<'tcx>(pub(crate) Interned<'tcx, PredefinedOpaquesData<'tcx>>);
 
 impl<'tcx> std::ops::Deref for PredefinedOpaques<'tcx> {
@@ -132,7 +134,7 @@ pub type CanonicalResponse<'tcx> = Canonical<'tcx, Response<'tcx>>;
 /// solver, merge the two responses again.
 pub type QueryResult<'tcx> = Result<CanonicalResponse<'tcx>, NoSolution>;
 
-#[derive(Debug, PartialEq, Eq, Copy, Clone, Hash)]
+#[derive(Debug, PartialEq, Eq, Copy, Clone, Hash, HashStable)]
 pub struct ExternalConstraints<'tcx>(pub(crate) Interned<'tcx, ExternalConstraintsData<'tcx>>);
 
 impl<'tcx> std::ops::Deref for ExternalConstraints<'tcx> {
@@ -144,7 +146,7 @@ impl<'tcx> std::ops::Deref for ExternalConstraints<'tcx> {
 }
 
 /// Additional constraints returned on success.
-#[derive(Debug, PartialEq, Eq, Clone, Hash, Default)]
+#[derive(Debug, PartialEq, Eq, Clone, Hash, HashStable, Default)]
 pub struct ExternalConstraintsData<'tcx> {
     // FIXME: implement this.
     pub region_constraints: QueryRegionConstraints<'tcx>,
 
@@ -0,0 +1,79 @@
+use super::{CanonicalInput, Certainty, Goal, NoSolution, QueryInput, QueryResult};
+use crate::{traits::IsNormalizesToHack, ty};
+use format::ProofTreeFormatter;
+use std::fmt::{Debug, Write};
+
+mod format;
+
+#[derive(Eq, PartialEq, Debug, Hash, HashStable)]
+pub enum CacheHit {
+    Provisional,
+    Global,
+}
+
+#[derive(Eq, PartialEq, Hash, HashStable)]
+pub struct GoalEvaluation<'tcx> {
+    pub uncanonicalized_goal: Goal<'tcx, ty::Predicate<'tcx>>,
+    pub canonicalized_goal: CanonicalInput<'tcx>,
+
+    pub kind: GoalEvaluationKind<'tcx>,
+    pub is_normalizes_to_hack: IsNormalizesToHack,
+    pub returned_goals: Vec<Goal<'tcx, ty::Predicate<'tcx>>>,
+
+    pub result: QueryResult<'tcx>,
+}
+#[derive(Eq, PartialEq, Hash, HashStable)]
+pub enum GoalEvaluationKind<'tcx> {
+    CacheHit(CacheHit),
+    Uncached { revisions: Vec<GoalEvaluationStep<'tcx>> },
+}
+impl Debug for GoalEvaluation<'_> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        ProofTreeFormatter { f, on_newline: true }.format_goal_evaluation(self)
+    }
+}
+
+#[derive(Eq, PartialEq, Hash, HashStable)]
+pub struct AddedGoalsEvaluation<'tcx> {
+    pub evaluations: Vec<Vec<GoalEvaluation<'tcx>>>,
+    pub result: Result<Certainty, NoSolution>,
+}
+impl Debug for AddedGoalsEvaluation<'_> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        ProofTreeFormatter { f, on_newline: true }.format_nested_goal_evaluation(self)
+    }
+}
+
+#[derive(Eq, PartialEq, Hash, HashStable)]
+pub struct GoalEvaluationStep<'tcx> {
+    pub instantiated_goal: QueryInput<'tcx, ty::Predicate<'tcx>>,
+
+    pub nested_goal_evaluations: Vec<AddedGoalsEvaluation<'tcx>>,
+    pub candidates: Vec<GoalCandidate<'tcx>>,
+
+    pub result: QueryResult<'tcx>,
+}
+impl Debug for GoalEvaluationStep<'_> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        ProofTreeFormatter { f, on_newline: true }.format_evaluation_step(self)
+    }
+}
+
+#[derive(Eq, PartialEq, Hash, HashStable)]
+pub struct GoalCandidate<'tcx> {
+    pub nested_goal_evaluations: Vec<AddedGoalsEvaluation<'tcx>>,
+    pub candidates: Vec<GoalCandidate<'tcx>>,
+    pub kind: CandidateKind<'tcx>,
+}
+#[derive(Eq, PartialEq, Debug, Hash, HashStable)]
+pub enum CandidateKind<'tcx> {
+    /// Probe entered when normalizing the self ty during candidate assembly
+    NormalizedSelfTyAssembly,
+    /// A normal candidate for proving a goal
+    Candidate { name: String, result: QueryResult<'tcx> },
+}
+impl Debug for GoalCandidate<'_> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        ProofTreeFormatter { f, on_newline: true }.format_candidate(self)
+    }
+}
@@ -0,0 +1,131 @@
+use super::*;
+
+pub(super) struct ProofTreeFormatter<'a, 'b> {
+    pub(super) f: &'a mut (dyn Write + 'b),
+    pub(super) on_newline: bool,
+}
+
+impl Write for ProofTreeFormatter<'_, '_> {
+    fn write_str(&mut self, s: &str) -> std::fmt::Result {
+        for line in s.split_inclusive("\n") {
+            if self.on_newline {
+                self.f.write_str("    ")?;
+            }
+            self.on_newline = line.ends_with("\n");
+            self.f.write_str(line)?;
+        }
+
+        Ok(())
+    }
+}
+
+impl ProofTreeFormatter<'_, '_> {
+    fn nested(&mut self) -> ProofTreeFormatter<'_, '_> {
+        ProofTreeFormatter { f: self, on_newline: true }
+    }
+
+    pub(super) fn format_goal_evaluation(&mut self, goal: &GoalEvaluation<'_>) -> std::fmt::Result {
+        let f = &mut *self.f;
+
+        let goal_text = match goal.is_normalizes_to_hack {
+            IsNormalizesToHack::Yes => "NORMALIZES-TO HACK GOAL",
+            IsNormalizesToHack::No => "GOAL",
+        };
+
+        writeln!(f, "{}: {:?}", goal_text, goal.uncanonicalized_goal,)?;
+        writeln!(f, "CANONICALIZED: {:?}", goal.canonicalized_goal)?;
+
+        match &goal.kind {
+            GoalEvaluationKind::CacheHit(CacheHit::Global) => {
+                writeln!(f, "GLOBAL CACHE HIT: {:?}", goal.result)
+            }
+            GoalEvaluationKind::CacheHit(CacheHit::Provisional) => {
+                writeln!(f, "PROVISIONAL CACHE HIT: {:?}", goal.result)
+            }
+            GoalEvaluationKind::Uncached { revisions } => {
+                for (n, step) in revisions.iter().enumerate() {
+                    let f = &mut *self.f;
+                    writeln!(f, "REVISION {n}: {:?}", step.result)?;
+                    let mut f = self.nested();
+                    f.format_evaluation_step(step)?;
+                }
+
+                let f = &mut *self.f;
+                writeln!(f, "RESULT: {:?}", goal.result)
+            }
+        }?;
+
+        if goal.returned_goals.len() > 0 {
+            let f = &mut *self.f;
+            writeln!(f, "NESTED GOALS ADDED TO CALLER: [")?;
+            let mut f = self.nested();
+            for goal in goal.returned_goals.iter() {
+                writeln!(f, "ADDED GOAL: {:?},", goal)?;
+            }
+            writeln!(self.f, "]")?;
+        }
+
+        Ok(())
+    }
+
+    pub(super) fn format_evaluation_step(
+        &mut self,
+        evaluation_step: &GoalEvaluationStep<'_>,
+    ) -> std::fmt::Result {
+        let f = &mut *self.f;
+        writeln!(f, "INSTANTIATED: {:?}", evaluation_step.instantiated_goal)?;
+
+        for candidate in &evaluation_step.candidates {
+            let mut f = self.nested();
+            f.format_candidate(candidate)?;
+        }
+        for nested_goal_evaluation in &evaluation_step.nested_goal_evaluations {
+            let mut f = self.nested();
+            f.format_nested_goal_evaluation(nested_goal_evaluation)?;
+        }
+
+        Ok(())
+    }
+
+    pub(super) fn format_candidate(&mut self, candidate: &GoalCandidate<'_>) -> std::fmt::Result {
+        let f = &mut *self.f;
+
+        match &candidate.kind {
+            CandidateKind::NormalizedSelfTyAssembly => {
+                writeln!(f, "NORMALIZING SELF TY FOR ASSEMBLY:")
+            }
+            CandidateKind::Candidate { name, result } => {
+                writeln!(f, "CANDIDATE {}: {:?}", name, result)
+            }
+        }?;
+
+        let mut f = self.nested();
+        for candidate in &candidate.candidates {
+            f.format_candidate(candidate)?;
+        }
+        for nested_evaluations in &candidate.nested_goal_evaluations {
+            f.format_nested_goal_evaluation(nested_evaluations)?;
+        }
+
+        Ok(())
+    }
+
+    pub(super) fn format_nested_goal_evaluation(
+        &mut self,
+        nested_goal_evaluation: &AddedGoalsEvaluation<'_>,
+    ) -> std::fmt::Result {
+        let f = &mut *self.f;
+        writeln!(f, "TRY_EVALUATE_ADDED_GOALS: {:?}", nested_goal_evaluation.result)?;
+
+        for (n, revision) in nested_goal_evaluation.evaluations.iter().enumerate() {
+            let f = &mut *self.f;
+            writeln!(f, "REVISION {n}")?;
+            let mut f = self.nested();
+            for goal_evaluation in revision {
+                f.format_goal_evaluation(goal_evaluation)?;
+            }
+        }
+
+        Ok(())
+    }
+}
@@ -1436,6 +1436,8 @@ options! {
         "output statistics about monomorphization collection"),
     dump_mono_stats_format: DumpMonoStatsFormat = (DumpMonoStatsFormat::Markdown, parse_dump_mono_stats, [UNTRACKED],
         "the format to use for -Z dump-mono-stats (`markdown` (default) or `json`)"),
+    dump_solver_proof_tree: bool = (false, parse_bool, [UNTRACKED],
+        "dump a proof tree for every goal evaluated by the new trait solver"),
     dwarf_version: Option<u32> = (None, parse_opt_number, [TRACKED],
         "version of DWARF debug information to emit (default: 2 or 4, depending on platform)"),
     dylib_lto: bool = (false, parse_bool, [UNTRACKED],