charon_driver/translate/
translate_generics.rs

1use crate::translate::translate_predicates::PredicateLocation;
2
3use super::translate_ctx::ItemTransCtx;
4use charon_lib::ast::*;
5use charon_lib::common::hash_by_addr::HashByAddr;
6use hax_frontend_exporter as hax;
7use std::collections::HashMap;
8use std::fmt::Debug;
9use std::sync::Arc;
10
11/// A level of binding for type-level variables. Each item has a top-level binding level
12/// corresponding to the parameters and clauses to the items. We may then encounter inner binding
13/// levels in the following cases:
14/// - `for<..>` binders in predicates;
15/// - `fn<..>` function pointer types;
16/// - `dyn Trait` types, represented as `dyn<T: Trait>` (TODO);
17/// - types in a trait declaration or implementation block (TODO);
18/// - methods in a trait declaration or implementation block (TODO).
19///
20/// At each level, we store two things: a `GenericParams` that contains the parameters bound at
21/// this level, and various maps from the rustc-internal indices to our indices.
22#[derive(Debug, Default)]
23pub(crate) struct BindingLevel {
24    /// The parameters and predicates bound at this level.
25    pub params: GenericParams,
26    /// Whether this binder corresponds to an item (method, type) or not (`for<..>` predicate, `fn`
27    /// pointer, etc). This indicates whether it corresponds to a rustc `ParamEnv` and therefore
28    /// whether we should resolve rustc variables there.
29    pub is_item_binder: bool,
30    /// Rust makes the distinction between early and late-bound region parameters. We do not make
31    /// this distinction, and merge early and late bound regions. For details, see:
32    /// <https://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/>
33    /// <https://smallcultfollowing.com/babysteps/blog/2013/11/04/intermingled-parameter-lists/>
34    ///
35    /// The map from rust early regions to translated region indices.
36    pub early_region_vars: std::collections::BTreeMap<hax::EarlyParamRegion, RegionId>,
37    /// The map from rust late/bound regions to translated region indices.
38    pub bound_region_vars: Vec<RegionId>,
39    /// The regions added for by-ref upvars, in order of upvars.
40    pub by_ref_upvar_regions: Vec<RegionId>,
41    /// The map from rust type variable indices to translated type variable indices.
42    pub type_vars_map: HashMap<u32, TypeVarId>,
43    /// The map from rust const generic variables to translate const generic variable indices.
44    pub const_generic_vars_map: HashMap<u32, ConstGenericVarId>,
45    /// Cache the translation of types. This harnesses the deduplication of `TyKind` that hax does.
46    // Important: we can't reuse type caches from earlier binders as the new binder may change what
47    // a given variable resolves to.
48    pub type_trans_cache: HashMap<HashByAddr<Arc<hax::TyKind>>, Ty>,
49}
50
51/// Small helper: we ignore some region names (when they are equal to "'_")
52fn translate_region_name(s: String) -> Option<String> {
53    if s == "'_" { None } else { Some(s) }
54}
55
56impl BindingLevel {
57    pub(crate) fn new(is_item_binder: bool) -> Self {
58        Self {
59            is_item_binder,
60            ..Default::default()
61        }
62    }
63
64    /// Important: we must push all the early-bound regions before pushing any other region.
65    pub(crate) fn push_early_region(&mut self, region: hax::EarlyParamRegion) -> RegionId {
66        let name = translate_region_name(region.name.clone());
67        // Check that there are no late-bound regions
68        assert!(
69            self.bound_region_vars.is_empty(),
70            "Early regions must be translated before late ones"
71        );
72        let rid = self
73            .params
74            .regions
75            .push_with(|index| RegionVar { index, name });
76        self.early_region_vars.insert(region, rid);
77        rid
78    }
79
80    /// Important: we must push all the early-bound regions before pushing any other region.
81    pub(crate) fn push_bound_region(&mut self, region: hax::BoundRegionKind) -> RegionId {
82        use hax::BoundRegionKind::*;
83        let name = match region {
84            Anon => None,
85            NamedAnon(symbol) | Named(_, symbol) => translate_region_name(symbol.clone()),
86            ClosureEnv => Some("@env".to_owned()),
87        };
88        let rid = self
89            .params
90            .regions
91            .push_with(|index| RegionVar { index, name });
92        self.bound_region_vars.push(rid);
93        rid
94    }
95
96    /// Add a region for a by_ref upvar in a closure.
97    pub fn push_upvar_region(&mut self) -> RegionId {
98        // We musn't push to `bound_region_vars` because that will contain the higher-kinded
99        // signature lifetimes if any and they must be lookup-able.
100        let region_id = self
101            .params
102            .regions
103            .push_with(|index| RegionVar { index, name: None });
104        self.by_ref_upvar_regions.push(region_id);
105        region_id
106    }
107
108    pub(crate) fn push_type_var(&mut self, rid: u32, name: String) -> TypeVarId {
109        let var_id = self.params.types.push_with(|index| TypeVar { 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| ConstGenericVar { 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
153    /// Get the only binding level. Panics if there are other binding levels.
154    pub(crate) fn the_only_binder_mut(&mut self) -> &mut BindingLevel {
155        assert_eq!(self.binding_levels.len(), 1);
156        self.innermost_binder_mut()
157    }
158
159    pub(crate) fn outermost_binder(&self) -> &BindingLevel {
160        self.binding_levels.outermost()
161    }
162
163    pub(crate) fn innermost_binder(&self) -> &BindingLevel {
164        self.binding_levels.innermost()
165    }
166
167    pub(crate) fn innermost_binder_mut(&mut self) -> &mut BindingLevel {
168        self.binding_levels.innermost_mut()
169    }
170
171    pub(crate) fn innermost_generics_mut(&mut self) -> &mut GenericParams {
172        &mut self.innermost_binder_mut().params
173    }
174
175    pub(crate) fn lookup_bound_region(
176        &mut self,
177        span: Span,
178        dbid: hax::DebruijnIndex,
179        var: hax::BoundVar,
180    ) -> Result<RegionDbVar, Error> {
181        let dbid = DeBruijnId::new(dbid);
182        if let Some(rid) = self
183            .binding_levels
184            .get(dbid)
185            .and_then(|bl| bl.bound_region_vars.get(var))
186        {
187            Ok(DeBruijnVar::bound(dbid, *rid))
188        } else {
189            raise_error!(
190                self,
191                span,
192                "Unexpected error: could not find region '{dbid}_{var}"
193            )
194        }
195    }
196
197    pub(crate) fn lookup_param<Id: Copy>(
198        &mut self,
199        span: Span,
200        f: impl for<'a> Fn(&'a BindingLevel) -> Option<Id>,
201        mk_err: impl FnOnce() -> String,
202    ) -> Result<DeBruijnVar<Id>, Error> {
203        for (dbid, bl) in self.binding_levels.iter_enumerated() {
204            if let Some(id) = f(bl) {
205                return Ok(DeBruijnVar::bound(dbid, id));
206            }
207        }
208        let err = mk_err();
209        raise_error!(self, span, "Unexpected error: could not find {}", err)
210    }
211
212    pub(crate) fn lookup_early_region(
213        &mut self,
214        span: Span,
215        region: &hax::EarlyParamRegion,
216    ) -> Result<RegionDbVar, Error> {
217        self.lookup_param(
218            span,
219            |bl| bl.early_region_vars.get(region).copied(),
220            || format!("the region variable {region:?}"),
221        )
222    }
223
224    pub(crate) fn lookup_type_var(
225        &mut self,
226        span: Span,
227        param: &hax::ParamTy,
228    ) -> Result<TypeDbVar, Error> {
229        self.lookup_param(
230            span,
231            |bl| bl.type_vars_map.get(&param.index).copied(),
232            || format!("the type variable {}", param.name),
233        )
234    }
235
236    pub(crate) fn lookup_const_generic_var(
237        &mut self,
238        span: Span,
239        param: &hax::ParamConst,
240    ) -> Result<ConstGenericDbVar, Error> {
241        self.lookup_param(
242            span,
243            |bl| bl.const_generic_vars_map.get(&param.index).copied(),
244            || format!("the const generic variable {}", param.name),
245        )
246    }
247
248    pub(crate) fn lookup_clause_var(
249        &mut self,
250        span: Span,
251        mut id: usize,
252    ) -> Result<ClauseDbVar, Error> {
253        // The clause indices returned by hax count clauses in order, starting from the parentmost.
254        // While adding clauses to a binding level we already need to translate types and clauses,
255        // so the innermost item binder may not have all the clauses yet. Hence for that binder we
256        // ignore the clause count.
257        let innermost_item_binder_id = self
258            .binding_levels
259            .iter_enumerated()
260            .find(|(_, bl)| bl.is_item_binder)
261            .unwrap()
262            .0;
263        // Iterate over the binders, starting from the outermost.
264        for (dbid, bl) in self.binding_levels.iter_enumerated().rev() {
265            let num_clauses_bound_at_this_level = bl.params.trait_clauses.elem_count();
266            if id < num_clauses_bound_at_this_level || dbid == innermost_item_binder_id {
267                let id = TraitClauseId::from_usize(id);
268                return Ok(DeBruijnVar::bound(dbid, id));
269            } else {
270                id -= num_clauses_bound_at_this_level
271            }
272        }
273        // Actually unreachable
274        raise_error!(
275            self,
276            span,
277            "Unexpected error: could not find clause variable {}",
278            id
279        )
280    }
281
282    pub(crate) fn push_generic_params(&mut self, generics: &hax::TyGenerics) -> Result<(), Error> {
283        for param in &generics.params {
284            self.push_generic_param(param)?;
285        }
286        Ok(())
287    }
288
289    pub(crate) fn push_generic_param(&mut self, param: &hax::GenericParamDef) -> Result<(), Error> {
290        match &param.kind {
291            hax::GenericParamDefKind::Lifetime => {
292                let region = hax::EarlyParamRegion {
293                    index: param.index,
294                    name: param.name.clone(),
295                };
296                let _ = self.innermost_binder_mut().push_early_region(region);
297            }
298            hax::GenericParamDefKind::Type { .. } => {
299                let _ = self
300                    .innermost_binder_mut()
301                    .push_type_var(param.index, param.name.clone());
302            }
303            hax::GenericParamDefKind::Const { ty, .. } => {
304                let span = self.def_span(&param.def_id);
305                // The type should be primitive, meaning it shouldn't contain variables,
306                // non-primitive adts, etc. As a result, we can use an empty context.
307                let ty = self.translate_ty(span, ty)?;
308                match ty.kind().as_literal() {
309                    Some(ty) => self.innermost_binder_mut().push_const_generic_var(
310                        param.index,
311                        *ty,
312                        param.name.clone(),
313                    ),
314                    None => raise_error!(
315                        self,
316                        span,
317                        "Constant parameters of non-literal type are not supported"
318                    ),
319                }
320            }
321        }
322
323        Ok(())
324    }
325
326    /// Add the generics and predicates of this item and its parents to the current context.
327    #[tracing::instrument(skip(self, span))]
328    fn push_generics_for_def(
329        &mut self,
330        span: Span,
331        def: &hax::FullDef,
332        is_parent: bool,
333    ) -> Result<(), Error> {
334        // Add generics from the parent item, recursively (recursivity is important for closures,
335        // as they can be nested).
336        if let Some(parent_item) = def.typing_parent(self.hax_state()) {
337            let parent_def = self.hax_def(&parent_item)?;
338            self.push_generics_for_def(span, &parent_def, true)?;
339        }
340        self.push_generics_for_def_without_parents(span, def, !is_parent, !is_parent)?;
341        Ok(())
342    }
343
344    /// Add the generics and predicates of this item. This does not include the parent generics;
345    /// use `push_generics_for_def` to get the full list.
346    fn push_generics_for_def_without_parents(
347        &mut self,
348        _span: Span,
349        def: &hax::FullDef,
350        include_late_bound: bool,
351        include_assoc_ty_clauses: bool,
352    ) -> Result<(), Error> {
353        use hax::FullDefKind;
354        if let Some(param_env) = def.param_env() {
355            // Add the generic params.
356            self.push_generic_params(&param_env.generics)?;
357            // Add the predicates.
358            let origin = match &def.kind {
359                FullDefKind::Adt { .. }
360                | FullDefKind::TyAlias { .. }
361                | FullDefKind::AssocTy { .. } => PredicateOrigin::WhereClauseOnType,
362                FullDefKind::Fn { .. }
363                | FullDefKind::AssocFn { .. }
364                | FullDefKind::Const { .. }
365                | FullDefKind::AssocConst { .. }
366                | FullDefKind::Static { .. } => PredicateOrigin::WhereClauseOnFn,
367                FullDefKind::TraitImpl { .. } | FullDefKind::InherentImpl { .. } => {
368                    PredicateOrigin::WhereClauseOnImpl
369                }
370                FullDefKind::Trait { .. } | FullDefKind::TraitAlias { .. } => {
371                    PredicateOrigin::WhereClauseOnTrait
372                }
373                _ => panic!("Unexpected def: {def:?}"),
374            };
375            self.register_predicates(
376                &param_env.predicates,
377                origin.clone(),
378                &PredicateLocation::Base,
379            )?;
380            // Also register implied predicates.
381            if let FullDefKind::Trait {
382                implied_predicates, ..
383            }
384            | FullDefKind::TraitAlias {
385                implied_predicates, ..
386            }
387            | FullDefKind::AssocTy {
388                implied_predicates, ..
389            } = &def.kind
390            {
391                self.register_predicates(implied_predicates, origin, &PredicateLocation::Parent)?;
392            }
393
394            if let hax::FullDefKind::Trait { items, .. } = &def.kind
395                && include_assoc_ty_clauses
396                && !self.monomorphize()
397            {
398                // Also add the predicates on associated types.
399                // FIXME(gat): don't skip GATs.
400                // FIXME: don't mix up implied and required predicates.
401                for assoc in items {
402                    let item_def = self.poly_hax_def(&assoc.def_id)?;
403                    if let hax::FullDefKind::AssocTy {
404                        param_env,
405                        implied_predicates,
406                        ..
407                    } = item_def.kind()
408                        && param_env.generics.params.is_empty()
409                    {
410                        let name = self.t_ctx.translate_trait_item_name(item_def.def_id())?;
411                        self.register_predicates(
412                            &implied_predicates,
413                            PredicateOrigin::TraitItem(name.clone()),
414                            &PredicateLocation::Item(name),
415                        )?;
416                    }
417                }
418            }
419        }
420
421        if let hax::FullDefKind::Closure { args, .. } = def.kind()
422            && include_late_bound
423        {
424            // Add the lifetime generics coming from the by-ref upvars.
425            args.upvar_tys.iter().for_each(|ty| {
426                if matches!(
427                    ty.kind(),
428                    hax::TyKind::Ref(
429                        hax::Region {
430                            kind: hax::RegionKind::ReErased
431                        },
432                        ..
433                    )
434                ) {
435                    self.the_only_binder_mut().push_upvar_region();
436                }
437            });
438        }
439
440        // The parameters (and in particular the lifetimes) are split between
441        // early bound and late bound parameters. See those blog posts for explanations:
442        // https://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/
443        // https://smallcultfollowing.com/babysteps/blog/2013/11/04/intermingled-parameter-lists/
444        // Note that only lifetimes can be late bound.
445        //
446        // [TyCtxt.generics_of] gives us the early-bound parameters. We add the late-bound
447        // parameters here.
448        let signature = match &def.kind {
449            hax::FullDefKind::Fn { sig, .. } => Some(sig),
450            hax::FullDefKind::AssocFn { sig, .. } => Some(sig),
451            _ => None,
452        };
453        if let Some(signature) = signature
454            && include_late_bound
455        {
456            let innermost_binder = self.innermost_binder_mut();
457            assert!(innermost_binder.bound_region_vars.is_empty());
458            innermost_binder.push_params_from_binder(signature.rebind(()))?;
459        }
460
461        Ok(())
462    }
463
464    /// Translate the generics and predicates of this item and its parents.
465    /// This adds generic parameters and predicates to the current environment (as a binder in `self.binding_levels`).
466    /// This is necessary to translate types that depend on these generics (such as `Ty` and `TraitRef`).
467    /// The constructed `GenericParams` can be recovered at the end using `self.into_generics()` and stored in the translated item.
468    pub(crate) fn translate_def_generics(
469        &mut self,
470        span: Span,
471        def: &hax::FullDef,
472    ) -> Result<(), Error> {
473        assert!(self.binding_levels.len() == 0);
474        self.binding_levels.push(BindingLevel::new(true));
475        self.push_generics_for_def(span, def, false)?;
476        self.innermost_binder_mut().params.check_consistency();
477        Ok(())
478    }
479
480    /// Translate the generics and predicates of this item without its parents.
481    pub(crate) fn translate_def_generics_without_parents(
482        &mut self,
483        span: Span,
484        def: &hax::FullDef,
485    ) -> Result<(), Error> {
486        self.binding_levels.push(BindingLevel::new(true));
487        self.push_generics_for_def_without_parents(span, def, true, true)?;
488        self.innermost_binder().params.check_consistency();
489        Ok(())
490    }
491
492    /// Push a new binding level corresponding to the provided `def` for the duration of the inner
493    /// function call.
494    pub(crate) fn translate_binder_for_def<F, U>(
495        &mut self,
496        span: Span,
497        kind: BinderKind,
498        def: &hax::FullDef,
499        f: F,
500    ) -> Result<Binder<U>, Error>
501    where
502        F: FnOnce(&mut Self) -> Result<U, Error>,
503    {
504        assert!(!self.binding_levels.is_empty());
505
506        // Register the type-level parameters. This pushes a new binding level.
507        self.translate_def_generics_without_parents(span, def)?;
508
509        // Call the continuation. Important: do not short-circuit on error here.
510        let res = f(self);
511
512        // Reset
513        let params = self.binding_levels.pop().unwrap().params;
514
515        // Return
516        res.map(|skip_binder| Binder {
517            kind,
518            params,
519            skip_binder,
520        })
521    }
522
523    /// Push a group of bound regions and call the continuation.
524    /// We use this when diving into a `for<'a>`, or inside an arrow type (because
525    /// it contains universally quantified regions).
526    pub(crate) fn translate_region_binder<F, T, U>(
527        &mut self,
528        _span: Span,
529        binder: &hax::Binder<T>,
530        f: F,
531    ) -> Result<RegionBinder<U>, Error>
532    where
533        F: FnOnce(&mut Self, &T) -> Result<U, Error>,
534    {
535        assert!(!self.binding_levels.is_empty());
536
537        // Register the variables
538        let mut binding_level = BindingLevel::new(false);
539        binding_level.push_params_from_binder(binder.rebind(()))?;
540        self.binding_levels.push(binding_level);
541
542        // Call the continuation. Important: do not short-circuit on error here.
543        let res = f(self, binder.hax_skip_binder_ref());
544
545        // Reset
546        let regions = self.binding_levels.pop().unwrap().params.regions;
547
548        // Return
549        res.map(|skip_binder| RegionBinder {
550            regions,
551            skip_binder,
552        })
553    }
554
555    pub(crate) fn into_generics(mut self) -> GenericParams {
556        assert!(self.binding_levels.len() == 1);
557        self.binding_levels.pop().unwrap().params
558    }
559}
charon_driver/translate/translate_generics.rs

charon_driver/translate/
translate_generics.rs
