charon_driver/translate/
translate_predicates.rs

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

charon_driver/translate/
translate_predicates.rs
