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    pub(crate) fn outermost_generics(&self) -> &GenericParams {
172        &self.outermost_binder().params
173    }
174    #[expect(dead_code)]
175    pub(crate) fn outermost_generics_mut(&mut self) -> &mut GenericParams {
176        &mut self.outermost_binder_mut().params
177    }
178    pub(crate) fn innermost_generics(&self) -> &GenericParams {
179        &self.innermost_binder().params
180    }
181    pub(crate) fn innermost_generics_mut(&mut self) -> &mut GenericParams {
182        &mut self.innermost_binder_mut().params
183    }
184
185    pub(crate) fn lookup_bound_region(
186        &mut self,
187        span: Span,
188        dbid: hax::DebruijnIndex,
189        var: hax::BoundVar,
190    ) -> Result<RegionDbVar, Error> {
191        let dbid = DeBruijnId::new(dbid);
192        if let Some(rid) = self
193            .binding_levels
194            .get(dbid)
195            .and_then(|bl| bl.bound_region_vars.get(var))
196        {
197            Ok(DeBruijnVar::bound(dbid, *rid))
198        } else {
199            raise_error!(
200                self,
201                span,
202                "Unexpected error: could not find region '{dbid}_{var}"
203            )
204        }
205    }
206
207    pub(crate) fn lookup_param<Id: Copy>(
208        &mut self,
209        span: Span,
210        f: impl for<'a> Fn(&'a BindingLevel) -> Option<Id>,
211        mk_err: impl FnOnce() -> String,
212    ) -> Result<DeBruijnVar<Id>, Error> {
213        for (dbid, bl) in self.binding_levels.iter_enumerated() {
214            if let Some(id) = f(bl) {
215                return Ok(DeBruijnVar::bound(dbid, id));
216            }
217        }
218        let err = mk_err();
219        raise_error!(self, span, "Unexpected error: could not find {}", err)
220    }
221
222    pub(crate) fn lookup_early_region(
223        &mut self,
224        span: Span,
225        region: &hax::EarlyParamRegion,
226    ) -> Result<RegionDbVar, Error> {
227        self.lookup_param(
228            span,
229            |bl| bl.early_region_vars.get(region).copied(),
230            || format!("the region variable {region:?}"),
231        )
232    }
233
234    pub(crate) fn lookup_type_var(
235        &mut self,
236        span: Span,
237        param: &hax::ParamTy,
238    ) -> Result<TypeDbVar, Error> {
239        self.lookup_param(
240            span,
241            |bl| bl.type_vars_map.get(&param.index).copied(),
242            || format!("the type variable {}", param.name),
243        )
244    }
245
246    pub(crate) fn lookup_const_generic_var(
247        &mut self,
248        span: Span,
249        param: &hax::ParamConst,
250    ) -> Result<ConstGenericDbVar, Error> {
251        self.lookup_param(
252            span,
253            |bl| bl.const_generic_vars_map.get(&param.index).copied(),
254            || format!("the const generic variable {}", param.name),
255        )
256    }
257
258    pub(crate) fn lookup_clause_var(
259        &mut self,
260        span: Span,
261        mut id: usize,
262    ) -> Result<ClauseDbVar, Error> {
263        // The clause indices returned by hax count clauses in order, starting from the parentmost.
264        // While adding clauses to a binding level we already need to translate types and clauses,
265        // so the innermost item binder may not have all the clauses yet. Hence for that binder we
266        // ignore the clause count.
267        let innermost_item_binder_id = self
268            .binding_levels
269            .iter_enumerated()
270            .find(|(_, bl)| bl.is_item_binder)
271            .unwrap()
272            .0;
273        // Iterate over the binders, starting from the outermost.
274        for (dbid, bl) in self.binding_levels.iter_enumerated().rev() {
275            let num_clauses_bound_at_this_level = bl.params.trait_clauses.elem_count();
276            if id < num_clauses_bound_at_this_level || dbid == innermost_item_binder_id {
277                let id = TraitClauseId::from_usize(id);
278                return Ok(DeBruijnVar::bound(dbid, id));
279            } else {
280                id -= num_clauses_bound_at_this_level
281            }
282        }
283        // Actually unreachable
284        raise_error!(
285            self,
286            span,
287            "Unexpected error: could not find clause variable {}",
288            id
289        )
290    }
291
292    pub(crate) fn push_generic_params(&mut self, generics: &hax::TyGenerics) -> Result<(), Error> {
293        for param in &generics.params {
294            self.push_generic_param(param)?;
295        }
296        Ok(())
297    }
298
299    pub(crate) fn push_generic_param(&mut self, param: &hax::GenericParamDef) -> Result<(), Error> {
300        match &param.kind {
301            hax::GenericParamDefKind::Lifetime => {
302                let region = hax::EarlyParamRegion {
303                    index: param.index,
304                    name: param.name.clone(),
305                };
306                let _ = self.innermost_binder_mut().push_early_region(region);
307            }
308            hax::GenericParamDefKind::Type { .. } => {
309                let _ = self
310                    .innermost_binder_mut()
311                    .push_type_var(param.index, param.name.clone());
312            }
313            hax::GenericParamDefKind::Const { ty, .. } => {
314                let span = self.def_span(&param.def_id);
315                // The type should be primitive, meaning it shouldn't contain variables,
316                // non-primitive adts, etc. As a result, we can use an empty context.
317                let ty = self.translate_ty(span, ty)?;
318                match ty.kind().as_literal() {
319                    Some(ty) => self.innermost_binder_mut().push_const_generic_var(
320                        param.index,
321                        *ty,
322                        param.name.clone(),
323                    ),
324                    None => raise_error!(
325                        self,
326                        span,
327                        "Constant parameters of non-literal type are not supported"
328                    ),
329                }
330            }
331        }
332
333        Ok(())
334    }
335
336    /// Add the generics and predicates of this item and its parents to the current context.
337    #[tracing::instrument(skip(self, span))]
338    fn push_generics_for_def(
339        &mut self,
340        span: Span,
341        def: &hax::FullDef,
342        is_parent: bool,
343    ) -> Result<(), Error> {
344        // Add generics from the parent item, recursively (recursivity is important for closures,
345        // as they can be nested).
346        if let Some(parent_item) = def.typing_parent(self.hax_state()) {
347            let parent_def = self.hax_def(&parent_item)?;
348            self.push_generics_for_def(span, &parent_def, true)?;
349        }
350        self.push_generics_for_def_without_parents(span, def, !is_parent)?;
351        Ok(())
352    }
353
354    /// Add the generics and predicates of this item. This does not include the parent generics;
355    /// use `push_generics_for_def` to get the full list.
356    fn push_generics_for_def_without_parents(
357        &mut self,
358        _span: Span,
359        def: &hax::FullDef,
360        include_late_bound: bool,
361    ) -> Result<(), Error> {
362        use hax::FullDefKind;
363        if let Some(param_env) = def.param_env() {
364            // Add the generic params.
365            self.push_generic_params(&param_env.generics)?;
366            // Add the predicates.
367            let origin = match &def.kind {
368                FullDefKind::Adt { .. }
369                | FullDefKind::TyAlias { .. }
370                | FullDefKind::AssocTy { .. } => PredicateOrigin::WhereClauseOnType,
371                FullDefKind::Fn { .. }
372                | FullDefKind::AssocFn { .. }
373                | FullDefKind::Const { .. }
374                | FullDefKind::AssocConst { .. }
375                | FullDefKind::Static { .. } => PredicateOrigin::WhereClauseOnFn,
376                FullDefKind::TraitImpl { .. } | FullDefKind::InherentImpl { .. } => {
377                    PredicateOrigin::WhereClauseOnImpl
378                }
379                FullDefKind::Trait { .. } | FullDefKind::TraitAlias { .. } => {
380                    PredicateOrigin::WhereClauseOnTrait
381                }
382                _ => panic!("Unexpected def: {def:?}"),
383            };
384            self.register_predicates(&param_env.predicates, origin.clone())?;
385        }
386
387        if let hax::FullDefKind::Closure { args, .. } = def.kind()
388            && include_late_bound
389        {
390            // Add the lifetime generics coming from the by-ref upvars.
391            args.upvar_tys.iter().for_each(|ty| {
392                if matches!(
393                    ty.kind(),
394                    hax::TyKind::Ref(
395                        hax::Region {
396                            kind: hax::RegionKind::ReErased
397                        },
398                        ..
399                    )
400                ) {
401                    self.the_only_binder_mut().push_upvar_region();
402                }
403            });
404        }
405
406        // The parameters (and in particular the lifetimes) are split between
407        // early bound and late bound parameters. See those blog posts for explanations:
408        // https://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/
409        // https://smallcultfollowing.com/babysteps/blog/2013/11/04/intermingled-parameter-lists/
410        // Note that only lifetimes can be late bound.
411        //
412        // [TyCtxt.generics_of] gives us the early-bound parameters. We add the late-bound
413        // parameters here.
414        let signature = match &def.kind {
415            hax::FullDefKind::Fn { sig, .. } => Some(sig),
416            hax::FullDefKind::AssocFn { sig, .. } => Some(sig),
417            _ => None,
418        };
419        if let Some(signature) = signature
420            && include_late_bound
421        {
422            let innermost_binder = self.innermost_binder_mut();
423            assert!(innermost_binder.bound_region_vars.is_empty());
424            innermost_binder.push_params_from_binder(signature.rebind(()))?;
425        }
426
427        Ok(())
428    }
429
430    /// Translate the generics and predicates of this item and its parents.
431    /// This adds generic parameters and predicates to the current environment (as a binder in `self.binding_levels`).
432    /// This is necessary to translate types that depend on these generics (such as `Ty` and `TraitRef`).
433    /// The constructed `GenericParams` can be recovered at the end using `self.into_generics()` and stored in the translated item.
434    pub(crate) fn translate_def_generics(
435        &mut self,
436        span: Span,
437        def: &hax::FullDef,
438    ) -> Result<(), Error> {
439        assert!(self.binding_levels.len() == 0);
440        self.binding_levels.push(BindingLevel::new(true));
441        self.push_generics_for_def(span, def, false)?;
442        self.innermost_binder_mut().params.check_consistency();
443        Ok(())
444    }
445
446    /// Translate the generics and predicates of this item without its parents.
447    pub(crate) fn translate_def_generics_without_parents(
448        &mut self,
449        span: Span,
450        def: &hax::FullDef,
451    ) -> Result<(), Error> {
452        self.binding_levels.push(BindingLevel::new(true));
453        self.push_generics_for_def_without_parents(span, def, true)?;
454        self.innermost_binder().params.check_consistency();
455        Ok(())
456    }
457
458    /// Push a new binding level corresponding to the provided `def` for the duration of the inner
459    /// function call.
460    pub(crate) fn translate_binder_for_def<F, U>(
461        &mut self,
462        span: Span,
463        kind: BinderKind,
464        def: &hax::FullDef,
465        f: F,
466    ) -> Result<Binder<U>, Error>
467    where
468        F: FnOnce(&mut Self) -> Result<U, Error>,
469    {
470        assert!(!self.binding_levels.is_empty());
471
472        // Register the type-level parameters. This pushes a new binding level.
473        self.translate_def_generics_without_parents(span, def)?;
474
475        // Call the continuation. Important: do not short-circuit on error here.
476        let res = f(self);
477
478        // Reset
479        let params = self.binding_levels.pop().unwrap().params;
480
481        // Return
482        res.map(|skip_binder| Binder {
483            kind,
484            params,
485            skip_binder,
486        })
487    }
488
489    /// Push a group of bound regions and call the continuation.
490    /// We use this when diving into a `for<'a>`, or inside an arrow type (because
491    /// it contains universally quantified regions).
492    pub(crate) fn translate_region_binder<F, T, U>(
493        &mut self,
494        _span: Span,
495        binder: &hax::Binder<T>,
496        f: F,
497    ) -> Result<RegionBinder<U>, Error>
498    where
499        F: FnOnce(&mut Self, &T) -> Result<U, Error>,
500    {
501        assert!(!self.binding_levels.is_empty());
502
503        // Register the variables
504        let mut binding_level = BindingLevel::new(false);
505        binding_level.push_params_from_binder(binder.rebind(()))?;
506        self.binding_levels.push(binding_level);
507
508        // Call the continuation. Important: do not short-circuit on error here.
509        let res = f(self, binder.hax_skip_binder_ref());
510
511        // Reset
512        let regions = self.binding_levels.pop().unwrap().params.regions;
513
514        // Return
515        res.map(|skip_binder| RegionBinder {
516            regions,
517            skip_binder,
518        })
519    }
520
521    pub(crate) fn into_generics(mut self) -> GenericParams {
522        assert!(self.binding_levels.len() == 1);
523        self.binding_levels.pop().unwrap().params
524    }
525}
charon_driver/translate/translate_generics.rs

charon_driver/translate/
translate_generics.rs
