charon_driver/translate/
translate_predicates.rs

1use super::translate_ctx::*;
2use crate::hax;
3use charon_lib::{ast::*, ids::IndexVec};
4
5impl<'tcx> TranslateCtx<'tcx> {
6    pub fn recognize_builtin_impl(
7        &self,
8        trait_data: &hax::BuiltinTraitData,
9    ) -> Option<BuiltinImplData> {
10        Some(match trait_data {
11            hax::BuiltinTraitData::Destruct(x) => {
12                match x {
13                    hax::DestructData::Noop => BuiltinImplData::NoopDestruct,
14                    hax::DestructData::Implicit => BuiltinImplData::UntrackedDestruct,
15                    // This is unconditionally replaced by a `TraitImpl` earlier.
16                    hax::DestructData::Glue { .. } => unreachable!(),
17                }
18            }
19            hax::BuiltinTraitData::Alias => unreachable!(),
20            hax::BuiltinTraitData::Auto => BuiltinImplData::Auto,
21            hax::BuiltinTraitData::Other(item) => {
22                use hax::SolverTraitLangItem;
23                // The ones for which we return `None` are those I don't think would show up in a
24                // builtin impl.
25                match item {
26                    SolverTraitLangItem::AsyncFn => BuiltinImplData::AsyncFn,
27                    SolverTraitLangItem::AsyncFnKindHelper => return None,
28                    SolverTraitLangItem::AsyncFnMut => BuiltinImplData::AsyncFnMut,
29                    SolverTraitLangItem::AsyncFnOnce => BuiltinImplData::AsyncFnOnce,
30                    SolverTraitLangItem::AsyncIterator => return None,
31                    SolverTraitLangItem::BikeshedGuaranteedNoDrop => return None,
32                    SolverTraitLangItem::Clone => BuiltinImplData::Clone,
33                    SolverTraitLangItem::Copy => BuiltinImplData::Copy,
34                    SolverTraitLangItem::Coroutine => BuiltinImplData::Coroutine,
35                    SolverTraitLangItem::Destruct => BuiltinImplData::UntrackedDestruct,
36                    SolverTraitLangItem::DiscriminantKind => BuiltinImplData::DiscriminantKind,
37                    SolverTraitLangItem::Drop => return None,
38                    SolverTraitLangItem::Field => return None,
39                    SolverTraitLangItem::Fn => BuiltinImplData::Fn,
40                    SolverTraitLangItem::FnMut => BuiltinImplData::FnMut,
41                    SolverTraitLangItem::FnOnce => BuiltinImplData::FnOnce,
42                    SolverTraitLangItem::FnPtrTrait => BuiltinImplData::FnPtr,
43                    SolverTraitLangItem::FusedIterator => return None,
44                    SolverTraitLangItem::Future => BuiltinImplData::Future,
45                    SolverTraitLangItem::Iterator => return None,
46                    SolverTraitLangItem::MetaSized => BuiltinImplData::MetaSized,
47                    SolverTraitLangItem::PointeeSized => BuiltinImplData::PointeeSized,
48                    SolverTraitLangItem::PointeeTrait => BuiltinImplData::Pointee,
49                    SolverTraitLangItem::Sized => BuiltinImplData::Sized,
50                    SolverTraitLangItem::TransmuteTrait => BuiltinImplData::Transmute,
51                    SolverTraitLangItem::TrivialClone => BuiltinImplData::Auto,
52                    SolverTraitLangItem::TryAsDyn => BuiltinImplData::TryAsDynCompatible,
53                    SolverTraitLangItem::Tuple => BuiltinImplData::Tuple,
54                    SolverTraitLangItem::Unpin => BuiltinImplData::Auto,
55                    SolverTraitLangItem::Unsize => BuiltinImplData::Unsize,
56                }
57            }
58        })
59    }
60}
61
62impl<'tcx, 'ctx> ItemTransCtx<'tcx, 'ctx> {
63    /// Translates the given predicates and stores them as resuired preciates of the innermost
64    /// binder.
65    ///
66    /// This function should be called **after** we translated the generics (type parameters,
67    /// regions...).
68    pub(crate) fn register_predicates(
69        &mut self,
70        preds: &hax::GenericPredicates,
71        origin: PredicateOrigin,
72    ) -> Result<(), Error> {
73        self.translate_predicates(preds, origin, None)?;
74        Ok(())
75    }
76
77    /// Translates the given predicates. This function should be called **after** we translated the
78    /// generics (type parameters, regions...).
79    pub(crate) fn translate_predicates(
80        &mut self,
81        preds: &hax::GenericPredicates,
82        origin: PredicateOrigin,
83        // Either put clauses there or in the innermost binder.
84        mut trait_clauses: Option<&mut IndexVec<TraitClauseId, TraitParam>>,
85    ) -> Result<(), Error> {
86        if trait_clauses.is_none() {
87            // Register the mapping from trait preds to their id early on, as these can be mentioned
88            // while translating any other predicate including themselves. Each trait pred gives rise
89            // to exactly one trait clause inserted into `trait_clauses`, which we use to compute
90            // clause ids.
91            let next_clause_id = self.innermost_generics_mut().trait_clauses.next_idx();
92            for (i, pred) in preds
93                .predicates
94                .iter()
95                .filter(|pred| {
96                    matches!(
97                        pred.clause.kind.hax_skip_binder_ref(),
98                        hax::ClauseKind::Trait(_)
99                    )
100                })
101                .enumerate()
102            {
103                self.innermost_binder_mut()
104                    .trait_preds
105                    .insert(pred.id.clone(), next_clause_id + i);
106            }
107        }
108
109        for pred in &preds.predicates {
110            self.translate_predicate(pred, origin.clone(), trait_clauses.as_deref_mut())?;
111        }
112        Ok(())
113    }
114
115    pub(crate) fn translate_poly_trait_ref(
116        &mut self,
117        span: Span,
118        bound_trait_ref: &hax::Binder<hax::TraitRef>,
119    ) -> Result<PolyTraitDeclRef, Error> {
120        self.translate_region_binder(span, bound_trait_ref, move |ctx, trait_ref| {
121            ctx.translate_trait_ref(span, trait_ref)
122        })
123    }
124
125    pub(crate) fn translate_trait_predicate(
126        &mut self,
127        span: Span,
128        trait_pred: &hax::TraitPredicate,
129    ) -> Result<TraitDeclRef, Error> {
130        // we don't handle negative trait predicates.
131        assert!(trait_pred.is_positive);
132        self.translate_trait_ref(span, &trait_pred.trait_ref)
133    }
134
135    pub(crate) fn translate_trait_ref(
136        &mut self,
137        span: Span,
138        trait_ref: &hax::TraitRef,
139    ) -> Result<TraitDeclRef, Error> {
140        self.translate_trait_decl_ref(span, trait_ref)
141    }
142
143    pub(crate) fn translate_predicate(
144        &mut self,
145        pred: &hax::GenericPredicate,
146        mut origin: PredicateOrigin,
147        // Either put clauses there or in the innermost binder.
148        mut trait_clauses: Option<&mut IndexVec<TraitClauseId, TraitParam>>,
149    ) -> Result<(), Error> {
150        use crate::hax::ClauseKind;
151        let clause = &pred.clause;
152        trace!("{:?}", clause);
153        let span = self.translate_span(&pred.span);
154        match clause.kind.hax_skip_binder_ref() {
155            ClauseKind::Trait(trait_pred) => {
156                if matches!(pred.id, hax::GenericPredicateId::TraitSelf) {
157                    origin = PredicateOrigin::TraitSelf;
158                }
159                let trait_pred = self.translate_region_binder(span, &clause.kind, |ctx, _| {
160                    ctx.translate_trait_predicate(span, trait_pred)
161                })?;
162                let clause_id = trait_clauses
163                    .as_deref_mut()
164                    .unwrap_or(&mut self.innermost_generics_mut().trait_clauses)
165                    .push_with(|clause_id| TraitParam {
166                        clause_id,
167                        origin,
168                        span: Some(span),
169                        trait_: trait_pred,
170                    });
171
172                if trait_clauses.is_none() {
173                    // Sanity check.
174                    let expected_clause_id = self
175                        .innermost_binder_mut()
176                        .trait_preds
177                        .get(&pred.id)
178                        .unwrap();
179                    debug_assert_eq!(clause_id, *expected_clause_id);
180                }
181            }
182            ClauseKind::RegionOutlives(p) => {
183                let pred = self.translate_region_binder(span, &clause.kind, |ctx, _| {
184                    let r0 = ctx.translate_region(span, &p.lhs)?;
185                    let r1 = ctx.translate_region(span, &p.rhs)?;
186                    Ok(OutlivesPred(r0, r1))
187                })?;
188                self.innermost_generics_mut().regions_outlive.push(pred);
189            }
190            ClauseKind::TypeOutlives(p) => {
191                let pred = self.translate_region_binder(span, &clause.kind, |ctx, _| {
192                    let ty = ctx.translate_ty(span, &p.lhs)?;
193                    let r = ctx.translate_region(span, &p.rhs)?;
194                    Ok(OutlivesPred(ty, r))
195                })?;
196                self.innermost_generics_mut().types_outlive.push(pred);
197            }
198            ClauseKind::Projection(p) => {
199                // This is used to express constraints over associated types.
200                // For instance:
201                // ```
202                // T : Foo<S = String>
203                //         ^^^^^^^^^^
204                // ```
205                let pred = self.translate_region_binder(span, &clause.kind, |ctx, _| {
206                    let trait_ref = ctx.translate_trait_proof(span, &p.trait_proof)?;
207                    let ty = ctx.translate_ty(span, &p.ty)?;
208                    let type_id =
209                        ctx.translate_assoc_type_id(trait_ref.trait_id(), &p.assoc_item.def_id)?;
210                    Ok(TraitTypeConstraint {
211                        trait_ref,
212                        type_id,
213                        ty,
214                    })
215                })?;
216                self.innermost_generics_mut()
217                    .trait_type_constraints
218                    .push(pred);
219            }
220            ClauseKind::ConstArgHasType(..) => {
221                // These are used for trait resolution to get access to the type of const generics.
222                // We don't need them.
223            }
224            ClauseKind::HostEffect(..) => {
225                // These are used for `const Trait` clauses. Part of the `const_traits` unstable
226                // features. We ignore them for now.
227            }
228            ClauseKind::WellFormed(..) | ClauseKind::ConstEvaluatable(..) => {
229                // This is e.g. a clause `[(); N+1]:` (without anything after the `:`). This is
230                // used to require that the fallible `N+1` expression succeeds, so that it can be
231                // used at the type level. Part of the `generic_const_exprs` unstable feature.
232            }
233            ClauseKind::UnstableFeature(..) => {
234                // Unclear what this means, related to stability markers which we don't care about.
235            }
236            #[expect(unreachable_patterns)]
237            kind => raise_error!(self, span, "Unsupported clause: {:?}", kind),
238        }
239        Ok(())
240    }
241
242    pub(crate) fn translate_trait_proofs(
243        &mut self,
244        span: Span,
245        impl_sources: &[hax::TraitProof],
246    ) -> Result<IndexVec<TraitClauseId, TraitRef>, Error> {
247        impl_sources
248            .iter()
249            .map(|x| self.translate_trait_proof(span, x))
250            .try_collect()
251    }
252
253    #[tracing::instrument(skip(self, span, trait_proof))]
254    pub(crate) fn translate_trait_proof(
255        &mut self,
256        span: Span,
257        trait_proof: &hax::TraitProof,
258    ) -> Result<TraitRef, Error> {
259        let trait_decl_ref = self.translate_poly_trait_ref(span, &trait_proof.pred)?;
260
261        match self.translate_trait_proof_aux(span, trait_proof, trait_decl_ref.clone()) {
262            Ok(res) => Ok(res),
263            Err(err) => {
264                register_error!(self, span, "Error during trait resolution: {}", &err.msg);
265                Ok(TraitRef::new(
266                    TraitRefKind::Unknown(err.msg),
267                    trait_decl_ref,
268                ))
269            }
270        }
271    }
272
273    pub(crate) fn translate_trait_proof_aux(
274        &mut self,
275        span: Span,
276        impl_source: &hax::TraitProof,
277        trait_decl_ref: PolyTraitDeclRef,
278    ) -> Result<TraitRef, Error> {
279        trace!("trait_proof: {:#?}", impl_source);
280        use crate::hax::DestructData;
281        use crate::hax::TraitProofKind;
282
283        let kind = match &impl_source.kind {
284            TraitProofKind::Concrete(item) => {
285                let impl_ref =
286                    self.translate_trait_impl_ref(span, item, TransImplSource::Normal)?;
287                TraitRefKind::TraitImpl(impl_ref)
288            }
289            TraitProofKind::SelfProof => TraitRefKind::SelfId,
290            TraitProofKind::LocalBound(id) => match self.lookup_clause_var(span, id) {
291                Ok(var) => TraitRefKind::Clause(var),
292                Err(err) => TraitRefKind::Unknown(err.msg),
293            },
294            TraitProofKind::Derived {
295                base,
296                path: path_elem,
297            } => {
298                let trait_ref = self.translate_trait_proof(span, base)?;
299                let trait_ref = Box::new(trait_ref);
300                match path_elem {
301                    hax::TraitProofImpliedPredicate::AssocItem { item, index, .. } => {
302                        let assoc_type_id =
303                            self.translate_assoc_type_id(trait_ref.trait_id(), &item.def_id)?;
304                        TraitRefKind::ItemClause(
305                            trait_ref,
306                            assoc_type_id,
307                            TraitClauseId::new(*index),
308                        )
309                    }
310                    hax::TraitProofImpliedPredicate::Parent { index, .. } => {
311                        TraitRefKind::ParentClause(trait_ref, TraitClauseId::new(*index))
312                    }
313                }
314            }
315            TraitProofKind::Dyn(proof) => {
316                // Translate the proof in the context of the clauses bound by the dyn type.
317                let bound_proof = self.translate_dyn_binder(span, proof, |ctx, _, proof| {
318                    ctx.translate_trait_proof(span, proof)
319                })?;
320
321                // Instantiate the fake type with the actual `dyn Trait` and a `TraitRefKind::Dyn`
322                // for each base clause. That way, `TraitRefKind::Dyn` is only used for clauses
323                // directly in the `dyn Trait1 + Trait2` type.
324                let args = {
325                    let dyn_ty = trait_decl_ref.clone().erase().generics.types[0].clone();
326                    assert!(dyn_ty.is_dyn_trait());
327                    let mut args = GenericArgs::new_types([dyn_ty].into());
328                    args.trait_refs = bound_proof
329                        .params
330                        .trait_clauses
331                        .clone()
332                        .substitute(&args)
333                        .map(|clause| TraitRef::new(TraitRefKind::Dyn, clause.trait_));
334                    args
335                };
336                let trait_ref = bound_proof.apply(&args);
337                assert_eq!(trait_ref.trait_id(), trait_decl_ref.skip_binder.id);
338                trait_ref.kind.clone()
339            }
340            TraitProofKind::Builtin {
341                trait_data,
342                proofs: trait_proofs,
343                types,
344                ..
345            } => {
346                let tref = &impl_source.pred;
347                let trait_def = self.poly_hax_def(&tref.hax_skip_binder_ref().def_id)?;
348                match trait_data {
349                    hax::BuiltinTraitData::Alias => {
350                        // We reuse the same `def_id` to generate a blanket impl for the trait.
351                        let mut impl_ref: TraitImplRef = self.translate_item(
352                            span,
353                            &tref.hax_skip_binder_ref().erase(self.hax_state_with_id()),
354                            TransItemSourceKind::TraitImpl(TransImplSource::TraitAlias),
355                        )?;
356                        assert!(
357                            impl_ref.generics.trait_refs.is_empty(),
358                            "found trait alias with non-empty required predicates"
359                        );
360                        impl_ref.generics.trait_refs =
361                            self.translate_trait_proofs(span, trait_proofs)?;
362                        TraitRefKind::TraitImpl(impl_ref)
363                    }
364                    hax::BuiltinTraitData::Destruct(DestructData::Glue { ty, .. }) => {
365                        let (hax::TyKind::Adt(item)
366                        | hax::TyKind::Closure(hax::ClosureArgs { item, .. })
367                        | hax::TyKind::Array(item)
368                        | hax::TyKind::Slice(item)
369                        | hax::TyKind::Tuple(item)) = ty.kind()
370                        else {
371                            raise_error!(
372                                self,
373                                span,
374                                "failed to translate drop glue for type {ty:?}"
375                            )
376                        };
377                        TraitRefKind::TraitImpl(self.translate_trait_impl_ref(
378                            span,
379                            item,
380                            TransImplSource::ImplicitDestruct,
381                        )?)
382                    }
383                    hax::BuiltinTraitData::Other(
384                        li @ (hax::SolverTraitLangItem::FnOnce
385                        | hax::SolverTraitLangItem::FnMut
386                        | hax::SolverTraitLangItem::Fn),
387                    ) if let Some(hax::GenericArg::Type(callable_ty)) =
388                        impl_source.pred.hax_skip_binder_ref().generic_args.first()
389                        && let Some(item) = match callable_ty.kind() {
390                            hax::TyKind::Closure(closure_args) => Some(&closure_args.item),
391                            hax::TyKind::FnDef { item, .. } => Some(item),
392                            _ => None,
393                        } =>
394                    {
395                        let closure_kind = match li {
396                            hax::SolverTraitLangItem::FnOnce => ClosureKind::FnOnce,
397                            hax::SolverTraitLangItem::FnMut => ClosureKind::FnMut,
398                            hax::SolverTraitLangItem::Fn => ClosureKind::Fn,
399                            _ => unreachable!(),
400                        };
401                        let binder =
402                            self.translate_region_binder(span, &impl_source.pred, |ctx, _tref| {
403                                ctx.translate_callable_impl_ref(span, item, closure_kind)
404                            })?;
405                        TraitRefKind::TraitImpl(self.erase_region_binder(binder))
406                    }
407                    _ if let Some(builtin_data) = self.recognize_builtin_impl(trait_data) => {
408                        let parent_trait_refs = self.translate_trait_proofs(span, trait_proofs)?;
409                        let types: IndexMap<AssocTypeId, _> = if self.monomorphize() {
410                            IndexMap::new()
411                        } else {
412                            let tdecl_id = trait_decl_ref.skip_binder.id;
413                            let mut type_map = IndexMap::new();
414                            for (def_id, ty, trait_proofs) in types {
415                                let assoc_type_id =
416                                    self.translate_assoc_type_id(tdecl_id, def_id)?;
417                                let assoc_ty = TraitAssocTyImpl {
418                                    value: self.translate_ty(span, ty)?,
419                                    implied_trait_refs: self
420                                        .translate_trait_proofs(span, trait_proofs)?,
421                                };
422                                type_map.set_slot_extend(assoc_type_id, assoc_ty);
423                            }
424                            type_map
425                        };
426                        let vtable = self.translate_vtable_instance_ref_no_enqueue(
427                            span,
428                            tref.hax_skip_binder_ref(),
429                            tref.hax_skip_binder_ref(),
430                            TransImplSource::Marker,
431                        )?;
432                        TraitRefKind::BuiltinOrAuto {
433                            builtin_data,
434                            parent_trait_refs,
435                            types,
436                            vtable,
437                        }
438                    }
439                    _ => raise_error!(
440                        self,
441                        span,
442                        "found a built-in trait impl we did not recognize: \
443                        {:?} (lang_item={:?})",
444                        trait_def.def_id(),
445                        trait_def.lang_item,
446                    ),
447                }
448            }
449            TraitProofKind::Error(msg) => {
450                if self.error_on_trait_proof_error {
451                    register_error!(self, span, "Error during trait resolution: {}", msg);
452                }
453                TraitRefKind::Unknown(msg.clone())
454            }
455        };
456        Ok(TraitRef::new(kind, trait_decl_ref))
457    }
458}
charon_driver/translate/translate_predicates.rs

charon_driver/translate/
translate_predicates.rs
