charon_driver/translate/
translate_generics.rs

1use super::translate_ctx::ItemTransCtx;
2use charon_lib::ast::*;
3use charon_lib::common::hash_by_addr::HashByAddr;
4use std::collections::HashMap;
5use std::fmt::Debug;
6use std::sync::Arc;
7
8/// A level of binding for type-level variables. Each item has a top-level binding level
9/// corresponding to the parameters and clauses to the items. We may then encounter inner binding
10/// levels in the following cases:
11/// - `for<..>` binders in predicates;
12/// - `fn<..>` function pointer types;
13/// - `dyn Trait` types, represented as `dyn<T: Trait>` (TODO);
14/// - types in a trait declaration or implementation block (TODO);
15/// - methods in a trait declaration or implementation block (TODO).
16///
17/// At each level, we store two things: a `GenericParams` that contains the parameters bound at
18/// this level, and various maps from the rustc-internal indices to our indices.
19#[derive(Debug, Default)]
20pub(crate) struct BindingLevel {
21    /// The parameters and predicates bound at this level.
22    pub params: GenericParams,
23    /// Whether this binder corresponds to an item (method, type) or not (`for<..>` predicate, `fn`
24    /// pointer, etc). This indicates whether it corresponds to a rustc `ParamEnv` and therefore
25    /// whether we should resolve rustc variables there.
26    pub is_item_binder: bool,
27    /// Rust makes the distinction between early and late-bound region parameters. We do not make
28    /// this distinction, and merge early and late bound regions. For details, see:
29    /// <https://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/>
30    /// <https://smallcultfollowing.com/babysteps/blog/2013/11/04/intermingled-parameter-lists/>
31    ///
32    /// The map from rust early regions to translated region indices.
33    pub early_region_vars: std::collections::BTreeMap<hax::EarlyParamRegion, RegionId>,
34    /// The map from rust late/bound regions to translated region indices.
35    pub bound_region_vars: Vec<RegionId>,
36    /// The regions added for by-ref upvars, in order of upvars.
37    pub by_ref_upvar_regions: Vec<RegionId>,
38    /// The map from rust type variable indices to translated type variable indices.
39    pub type_vars_map: HashMap<u32, TypeVarId>,
40    /// The map from rust const generic variables to translate const generic variable indices.
41    pub const_generic_vars_map: HashMap<u32, ConstGenericVarId>,
42    /// Cache the translation of types. This harnesses the deduplication of `TyKind` that hax does.
43    // Important: we can't reuse type caches from earlier binders as the new binder may change what
44    // a given variable resolves to.
45    pub type_trans_cache: HashMap<HashByAddr<Arc<hax::TyKind>>, Ty>,
46}
47
48/// Small helper: we ignore some region names (when they are equal to "'_")
49fn translate_region_name(s: String) -> Option<String> {
50    if s == "'_" { None } else { Some(s) }
51}
52
53impl BindingLevel {
54    pub(crate) fn new(is_item_binder: bool) -> Self {
55        Self {
56            is_item_binder,
57            ..Default::default()
58        }
59    }
60
61    /// Important: we must push all the early-bound regions before pushing any other region.
62    pub(crate) fn push_early_region(&mut self, region: hax::EarlyParamRegion) -> RegionId {
63        let name = translate_region_name(region.name.clone());
64        // Check that there are no late-bound regions
65        assert!(
66            self.bound_region_vars.is_empty(),
67            "Early regions must be translated before late ones"
68        );
69        let rid = self
70            .params
71            .regions
72            .push_with(|index| RegionParam { index, name });
73        self.early_region_vars.insert(region, rid);
74        rid
75    }
76
77    /// Important: we must push all the early-bound regions before pushing any other region.
78    pub(crate) fn push_bound_region(&mut self, region: hax::BoundRegionKind) -> RegionId {
79        use hax::BoundRegionKind::*;
80        let name = match region {
81            Anon => None,
82            NamedAnon(symbol) | Named(_, symbol) => translate_region_name(symbol.clone()),
83            ClosureEnv => Some("@env".to_owned()),
84        };
85        let rid = self
86            .params
87            .regions
88            .push_with(|index| RegionParam { index, name });
89        self.bound_region_vars.push(rid);
90        rid
91    }
92
93    /// Add a region for a by_ref upvar in a closure.
94    pub fn push_upvar_region(&mut self) -> RegionId {
95        // We musn't push to `bound_region_vars` because that will contain the higher-kinded
96        // signature lifetimes if any and they must be lookup-able.
97        let region_id = self
98            .params
99            .regions
100            .push_with(|index| RegionParam { index, name: None });
101        self.by_ref_upvar_regions.push(region_id);
102        region_id
103    }
104
105    pub(crate) fn push_type_var(&mut self, rid: u32, name: String) -> TypeVarId {
106        let var_id = self
107            .params
108            .types
109            .push_with(|index| TypeParam { index, name });
110        self.type_vars_map.insert(rid, var_id);
111        var_id
112    }
113
114    pub(crate) fn push_const_generic_var(&mut self, rid: u32, ty: LiteralTy, name: String) {
115        let var_id = self
116            .params
117            .const_generics
118            .push_with(|index| ConstGenericParam { index, name, ty });
119        self.const_generic_vars_map.insert(rid, var_id);
120    }
121
122    /// Translate a binder of regions by appending the stored reguions to the given vector.
123    pub(crate) fn push_params_from_binder(&mut self, binder: hax::Binder<()>) -> Result<(), Error> {
124        assert!(
125            self.bound_region_vars.is_empty(),
126            "Trying to use two binders at the same binding level"
127        );
128        use hax::BoundVariableKind::*;
129        for p in binder.bound_vars {
130            match p {
131                Region(region) => {
132                    self.push_bound_region(region);
133                }
134                Ty(_) => {
135                    panic!("Unexpected locally bound type variable");
136                }
137                Const => {
138                    panic!("Unexpected locally bound const generic variable");
139                }
140            }
141        }
142        Ok(())
143    }
144}
145
146impl<'tcx, 'ctx> ItemTransCtx<'tcx, 'ctx> {
147    /// Get the only binding level. Panics if there are other binding levels.
148    pub(crate) fn the_only_binder(&self) -> &BindingLevel {
149        assert_eq!(self.binding_levels.len(), 1);
150        self.innermost_binder()
151    }
152    /// Get the only binding level. Panics if there are other binding levels.
153    pub(crate) fn the_only_binder_mut(&mut self) -> &mut BindingLevel {
154        assert_eq!(self.binding_levels.len(), 1);
155        self.innermost_binder_mut()
156    }
157
158    pub(crate) fn outermost_binder(&self) -> &BindingLevel {
159        self.binding_levels.outermost()
160    }
161    pub(crate) fn outermost_binder_mut(&mut self) -> &mut BindingLevel {
162        self.binding_levels.outermost_mut()
163    }
164    pub(crate) fn innermost_binder(&self) -> &BindingLevel {
165        self.binding_levels.innermost()
166    }
167    pub(crate) fn innermost_binder_mut(&mut self) -> &mut BindingLevel {
168        self.binding_levels.innermost_mut()
169    }
170
171    #[expect(dead_code)]
172    pub(crate) fn outermost_generics(&self) -> &GenericParams {
173        &self.outermost_binder().params
174    }
175    #[expect(dead_code)]
176    pub(crate) fn outermost_generics_mut(&mut self) -> &mut GenericParams {
177        &mut self.outermost_binder_mut().params
178    }
179    #[expect(dead_code)]
180    pub(crate) fn innermost_generics(&self) -> &GenericParams {
181        &self.innermost_binder().params
182    }
183    pub(crate) fn innermost_generics_mut(&mut self) -> &mut GenericParams {
184        &mut self.innermost_binder_mut().params
185    }
186
187    pub(crate) fn lookup_bound_region(
188        &mut self,
189        span: Span,
190        dbid: hax::DebruijnIndex,
191        var: hax::BoundVar,
192    ) -> Result<RegionDbVar, Error> {
193        let dbid = DeBruijnId::new(dbid);
194        if let Some(rid) = self
195            .binding_levels
196            .get(dbid)
197            .and_then(|bl| bl.bound_region_vars.get(var))
198        {
199            Ok(DeBruijnVar::bound(dbid, *rid))
200        } else {
201            raise_error!(
202                self,
203                span,
204                "Unexpected error: could not find region '{dbid}_{var}"
205            )
206        }
207    }
208
209    pub(crate) fn lookup_param<Id: Copy>(
210        &mut self,
211        span: Span,
212        f: impl for<'a> Fn(&'a BindingLevel) -> Option<Id>,
213        mk_err: impl FnOnce() -> String,
214    ) -> Result<DeBruijnVar<Id>, Error> {
215        for (dbid, bl) in self.binding_levels.iter_enumerated() {
216            if let Some(id) = f(bl) {
217                return Ok(DeBruijnVar::bound(dbid, id));
218            }
219        }
220        let err = mk_err();
221        raise_error!(self, span, "Unexpected error: could not find {}", err)
222    }
223
224    pub(crate) fn lookup_early_region(
225        &mut self,
226        span: Span,
227        region: &hax::EarlyParamRegion,
228    ) -> Result<RegionDbVar, Error> {
229        self.lookup_param(
230            span,
231            |bl| bl.early_region_vars.get(region).copied(),
232            || format!("the region variable {region:?}"),
233        )
234    }
235
236    pub(crate) fn lookup_type_var(
237        &mut self,
238        span: Span,
239        param: &hax::ParamTy,
240    ) -> Result<TypeDbVar, Error> {
241        self.lookup_param(
242            span,
243            |bl| bl.type_vars_map.get(&param.index).copied(),
244            || format!("the type variable {}", param.name),
245        )
246    }
247
248    pub(crate) fn lookup_const_generic_var(
249        &mut self,
250        span: Span,
251        param: &hax::ParamConst,
252    ) -> Result<ConstGenericDbVar, Error> {
253        self.lookup_param(
254            span,
255            |bl| bl.const_generic_vars_map.get(&param.index).copied(),
256            || format!("the const generic variable {}", param.name),
257        )
258    }
259
260    pub(crate) fn lookup_clause_var(
261        &mut self,
262        span: Span,
263        mut id: usize,
264    ) -> Result<ClauseDbVar, Error> {
265        // The clause indices returned by hax count clauses in order, starting from the parentmost.
266        // While adding clauses to a binding level we already need to translate types and clauses,
267        // so the innermost item binder may not have all the clauses yet. Hence for that binder we
268        // ignore the clause count.
269        let innermost_item_binder_id = self
270            .binding_levels
271            .iter_enumerated()
272            .find(|(_, bl)| bl.is_item_binder)
273            .unwrap()
274            .0;
275        // Iterate over the binders, starting from the outermost.
276        for (dbid, bl) in self.binding_levels.iter_enumerated().rev() {
277            let num_clauses_bound_at_this_level = bl.params.trait_clauses.elem_count();
278            if id < num_clauses_bound_at_this_level || dbid == innermost_item_binder_id {
279                let id = TraitClauseId::from_usize(id);
280                return Ok(DeBruijnVar::bound(dbid, id));
281            } else {
282                id -= num_clauses_bound_at_this_level
283            }
284        }
285        // Actually unreachable
286        raise_error!(
287            self,
288            span,
289            "Unexpected error: could not find clause variable {}",
290            id
291        )
292    }
293
294    pub(crate) fn push_generic_params(&mut self, generics: &hax::TyGenerics) -> Result<(), Error> {
295        for param in &generics.params {
296            self.push_generic_param(param)?;
297        }
298        Ok(())
299    }
300
301    pub(crate) fn push_generic_param(&mut self, param: &hax::GenericParamDef) -> Result<(), Error> {
302        match &param.kind {
303            hax::GenericParamDefKind::Lifetime => {
304                let region = hax::EarlyParamRegion {
305                    index: param.index,
306                    name: param.name.clone(),
307                };
308                let _ = self.innermost_binder_mut().push_early_region(region);
309            }
310            hax::GenericParamDefKind::Type { .. } => {
311                let _ = self
312                    .innermost_binder_mut()
313                    .push_type_var(param.index, param.name.clone());
314            }
315            hax::GenericParamDefKind::Const { ty, .. } => {
316                let span = self.def_span(&param.def_id);
317                // The type should be primitive, meaning it shouldn't contain variables,
318                // non-primitive adts, etc. As a result, we can use an empty context.
319                let ty = self.translate_ty(span, ty)?;
320                match ty.kind().as_literal() {
321                    Some(ty) => self.innermost_binder_mut().push_const_generic_var(
322                        param.index,
323                        *ty,
324                        param.name.clone(),
325                    ),
326                    None => raise_error!(
327                        self,
328                        span,
329                        "Constant parameters of non-literal type are not supported"
330                    ),
331                }
332            }
333        }
334
335        Ok(())
336    }
337
338    /// Add the generics and predicates of this item and its parents to the current context.
339    #[tracing::instrument(skip(self, span))]
340    fn push_generics_for_def(
341        &mut self,
342        span: Span,
343        def: &hax::FullDef,
344        is_parent: bool,
345    ) -> Result<(), Error> {
346        // Add generics from the parent item, recursively (recursivity is important for closures,
347        // as they can be nested).
348        if let Some(parent_item) = def.typing_parent(self.hax_state()) {
349            let parent_def = self.hax_def(&parent_item)?;
350            self.push_generics_for_def(span, &parent_def, true)?;
351        }
352        self.push_generics_for_def_without_parents(span, def, !is_parent)?;
353        Ok(())
354    }
355
356    /// Add the generics and predicates of this item. This does not include the parent generics;
357    /// use `push_generics_for_def` to get the full list.
358    fn push_generics_for_def_without_parents(
359        &mut self,
360        _span: Span,
361        def: &hax::FullDef,
362        include_late_bound: bool,
363    ) -> Result<(), Error> {
364        use hax::FullDefKind;
365        if let Some(param_env) = def.param_env() {
366            // Add the generic params.
367            self.push_generic_params(&param_env.generics)?;
368            // Add the predicates.
369            let origin = match &def.kind {
370                FullDefKind::Adt { .. }
371                | FullDefKind::TyAlias { .. }
372                | FullDefKind::AssocTy { .. } => PredicateOrigin::WhereClauseOnType,
373                FullDefKind::Fn { .. }
374                | FullDefKind::AssocFn { .. }
375                | FullDefKind::Const { .. }
376                | FullDefKind::AssocConst { .. }
377                | FullDefKind::Static { .. } => PredicateOrigin::WhereClauseOnFn,
378                FullDefKind::TraitImpl { .. } | FullDefKind::InherentImpl { .. } => {
379                    PredicateOrigin::WhereClauseOnImpl
380                }
381                FullDefKind::Trait { .. } | FullDefKind::TraitAlias { .. } => {
382                    PredicateOrigin::WhereClauseOnTrait
383                }
384                _ => panic!("Unexpected def: {def:?}"),
385            };
386            self.register_predicates(&param_env.predicates, origin.clone())?;
387        }
388
389        if let hax::FullDefKind::Closure { args, .. } = def.kind()
390            && include_late_bound
391        {
392            // Add the lifetime generics coming from the by-ref upvars.
393            args.upvar_tys.iter().for_each(|ty| {
394                if matches!(
395                    ty.kind(),
396                    hax::TyKind::Ref(
397                        hax::Region {
398                            kind: hax::RegionKind::ReErased
399                        },
400                        ..
401                    )
402                ) {
403                    self.the_only_binder_mut().push_upvar_region();
404                }
405            });
406        }
407
408        // The parameters (and in particular the lifetimes) are split between
409        // early bound and late bound parameters. See those blog posts for explanations:
410        // https://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/
411        // https://smallcultfollowing.com/babysteps/blog/2013/11/04/intermingled-parameter-lists/
412        // Note that only lifetimes can be late bound.
413        //
414        // [TyCtxt.generics_of] gives us the early-bound parameters. We add the late-bound
415        // parameters here.
416        let signature = match &def.kind {
417            hax::FullDefKind::Fn { sig, .. } => Some(sig),
418            hax::FullDefKind::AssocFn { sig, .. } => Some(sig),
419            _ => None,
420        };
421        if let Some(signature) = signature
422            && include_late_bound
423        {
424            let innermost_binder = self.innermost_binder_mut();
425            assert!(innermost_binder.bound_region_vars.is_empty());
426            innermost_binder.push_params_from_binder(signature.rebind(()))?;
427        }
428
429        Ok(())
430    }
431
432    /// Translate the generics and predicates of this item and its parents.
433    /// This adds generic parameters and predicates to the current environment (as a binder in `self.binding_levels`).
434    /// This is necessary to translate types that depend on these generics (such as `Ty` and `TraitRef`).
435    /// The constructed `GenericParams` can be recovered at the end using `self.into_generics()` and stored in the translated item.
436    pub(crate) fn translate_def_generics(
437        &mut self,
438        span: Span,
439        def: &hax::FullDef,
440    ) -> Result<(), Error> {
441        assert!(self.binding_levels.len() == 0);
442        self.binding_levels.push(BindingLevel::new(true));
443        self.push_generics_for_def(span, def, false)?;
444        self.innermost_binder_mut().params.check_consistency();
445        Ok(())
446    }
447
448    /// Translate the generics and predicates of this item without its parents.
449    pub(crate) fn translate_def_generics_without_parents(
450        &mut self,
451        span: Span,
452        def: &hax::FullDef,
453    ) -> Result<(), Error> {
454        self.binding_levels.push(BindingLevel::new(true));
455        self.push_generics_for_def_without_parents(span, def, true)?;
456        self.innermost_binder().params.check_consistency();
457        Ok(())
458    }
459
460    /// Push a new binding level corresponding to the provided `def` for the duration of the inner
461    /// function call.
462    pub(crate) fn translate_binder_for_def<F, U>(
463        &mut self,
464        span: Span,
465        kind: BinderKind,
466        def: &hax::FullDef,
467        f: F,
468    ) -> Result<Binder<U>, Error>
469    where
470        F: FnOnce(&mut Self) -> Result<U, Error>,
471    {
472        assert!(!self.binding_levels.is_empty());
473
474        // Register the type-level parameters. This pushes a new binding level.
475        self.translate_def_generics_without_parents(span, def)?;
476
477        // Call the continuation. Important: do not short-circuit on error here.
478        let res = f(self);
479
480        // Reset
481        let params = self.binding_levels.pop().unwrap().params;
482
483        // Return
484        res.map(|skip_binder| Binder {
485            kind,
486            params,
487            skip_binder,
488        })
489    }
490
491    /// Push a group of bound regions and call the continuation.
492    /// We use this when diving into a `for<'a>`, or inside an arrow type (because
493    /// it contains universally quantified regions).
494    pub(crate) fn translate_region_binder<F, T, U>(
495        &mut self,
496        _span: Span,
497        binder: &hax::Binder<T>,
498        f: F,
499    ) -> Result<RegionBinder<U>, Error>
500    where
501        F: FnOnce(&mut Self, &T) -> Result<U, Error>,
502    {
503        assert!(!self.binding_levels.is_empty());
504
505        // Register the variables
506        let mut binding_level = BindingLevel::new(false);
507        binding_level.push_params_from_binder(binder.rebind(()))?;
508        self.binding_levels.push(binding_level);
509
510        // Call the continuation. Important: do not short-circuit on error here.
511        let res = f(self, binder.hax_skip_binder_ref());
512
513        // Reset
514        let regions = self.binding_levels.pop().unwrap().params.regions;
515
516        // Return
517        res.map(|skip_binder| RegionBinder {
518            regions,
519            skip_binder,
520        })
521    }
522
523    pub(crate) fn into_generics(mut self) -> GenericParams {
524        assert!(self.binding_levels.len() == 1);
525        self.binding_levels.pop().unwrap().params
526    }
527}
charon_driver/translate/translate_generics.rs

charon_driver/translate/
translate_generics.rs
