Auto merge of #133502 - lcnr:rust4, r=<try>

[DO NOT MERGE] bootstrap with `-Znext-solver=globally`

Author: rust-bors[bot]

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -1,6 +1,7 @@
 use rustc_ast as ast;
 use rustc_ast::visit::{self, AssocCtxt, FnCtxt, FnKind, Visitor};
 use rustc_ast::{NodeId, PatKind, attr, token};
+use rustc_errors::E0001;
 use rustc_feature::{AttributeGate, BUILTIN_ATTRIBUTE_MAP, BuiltinAttribute, Features};
 use rustc_session::Session;
 use rustc_session::parse::{feature_err, feature_warn};
@@ -654,10 +655,13 @@ fn check_new_solver_banned_features(sess: &Session, features: &Features) {
         .map(|feat| feat.attr_sp)
     {
         #[allow(rustc::symbol_intern_string_literal)]
-        sess.dcx().emit_err(errors::IncompatibleFeatures {
-            spans: vec![gce_span],
-            f1: Symbol::intern("-Znext-solver=globally"),
-            f2: sym::generic_const_exprs,
-        });
+        sess.dcx()
+            .create_fatal(errors::IncompatibleFeatures {
+                spans: vec![gce_span],
+                f1: Symbol::intern("-Znext-solver=globally"),
+                f2: sym::generic_const_exprs,
+            })
+            .with_code(E0001)
+            .emit();
     }
 }

compiler/rustc_hir_typeck/src/expr.rs

@@ -1634,7 +1634,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) -> Ty<'tcx> {
         let rcvr_t = self.check_expr(rcvr);
         // no need to check for bot/err -- callee does that
-        let rcvr_t = self.structurally_resolve_type(rcvr.span, rcvr_t);
+        let rcvr_t = self.try_structurally_resolve_type(rcvr.span, rcvr_t);
 
         match self.lookup_method(rcvr_t, segment, segment.ident.span, expr, rcvr, args) {
             Ok(method) => {

compiler/rustc_hir_typeck/src/fn_ctxt/inspect_obligations.rs

@@ -1,7 +1,6 @@
 //! A utility module to inspect currently ambiguous obligations in the current context.
 
 use rustc_infer::traits::{self, ObligationCause, PredicateObligations};
-use rustc_middle::traits::solve::GoalSource;
 use rustc_middle::ty::{self, Ty, TypeVisitableExt};
 use rustc_span::Span;
 use rustc_trait_selection::solve::Certainty;
@@ -127,21 +126,7 @@ impl<'a, 'tcx> ProofTreeVisitor<'tcx> for NestedObligationsForSelfTy<'a, 'tcx> {
 
         let tcx = self.fcx.tcx;
         let goal = inspect_goal.goal();
-        if self.fcx.predicate_has_self_ty(goal.predicate, self.self_ty)
-            // We do not push the instantiated forms of goals as it would cause any
-            // aliases referencing bound vars to go from having escaping bound vars to
-            // being able to be normalized to an inference variable.
-            //
-            // This is mostly just a hack as arbitrary nested goals could still contain
-            // such aliases while having a different `GoalSource`. Closure signature inference
-            // however can't really handle *every* higher ranked `Fn` goal also being present
-            // in the form of `?c: Fn<(<?x as Trait<'!a>>::Assoc)`.
-            //
-            // This also just better matches the behaviour of the old solver where we do not
-            // encounter instantiated forms of goals, only nested goals that referred to bound
-            // vars from instantiated goals.
-            && !matches!(inspect_goal.source(), GoalSource::InstantiateHigherRanked)
-        {
+        if self.fcx.predicate_has_self_ty(goal.predicate, self.self_ty) {
             self.obligations_for_self_ty.push(traits::Obligation::new(
                 tcx,
                 self.root_cause.clone(),

compiler/rustc_hir_typeck/src/method/confirm.rs

@@ -182,7 +182,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
         assert_eq!(n, pick.autoderefs);
 
         let mut adjustments = self.adjust_steps(&autoderef);
-        let mut target = self.structurally_resolve_type(autoderef.span(), ty);
+        let mut target = self.try_structurally_resolve_type(autoderef.span(), ty);
 
         match pick.autoref_or_ptr_adjustment {
             Some(probe::AutorefOrPtrAdjustment::Autoref { mutbl, unsize }) => {

compiler/rustc_hir_typeck/src/method/probe.rs

@@ -12,7 +12,9 @@ use rustc_hir::HirId;
 use rustc_hir::def::DefKind;
 use rustc_hir_analysis::autoderef::{self, Autoderef};
 use rustc_infer::infer::canonical::{Canonical, OriginalQueryValues, QueryResponse};
-use rustc_infer::infer::{BoundRegionConversionTime, DefineOpaqueTypes, InferOk, TyCtxtInferExt};
+use rustc_infer::infer::{
+    BoundRegionConversionTime, DefineOpaqueTypes, InferCtxt, InferOk, TyCtxtInferExt,
+};
 use rustc_infer::traits::ObligationCauseCode;
 use rustc_middle::middle::stability;
 use rustc_middle::ty::elaborate::supertrait_def_ids;
@@ -441,7 +443,17 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // If we encountered an `_` type or an error type during autoderef, this is
         // ambiguous.
         if let Some(bad_ty) = &steps.opt_bad_ty {
-            if is_suggestion.0 {
+            // Ended up encountering a type variable when doing autoderef,
+            // but it may not be a type variable after processing obligations
+            // in our local `FnCtxt`, so don't call `structurally_resolve_type`.
+            let ty = &bad_ty.ty;
+            let ty = self
+                .probe_instantiate_query_response(span, &orig_values, ty)
+                .unwrap_or_else(|_| span_bug!(span, "instantiating {:?} failed?", ty));
+            if bad_ty.is_opaque_type || final_ty_is_opaque(&self.infcx, ty.value) {
+                // FIXME(-Znext-solver): This isn't really what we want :<
+                assert!(self.tcx.next_trait_solver_globally());
+            } else if is_suggestion.0 {
                 // Ambiguity was encountered during a suggestion. There's really
                 // not much use in suggesting methods in this case.
                 return Err(MethodError::NoMatch(NoMatchData {
@@ -467,13 +479,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     },
                 );
             } else {
-                // Ended up encountering a type variable when doing autoderef,
-                // but it may not be a type variable after processing obligations
-                // in our local `FnCtxt`, so don't call `structurally_resolve_type`.
-                let ty = &bad_ty.ty;
-                let ty = self
-                    .probe_instantiate_query_response(span, &orig_values, ty)
-                    .unwrap_or_else(|_| span_bug!(span, "instantiating {:?} failed?", ty));
                 let ty = self.resolve_vars_if_possible(ty.value);
                 let guar = match *ty.kind() {
                     ty::Infer(ty::TyVar(_)) => {
@@ -629,8 +634,14 @@ pub(crate) fn method_autoderef_steps<'tcx>(
     };
     let final_ty = autoderef_via_deref.final_ty();
     let opt_bad_ty = match final_ty.kind() {
-        ty::Infer(ty::TyVar(_)) | ty::Error(_) => Some(MethodAutoderefBadTy {
+        ty::Infer(ty::TyVar(_)) => Some(MethodAutoderefBadTy {
             reached_raw_pointer,
+            is_opaque_type: final_ty_is_opaque(infcx, final_ty),
+            ty: infcx.make_query_response_ignoring_pending_obligations(inference_vars, final_ty),
+        }),
+        ty::Error(_) => Some(MethodAutoderefBadTy {
+            reached_raw_pointer,
+            is_opaque_type: false,
             ty: infcx.make_query_response_ignoring_pending_obligations(inference_vars, final_ty),
         }),
         ty::Array(elem_ty, _) => {
@@ -663,6 +674,15 @@ pub(crate) fn method_autoderef_steps<'tcx>(
     }
 }
 
+/// Returns `true` in case the final type is the hidden type of an opaque.
+#[instrument(level = "debug", skip(infcx), ret)]
+fn final_ty_is_opaque<'tcx>(infcx: &InferCtxt<'tcx>, final_ty: Ty<'tcx>) -> bool {
+    let &ty::Infer(ty::TyVar(vid)) = final_ty.kind() else {
+        return false;
+    };
+    infcx.has_opaques_with_sub_unified_hidden_type(vid)
+}
+
 impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
     fn new(
         fcx: &'a FnCtxt<'a, 'tcx>,
@@ -1871,31 +1891,39 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                     (xform_self_ty, xform_ret_ty) =
                         self.xform_self_ty(probe.item, trait_ref.self_ty(), trait_ref.args);
                     xform_self_ty = ocx.normalize(cause, self.param_env, xform_self_ty);
-                    match self_ty.kind() {
-                        // HACK: opaque types will match anything for which their bounds hold.
-                        // Thus we need to prevent them from trying to match the `&_` autoref
-                        // candidates that get created for `&self` trait methods.
-                        ty::Alias(ty::Opaque, alias_ty)
-                            if !self.next_trait_solver()
-                                && self.infcx.can_define_opaque_ty(alias_ty.def_id)
-                                && !xform_self_ty.is_ty_var() =>
-                        {
-                            return ProbeResult::NoMatch;
-                        }
-                        _ => match ocx.relate(
-                            cause,
-                            self.param_env,
-                            self.variance(),
-                            self_ty,
-                            xform_self_ty,
-                        ) {
-                            Ok(()) => {}
-                            Err(err) => {
-                                debug!("--> cannot relate self-types {:?}", err);
+
+                    // HACK: opaque types will match anything for which their bounds hold.
+                    // Thus we need to prevent them from trying to match the `&_` autoref
+                    // candidates that get created for `&self` trait methods.
+                    if self.mode == Mode::MethodCall {
+                        match self_ty.kind() {
+                            ty::Infer(ty::TyVar(_)) => {
+                                assert!(self.infcx.next_trait_solver());
+                                if !xform_self_ty.is_ty_var() {
+                                    return ProbeResult::NoMatch;
+                                }
+                            }
+                            ty::Alias(ty::Opaque, alias_ty)
+                                if !self.infcx.next_trait_solver()
+                                    && self.infcx.can_define_opaque_ty(alias_ty.def_id)
+                                    && !xform_self_ty.is_ty_var() =>
+                            {
+                                assert!(!self.infcx.next_trait_solver());
                                 return ProbeResult::NoMatch;
                             }
-                        },
+                            _ => {}
+                        }
+                    }
+
+                    match ocx.relate(cause, self.param_env, self.variance(), self_ty, xform_self_ty)
+                    {
+                        Ok(()) => {}
+                        Err(err) => {
+                            debug!("--> cannot relate self-types {:?}", err);
+                            return ProbeResult::NoMatch;
+                        }
                     }
+
                     let obligation = traits::Obligation::new(
                         self.tcx,
                         cause.clone(),

compiler/rustc_middle/src/traits/query.rs

@@ -178,6 +178,7 @@ pub struct MethodAutoderefStepsResult<'tcx> {
 #[derive(Debug, HashStable)]
 pub struct MethodAutoderefBadTy<'tcx> {
     pub reached_raw_pointer: bool,
+    pub is_opaque_type: bool,
     pub ty: Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>,
 }
 

compiler/rustc_middle/src/ty/context.rs

@@ -3433,7 +3433,7 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     pub fn next_trait_solver_globally(self) -> bool {
-        self.sess.opts.unstable_opts.next_solver.globally
+        self.sess.opts.unstable_opts.next_solver.globally && !self.features().generic_const_exprs()
     }
 
     pub fn next_trait_solver_in_coherence(self) -> bool {

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

@@ -293,9 +293,6 @@ where
             // corecursive functions as explained in #136824, relating types never
             // introduces a constructor which could cause the recursion to be guarded.
             GoalSource::TypeRelating => PathKind::Inductive,
-            // Instantiating a higher ranked goal can never cause the recursion to be
-            // guarded and is therefore unproductive.
-            GoalSource::InstantiateHigherRanked => PathKind::Inductive,
             // These goal sources are likely unproductive and can be changed to
             // `PathKind::Inductive`. Keeping them as unknown until we're confident
             // about this and have an example where it is necessary.
@@ -565,66 +562,56 @@ where
     pub(super) fn compute_goal(&mut self, goal: Goal<I, I::Predicate>) -> QueryResult<I> {
         let Goal { param_env, predicate } = goal;
         let kind = predicate.kind();
-        if let Some(kind) = kind.no_bound_vars() {
-            match kind {
-                ty::PredicateKind::Clause(ty::ClauseKind::Trait(predicate)) => {
-                    self.compute_trait_goal(Goal { param_env, predicate }).map(|(r, _via)| r)
-                }
-                ty::PredicateKind::Clause(ty::ClauseKind::HostEffect(predicate)) => {
-                    self.compute_host_effect_goal(Goal { param_env, predicate })
-                }
-                ty::PredicateKind::Clause(ty::ClauseKind::Projection(predicate)) => {
-                    self.compute_projection_goal(Goal { param_env, predicate })
-                }
-                ty::PredicateKind::Clause(ty::ClauseKind::TypeOutlives(predicate)) => {
-                    self.compute_type_outlives_goal(Goal { param_env, predicate })
-                }
-                ty::PredicateKind::Clause(ty::ClauseKind::RegionOutlives(predicate)) => {
-                    self.compute_region_outlives_goal(Goal { param_env, predicate })
-                }
-                ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType(ct, ty)) => {
-                    self.compute_const_arg_has_type_goal(Goal { param_env, predicate: (ct, ty) })
-                }
-                ty::PredicateKind::Clause(ty::ClauseKind::UnstableFeature(symbol)) => {
-                    self.compute_unstable_feature_goal(param_env, symbol)
-                }
-                ty::PredicateKind::Subtype(predicate) => {
-                    self.compute_subtype_goal(Goal { param_env, predicate })
-                }
-                ty::PredicateKind::Coerce(predicate) => {
-                    self.compute_coerce_goal(Goal { param_env, predicate })
-                }
-                ty::PredicateKind::DynCompatible(trait_def_id) => {
-                    self.compute_dyn_compatible_goal(trait_def_id)
-                }
-                ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(term)) => {
-                    self.compute_well_formed_goal(Goal { param_env, predicate: term })
-                }
-                ty::PredicateKind::Clause(ty::ClauseKind::ConstEvaluatable(ct)) => {
-                    self.compute_const_evaluatable_goal(Goal { param_env, predicate: ct })
-                }
-                ty::PredicateKind::ConstEquate(_, _) => {
-                    panic!("ConstEquate should not be emitted when `-Znext-solver` is active")
-                }
-                ty::PredicateKind::NormalizesTo(predicate) => {
-                    self.compute_normalizes_to_goal(Goal { param_env, predicate })
-                }
-                ty::PredicateKind::AliasRelate(lhs, rhs, direction) => self
-                    .compute_alias_relate_goal(Goal {
-                        param_env,
-                        predicate: (lhs, rhs, direction),
-                    }),
-                ty::PredicateKind::Ambiguous => {
-                    self.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS)
-                }
+        self.enter_forall(kind, |ecx, kind| match kind {
+            ty::PredicateKind::Clause(ty::ClauseKind::Trait(predicate)) => {
+                ecx.compute_trait_goal(Goal { param_env, predicate }).map(|(r, _via)| r)
             }
-        } else {
-            self.enter_forall(kind, |ecx, kind| {
-                let goal = goal.with(ecx.cx(), ty::Binder::dummy(kind));
-                ecx.add_goal(GoalSource::InstantiateHigherRanked, goal);
-                ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
-            })
-        }
+            ty::PredicateKind::Clause(ty::ClauseKind::HostEffect(predicate)) => {
+                ecx.compute_host_effect_goal(Goal { param_env, predicate })
+            }
+            ty::PredicateKind::Clause(ty::ClauseKind::Projection(predicate)) => {
+                ecx.compute_projection_goal(Goal { param_env, predicate })
+            }
+            ty::PredicateKind::Clause(ty::ClauseKind::TypeOutlives(predicate)) => {
+                ecx.compute_type_outlives_goal(Goal { param_env, predicate })
+            }
+            ty::PredicateKind::Clause(ty::ClauseKind::RegionOutlives(predicate)) => {
+                ecx.compute_region_outlives_goal(Goal { param_env, predicate })
+            }
+            ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType(ct, ty)) => {
+                ecx.compute_const_arg_has_type_goal(Goal { param_env, predicate: (ct, ty) })
+            }
+            ty::PredicateKind::Clause(ty::ClauseKind::UnstableFeature(symbol)) => {
+                ecx.compute_unstable_feature_goal(param_env, symbol)
+            }
+            ty::PredicateKind::Subtype(predicate) => {
+                ecx.compute_subtype_goal(Goal { param_env, predicate })
+            }
+            ty::PredicateKind::Coerce(predicate) => {
+                ecx.compute_coerce_goal(Goal { param_env, predicate })
+            }
+            ty::PredicateKind::DynCompatible(trait_def_id) => {
+                ecx.compute_dyn_compatible_goal(trait_def_id)
+            }
+            ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(term)) => {
+                ecx.compute_well_formed_goal(Goal { param_env, predicate: term })
+            }
+            ty::PredicateKind::Clause(ty::ClauseKind::ConstEvaluatable(ct)) => {
+                ecx.compute_const_evaluatable_goal(Goal { param_env, predicate: ct })
+            }
+            ty::PredicateKind::ConstEquate(_, _) => {
+                panic!("ConstEquate should not be emitted when `-Znext-solver` is active")
+            }
+            ty::PredicateKind::NormalizesTo(predicate) => {
+                ecx.compute_normalizes_to_goal(Goal { param_env, predicate })
+            }
+            ty::PredicateKind::AliasRelate(lhs, rhs, direction) => {
+                ecx.compute_alias_relate_goal(Goal { param_env, predicate: (lhs, rhs, direction) })
+            }
+            ty::PredicateKind::Ambiguous => {
+                ecx.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS)
+            }
+        })
     }
 
     // Recursively evaluates all the goals added to this `EvalCtxt` to completion, returning

compiler/rustc_session/src/config.rs

@@ -1055,7 +1055,7 @@ pub struct NextSolverConfig {
     pub coherence: bool = true,
     /// Whether the new trait solver should be enabled everywhere.
     /// This is only `true` if `coherence` is also enabled.
-    pub globally: bool = false,
+    pub globally: bool = true,
 }
 
 #[derive(Clone)]

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

@@ -231,7 +231,6 @@ impl<'tcx> BestObligation<'tcx> {
                                         nested_goal.source(),
                                         GoalSource::ImplWhereBound
                                             | GoalSource::AliasBoundConstCondition
-                                            | GoalSource::InstantiateHigherRanked
                                             | GoalSource::AliasWellFormed
                                     ) && nested_goal.result().is_err()
                                 },
@@ -523,10 +522,6 @@ impl<'tcx> ProofTreeVisitor<'tcx> for BestObligation<'tcx> {
                     ));
                     impl_where_bound_count += 1;
                 }
-                // Skip over a higher-ranked predicate.
-                (_, GoalSource::InstantiateHigherRanked) => {
-                    obligation = self.obligation.clone();
-                }
                 (ChildMode::PassThrough, _)
                 | (_, GoalSource::AliasWellFormed | GoalSource::AliasBoundConstCondition) => {
                     obligation = make_obligation(self.obligation.cause.clone());