rustc_middle/ty/
predicate.rs

Help
1use std::cmp::Ordering;
2
3use rustc_data_structures::intern::Interned;
4use rustc_hir::def_id::DefId;
5use rustc_macros::{HashStable, extension};
6use rustc_type_ir as ir;
7
8use crate::ty::{
9    self, DebruijnIndex, EarlyBinder, PredicatePolarity, Ty, TyCtxt, TypeFlags, Upcast, UpcastFrom,
10    WithCachedTypeInfo,
11};
12
13pub type TraitRef<'tcx> = ir::TraitRef<TyCtxt<'tcx>>;
14pub type AliasTerm<'tcx> = ir::AliasTerm<TyCtxt<'tcx>>;
15pub type ProjectionPredicate<'tcx> = ir::ProjectionPredicate<TyCtxt<'tcx>>;
16pub type ExistentialPredicate<'tcx> = ir::ExistentialPredicate<TyCtxt<'tcx>>;
17pub type ExistentialTraitRef<'tcx> = ir::ExistentialTraitRef<TyCtxt<'tcx>>;
18pub type ExistentialProjection<'tcx> = ir::ExistentialProjection<TyCtxt<'tcx>>;
19pub type TraitPredicate<'tcx> = ir::TraitPredicate<TyCtxt<'tcx>>;
20pub type HostEffectPredicate<'tcx> = ir::HostEffectPredicate<TyCtxt<'tcx>>;
21pub type ClauseKind<'tcx> = ir::ClauseKind<TyCtxt<'tcx>>;
22pub type PredicateKind<'tcx> = ir::PredicateKind<TyCtxt<'tcx>>;
23pub type NormalizesTo<'tcx> = ir::NormalizesTo<TyCtxt<'tcx>>;
24pub type CoercePredicate<'tcx> = ir::CoercePredicate<TyCtxt<'tcx>>;
25pub type SubtypePredicate<'tcx> = ir::SubtypePredicate<TyCtxt<'tcx>>;
26pub type OutlivesPredicate<'tcx, T> = ir::OutlivesPredicate<TyCtxt<'tcx>, T>;
27pub type RegionOutlivesPredicate<'tcx> = OutlivesPredicate<'tcx, ty::Region<'tcx>>;
28pub type TypeOutlivesPredicate<'tcx> = OutlivesPredicate<'tcx, Ty<'tcx>>;
29pub type PolyTraitPredicate<'tcx> = ty::Binder<'tcx, TraitPredicate<'tcx>>;
30pub type PolyRegionOutlivesPredicate<'tcx> = ty::Binder<'tcx, RegionOutlivesPredicate<'tcx>>;
31pub type PolyTypeOutlivesPredicate<'tcx> = ty::Binder<'tcx, TypeOutlivesPredicate<'tcx>>;
32pub type PolySubtypePredicate<'tcx> = ty::Binder<'tcx, SubtypePredicate<'tcx>>;
33pub type PolyCoercePredicate<'tcx> = ty::Binder<'tcx, CoercePredicate<'tcx>>;
34pub type PolyProjectionPredicate<'tcx> = ty::Binder<'tcx, ProjectionPredicate<'tcx>>;
35
36/// A statement that can be proven by a trait solver. This includes things that may
37/// show up in where clauses, such as trait predicates and projection predicates,
38/// and also things that are emitted as part of type checking such as `DynCompatible`
39/// predicate which is emitted when a type is coerced to a trait object.
40///
41/// Use this rather than `PredicateKind`, whenever possible.
42#[derive(Clone, Copy, PartialEq, Eq, Hash, HashStable)]
43#[rustc_pass_by_value]
44pub struct Predicate<'tcx>(
45    pub(super) Interned<'tcx, WithCachedTypeInfo<ty::Binder<'tcx, PredicateKind<'tcx>>>>,
46);
47
48impl<'tcx> rustc_type_ir::inherent::Predicate<TyCtxt<'tcx>> for Predicate<'tcx> {
49    fn as_clause(self) -> Option<ty::Clause<'tcx>> {
50        self.as_clause()
51    }
52
53    fn allow_normalization(self) -> bool {
54        self.allow_normalization()
55    }
56}
57
58impl<'tcx> rustc_type_ir::inherent::IntoKind for Predicate<'tcx> {
59    type Kind = ty::Binder<'tcx, ty::PredicateKind<'tcx>>;
60
61    fn kind(self) -> Self::Kind {
62        self.kind()
63    }
64}
65
66impl<'tcx> rustc_type_ir::Flags for Predicate<'tcx> {
67    fn flags(&self) -> TypeFlags {
68        self.0.flags
69    }
70
71    fn outer_exclusive_binder(&self) -> ty::DebruijnIndex {
72        self.0.outer_exclusive_binder
73    }
74}
75
76impl<'tcx> Predicate<'tcx> {
77    /// Gets the inner `ty::Binder<'tcx, PredicateKind<'tcx>>`.
78    #[inline]
79    pub fn kind(self) -> ty::Binder<'tcx, PredicateKind<'tcx>> {
80        self.0.internee
81    }
82
83    // FIXME(compiler-errors): Think about removing this.
84    #[inline(always)]
85    pub fn flags(self) -> TypeFlags {
86        self.0.flags
87    }
88
89    // FIXME(compiler-errors): Think about removing this.
90    #[inline(always)]
91    pub fn outer_exclusive_binder(self) -> DebruijnIndex {
92        self.0.outer_exclusive_binder
93    }
94
95    /// Flips the polarity of a Predicate.
96    ///
97    /// Given `T: Trait` predicate it returns `T: !Trait` and given `T: !Trait` returns `T: Trait`.
98    pub fn flip_polarity(self, tcx: TyCtxt<'tcx>) -> Option<Predicate<'tcx>> {
99        let kind = self
100            .kind()
101            .map_bound(|kind| match kind {
102                PredicateKind::Clause(ClauseKind::Trait(TraitPredicate {
103                    trait_ref,
104                    polarity,
105                })) => Some(PredicateKind::Clause(ClauseKind::Trait(TraitPredicate {
106                    trait_ref,
107                    polarity: polarity.flip(),
108                }))),
109
110                _ => None,
111            })
112            .transpose()?;
113
114        Some(tcx.mk_predicate(kind))
115    }
116
117    /// Whether this projection can be soundly normalized.
118    ///
119    /// Wf predicates must not be normalized, as normalization
120    /// can remove required bounds which would cause us to
121    /// unsoundly accept some programs. See #91068.
122    #[inline]
123    pub fn allow_normalization(self) -> bool {
124        // Keep this in sync with the one in `rustc_type_ir::inherent`!
125        match self.kind().skip_binder() {
126            PredicateKind::Clause(ClauseKind::WellFormed(_))
127            | PredicateKind::AliasRelate(..)
128            | PredicateKind::NormalizesTo(..) => false,
129            PredicateKind::Clause(ClauseKind::Trait(_))
130            | PredicateKind::Clause(ClauseKind::HostEffect(..))
131            | PredicateKind::Clause(ClauseKind::RegionOutlives(_))
132            | PredicateKind::Clause(ClauseKind::TypeOutlives(_))
133            | PredicateKind::Clause(ClauseKind::Projection(_))
134            | PredicateKind::Clause(ClauseKind::ConstArgHasType(..))
135            | PredicateKind::DynCompatible(_)
136            | PredicateKind::Subtype(_)
137            | PredicateKind::Coerce(_)
138            | PredicateKind::Clause(ClauseKind::ConstEvaluatable(_))
139            | PredicateKind::ConstEquate(_, _)
140            | PredicateKind::Ambiguous => true,
141        }
142    }
143}
144
145impl<'tcx> rustc_errors::IntoDiagArg for Predicate<'tcx> {
146    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> rustc_errors::DiagArgValue {
147        ty::tls::with(|tcx| {
148            let pred = tcx.short_string(self, path);
149            rustc_errors::DiagArgValue::Str(std::borrow::Cow::Owned(pred))
150        })
151    }
152}
153
154impl<'tcx> rustc_errors::IntoDiagArg for Clause<'tcx> {
155    fn into_diag_arg(self, path: &mut Option<std::path::PathBuf>) -> rustc_errors::DiagArgValue {
156        ty::tls::with(|tcx| {
157            let clause = tcx.short_string(self, path);
158            rustc_errors::DiagArgValue::Str(std::borrow::Cow::Owned(clause))
159        })
160    }
161}
162
163/// A subset of predicates which can be assumed by the trait solver. They show up in
164/// an item's where clauses, hence the name `Clause`, and may either be user-written
165/// (such as traits) or may be inserted during lowering.
166#[derive(Clone, Copy, PartialEq, Eq, Hash, HashStable)]
167#[rustc_pass_by_value]
168pub struct Clause<'tcx>(
169    pub(super) Interned<'tcx, WithCachedTypeInfo<ty::Binder<'tcx, PredicateKind<'tcx>>>>,
170);
171
172impl<'tcx> rustc_type_ir::inherent::Clause<TyCtxt<'tcx>> for Clause<'tcx> {
173    fn as_predicate(self) -> Predicate<'tcx> {
174        self.as_predicate()
175    }
176
177    fn instantiate_supertrait(self, tcx: TyCtxt<'tcx>, trait_ref: ty::PolyTraitRef<'tcx>) -> Self {
178        self.instantiate_supertrait(tcx, trait_ref)
179    }
180}
181
182impl<'tcx> rustc_type_ir::inherent::IntoKind for Clause<'tcx> {
183    type Kind = ty::Binder<'tcx, ClauseKind<'tcx>>;
184
185    fn kind(self) -> Self::Kind {
186        self.kind()
187    }
188}
189
190impl<'tcx> Clause<'tcx> {
191    pub fn as_predicate(self) -> Predicate<'tcx> {
192        Predicate(self.0)
193    }
194
195    pub fn kind(self) -> ty::Binder<'tcx, ClauseKind<'tcx>> {
196        self.0.internee.map_bound(|kind| match kind {
197            PredicateKind::Clause(clause) => clause,
198            _ => unreachable!(),
199        })
200    }
201
202    pub fn as_trait_clause(self) -> Option<ty::Binder<'tcx, TraitPredicate<'tcx>>> {
203        let clause = self.kind();
204        if let ty::ClauseKind::Trait(trait_clause) = clause.skip_binder() {
205            Some(clause.rebind(trait_clause))
206        } else {
207            None
208        }
209    }
210
211    pub fn as_projection_clause(self) -> Option<ty::Binder<'tcx, ProjectionPredicate<'tcx>>> {
212        let clause = self.kind();
213        if let ty::ClauseKind::Projection(projection_clause) = clause.skip_binder() {
214            Some(clause.rebind(projection_clause))
215        } else {
216            None
217        }
218    }
219
220    pub fn as_type_outlives_clause(self) -> Option<ty::Binder<'tcx, TypeOutlivesPredicate<'tcx>>> {
221        let clause = self.kind();
222        if let ty::ClauseKind::TypeOutlives(o) = clause.skip_binder() {
223            Some(clause.rebind(o))
224        } else {
225            None
226        }
227    }
228
229    pub fn as_region_outlives_clause(
230        self,
231    ) -> Option<ty::Binder<'tcx, RegionOutlivesPredicate<'tcx>>> {
232        let clause = self.kind();
233        if let ty::ClauseKind::RegionOutlives(o) = clause.skip_binder() {
234            Some(clause.rebind(o))
235        } else {
236            None
237        }
238    }
239}
240
241#[extension(pub trait ExistentialPredicateStableCmpExt<'tcx>)]
242impl<'tcx> ExistentialPredicate<'tcx> {
243    /// Compares via an ordering that will not change if modules are reordered or other changes are
244    /// made to the tree. In particular, this ordering is preserved across incremental compilations.
245    fn stable_cmp(&self, tcx: TyCtxt<'tcx>, other: &Self) -> Ordering {
246        match (*self, *other) {
247            (ExistentialPredicate::Trait(_), ExistentialPredicate::Trait(_)) => Ordering::Equal,
248            (ExistentialPredicate::Projection(ref a), ExistentialPredicate::Projection(ref b)) => {
249                tcx.def_path_hash(a.def_id).cmp(&tcx.def_path_hash(b.def_id))
250            }
251            (ExistentialPredicate::AutoTrait(ref a), ExistentialPredicate::AutoTrait(ref b)) => {
252                tcx.def_path_hash(*a).cmp(&tcx.def_path_hash(*b))
253            }
254            (ExistentialPredicate::Trait(_), _) => Ordering::Less,
255            (ExistentialPredicate::Projection(_), ExistentialPredicate::Trait(_)) => {
256                Ordering::Greater
257            }
258            (ExistentialPredicate::Projection(_), _) => Ordering::Less,
259            (ExistentialPredicate::AutoTrait(_), _) => Ordering::Greater,
260        }
261    }
262}
263
264pub type PolyExistentialPredicate<'tcx> = ty::Binder<'tcx, ExistentialPredicate<'tcx>>;
265
266impl<'tcx> rustc_type_ir::inherent::BoundExistentialPredicates<TyCtxt<'tcx>>
267    for &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>
268{
269    fn principal_def_id(self) -> Option<DefId> {
270        self.principal_def_id()
271    }
272
273    fn principal(self) -> Option<ty::PolyExistentialTraitRef<'tcx>> {
274        self.principal()
275    }
276
277    fn auto_traits(self) -> impl IntoIterator<Item = DefId> {
278        self.auto_traits()
279    }
280
281    fn projection_bounds(
282        self,
283    ) -> impl IntoIterator<Item = ty::Binder<'tcx, ExistentialProjection<'tcx>>> {
284        self.projection_bounds()
285    }
286}
287
288impl<'tcx> ty::List<ty::PolyExistentialPredicate<'tcx>> {
289    /// Returns the "principal `DefId`" of this set of existential predicates.
290    ///
291    /// A Rust trait object type consists (in addition to a lifetime bound)
292    /// of a set of trait bounds, which are separated into any number
293    /// of auto-trait bounds, and at most one non-auto-trait bound. The
294    /// non-auto-trait bound is called the "principal" of the trait
295    /// object.
296    ///
297    /// Only the principal can have methods or type parameters (because
298    /// auto traits can have neither of them). This is important, because
299    /// it means the auto traits can be treated as an unordered set (methods
300    /// would force an order for the vtable, while relating traits with
301    /// type parameters without knowing the order to relate them in is
302    /// a rather non-trivial task).
303    ///
304    /// For example, in the trait object `dyn std::fmt::Debug + Sync`, the
305    /// principal bound is `Some(std::fmt::Debug)`, while the auto-trait bounds
306    /// are the set `{Sync}`.
307    ///
308    /// It is also possible to have a "trivial" trait object that
309    /// consists only of auto traits, with no principal - for example,
310    /// `dyn Send + Sync`. In that case, the set of auto-trait bounds
311    /// is `{Send, Sync}`, while there is no principal. These trait objects
312    /// have a "trivial" vtable consisting of just the size, alignment,
313    /// and destructor.
314    pub fn principal(&self) -> Option<ty::Binder<'tcx, ExistentialTraitRef<'tcx>>> {
315        self[0]
316            .map_bound(|this| match this {
317                ExistentialPredicate::Trait(tr) => Some(tr),
318                _ => None,
319            })
320            .transpose()
321    }
322
323    pub fn principal_def_id(&self) -> Option<DefId> {
324        self.principal().map(|trait_ref| trait_ref.skip_binder().def_id)
325    }
326
327    #[inline]
328    pub fn projection_bounds(
329        &self,
330    ) -> impl Iterator<Item = ty::Binder<'tcx, ExistentialProjection<'tcx>>> {
331        self.iter().filter_map(|predicate| {
332            predicate
333                .map_bound(|pred| match pred {
334                    ExistentialPredicate::Projection(projection) => Some(projection),
335                    _ => None,
336                })
337                .transpose()
338        })
339    }
340
341    #[inline]
342    pub fn auto_traits(&self) -> impl Iterator<Item = DefId> {
343        self.iter().filter_map(|predicate| match predicate.skip_binder() {
344            ExistentialPredicate::AutoTrait(did) => Some(did),
345            _ => None,
346        })
347    }
348
349    pub fn without_auto_traits(&self) -> impl Iterator<Item = ty::PolyExistentialPredicate<'tcx>> {
350        self.iter().filter(|predicate| {
351            !matches!(predicate.as_ref().skip_binder(), ExistentialPredicate::AutoTrait(_))
352        })
353    }
354}
355
356pub type PolyTraitRef<'tcx> = ty::Binder<'tcx, TraitRef<'tcx>>;
357pub type PolyExistentialTraitRef<'tcx> = ty::Binder<'tcx, ExistentialTraitRef<'tcx>>;
358pub type PolyExistentialProjection<'tcx> = ty::Binder<'tcx, ExistentialProjection<'tcx>>;
359
360impl<'tcx> Clause<'tcx> {
361    /// Performs a instantiation suitable for going from a
362    /// poly-trait-ref to supertraits that must hold if that
363    /// poly-trait-ref holds. This is slightly different from a normal
364    /// instantiation in terms of what happens with bound regions. See
365    /// lengthy comment below for details.
366    pub fn instantiate_supertrait(
367        self,
368        tcx: TyCtxt<'tcx>,
369        trait_ref: ty::PolyTraitRef<'tcx>,
370    ) -> Clause<'tcx> {
371        // The interaction between HRTB and supertraits is not entirely
372        // obvious. Let me walk you (and myself) through an example.
373        //
374        // Let's start with an easy case. Consider two traits:
375        //
376        //     trait Foo<'a>: Bar<'a,'a> { }
377        //     trait Bar<'b,'c> { }
378        //
379        // Now, if we have a trait reference `for<'x> T: Foo<'x>`, then
380        // we can deduce that `for<'x> T: Bar<'x,'x>`. Basically, if we
381        // knew that `Foo<'x>` (for any 'x) then we also know that
382        // `Bar<'x,'x>` (for any 'x). This more-or-less falls out from
383        // normal instantiation.
384        //
385        // In terms of why this is sound, the idea is that whenever there
386        // is an impl of `T:Foo<'a>`, it must show that `T:Bar<'a,'a>`
387        // holds. So if there is an impl of `T:Foo<'a>` that applies to
388        // all `'a`, then we must know that `T:Bar<'a,'a>` holds for all
389        // `'a`.
390        //
391        // Another example to be careful of is this:
392        //
393        //     trait Foo1<'a>: for<'b> Bar1<'a,'b> { }
394        //     trait Bar1<'b,'c> { }
395        //
396        // Here, if we have `for<'x> T: Foo1<'x>`, then what do we know?
397        // The answer is that we know `for<'x,'b> T: Bar1<'x,'b>`. The
398        // reason is similar to the previous example: any impl of
399        // `T:Foo1<'x>` must show that `for<'b> T: Bar1<'x, 'b>`. So
400        // basically we would want to collapse the bound lifetimes from
401        // the input (`trait_ref`) and the supertraits.
402        //
403        // To achieve this in practice is fairly straightforward. Let's
404        // consider the more complicated scenario:
405        //
406        // - We start out with `for<'x> T: Foo1<'x>`. In this case, `'x`
407        //   has a De Bruijn index of 1. We want to produce `for<'x,'b> T: Bar1<'x,'b>`,
408        //   where both `'x` and `'b` would have a DB index of 1.
409        //   The instantiation from the input trait-ref is therefore going to be
410        //   `'a => 'x` (where `'x` has a DB index of 1).
411        // - The supertrait-ref is `for<'b> Bar1<'a,'b>`, where `'a` is an
412        //   early-bound parameter and `'b` is a late-bound parameter with a
413        //   DB index of 1.
414        // - If we replace `'a` with `'x` from the input, it too will have
415        //   a DB index of 1, and thus we'll have `for<'x,'b> Bar1<'x,'b>`
416        //   just as we wanted.
417        //
418        // There is only one catch. If we just apply the instantiation `'a
419        // => 'x` to `for<'b> Bar1<'a,'b>`, the instantiation code will
420        // adjust the DB index because we instantiating into a binder (it
421        // tries to be so smart...) resulting in `for<'x> for<'b>
422        // Bar1<'x,'b>` (we have no syntax for this, so use your
423        // imagination). Basically the 'x will have DB index of 2 and 'b
424        // will have DB index of 1. Not quite what we want. So we apply
425        // the instantiation to the *contents* of the trait reference,
426        // rather than the trait reference itself (put another way, the
427        // instantiation code expects equal binding levels in the values
428        // from the instantiation and the value being instantiated into, and
429        // this trick achieves that).
430
431        // Working through the second example:
432        // trait_ref: for<'x> T: Foo1<'^0.0>; args: [T, '^0.0]
433        // predicate: for<'b> Self: Bar1<'a, '^0.0>; args: [Self, 'a, '^0.0]
434        // We want to end up with:
435        //     for<'x, 'b> T: Bar1<'^0.0, '^0.1>
436        // To do this:
437        // 1) We must shift all bound vars in predicate by the length
438        //    of trait ref's bound vars. So, we would end up with predicate like
439        //    Self: Bar1<'a, '^0.1>
440        // 2) We can then apply the trait args to this, ending up with
441        //    T: Bar1<'^0.0, '^0.1>
442        // 3) Finally, to create the final bound vars, we concatenate the bound
443        //    vars of the trait ref with those of the predicate:
444        //    ['x, 'b]
445        let bound_pred = self.kind();
446        let pred_bound_vars = bound_pred.bound_vars();
447        let trait_bound_vars = trait_ref.bound_vars();
448        // 1) Self: Bar1<'a, '^0.0> -> Self: Bar1<'a, '^0.1>
449        let shifted_pred =
450            tcx.shift_bound_var_indices(trait_bound_vars.len(), bound_pred.skip_binder());
451        // 2) Self: Bar1<'a, '^0.1> -> T: Bar1<'^0.0, '^0.1>
452        let new = EarlyBinder::bind(shifted_pred).instantiate(tcx, trait_ref.skip_binder().args);
453        // 3) ['x] + ['b] -> ['x, 'b]
454        let bound_vars =
455            tcx.mk_bound_variable_kinds_from_iter(trait_bound_vars.iter().chain(pred_bound_vars));
456
457        // FIXME: Is it really perf sensitive to use reuse_or_mk_predicate here?
458        tcx.reuse_or_mk_predicate(
459            self.as_predicate(),
460            ty::Binder::bind_with_vars(PredicateKind::Clause(new), bound_vars),
461        )
462        .expect_clause()
463    }
464}
465
466impl<'tcx> UpcastFrom<TyCtxt<'tcx>, PredicateKind<'tcx>> for Predicate<'tcx> {
467    fn upcast_from(from: PredicateKind<'tcx>, tcx: TyCtxt<'tcx>) -> Self {
468        ty::Binder::dummy(from).upcast(tcx)
469    }
470}
471
472impl<'tcx> UpcastFrom<TyCtxt<'tcx>, ty::Binder<'tcx, PredicateKind<'tcx>>> for Predicate<'tcx> {
473    fn upcast_from(from: ty::Binder<'tcx, PredicateKind<'tcx>>, tcx: TyCtxt<'tcx>) -> Self {
474        tcx.mk_predicate(from)
475    }
476}
477
478impl<'tcx> UpcastFrom<TyCtxt<'tcx>, ClauseKind<'tcx>> for Predicate<'tcx> {
479    fn upcast_from(from: ClauseKind<'tcx>, tcx: TyCtxt<'tcx>) -> Self {
480        tcx.mk_predicate(ty::Binder::dummy(PredicateKind::Clause(from)))
481    }
482}
483
484impl<'tcx> UpcastFrom<TyCtxt<'tcx>, ty::Binder<'tcx, ClauseKind<'tcx>>> for Predicate<'tcx> {
485    fn upcast_from(from: ty::Binder<'tcx, ClauseKind<'tcx>>, tcx: TyCtxt<'tcx>) -> Self {
486        tcx.mk_predicate(from.map_bound(PredicateKind::Clause))
487    }
488}
489
490impl<'tcx> UpcastFrom<TyCtxt<'tcx>, Clause<'tcx>> for Predicate<'tcx> {
491    fn upcast_from(from: Clause<'tcx>, _tcx: TyCtxt<'tcx>) -> Self {
492        from.as_predicate()
493    }
494}
495
496impl<'tcx> UpcastFrom<TyCtxt<'tcx>, ClauseKind<'tcx>> for Clause<'tcx> {
497    fn upcast_from(from: ClauseKind<'tcx>, tcx: TyCtxt<'tcx>) -> Self {
498        tcx.mk_predicate(ty::Binder::dummy(PredicateKind::Clause(from))).expect_clause()
499    }
500}
501
502impl<'tcx> UpcastFrom<TyCtxt<'tcx>, ty::Binder<'tcx, ClauseKind<'tcx>>> for Clause<'tcx> {
503    fn upcast_from(from: ty::Binder<'tcx, ClauseKind<'tcx>>, tcx: TyCtxt<'tcx>) -> Self {
504        tcx.mk_predicate(from.map_bound(|clause| PredicateKind::Clause(clause))).expect_clause()
505    }
506}
507
508impl<'tcx> UpcastFrom<TyCtxt<'tcx>, TraitRef<'tcx>> for Predicate<'tcx> {
509    fn upcast_from(from: TraitRef<'tcx>, tcx: TyCtxt<'tcx>) -> Self {
510        ty::Binder::dummy(from).upcast(tcx)
511    }
512}
513
514impl<'tcx> UpcastFrom<TyCtxt<'tcx>, TraitRef<'tcx>> for Clause<'tcx> {
515    fn upcast_from(from: TraitRef<'tcx>, tcx: TyCtxt<'tcx>) -> Self {
516        let p: Predicate<'tcx> = from.upcast(tcx);
517        p.expect_clause()
518    }
519}
520
521impl<'tcx> UpcastFrom<TyCtxt<'tcx>, ty::Binder<'tcx, TraitRef<'tcx>>> for Predicate<'tcx> {
522    fn upcast_from(from: ty::Binder<'tcx, TraitRef<'tcx>>, tcx: TyCtxt<'tcx>) -> Self {
523        let pred: PolyTraitPredicate<'tcx> = from.upcast(tcx);
524        pred.upcast(tcx)
525    }
526}
527
528impl<'tcx> UpcastFrom<TyCtxt<'tcx>, ty::Binder<'tcx, TraitRef<'tcx>>> for Clause<'tcx> {
529    fn upcast_from(from: ty::Binder<'tcx, TraitRef<'tcx>>, tcx: TyCtxt<'tcx>) -> Self {
530        let pred: PolyTraitPredicate<'tcx> = from.upcast(tcx);
531        pred.upcast(tcx)
532    }
533}
534
535impl<'tcx> UpcastFrom<TyCtxt<'tcx>, ty::Binder<'tcx, TraitRef<'tcx>>> for PolyTraitPredicate<'tcx> {
536    fn upcast_from(from: ty::Binder<'tcx, TraitRef<'tcx>>, _tcx: TyCtxt<'tcx>) -> Self {
537        from.map_bound(|trait_ref| TraitPredicate {
538            trait_ref,
539            polarity: PredicatePolarity::Positive,
540        })
541    }
542}
543
544impl<'tcx> UpcastFrom<TyCtxt<'tcx>, TraitPredicate<'tcx>> for Predicate<'tcx> {
545    fn upcast_from(from: TraitPredicate<'tcx>, tcx: TyCtxt<'tcx>) -> Self {
546        PredicateKind::Clause(ClauseKind::Trait(from)).upcast(tcx)
547    }
548}
549
550impl<'tcx> UpcastFrom<TyCtxt<'tcx>, PolyTraitPredicate<'tcx>> for Predicate<'tcx> {
551    fn upcast_from(from: PolyTraitPredicate<'tcx>, tcx: TyCtxt<'tcx>) -> Self {
552        from.map_bound(|p| PredicateKind::Clause(ClauseKind::Trait(p))).upcast(tcx)
553    }
554}
555
556impl<'tcx> UpcastFrom<TyCtxt<'tcx>, TraitPredicate<'tcx>> for Clause<'tcx> {
557    fn upcast_from(from: TraitPredicate<'tcx>, tcx: TyCtxt<'tcx>) -> Self {
558        let p: Predicate<'tcx> = from.upcast(tcx);
559        p.expect_clause()
560    }
561}
562
563impl<'tcx> UpcastFrom<TyCtxt<'tcx>, PolyTraitPredicate<'tcx>> for Clause<'tcx> {
564    fn upcast_from(from: PolyTraitPredicate<'tcx>, tcx: TyCtxt<'tcx>) -> Self {
565        let p: Predicate<'tcx> = from.upcast(tcx);
566        p.expect_clause()
567    }
568}
569
570impl<'tcx> UpcastFrom<TyCtxt<'tcx>, RegionOutlivesPredicate<'tcx>> for Predicate<'tcx> {
571    fn upcast_from(from: RegionOutlivesPredicate<'tcx>, tcx: TyCtxt<'tcx>) -> Self {
572        ty::Binder::dummy(PredicateKind::Clause(ClauseKind::RegionOutlives(from))).upcast(tcx)
573    }
574}
575
576impl<'tcx> UpcastFrom<TyCtxt<'tcx>, PolyRegionOutlivesPredicate<'tcx>> for Predicate<'tcx> {
577    fn upcast_from(from: PolyRegionOutlivesPredicate<'tcx>, tcx: TyCtxt<'tcx>) -> Self {
578        from.map_bound(|p| PredicateKind::Clause(ClauseKind::RegionOutlives(p))).upcast(tcx)
579    }
580}
581
582impl<'tcx> UpcastFrom<TyCtxt<'tcx>, TypeOutlivesPredicate<'tcx>> for Predicate<'tcx> {
583    fn upcast_from(from: TypeOutlivesPredicate<'tcx>, tcx: TyCtxt<'tcx>) -> Self {
584        ty::Binder::dummy(PredicateKind::Clause(ClauseKind::TypeOutlives(from))).upcast(tcx)
585    }
586}
587
588impl<'tcx> UpcastFrom<TyCtxt<'tcx>, ProjectionPredicate<'tcx>> for Predicate<'tcx> {
589    fn upcast_from(from: ProjectionPredicate<'tcx>, tcx: TyCtxt<'tcx>) -> Self {
590        ty::Binder::dummy(PredicateKind::Clause(ClauseKind::Projection(from))).upcast(tcx)
591    }
592}
593
594impl<'tcx> UpcastFrom<TyCtxt<'tcx>, PolyProjectionPredicate<'tcx>> for Predicate<'tcx> {
595    fn upcast_from(from: PolyProjectionPredicate<'tcx>, tcx: TyCtxt<'tcx>) -> Self {
596        from.map_bound(|p| PredicateKind::Clause(ClauseKind::Projection(p))).upcast(tcx)
597    }
598}
599
600impl<'tcx> UpcastFrom<TyCtxt<'tcx>, ProjectionPredicate<'tcx>> for Clause<'tcx> {
601    fn upcast_from(from: ProjectionPredicate<'tcx>, tcx: TyCtxt<'tcx>) -> Self {
602        let p: Predicate<'tcx> = from.upcast(tcx);
603        p.expect_clause()
604    }
605}
606
607impl<'tcx> UpcastFrom<TyCtxt<'tcx>, PolyProjectionPredicate<'tcx>> for Clause<'tcx> {
608    fn upcast_from(from: PolyProjectionPredicate<'tcx>, tcx: TyCtxt<'tcx>) -> Self {
609        let p: Predicate<'tcx> = from.upcast(tcx);
610        p.expect_clause()
611    }
612}
613
614impl<'tcx> UpcastFrom<TyCtxt<'tcx>, ty::Binder<'tcx, ty::HostEffectPredicate<'tcx>>>
615    for Predicate<'tcx>
616{
617    fn upcast_from(
618        from: ty::Binder<'tcx, ty::HostEffectPredicate<'tcx>>,
619        tcx: TyCtxt<'tcx>,
620    ) -> Self {
621        from.map_bound(ty::ClauseKind::HostEffect).upcast(tcx)
622    }
623}
624
625impl<'tcx> UpcastFrom<TyCtxt<'tcx>, ty::Binder<'tcx, ty::HostEffectPredicate<'tcx>>>
626    for Clause<'tcx>
627{
628    fn upcast_from(
629        from: ty::Binder<'tcx, ty::HostEffectPredicate<'tcx>>,
630        tcx: TyCtxt<'tcx>,
631    ) -> Self {
632        from.map_bound(ty::ClauseKind::HostEffect).upcast(tcx)
633    }
634}
635
636impl<'tcx> UpcastFrom<TyCtxt<'tcx>, NormalizesTo<'tcx>> for Predicate<'tcx> {
637    fn upcast_from(from: NormalizesTo<'tcx>, tcx: TyCtxt<'tcx>) -> Self {
638        PredicateKind::NormalizesTo(from).upcast(tcx)
639    }
640}
641
642impl<'tcx> Predicate<'tcx> {
643    pub fn as_trait_clause(self) -> Option<PolyTraitPredicate<'tcx>> {
644        let predicate = self.kind();
645        match predicate.skip_binder() {
646            PredicateKind::Clause(ClauseKind::Trait(t)) => Some(predicate.rebind(t)),
647            PredicateKind::Clause(ClauseKind::Projection(..))
648            | PredicateKind::Clause(ClauseKind::HostEffect(..))
649            | PredicateKind::Clause(ClauseKind::ConstArgHasType(..))
650            | PredicateKind::NormalizesTo(..)
651            | PredicateKind::AliasRelate(..)
652            | PredicateKind::Subtype(..)
653            | PredicateKind::Coerce(..)
654            | PredicateKind::Clause(ClauseKind::RegionOutlives(..))
655            | PredicateKind::Clause(ClauseKind::WellFormed(..))
656            | PredicateKind::DynCompatible(..)
657            | PredicateKind::Clause(ClauseKind::TypeOutlives(..))
658            | PredicateKind::Clause(ClauseKind::ConstEvaluatable(..))
659            | PredicateKind::ConstEquate(..)
660            | PredicateKind::Ambiguous => None,
661        }
662    }
663
664    pub fn as_projection_clause(self) -> Option<PolyProjectionPredicate<'tcx>> {
665        let predicate = self.kind();
666        match predicate.skip_binder() {
667            PredicateKind::Clause(ClauseKind::Projection(t)) => Some(predicate.rebind(t)),
668            PredicateKind::Clause(ClauseKind::Trait(..))
669            | PredicateKind::Clause(ClauseKind::HostEffect(..))
670            | PredicateKind::Clause(ClauseKind::ConstArgHasType(..))
671            | PredicateKind::NormalizesTo(..)
672            | PredicateKind::AliasRelate(..)
673            | PredicateKind::Subtype(..)
674            | PredicateKind::Coerce(..)
675            | PredicateKind::Clause(ClauseKind::RegionOutlives(..))
676            | PredicateKind::Clause(ClauseKind::WellFormed(..))
677            | PredicateKind::DynCompatible(..)
678            | PredicateKind::Clause(ClauseKind::TypeOutlives(..))
679            | PredicateKind::Clause(ClauseKind::ConstEvaluatable(..))
680            | PredicateKind::ConstEquate(..)
681            | PredicateKind::Ambiguous => None,
682        }
683    }
684
685    /// Matches a `PredicateKind::Clause` and turns it into a `Clause`, otherwise returns `None`.
686    pub fn as_clause(self) -> Option<Clause<'tcx>> {
687        match self.kind().skip_binder() {
688            PredicateKind::Clause(..) => Some(self.expect_clause()),
689            _ => None,
690        }
691    }
692
693    /// Assert that the predicate is a clause.
694    pub fn expect_clause(self) -> Clause<'tcx> {
695        match self.kind().skip_binder() {
696            PredicateKind::Clause(..) => Clause(self.0),
697            _ => bug!("{self} is not a clause"),
698        }
699    }
700}
rustc_middle/ty/predicate.rs

rustc_middle/ty/
predicate.rs
