Split out PredicatePolarity from ImplPolarity

compiler/rustc_borrowck/src/type_check/canonical.rs

@@ -82,7 +82,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
     ) {
         self.prove_predicate(
             ty::Binder::dummy(ty::PredicateKind::Clause(ty::ClauseKind::Trait(
-                ty::TraitPredicate { trait_ref, polarity: ty::ImplPolarity::Positive },
+                ty::TraitPredicate { trait_ref, polarity: ty::PredicatePolarity::Positive },
             ))),
             locations,
             category,

compiler/rustc_hir_analysis/src/bounds.rs

@@ -42,7 +42,7 @@ impl<'tcx> Bounds<'tcx> {
         tcx: TyCtxt<'tcx>,
         trait_ref: ty::PolyTraitRef<'tcx>,
         span: Span,
-        polarity: ty::ImplPolarity,
+        polarity: ty::PredicatePolarity,
     ) {
         self.push_trait_bound_inner(tcx, trait_ref, span, polarity);
     }
@@ -52,7 +52,7 @@ impl<'tcx> Bounds<'tcx> {
         tcx: TyCtxt<'tcx>,
         trait_ref: ty::PolyTraitRef<'tcx>,
         span: Span,
-        polarity: ty::ImplPolarity,
+        polarity: ty::PredicatePolarity,
     ) {
         self.clauses.push((
             trait_ref

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -1322,7 +1322,7 @@ fn check_impl<'tcx>(
                     trait_ref,
                 );
                 let trait_pred =
-                    ty::TraitPredicate { trait_ref, polarity: ty::ImplPolarity::Positive };
+                    ty::TraitPredicate { trait_ref, polarity: ty::PredicatePolarity::Positive };
                 let mut obligations = traits::wf::trait_obligations(
                     wfcx.infcx,
                     wfcx.param_env,

compiler/rustc_hir_analysis/src/coherence/builtin.rs

@@ -551,7 +551,7 @@ fn infringing_fields_error(
                     }
                     if let ty::PredicateKind::Clause(ty::ClauseKind::Trait(ty::TraitPredicate {
                         trait_ref,
-                        polarity: ty::ImplPolarity::Positive,
+                        polarity: ty::PredicatePolarity::Positive,
                         ..
                     })) = error_predicate.kind().skip_binder()
                     {

compiler/rustc_hir_analysis/src/collect/predicates_of.rs

@@ -624,7 +624,7 @@ pub(super) fn implied_predicates_with_filter(
             for &(pred, span) in implied_bounds {
                 debug!("superbound: {:?}", pred);
                 if let ty::ClauseKind::Trait(bound) = pred.kind().skip_binder()
-                    && bound.polarity == ty::ImplPolarity::Positive
+                    && bound.polarity == ty::PredicatePolarity::Positive
                 {
                     tcx.at(span).super_predicates_of(bound.def_id());
                 }
@@ -634,7 +634,7 @@ pub(super) fn implied_predicates_with_filter(
             for &(pred, span) in implied_bounds {
                 debug!("superbound: {:?}", pred);
                 if let ty::ClauseKind::Trait(bound) = pred.kind().skip_binder()
-                    && bound.polarity == ty::ImplPolarity::Positive
+                    && bound.polarity == ty::PredicatePolarity::Positive
                 {
                     tcx.at(span).implied_predicates_of(bound.def_id());
                 }

compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs

@@ -140,16 +140,16 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 hir::GenericBound::Trait(poly_trait_ref, modifier) => {
                     let (constness, polarity) = match modifier {
                         hir::TraitBoundModifier::Const => {
-                            (ty::BoundConstness::Const, ty::ImplPolarity::Positive)
+                            (ty::BoundConstness::Const, ty::PredicatePolarity::Positive)
                         }
                         hir::TraitBoundModifier::MaybeConst => {
-                            (ty::BoundConstness::ConstIfConst, ty::ImplPolarity::Positive)
+                            (ty::BoundConstness::ConstIfConst, ty::PredicatePolarity::Positive)
                         }
                         hir::TraitBoundModifier::None => {
-                            (ty::BoundConstness::NotConst, ty::ImplPolarity::Positive)
+                            (ty::BoundConstness::NotConst, ty::PredicatePolarity::Positive)
                         }
                         hir::TraitBoundModifier::Negative => {
-                            (ty::BoundConstness::NotConst, ty::ImplPolarity::Negative)
+                            (ty::BoundConstness::NotConst, ty::PredicatePolarity::Negative)
                         }
                         hir::TraitBoundModifier::Maybe => continue,
                     };

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -673,7 +673,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         trait_ref: &hir::TraitRef<'tcx>,
         span: Span,
         constness: ty::BoundConstness,
-        polarity: ty::ImplPolarity,
+        polarity: ty::PredicatePolarity,
         self_ty: Ty<'tcx>,
         bounds: &mut Bounds<'tcx>,
         only_self_bounds: OnlySelfBounds,
@@ -710,7 +710,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             // Don't register additional associated type bounds for negative bounds,
             // since we should have emitten an error for them earlier, and they will
             // not be well-formed!
-            if polarity == ty::ImplPolarity::Negative {
+            if polarity != ty::PredicatePolarity::Positive {
                 assert!(
                     self.tcx().dcx().has_errors().is_some(),
                     "negative trait bounds should not have bindings",

compiler/rustc_hir_analysis/src/hir_ty_lowering/object_safety.rs

@@ -43,7 +43,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 &trait_bound.trait_ref,
                 trait_bound.span,
                 ty::BoundConstness::NotConst,
-                ty::ImplPolarity::Positive,
+                ty::PredicatePolarity::Positive,
                 dummy_self,
                 &mut bounds,
                 // True so we don't populate `bounds` with associated type bounds, even
@@ -60,7 +60,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             let bound_pred = pred.kind();
             match bound_pred.skip_binder() {
                 ty::ClauseKind::Trait(trait_pred) => {
-                    assert_eq!(trait_pred.polarity, ty::ImplPolarity::Positive);
+                    assert_eq!(trait_pred.polarity, ty::PredicatePolarity::Positive);
                     trait_bounds.push((bound_pred.rebind(trait_pred.trait_ref), span));
                 }
                 ty::ClauseKind::Projection(proj) => {

compiler/rustc_hir_typeck/src/expr.rs

@@ -3100,7 +3100,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     cause.clone().derived_cause(
                         ty::Binder::dummy(ty::TraitPredicate {
                             trait_ref: impl_trait_ref,
-                            polarity: ty::ImplPolarity::Positive,
+                            polarity: ty::PredicatePolarity::Positive,
                         }),
                         |derived| {
                             traits::ImplDerivedObligation(Box::new(

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -875,7 +875,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                 match pred.kind().skip_binder() {
                                     ty::PredicateKind::Clause(ty::ClauseKind::Trait(pred)) => {
                                         Some(pred.def_id()) == self.tcx.lang_items().sized_trait()
-                                            && pred.polarity == ty::ImplPolarity::Positive
+                                            && pred.polarity == ty::PredicatePolarity::Positive
                                     }
                                     _ => false,
                                 }
@@ -3367,7 +3367,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                 "inherent impls can't be candidates, only trait impls can be",
                             )
                         })
-                        .filter(|header| header.polarity == ty::ImplPolarity::Negative)
+                        .filter(|header| header.polarity != ty::ImplPolarity::Positive)
                         .any(|header| {
                             let imp = header.trait_ref.instantiate_identity();
                             let imp_simp =

compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs

@@ -306,7 +306,7 @@ impl<T> Trait<T> for X {
                                 .any(|(pred, _span)| match pred.kind().skip_binder() {
                                     ty::ClauseKind::Trait(trait_predicate)
                                         if trait_predicate.polarity
-                                            == ty::ImplPolarity::Positive =>
+                                            == ty::PredicatePolarity::Positive =>
                                     {
                                         trait_predicate.def_id() == def_id
                                     }
@@ -420,7 +420,7 @@ impl<T> Trait<T> for X {
                             else {
                                 continue;
                             };
-                            if trait_predicate.polarity != ty::ImplPolarity::Positive {
+                            if trait_predicate.polarity != ty::PredicatePolarity::Positive {
                                 continue;
                             }
                             let def_id = trait_predicate.def_id();

compiler/rustc_infer/src/traits/mod.rs

@@ -209,7 +209,7 @@ impl<'tcx> FulfillmentError<'tcx> {
 }
 
 impl<'tcx> PolyTraitObligation<'tcx> {
-    pub fn polarity(&self) -> ty::ImplPolarity {
+    pub fn polarity(&self) -> ty::PredicatePolarity {
         self.predicate.skip_binder().polarity
     }
 

compiler/rustc_infer/src/traits/util.rs

@@ -270,7 +270,7 @@ impl<'tcx, O: Elaboratable<'tcx>> Elaborator<'tcx, O> {
         match bound_clause.skip_binder() {
             ty::ClauseKind::Trait(data) => {
                 // Negative trait bounds do not imply any supertrait bounds
-                if data.polarity == ty::ImplPolarity::Negative {
+                if data.polarity != ty::PredicatePolarity::Positive {
                     return;
                 }
                 // Get predicates implied by the trait, or only super predicates if we only care about self predicates.

compiler/rustc_lint/src/builtin.rs

@@ -726,7 +726,7 @@ fn type_implements_negative_copy_modulo_regions<'tcx>(
     param_env: ty::ParamEnv<'tcx>,
 ) -> bool {
     let trait_ref = ty::TraitRef::new(tcx, tcx.require_lang_item(hir::LangItem::Copy, None), [ty]);
-    let pred = ty::TraitPredicate { trait_ref, polarity: ty::ImplPolarity::Negative };
+    let pred = ty::TraitPredicate { trait_ref, polarity: ty::PredicatePolarity::Negative };
     let obligation = traits::Obligation {
         cause: traits::ObligationCause::dummy(),
         param_env,

compiler/rustc_middle/src/ty/context.rs

@@ -27,8 +27,8 @@ use crate::traits::solve::{
 use crate::ty::{
     self, AdtDef, AdtDefData, AdtKind, Binder, Clause, Const, ConstData, GenericParamDefKind,
     ImplPolarity, List, ParamConst, ParamTy, PolyExistentialPredicate, PolyFnSig, Predicate,
-    PredicateKind, Region, RegionKind, ReprOptions, TraitObjectVisitor, Ty, TyKind, TyVid,
-    TypeVisitable, Visibility,
+    PredicateKind, PredicatePolarity, Region, RegionKind, ReprOptions, TraitObjectVisitor, Ty,
+    TyKind, TyVid, TypeVisitable, Visibility,
 };
 use crate::ty::{GenericArg, GenericArgs, GenericArgsRef};
 use rustc_ast::{self as ast, attr};
@@ -1526,7 +1526,7 @@ macro_rules! nop_slice_lift {
 nop_slice_lift! {ty::ValTree<'a> => ty::ValTree<'tcx>}
 
 TrivialLiftImpls! {
-    ImplPolarity, Promoted
+    ImplPolarity, PredicatePolarity, Promoted
 }
 
 macro_rules! sty_debug_print {
@@ -1833,7 +1833,7 @@ impl<'tcx> TyCtxt<'tcx> {
                 return false;
             };
             trait_predicate.trait_ref.def_id == future_trait
-                && trait_predicate.polarity == ImplPolarity::Positive
+                && trait_predicate.polarity == PredicatePolarity::Positive
         })
     }
 

compiler/rustc_middle/src/ty/error.rs

@@ -32,7 +32,7 @@ impl<T> ExpectedFound<T> {
 pub enum TypeError<'tcx> {
     Mismatch,
     ConstnessMismatch(ExpectedFound<ty::BoundConstness>),
-    PolarityMismatch(ExpectedFound<ty::ImplPolarity>),
+    PolarityMismatch(ExpectedFound<ty::PredicatePolarity>),
     UnsafetyMismatch(ExpectedFound<hir::Unsafety>),
     AbiMismatch(ExpectedFound<abi::Abi>),
     Mutability,

compiler/rustc_middle/src/ty/mod.rs

@@ -280,23 +280,43 @@ pub enum ImplPolarity {
     Reservation,
 }
 
-impl ImplPolarity {
+impl fmt::Display for ImplPolarity {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Positive => f.write_str("positive"),
+            Self::Negative => f.write_str("negative"),
+            Self::Reservation => f.write_str("reservation"),
+        }
+    }
+}
+
+/// Polarity for a trait predicate. May either be negative or positive.
+/// Distinguished from [`ImplPolarity`] since we never compute goals with
+/// "reservation" level.
+#[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, HashStable, Debug)]
+#[derive(TypeFoldable, TypeVisitable)]
+pub enum PredicatePolarity {
+    /// `Type: Trait`
+    Positive,
+    /// `Type: !Trait`
+    Negative,
+}
+
+impl PredicatePolarity {
     /// Flips polarity by turning `Positive` into `Negative` and `Negative` into `Positive`.
-    pub fn flip(&self) -> Option<ImplPolarity> {
+    pub fn flip(&self) -> PredicatePolarity {
         match self {
-            ImplPolarity::Positive => Some(ImplPolarity::Negative),
-            ImplPolarity::Negative => Some(ImplPolarity::Positive),
-            ImplPolarity::Reservation => None,
+            PredicatePolarity::Positive => PredicatePolarity::Negative,
+            PredicatePolarity::Negative => PredicatePolarity::Positive,
         }
     }
 }
 
-impl fmt::Display for ImplPolarity {
+impl fmt::Display for PredicatePolarity {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             Self::Positive => f.write_str("positive"),
             Self::Negative => f.write_str("negative"),
-            Self::Reservation => f.write_str("reservation"),
         }
     }
 }

compiler/rustc_middle/src/ty/predicate.rs

@@ -11,7 +11,7 @@ use std::cmp::Ordering;
 use crate::ty::visit::TypeVisitableExt;
 use crate::ty::{
     self, AliasTy, Binder, DebruijnIndex, DebugWithInfcx, EarlyBinder, GenericArg, GenericArgs,
-    GenericArgsRef, ImplPolarity, Term, Ty, TyCtxt, TypeFlags, WithCachedTypeInfo,
+    GenericArgsRef, PredicatePolarity, Term, Ty, TyCtxt, TypeFlags, WithCachedTypeInfo,
 };
 
 pub type ClauseKind<'tcx> = IrClauseKind<TyCtxt<'tcx>>;
@@ -70,7 +70,7 @@ impl<'tcx> Predicate<'tcx> {
                     polarity,
                 })) => Some(PredicateKind::Clause(ClauseKind::Trait(TraitPredicate {
                     trait_ref,
-                    polarity: polarity.flip()?,
+                    polarity: polarity.flip(),
                 }))),
 
                 _ => None,
@@ -663,7 +663,7 @@ pub struct TraitPredicate<'tcx> {
     /// exist via a series of predicates.)
     ///
     /// If polarity is Reserved: that's a bug.
-    pub polarity: ImplPolarity,
+    pub polarity: PredicatePolarity,
 }
 
 pub type PolyTraitPredicate<'tcx> = ty::Binder<'tcx, TraitPredicate<'tcx>>;
@@ -693,7 +693,7 @@ impl<'tcx> PolyTraitPredicate<'tcx> {
     }
 
     #[inline]
-    pub fn polarity(self) -> ImplPolarity {
+    pub fn polarity(self) -> PredicatePolarity {
         self.skip_binder().polarity
     }
 }
@@ -907,7 +907,7 @@ impl<'tcx> ToPredicate<'tcx> for TraitRef<'tcx> {
 impl<'tcx> ToPredicate<'tcx, TraitPredicate<'tcx>> for TraitRef<'tcx> {
     #[inline(always)]
     fn to_predicate(self, _tcx: TyCtxt<'tcx>) -> TraitPredicate<'tcx> {
-        TraitPredicate { trait_ref: self, polarity: ImplPolarity::Positive }
+        TraitPredicate { trait_ref: self, polarity: PredicatePolarity::Positive }
     }
 }
 
@@ -940,7 +940,7 @@ impl<'tcx> ToPredicate<'tcx, PolyTraitPredicate<'tcx>> for Binder<'tcx, TraitRef
     fn to_predicate(self, _: TyCtxt<'tcx>) -> PolyTraitPredicate<'tcx> {
         self.map_bound(|trait_ref| TraitPredicate {
             trait_ref,
-            polarity: ty::ImplPolarity::Positive,
+            polarity: ty::PredicatePolarity::Positive,
         })
     }
 }