charon_driver/translate/
translate_predicates.rs

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

charon_driver/translate/
translate_predicates.rs
