Merging upstream version 1.72.1+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 37 insertions, 129 deletions

diff --git a/compiler/rustc_trait_selection/src/solve/mod.rs b/compiler/rustc_trait_selection/src/solve/mod.rs
index 56a254d9c..77809d8d2 100644
--- a/compiler/rustc_trait_selection/src/solve/mod.rs
+++ b/compiler/rustc_trait_selection/src/solve/mod.rs
@@ -20,17 +20,24 @@ use rustc_middle::ty::{
     CoercePredicate, RegionOutlivesPredicate, SubtypePredicate, TypeOutlivesPredicate,
 };
 
+mod alias_relate;
 mod assembly;
 mod canonicalize;
 mod eval_ctxt;
 mod fulfill;
+pub mod inspect;
+mod normalize;
 mod opaques;
 mod project_goals;
 mod search_graph;
 mod trait_goals;
+mod weak_types;
 
-pub use eval_ctxt::{EvalCtxt, InferCtxtEvalExt};
+pub use eval_ctxt::{
+    EvalCtxt, GenerateProofTree, InferCtxtEvalExt, InferCtxtSelectExt, UseGlobalCache,
+};
 pub use fulfill::FulfillmentCtxt;
+pub(crate) use normalize::deeply_normalize;
 
 #[derive(Debug, Clone, Copy)]
 enum SolverMode {
@@ -154,139 +161,40 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
         }
     }
 
-    #[instrument(level = "debug", skip(self), ret)]
-    fn compute_alias_relate_goal(
+    #[instrument(level = "debug", skip(self))]
+    fn compute_const_evaluatable_goal(
         &mut self,
-        goal: Goal<'tcx, (ty::Term<'tcx>, ty::Term<'tcx>, ty::AliasRelationDirection)>,
+        Goal { param_env, predicate: ct }: Goal<'tcx, ty::Const<'tcx>>,
     ) -> QueryResult<'tcx> {
-        let tcx = self.tcx();
-        // We may need to invert the alias relation direction if dealing an alias on the RHS.
-        #[derive(Debug)]
-        enum Invert {
-            No,
-            Yes,
-        }
-        let evaluate_normalizes_to =
-            |ecx: &mut EvalCtxt<'_, 'tcx>, alias, other, direction, invert| {
-                let span = tracing::span!(
-                    tracing::Level::DEBUG,
-                    "compute_alias_relate_goal(evaluate_normalizes_to)",
-                    ?alias,
-                    ?other,
-                    ?direction,
-                    ?invert
-                );
-                let _enter = span.enter();
-                let result = ecx.probe(|ecx| {
-                    let other = match direction {
-                        // This is purely an optimization.
-                        ty::AliasRelationDirection::Equate => other,
-
-                        ty::AliasRelationDirection::Subtype => {
-                            let fresh = ecx.next_term_infer_of_kind(other);
-                            let (sub, sup) = match invert {
-                                Invert::No => (fresh, other),
-                                Invert::Yes => (other, fresh),
-                            };
-                            ecx.sub(goal.param_env, sub, sup)?;
-                            fresh
-                        }
-                    };
-                    ecx.add_goal(goal.with(
-                        tcx,
-                        ty::Binder::dummy(ty::ProjectionPredicate {
-                            projection_ty: alias,
-                            term: other,
-                        }),
-                    ));
-                    ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
-                });
-                debug!(?result);
-                result
-            };
-
-        let (lhs, rhs, direction) = goal.predicate;
-
-        if lhs.is_infer() || rhs.is_infer() {
-            bug!(
-                "`AliasRelate` goal with an infer var on lhs or rhs which should have been instantiated"
-            );
-        }
-
-        match (lhs.to_alias_ty(tcx), rhs.to_alias_ty(tcx)) {
-            (None, None) => bug!("`AliasRelate` goal without an alias on either lhs or rhs"),
-
-            // RHS is not a projection, only way this is true is if LHS normalizes-to RHS
-            (Some(alias_lhs), None) => {
-                evaluate_normalizes_to(self, alias_lhs, rhs, direction, Invert::No)
-            }
-
-            // LHS is not a projection, only way this is true is if RHS normalizes-to LHS
-            (None, Some(alias_rhs)) => {
-                evaluate_normalizes_to(self, alias_rhs, lhs, direction, Invert::Yes)
-            }
-
-            (Some(alias_lhs), Some(alias_rhs)) => {
-                debug!("both sides are aliases");
-
-                let mut candidates = Vec::new();
-                // LHS normalizes-to RHS
-                candidates.extend(evaluate_normalizes_to(
-                    self,
-                    alias_lhs,
-                    rhs,
-                    direction,
-                    Invert::No,
-                ));
-                // RHS normalizes-to RHS
-                candidates.extend(evaluate_normalizes_to(
-                    self,
-                    alias_rhs,
-                    lhs,
-                    direction,
-                    Invert::Yes,
-                ));
-                // Relate via substs
-                let subst_relate_response = self.probe(|ecx| {
-                    let span = tracing::span!(
-                        tracing::Level::DEBUG,
-                        "compute_alias_relate_goal(relate_via_substs)",
-                        ?alias_lhs,
-                        ?alias_rhs,
-                        ?direction
-                    );
-                    let _enter = span.enter();
-
-                    match direction {
-                        ty::AliasRelationDirection::Equate => {
-                            ecx.eq(goal.param_env, alias_lhs, alias_rhs)?;
-                        }
-                        ty::AliasRelationDirection::Subtype => {
-                            ecx.sub(goal.param_env, alias_lhs, alias_rhs)?;
-                        }
-                    }
-
-                    ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
-                });
-                candidates.extend(subst_relate_response);
-                debug!(?candidates);
-
-                if let Some(merged) = self.try_merge_responses(&candidates) {
-                    Ok(merged)
+        match ct.kind() {
+            ty::ConstKind::Unevaluated(uv) => {
+                // We never return `NoSolution` here as `try_const_eval_resolve` emits an
+                // error itself when failing to evaluate, so emitting an additional fulfillment
+                // error in that case is unnecessary noise. This may change in the future once
+                // evaluation failures are allowed to impact selection, e.g. generic const
+                // expressions in impl headers or `where`-clauses.
+
+                // FIXME(generic_const_exprs): Implement handling for generic
+                // const expressions here.
+                if let Some(_normalized) = self.try_const_eval_resolve(param_env, uv, ct.ty()) {
+                    self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
                 } else {
-                    // When relating two aliases and we have ambiguity, we prefer
-                    // relating the generic arguments of the aliases over normalizing
-                    // them. This is necessary for inference during typeck.
-                    //
-                    // As this is incomplete, we must not do so during coherence.
-                    match (self.solver_mode(), subst_relate_response) {
-                        (SolverMode::Normal, Ok(response)) => Ok(response),
-                        (SolverMode::Normal, Err(NoSolution)) | (SolverMode::Coherence, _) => {
-                            self.flounder(&candidates)
-                        }
-                    }
+                    self.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS)
                 }
             }
+            ty::ConstKind::Infer(_) => {
+                self.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS)
+            }
+            ty::ConstKind::Placeholder(_) | ty::ConstKind::Value(_) | ty::ConstKind::Error(_) => {
+                self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
+            }
+            // We can freely ICE here as:
+            // - `Param` gets replaced with a placeholder during canonicalization
+            // - `Bound` cannot exist as we don't have a binder around the self Type
+            // - `Expr` is part of `feature(generic_const_exprs)` and is not implemented yet
+            ty::ConstKind::Param(_) | ty::ConstKind::Bound(_, _) | ty::ConstKind::Expr(_) => {
+                bug!("unexpect const kind: {:?}", ct)
+            }
         }
     }