rustc_type_ir/
relate.rs

1use std::iter;
2
3use derive_where::derive_where;
4use rustc_ast_ir::Mutability;
5use tracing::{instrument, trace};
6
7use crate::error::{ExpectedFound, TypeError};
8use crate::fold::TypeFoldable;
9use crate::inherent::*;
10use crate::{self as ty, Interner};
11
12pub mod combine;
13pub mod solver_relating;
14
15pub type RelateResult<I, T> = Result<T, TypeError<I>>;
16
17/// Whether aliases should be related structurally or not. Used
18/// to adjust the behavior of generalization and combine.
19///
20/// This should always be `No` unless in a few special-cases when
21/// instantiating canonical responses and in the new solver. Each
22/// such case should have a comment explaining why it is used.
23#[derive(Debug, Copy, Clone)]
24pub enum StructurallyRelateAliases {
25    Yes,
26    No,
27}
28
29/// Extra information about why we ended up with a particular variance.
30/// This is only used to add more information to error messages, and
31/// has no effect on soundness. While choosing the 'wrong' `VarianceDiagInfo`
32/// may lead to confusing notes in error messages, it will never cause
33/// a miscompilation or unsoundness.
34///
35/// When in doubt, use `VarianceDiagInfo::default()`
36#[derive_where(Clone, Copy, PartialEq, Debug, Default; I: Interner)]
37pub enum VarianceDiagInfo<I: Interner> {
38    /// No additional information - this is the default.
39    /// We will not add any additional information to error messages.
40    #[derive_where(default)]
41    None,
42    /// We switched our variance because a generic argument occurs inside
43    /// the invariant generic argument of another type.
44    Invariant {
45        /// The generic type containing the generic parameter
46        /// that changes the variance (e.g. `*mut T`, `MyStruct<T>`)
47        ty: I::Ty,
48        /// The index of the generic parameter being used
49        /// (e.g. `0` for `*mut T`, `1` for `MyStruct<'CovariantParam, 'InvariantParam>`)
50        param_index: u32,
51    },
52}
53
54impl<I: Interner> Eq for VarianceDiagInfo<I> {}
55
56impl<I: Interner> VarianceDiagInfo<I> {
57    /// Mirrors `Variance::xform` - used to 'combine' the existing
58    /// and new `VarianceDiagInfo`s when our variance changes.
59    pub fn xform(self, other: VarianceDiagInfo<I>) -> VarianceDiagInfo<I> {
60        // For now, just use the first `VarianceDiagInfo::Invariant` that we see
61        match self {
62            VarianceDiagInfo::None => other,
63            VarianceDiagInfo::Invariant { .. } => self,
64        }
65    }
66}
67
68pub trait TypeRelation<I: Interner>: Sized {
69    fn cx(&self) -> I;
70
71    /// Generic relation routine suitable for most anything.
72    fn relate<T: Relate<I>>(&mut self, a: T, b: T) -> RelateResult<I, T> {
73        Relate::relate(self, a, b)
74    }
75
76    fn relate_ty_args(
77        &mut self,
78        a_ty: I::Ty,
79        b_ty: I::Ty,
80        ty_def_id: I::DefId,
81        a_arg: I::GenericArgs,
82        b_arg: I::GenericArgs,
83        mk: impl FnOnce(I::GenericArgs) -> I::Ty,
84    ) -> RelateResult<I, I::Ty>;
85
86    /// Switch variance for the purpose of relating `a` and `b`.
87    fn relate_with_variance<T: Relate<I>>(
88        &mut self,
89        variance: ty::Variance,
90        info: VarianceDiagInfo<I>,
91        a: T,
92        b: T,
93    ) -> RelateResult<I, T>;
94
95    // Overridable relations. You shouldn't typically call these
96    // directly, instead call `relate()`, which in turn calls
97    // these. This is both more uniform but also allows us to add
98    // additional hooks for other types in the future if needed
99    // without making older code, which called `relate`, obsolete.
100
101    fn tys(&mut self, a: I::Ty, b: I::Ty) -> RelateResult<I, I::Ty>;
102
103    fn regions(&mut self, a: I::Region, b: I::Region) -> RelateResult<I, I::Region>;
104
105    fn consts(&mut self, a: I::Const, b: I::Const) -> RelateResult<I, I::Const>;
106
107    fn binders<T>(
108        &mut self,
109        a: ty::Binder<I, T>,
110        b: ty::Binder<I, T>,
111    ) -> RelateResult<I, ty::Binder<I, T>>
112    where
113        T: Relate<I>;
114}
115
116pub trait Relate<I: Interner>: TypeFoldable<I> + PartialEq + Copy {
117    fn relate<R: TypeRelation<I>>(relation: &mut R, a: Self, b: Self) -> RelateResult<I, Self>;
118}
119
120///////////////////////////////////////////////////////////////////////////
121// Relate impls
122
123#[inline]
124pub fn relate_args_invariantly<I: Interner, R: TypeRelation<I>>(
125    relation: &mut R,
126    a_arg: I::GenericArgs,
127    b_arg: I::GenericArgs,
128) -> RelateResult<I, I::GenericArgs> {
129    relation.cx().mk_args_from_iter(iter::zip(a_arg.iter(), b_arg.iter()).map(|(a, b)| {
130        relation.relate_with_variance(ty::Invariant, VarianceDiagInfo::default(), a, b)
131    }))
132}
133
134pub fn relate_args_with_variances<I: Interner, R: TypeRelation<I>>(
135    relation: &mut R,
136    variances: I::VariancesOf,
137    a_args: I::GenericArgs,
138    b_args: I::GenericArgs,
139) -> RelateResult<I, I::GenericArgs> {
140    let cx = relation.cx();
141    let args = iter::zip(a_args.iter(), b_args.iter()).enumerate().map(|(i, (a, b))| {
142        let variance = variances.get(i).unwrap();
143        relation.relate_with_variance(variance, VarianceDiagInfo::None, a, b)
144    });
145    // FIXME: We can probably try to reuse `a_args` here if it did not change.
146    cx.mk_args_from_iter(args)
147}
148
149impl<I: Interner> Relate<I> for ty::FnSig<I> {
150    fn relate<R: TypeRelation<I>>(
151        relation: &mut R,
152        a: ty::FnSig<I>,
153        b: ty::FnSig<I>,
154    ) -> RelateResult<I, ty::FnSig<I>> {
155        let cx = relation.cx();
156
157        if a.c_variadic != b.c_variadic {
158            return Err(TypeError::VariadicMismatch(ExpectedFound::new(
159                a.c_variadic,
160                b.c_variadic,
161            )));
162        }
163
164        if a.safety != b.safety {
165            return Err(TypeError::SafetyMismatch(ExpectedFound::new(a.safety, b.safety)));
166        }
167
168        if a.abi != b.abi {
169            return Err(TypeError::AbiMismatch(ExpectedFound::new(a.abi, b.abi)));
170        };
171
172        let a_inputs = a.inputs();
173        let b_inputs = b.inputs();
174        if a_inputs.len() != b_inputs.len() {
175            return Err(TypeError::ArgCount);
176        }
177
178        let inputs_and_output = iter::zip(a_inputs.iter(), b_inputs.iter())
179            .map(|(a, b)| ((a, b), false))
180            .chain(iter::once(((a.output(), b.output()), true)))
181            .map(|((a, b), is_output)| {
182                if is_output {
183                    relation.relate(a, b)
184                } else {
185                    relation.relate_with_variance(
186                        ty::Contravariant,
187                        VarianceDiagInfo::default(),
188                        a,
189                        b,
190                    )
191                }
192            })
193            .enumerate()
194            .map(|(i, r)| match r {
195                Err(TypeError::Sorts(exp_found) | TypeError::ArgumentSorts(exp_found, _)) => {
196                    Err(TypeError::ArgumentSorts(exp_found, i))
197                }
198                Err(TypeError::Mutability | TypeError::ArgumentMutability(_)) => {
199                    Err(TypeError::ArgumentMutability(i))
200                }
201                r => r,
202            });
203        Ok(ty::FnSig {
204            inputs_and_output: cx.mk_type_list_from_iter(inputs_and_output)?,
205            c_variadic: a.c_variadic,
206            safety: a.safety,
207            abi: a.abi,
208        })
209    }
210}
211
212impl<I: Interner> Relate<I> for ty::AliasTy<I> {
213    fn relate<R: TypeRelation<I>>(
214        relation: &mut R,
215        a: ty::AliasTy<I>,
216        b: ty::AliasTy<I>,
217    ) -> RelateResult<I, ty::AliasTy<I>> {
218        if a.def_id != b.def_id {
219            Err(TypeError::ProjectionMismatched(ExpectedFound::new(a.def_id, b.def_id)))
220        } else {
221            let cx = relation.cx();
222            let args = if let Some(variances) = cx.opt_alias_variances(a.kind(cx), a.def_id) {
223                relate_args_with_variances(relation, variances, a.args, b.args)?
224            } else {
225                relate_args_invariantly(relation, a.args, b.args)?
226            };
227            Ok(ty::AliasTy::new_from_args(relation.cx(), a.def_id, args))
228        }
229    }
230}
231
232impl<I: Interner> Relate<I> for ty::AliasTerm<I> {
233    fn relate<R: TypeRelation<I>>(
234        relation: &mut R,
235        a: ty::AliasTerm<I>,
236        b: ty::AliasTerm<I>,
237    ) -> RelateResult<I, ty::AliasTerm<I>> {
238        if a.def_id != b.def_id {
239            Err(TypeError::ProjectionMismatched(ExpectedFound::new(a.def_id, b.def_id)))
240        } else {
241            let args = match a.kind(relation.cx()) {
242                ty::AliasTermKind::OpaqueTy => relate_args_with_variances(
243                    relation,
244                    relation.cx().variances_of(a.def_id),
245                    a.args,
246                    b.args,
247                )?,
248                ty::AliasTermKind::ProjectionTy
249                | ty::AliasTermKind::FreeConst
250                | ty::AliasTermKind::FreeTy
251                | ty::AliasTermKind::InherentTy
252                | ty::AliasTermKind::InherentConst
253                | ty::AliasTermKind::UnevaluatedConst
254                | ty::AliasTermKind::ProjectionConst => {
255                    relate_args_invariantly(relation, a.args, b.args)?
256                }
257            };
258            Ok(ty::AliasTerm::new_from_args(relation.cx(), a.def_id, args))
259        }
260    }
261}
262
263impl<I: Interner> Relate<I> for ty::ExistentialProjection<I> {
264    fn relate<R: TypeRelation<I>>(
265        relation: &mut R,
266        a: ty::ExistentialProjection<I>,
267        b: ty::ExistentialProjection<I>,
268    ) -> RelateResult<I, ty::ExistentialProjection<I>> {
269        if a.def_id != b.def_id {
270            Err(TypeError::ProjectionMismatched(ExpectedFound::new(a.def_id, b.def_id)))
271        } else {
272            let term = relation.relate_with_variance(
273                ty::Invariant,
274                VarianceDiagInfo::default(),
275                a.term,
276                b.term,
277            )?;
278            let args = relation.relate_with_variance(
279                ty::Invariant,
280                VarianceDiagInfo::default(),
281                a.args,
282                b.args,
283            )?;
284            Ok(ty::ExistentialProjection::new_from_args(relation.cx(), a.def_id, args, term))
285        }
286    }
287}
288
289impl<I: Interner> Relate<I> for ty::TraitRef<I> {
290    fn relate<R: TypeRelation<I>>(
291        relation: &mut R,
292        a: ty::TraitRef<I>,
293        b: ty::TraitRef<I>,
294    ) -> RelateResult<I, ty::TraitRef<I>> {
295        // Different traits cannot be related.
296        if a.def_id != b.def_id {
297            Err(TypeError::Traits({
298                let a = a.def_id;
299                let b = b.def_id;
300                ExpectedFound::new(a, b)
301            }))
302        } else {
303            let args = relate_args_invariantly(relation, a.args, b.args)?;
304            Ok(ty::TraitRef::new_from_args(relation.cx(), a.def_id, args))
305        }
306    }
307}
308
309impl<I: Interner> Relate<I> for ty::ExistentialTraitRef<I> {
310    fn relate<R: TypeRelation<I>>(
311        relation: &mut R,
312        a: ty::ExistentialTraitRef<I>,
313        b: ty::ExistentialTraitRef<I>,
314    ) -> RelateResult<I, ty::ExistentialTraitRef<I>> {
315        // Different traits cannot be related.
316        if a.def_id != b.def_id {
317            Err(TypeError::Traits({
318                let a = a.def_id;
319                let b = b.def_id;
320                ExpectedFound::new(a, b)
321            }))
322        } else {
323            let args = relate_args_invariantly(relation, a.args, b.args)?;
324            Ok(ty::ExistentialTraitRef::new_from_args(relation.cx(), a.def_id, args))
325        }
326    }
327}
328
329/// Relates `a` and `b` structurally, calling the relation for all nested values.
330/// Any semantic equality, e.g. of projections, and inference variables have to be
331/// handled by the caller.
332#[instrument(level = "trace", skip(relation), ret)]
333pub fn structurally_relate_tys<I: Interner, R: TypeRelation<I>>(
334    relation: &mut R,
335    a: I::Ty,
336    b: I::Ty,
337) -> RelateResult<I, I::Ty> {
338    let cx = relation.cx();
339    match (a.kind(), b.kind()) {
340        (ty::Infer(_), _) | (_, ty::Infer(_)) => {
341            // The caller should handle these cases!
342            panic!("var types encountered in structurally_relate_tys")
343        }
344
345        (ty::Bound(..), _) | (_, ty::Bound(..)) => {
346            panic!("bound types encountered in structurally_relate_tys")
347        }
348
349        (ty::Error(guar), _) | (_, ty::Error(guar)) => Ok(Ty::new_error(cx, guar)),
350
351        (ty::Never, _)
352        | (ty::Char, _)
353        | (ty::Bool, _)
354        | (ty::Int(_), _)
355        | (ty::Uint(_), _)
356        | (ty::Float(_), _)
357        | (ty::Str, _)
358            if a == b =>
359        {
360            Ok(a)
361        }
362
363        (ty::Param(a_p), ty::Param(b_p)) if a_p.index() == b_p.index() => {
364            // FIXME: Put this back
365            //debug_assert_eq!(a_p.name(), b_p.name(), "param types with same index differ in name");
366            Ok(a)
367        }
368
369        (ty::Placeholder(p1), ty::Placeholder(p2)) if p1 == p2 => Ok(a),
370
371        (ty::Adt(a_def, a_args), ty::Adt(b_def, b_args)) if a_def == b_def => {
372            if a_args.is_empty() {
373                Ok(a)
374            } else {
375                relation.relate_ty_args(a, b, a_def.def_id().into(), a_args, b_args, |args| {
376                    Ty::new_adt(cx, a_def, args)
377                })
378            }
379        }
380
381        (ty::Foreign(a_id), ty::Foreign(b_id)) if a_id == b_id => Ok(Ty::new_foreign(cx, a_id)),
382
383        (ty::Dynamic(a_obj, a_region), ty::Dynamic(b_obj, b_region)) => Ok(Ty::new_dynamic(
384            cx,
385            relation.relate(a_obj, b_obj)?,
386            relation.relate(a_region, b_region)?,
387        )),
388
389        (ty::Coroutine(a_id, a_args), ty::Coroutine(b_id, b_args)) if a_id == b_id => {
390            // All Coroutine types with the same id represent
391            // the (anonymous) type of the same coroutine expression. So
392            // all of their regions should be equated.
393            let args = relate_args_invariantly(relation, a_args, b_args)?;
394            Ok(Ty::new_coroutine(cx, a_id, args))
395        }
396
397        (ty::CoroutineWitness(a_id, a_args), ty::CoroutineWitness(b_id, b_args))
398            if a_id == b_id =>
399        {
400            // All CoroutineWitness types with the same id represent
401            // the (anonymous) type of the same coroutine expression. So
402            // all of their regions should be equated.
403            let args = relate_args_invariantly(relation, a_args, b_args)?;
404            Ok(Ty::new_coroutine_witness(cx, a_id, args))
405        }
406
407        (ty::Closure(a_id, a_args), ty::Closure(b_id, b_args)) if a_id == b_id => {
408            // All Closure types with the same id represent
409            // the (anonymous) type of the same closure expression. So
410            // all of their regions should be equated.
411            let args = relate_args_invariantly(relation, a_args, b_args)?;
412            Ok(Ty::new_closure(cx, a_id, args))
413        }
414
415        (ty::CoroutineClosure(a_id, a_args), ty::CoroutineClosure(b_id, b_args))
416            if a_id == b_id =>
417        {
418            let args = relate_args_invariantly(relation, a_args, b_args)?;
419            Ok(Ty::new_coroutine_closure(cx, a_id, args))
420        }
421
422        (ty::RawPtr(a_ty, a_mutbl), ty::RawPtr(b_ty, b_mutbl)) => {
423            if a_mutbl != b_mutbl {
424                return Err(TypeError::Mutability);
425            }
426
427            let (variance, info) = match a_mutbl {
428                Mutability::Not => (ty::Covariant, VarianceDiagInfo::None),
429                Mutability::Mut => {
430                    (ty::Invariant, VarianceDiagInfo::Invariant { ty: a, param_index: 0 })
431                }
432            };
433
434            let ty = relation.relate_with_variance(variance, info, a_ty, b_ty)?;
435
436            Ok(Ty::new_ptr(cx, ty, a_mutbl))
437        }
438
439        (ty::Ref(a_r, a_ty, a_mutbl), ty::Ref(b_r, b_ty, b_mutbl)) => {
440            if a_mutbl != b_mutbl {
441                return Err(TypeError::Mutability);
442            }
443
444            let (variance, info) = match a_mutbl {
445                Mutability::Not => (ty::Covariant, VarianceDiagInfo::None),
446                Mutability::Mut => {
447                    (ty::Invariant, VarianceDiagInfo::Invariant { ty: a, param_index: 0 })
448                }
449            };
450
451            let r = relation.relate(a_r, b_r)?;
452            let ty = relation.relate_with_variance(variance, info, a_ty, b_ty)?;
453
454            Ok(Ty::new_ref(cx, r, ty, a_mutbl))
455        }
456
457        (ty::Array(a_t, sz_a), ty::Array(b_t, sz_b)) => {
458            let t = relation.relate(a_t, b_t)?;
459            match relation.relate(sz_a, sz_b) {
460                Ok(sz) => Ok(Ty::new_array_with_const_len(cx, t, sz)),
461                Err(TypeError::ConstMismatch(_)) => {
462                    Err(TypeError::ArraySize(ExpectedFound::new(sz_a, sz_b)))
463                }
464                Err(e) => Err(e),
465            }
466        }
467
468        (ty::Slice(a_t), ty::Slice(b_t)) => {
469            let t = relation.relate(a_t, b_t)?;
470            Ok(Ty::new_slice(cx, t))
471        }
472
473        (ty::Tuple(as_), ty::Tuple(bs)) => {
474            if as_.len() == bs.len() {
475                Ok(Ty::new_tup_from_iter(
476                    cx,
477                    iter::zip(as_.iter(), bs.iter()).map(|(a, b)| relation.relate(a, b)),
478                )?)
479            } else if !(as_.is_empty() || bs.is_empty()) {
480                Err(TypeError::TupleSize(ExpectedFound::new(as_.len(), bs.len())))
481            } else {
482                Err(TypeError::Sorts(ExpectedFound::new(a, b)))
483            }
484        }
485
486        (ty::FnDef(a_def_id, a_args), ty::FnDef(b_def_id, b_args)) if a_def_id == b_def_id => {
487            if a_args.is_empty() {
488                Ok(a)
489            } else {
490                relation.relate_ty_args(a, b, a_def_id.into(), a_args, b_args, |args| {
491                    Ty::new_fn_def(cx, a_def_id, args)
492                })
493            }
494        }
495
496        (ty::FnPtr(a_sig_tys, a_hdr), ty::FnPtr(b_sig_tys, b_hdr)) => {
497            let fty = relation.relate(a_sig_tys.with(a_hdr), b_sig_tys.with(b_hdr))?;
498            Ok(Ty::new_fn_ptr(cx, fty))
499        }
500
501        // Alias tend to mostly already be handled downstream due to normalization.
502        (ty::Alias(a_kind, a_data), ty::Alias(b_kind, b_data)) => {
503            let alias_ty = relation.relate(a_data, b_data)?;
504            assert_eq!(a_kind, b_kind);
505            Ok(Ty::new_alias(cx, a_kind, alias_ty))
506        }
507
508        (ty::Pat(a_ty, a_pat), ty::Pat(b_ty, b_pat)) => {
509            let ty = relation.relate(a_ty, b_ty)?;
510            let pat = relation.relate(a_pat, b_pat)?;
511            Ok(Ty::new_pat(cx, ty, pat))
512        }
513
514        (ty::UnsafeBinder(a_binder), ty::UnsafeBinder(b_binder)) => {
515            Ok(Ty::new_unsafe_binder(cx, relation.binders(*a_binder, *b_binder)?))
516        }
517
518        _ => Err(TypeError::Sorts(ExpectedFound::new(a, b))),
519    }
520}
521
522/// Relates `a` and `b` structurally, calling the relation for all nested values.
523/// Any semantic equality, e.g. of unevaluated consts, and inference variables have
524/// to be handled by the caller.
525///
526/// FIXME: This is not totally structural, which probably should be fixed.
527/// See the HACKs below.
528pub fn structurally_relate_consts<I: Interner, R: TypeRelation<I>>(
529    relation: &mut R,
530    mut a: I::Const,
531    mut b: I::Const,
532) -> RelateResult<I, I::Const> {
533    trace!(
534        "structurally_relate_consts::<{}>(a = {:?}, b = {:?})",
535        std::any::type_name::<R>(),
536        a,
537        b
538    );
539    let cx = relation.cx();
540
541    if cx.features().generic_const_exprs() {
542        a = cx.expand_abstract_consts(a);
543        b = cx.expand_abstract_consts(b);
544    }
545
546    trace!(
547        "structurally_relate_consts::<{}>(normed_a = {:?}, normed_b = {:?})",
548        std::any::type_name::<R>(),
549        a,
550        b
551    );
552
553    // Currently, the values that can be unified are primitive types,
554    // and those that derive both `PartialEq` and `Eq`, corresponding
555    // to structural-match types.
556    let is_match = match (a.kind(), b.kind()) {
557        (ty::ConstKind::Infer(_), _) | (_, ty::ConstKind::Infer(_)) => {
558            // The caller should handle these cases!
559            panic!("var types encountered in structurally_relate_consts: {:?} {:?}", a, b)
560        }
561
562        (ty::ConstKind::Error(_), _) => return Ok(a),
563        (_, ty::ConstKind::Error(_)) => return Ok(b),
564
565        (ty::ConstKind::Param(a_p), ty::ConstKind::Param(b_p)) if a_p.index() == b_p.index() => {
566            // FIXME: Put this back
567            // debug_assert_eq!(a_p.name, b_p.name, "param types with same index differ in name");
568            true
569        }
570        (ty::ConstKind::Placeholder(p1), ty::ConstKind::Placeholder(p2)) => p1 == p2,
571        (ty::ConstKind::Value(a_val), ty::ConstKind::Value(b_val)) => {
572            match (a_val.valtree().kind(), b_val.valtree().kind()) {
573                (ty::ValTreeKind::Leaf(scalar_a), ty::ValTreeKind::Leaf(scalar_b)) => {
574                    scalar_a == scalar_b
575                }
576                (ty::ValTreeKind::Branch(branches_a), ty::ValTreeKind::Branch(branches_b))
577                    if branches_a.len() == branches_b.len() =>
578                {
579                    branches_a
580                        .into_iter()
581                        .zip(branches_b)
582                        .all(|(a, b)| relation.relate(*a, *b).is_ok())
583                }
584                _ => false,
585            }
586        }
587
588        // While this is slightly incorrect, it shouldn't matter for `min_const_generics`
589        // and is the better alternative to waiting until `generic_const_exprs` can
590        // be stabilized.
591        (ty::ConstKind::Unevaluated(au), ty::ConstKind::Unevaluated(bu)) if au.def == bu.def => {
592            // FIXME(mgca): remove this
593            if cfg!(debug_assertions) {
594                let a_ty = cx.type_of(au.def.into()).instantiate(cx, au.args);
595                let b_ty = cx.type_of(bu.def.into()).instantiate(cx, bu.args);
596                assert_eq!(a_ty, b_ty);
597            }
598
599            let args = relation.relate_with_variance(
600                ty::Invariant,
601                VarianceDiagInfo::default(),
602                au.args,
603                bu.args,
604            )?;
605            return Ok(Const::new_unevaluated(cx, ty::UnevaluatedConst { def: au.def, args }));
606        }
607        (ty::ConstKind::Expr(ae), ty::ConstKind::Expr(be)) => {
608            let expr = relation.relate(ae, be)?;
609            return Ok(Const::new_expr(cx, expr));
610        }
611        _ => false,
612    };
613    if is_match { Ok(a) } else { Err(TypeError::ConstMismatch(ExpectedFound::new(a, b))) }
614}
615
616impl<I: Interner, T: Relate<I>> Relate<I> for ty::Binder<I, T> {
617    fn relate<R: TypeRelation<I>>(
618        relation: &mut R,
619        a: ty::Binder<I, T>,
620        b: ty::Binder<I, T>,
621    ) -> RelateResult<I, ty::Binder<I, T>> {
622        relation.binders(a, b)
623    }
624}
625
626impl<I: Interner> Relate<I> for ty::TraitPredicate<I> {
627    fn relate<R: TypeRelation<I>>(
628        relation: &mut R,
629        a: ty::TraitPredicate<I>,
630        b: ty::TraitPredicate<I>,
631    ) -> RelateResult<I, ty::TraitPredicate<I>> {
632        let trait_ref = relation.relate(a.trait_ref, b.trait_ref)?;
633        if a.polarity != b.polarity {
634            return Err(TypeError::PolarityMismatch(ExpectedFound::new(a.polarity, b.polarity)));
635        }
636        Ok(ty::TraitPredicate { trait_ref, polarity: a.polarity })
637    }
638}
rustc_type_ir/relate.rs

rustc_type_ir/
relate.rs
