propagate nested goal path kind

Author: lcnr

compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs

@@ -275,7 +275,8 @@ where
             // as inductive even though it should not be, it may be unsound during coherence and
             // fixing it may cause inference breakage or introduce ambiguity.
             GoalSource::Misc => PathKind::Unknown,
-            GoalSource::NormalizeGoal(path_kind) => path_kind,
+            GoalSource::NormalizeGoal(path_kind)
+            | GoalSource::NestedNormalizationGoal(path_kind) => path_kind,
             GoalSource::ImplWhereBound => match self.current_goal_kind {
                 // We currently only consider a cycle coinductive if it steps
                 // into a where-clause of a coinductive trait.
@@ -679,7 +680,11 @@ where
                 ) = self.evaluate_goal_raw(source, unconstrained_goal, stalled_on)?;
                 // Add the nested goals from normalization to our own nested goals.
                 trace!(?nested_goals);
-                self.nested_goals.extend(nested_goals.into_iter().map(|(s, g)| (s, g, None)));
+                self.nested_goals.extend(
+                    nested_goals
+                        .into_iter()
+                        .map(|(s, g)| (GoalSource::NestedNormalizationGoal(s), g, None)),
+                );
 
                 // Finally, equate the goal's RHS with the unconstrained var.
                 //
@@ -1258,7 +1263,10 @@ where
                     (
                         Certainty::Yes,
                         NestedNormalizationGoals(
-                            goals.into_iter().map(|(s, g, _)| (s, g)).collect(),
+                            goals
+                                .into_iter()
+                                .map(|(s, g, _)| (self.step_kind_for_source(s), g))
+                                .collect(),
                         ),
                     )
                 }

compiler/rustc_trait_selection/src/solve/fulfill/derive_errors.rs

@@ -495,7 +495,10 @@ impl<'tcx> ProofTreeVisitor<'tcx> for BestObligation<'tcx> {
             match (child_mode, nested_goal.source()) {
                 (
                     ChildMode::Trait(_) | ChildMode::Host(_),
-                    GoalSource::Misc | GoalSource::TypeRelating | GoalSource::NormalizeGoal(_),
+                    GoalSource::Misc
+                    | GoalSource::TypeRelating
+                    | GoalSource::NormalizeGoal(_)
+                    | GoalSource::NestedNormalizationGoal(_),
                 ) => {
                     continue;
                 }

compiler/rustc_type_ir/src/search_graph/mod.rs

@@ -22,7 +22,9 @@ use std::marker::PhantomData;
 use derive_where::derive_where;
 #[cfg(feature = "nightly")]
 use rustc_macros::{Decodable_NoContext, Encodable_NoContext, HashStable_NoContext};
+use rustc_type_ir::Interner;
 use rustc_type_ir::data_structures::HashMap;
+use rustc_type_ir_macros::{TypeFoldable_Generic, TypeVisitable_Generic};
 use tracing::{debug, instrument};
 
 mod stack;
@@ -122,6 +124,7 @@ pub trait Delegate: Sized {
     feature = "nightly",
     derive(Decodable_NoContext, Encodable_NoContext, HashStable_NoContext)
 )]
+#[derive(TypeVisitable_Generic, TypeFoldable_Generic)]
 pub enum PathKind {
     /// A path consisting of only inductive/unproductive steps. Their initial
     /// provisional result is `Err(NoSolution)`. We currently treat them as

compiler/rustc_type_ir/src/solve/mod.rs

@@ -85,6 +85,8 @@ pub enum GoalSource {
     /// 2. for rigid projections's trait goal,
     /// 3. for GAT where clauses.
     AliasWellFormed,
+    /// A goal from a nested `NormalizesTo` goal which has been propagated to its caller.
+    NestedNormalizationGoal(PathKind),
     /// In case normalizing aliases in nested goals cycles, eagerly normalizing these
     /// aliases in the context of the parent may incorrectly change the cycle kind.
     /// Normalizing aliases in goals therefore tracks the original path kind for this
@@ -269,7 +271,7 @@ impl<I: Interner> ExternalConstraintsData<I> {
 #[derive_where(Clone, Hash, PartialEq, Debug, Default; I: Interner)]
 #[derive(TypeVisitable_Generic, TypeFoldable_Generic)]
 #[cfg_attr(feature = "nightly", derive(HashStable_NoContext))]
-pub struct NestedNormalizationGoals<I: Interner>(pub Vec<(GoalSource, Goal<I, I::Predicate>)>);
+pub struct NestedNormalizationGoals<I: Interner>(pub Vec<(PathKind, Goal<I, I::Predicate>)>);
 
 impl<I: Interner> Eq for NestedNormalizationGoals<I> {}