Rollup of 9 pull requests

compiler/rustc_hir_typeck/src/generator_interior/mod.rs

@@ -239,8 +239,7 @@ pub fn resolve_interior<'a, 'tcx>(
             // typeck had previously found constraints that would cause them to be related.
 
             let mut counter = 0;
-            let mut mk_bound_region = |span| {
-                let kind = ty::BrAnon(span);
+            let mut mk_bound_region = |kind| {
                 let var = ty::BoundVar::from_u32(counter);
                 counter += 1;
                 ty::BoundRegion { var, kind }
@@ -252,24 +251,23 @@ pub fn resolve_interior<'a, 'tcx>(
                         let origin = fcx.region_var_origin(vid);
                         match origin {
                             RegionVariableOrigin::EarlyBoundRegion(span, _) => {
-                                mk_bound_region(Some(span))
+                                mk_bound_region(ty::BrAnon(Some(span)))
                             }
-                            _ => mk_bound_region(None),
+                            _ => mk_bound_region(ty::BrAnon(None)),
                         }
                     }
-                    // FIXME: these should use `BrNamed`
                     ty::ReEarlyBound(region) => {
-                        mk_bound_region(Some(fcx.tcx.def_span(region.def_id)))
+                        mk_bound_region(ty::BrNamed(region.def_id, region.name))
                     }
                     ty::ReLateBound(_, ty::BoundRegion { kind, .. })
                     | ty::ReFree(ty::FreeRegion { bound_region: kind, .. }) => match kind {
-                        ty::BoundRegionKind::BrAnon(span) => mk_bound_region(span),
-                        ty::BoundRegionKind::BrNamed(def_id, _) => {
-                            mk_bound_region(Some(fcx.tcx.def_span(def_id)))
+                        ty::BoundRegionKind::BrAnon(span) => mk_bound_region(ty::BrAnon(span)),
+                        ty::BoundRegionKind::BrNamed(def_id, sym) => {
+                            mk_bound_region(ty::BrNamed(def_id, sym))
                         }
-                        ty::BoundRegionKind::BrEnv => mk_bound_region(None),
+                        ty::BoundRegionKind::BrEnv => mk_bound_region(ty::BrAnon(None)),
                     },
-                    _ => mk_bound_region(None),
+                    _ => mk_bound_region(ty::BrAnon(None)),
                 };
                 let r = fcx.tcx.mk_re_late_bound(current_depth, br);
                 r
@@ -293,10 +291,7 @@ pub fn resolve_interior<'a, 'tcx>(
             type_causes,
             FnMutDelegate {
                 regions: &mut |br| {
-                    let kind = match br.kind {
-                        ty::BrAnon(span) => ty::BrAnon(span),
-                        _ => br.kind,
-                    };
+                    let kind = br.kind;
                     let var = ty::BoundVar::from_usize(bound_vars.len());
                     bound_vars.push(ty::BoundVariableKind::Region(kind));
                     counter += 1;

compiler/rustc_middle/src/hir/mod.rs

@@ -7,7 +7,7 @@ pub mod nested_filter;
 pub mod place;
 
 use crate::ty::query::Providers;
-use crate::ty::{ImplSubject, TyCtxt};
+use crate::ty::{EarlyBinder, ImplSubject, TyCtxt};
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::sync::{par_for_each_in, Send, Sync};
 use rustc_hir::def_id::{DefId, LocalDefId};
@@ -104,11 +104,11 @@ impl<'tcx> TyCtxt<'tcx> {
         self.parent_module_from_def_id(id.owner.def_id)
     }
 
-    pub fn impl_subject(self, def_id: DefId) -> ImplSubject<'tcx> {
-        self.impl_trait_ref(def_id)
-            .map(|t| t.subst_identity())
-            .map(ImplSubject::Trait)
-            .unwrap_or_else(|| ImplSubject::Inherent(self.type_of(def_id).subst_identity()))
+    pub fn impl_subject(self, def_id: DefId) -> EarlyBinder<ImplSubject<'tcx>> {
+        match self.impl_trait_ref(def_id) {
+            Some(t) => t.map_bound(ImplSubject::Trait),
+            None => self.type_of(def_id).map_bound(ImplSubject::Inherent),
+        }
     }
 }
 

compiler/rustc_middle/src/ty/util.rs

@@ -708,10 +708,6 @@ impl<'tcx> TyCtxt<'tcx> {
         ty::EarlyBinder(self.explicit_item_bounds(def_id))
     }
 
-    pub fn bound_impl_subject(self, def_id: DefId) -> ty::EarlyBinder<ty::ImplSubject<'tcx>> {
-        ty::EarlyBinder(self.impl_subject(def_id))
-    }
-
     /// Returns names of captured upvars for closures and generators.
     ///
     /// Here are some examples:

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

@@ -348,6 +348,14 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
     ) {
         let lang_items = self.tcx().lang_items();
         let trait_def_id = goal.predicate.trait_def_id(self.tcx());
+
+        // N.B. When assembling built-in candidates for lang items that are also
+        // `auto` traits, then the auto trait candidate that is assembled in
+        // `consider_auto_trait_candidate` MUST be disqualified to remain sound.
+        //
+        // Instead of adding the logic here, it's a better idea to add it in
+        // `EvalCtxt::disqualify_auto_trait_candidate_due_to_possible_impl` in
+        // `solve::trait_goals` instead.
         let result = if self.tcx().trait_is_auto(trait_def_id) {
             G::consider_auto_trait_candidate(self, goal)
         } else if self.tcx().trait_is_alias(trait_def_id) {

compiler/rustc_trait_selection/src/solve/canonicalize.rs

@@ -125,8 +125,9 @@ impl<'a, 'tcx> Canonicalizer<'a, 'tcx> {
         // - var_infos: [E0, U1, E1, U1, E1, E6, U6], curr_compressed_uv: 1, next_orig_uv: 6
         // - var_infos: [E0, U1, E1, U1, E1, E2, U2], curr_compressed_uv: 2, next_orig_uv: -
         //
-        // This algorithm runs in `O(n²)` where `n` is the number of different universe
-        // indices in the input. This should be fine as `n` is expected to be small.
+        // This algorithm runs in `O(nm)` where `n` is the number of different universe
+        // indices in the input and `m` is the number of canonical variables.
+        // This should be fine as both `n` and `m` are expected to be small.
         let mut curr_compressed_uv = ty::UniverseIndex::ROOT;
         let mut existential_in_new_uv = false;
         let mut next_orig_uv = Some(ty::UniverseIndex::ROOT);
@@ -245,18 +246,14 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for Canonicalizer<'_, 'tcx> {
             ty::ReError(_) => return r,
         };
 
-        let existing_bound_var = match self.canonicalize_mode {
-            CanonicalizeMode::Input => None,
-            CanonicalizeMode::Response { .. } => {
-                self.variables.iter().position(|&v| v == r.into()).map(ty::BoundVar::from)
-            }
-        };
-        let var = existing_bound_var.unwrap_or_else(|| {
-            let var = ty::BoundVar::from(self.variables.len());
-            self.variables.push(r.into());
-            self.primitive_var_infos.push(CanonicalVarInfo { kind });
-            var
-        });
+        let var = ty::BoundVar::from(
+            self.variables.iter().position(|&v| v == r.into()).unwrap_or_else(|| {
+                let var = self.variables.len();
+                self.variables.push(r.into());
+                self.primitive_var_infos.push(CanonicalVarInfo { kind });
+                var
+            }),
+        );
         let br = ty::BoundRegion { var, kind: BrAnon(None) };
         self.interner().mk_re_late_bound(self.binder_index, br)
     }

compiler/rustc_trait_selection/src/solve/trait_goals.rs

@@ -3,7 +3,7 @@
 use super::assembly::{self, structural_traits};
 use super::{EvalCtxt, SolverMode};
 use rustc_hir::def_id::DefId;
-use rustc_hir::LangItem;
+use rustc_hir::{LangItem, Movability};
 use rustc_infer::traits::query::NoSolution;
 use rustc_infer::traits::util::supertraits;
 use rustc_middle::traits::solve::{CanonicalResponse, Certainty, Goal, QueryResult};
@@ -147,66 +147,8 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
         ecx: &mut EvalCtxt<'_, 'tcx>,
         goal: Goal<'tcx, Self>,
     ) -> QueryResult<'tcx> {
-        let self_ty = goal.predicate.self_ty();
-        match *self_ty.kind() {
-            // Stall int and float vars until they are resolved to a concrete
-            // numerical type. That's because the check for impls below treats
-            // int vars as matching any impl. Even if we filtered such impls,
-            // we probably don't want to treat an `impl !AutoTrait for i32` as
-            // disqualifying the built-in auto impl for `i64: AutoTrait` either.
-            ty::Infer(ty::IntVar(_) | ty::FloatVar(_)) => {
-                return ecx.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS);
-            }
-
-            // These types cannot be structurally decomposed into constitutent
-            // types, and therefore have no builtin impl.
-            ty::Dynamic(..)
-            | ty::Param(..)
-            | ty::Foreign(..)
-            | ty::Alias(ty::Projection, ..)
-            | ty::Placeholder(..) => return Err(NoSolution),
-
-            ty::Infer(_) | ty::Bound(_, _) => bug!("unexpected type `{self_ty}`"),
-
-            // For rigid types, we only register a builtin auto implementation
-            // if there is no implementation that could ever apply to the self
-            // type.
-            //
-            // This differs from the current stable behavior and fixes #84857.
-            // Due to breakage found via crater, we currently instead lint
-            // patterns which can be used to exploit this unsoundness on stable,
-            // see #93367 for more details.
-            ty::Bool
-            | ty::Char
-            | ty::Int(_)
-            | ty::Uint(_)
-            | ty::Float(_)
-            | ty::Str
-            | ty::Array(_, _)
-            | ty::Slice(_)
-            | ty::RawPtr(_)
-            | ty::Ref(_, _, _)
-            | ty::FnDef(_, _)
-            | ty::FnPtr(_)
-            | ty::Closure(_, _)
-            | ty::Generator(_, _, _)
-            | ty::GeneratorWitness(_)
-            | ty::GeneratorWitnessMIR(_, _)
-            | ty::Never
-            | ty::Tuple(_)
-            | ty::Error(_)
-            | ty::Adt(_, _)
-            | ty::Alias(ty::Opaque, _) => {
-                if let Some(def_id) = ecx.tcx().find_map_relevant_impl(
-                    goal.predicate.def_id(),
-                    goal.predicate.self_ty(),
-                    TreatProjections::NextSolverLookup,
-                    Some,
-                ) {
-                    debug!(?def_id, ?goal, "disqualified auto-trait implementation");
-                    return Err(NoSolution);
-                }
-            }
+        if let Some(result) = ecx.disqualify_auto_trait_candidate_due_to_possible_impl(goal) {
+            return result;
         }
 
         ecx.probe_and_evaluate_goal_for_constituent_tys(
@@ -630,6 +572,97 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
 }
 
 impl<'tcx> EvalCtxt<'_, 'tcx> {
+    // Return `Some` if there is an impl (built-in or user provided) that may
+    // hold for the self type of the goal, which for coherence and soundness
+    // purposes must disqualify the built-in auto impl assembled by considering
+    // the type's constituent types.
+    fn disqualify_auto_trait_candidate_due_to_possible_impl(
+        &mut self,
+        goal: Goal<'tcx, TraitPredicate<'tcx>>,
+    ) -> Option<QueryResult<'tcx>> {
+        let self_ty = goal.predicate.self_ty();
+        match *self_ty.kind() {
+            // Stall int and float vars until they are resolved to a concrete
+            // numerical type. That's because the check for impls below treats
+            // int vars as matching any impl. Even if we filtered such impls,
+            // we probably don't want to treat an `impl !AutoTrait for i32` as
+            // disqualifying the built-in auto impl for `i64: AutoTrait` either.
+            ty::Infer(ty::IntVar(_) | ty::FloatVar(_)) => {
+                Some(self.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS))
+            }
+
+            // These types cannot be structurally decomposed into constitutent
+            // types, and therefore have no built-in auto impl.
+            ty::Dynamic(..)
+            | ty::Param(..)
+            | ty::Foreign(..)
+            | ty::Alias(ty::Projection, ..)
+            | ty::Placeholder(..) => Some(Err(NoSolution)),
+
+            ty::Infer(_) | ty::Bound(_, _) => bug!("unexpected type `{self_ty}`"),
+
+            // Generators have one special built-in candidate, `Unpin`, which
+            // takes precedence over the structural auto trait candidate being
+            // assembled.
+            ty::Generator(_, _, movability)
+                if Some(goal.predicate.def_id()) == self.tcx().lang_items().unpin_trait() =>
+            {
+                match movability {
+                    Movability::Static => Some(Err(NoSolution)),
+                    Movability::Movable => {
+                        Some(self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes))
+                    }
+                }
+            }
+
+            // For rigid types, any possible implementation that could apply to
+            // the type (even if after unification and processing nested goals
+            // it does not hold) will disqualify the built-in auto impl.
+            //
+            // This differs from the current stable behavior and fixes #84857.
+            // Due to breakage found via crater, we currently instead lint
+            // patterns which can be used to exploit this unsoundness on stable,
+            // see #93367 for more details.
+            ty::Bool
+            | ty::Char
+            | ty::Int(_)
+            | ty::Uint(_)
+            | ty::Float(_)
+            | ty::Str
+            | ty::Array(_, _)
+            | ty::Slice(_)
+            | ty::RawPtr(_)
+            | ty::Ref(_, _, _)
+            | ty::FnDef(_, _)
+            | ty::FnPtr(_)
+            | ty::Closure(_, _)
+            | ty::Generator(_, _, _)
+            | ty::GeneratorWitness(_)
+            | ty::GeneratorWitnessMIR(_, _)
+            | ty::Never
+            | ty::Tuple(_)
+            | ty::Adt(_, _)
+            // FIXME: Handling opaques here is kinda sus. Especially because we
+            // simplify them to PlaceholderSimplifiedType.
+            | ty::Alias(ty::Opaque, _) => {
+                if let Some(def_id) = self.tcx().find_map_relevant_impl(
+                    goal.predicate.def_id(),
+                    goal.predicate.self_ty(),
+                    TreatProjections::NextSolverLookup,
+                    Some,
+                ) {
+                    debug!(?def_id, ?goal, "disqualified auto-trait implementation");
+                    // No need to actually consider the candidate here,
+                    // since we do that in `consider_impl_candidate`.
+                    return Some(Err(NoSolution));
+                } else {
+                    None
+                }
+            }
+            ty::Error(_) => None,
+        }
+    }
+
     /// Convenience function for traits that are structural, i.e. that only
     /// have nested subgoals that only change the self type. Unlike other
     /// evaluate-like helpers, this does a probe, so it doesn't need to be

compiler/rustc_trait_selection/src/traits/coherence.rs

@@ -306,7 +306,7 @@ fn negative_impl(tcx: TyCtxt<'_>, impl1_def_id: DefId, impl2_def_id: DefId) -> b
         &infcx,
         ObligationCause::dummy(),
         impl_env,
-        tcx.impl_subject(impl1_def_id),
+        tcx.impl_subject(impl1_def_id).subst_identity(),
     ) {
         Ok(s) => s,
         Err(err) => {