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| -rw-r--r-- | src/librustc/traits/auto_trait.rs | 804 | ||||
| -rw-r--r-- | src/librustc/traits/mod.rs | 2 |
2 files changed, 806 insertions, 0 deletions
diff --git a/src/librustc/traits/auto_trait.rs b/src/librustc/traits/auto_trait.rs new file mode 100644 index 00000000000..7cdec4b84f6 --- /dev/null +++ b/src/librustc/traits/auto_trait.rs @@ -0,0 +1,804 @@ +// Copyright 2018 The Rust Project Developers. See the COPYRIGHT +// file at the top-level directory of this distribution and at +// http://rust-lang.org/COPYRIGHT. +// +// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or +// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license +// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +use super::*; + +use std::collections::VecDeque; +use std::collections::hash_map::Entry; + +use rustc_data_structures::fx::{FxHashMap, FxHashSet}; + +use hir::WherePredicate; + +use infer::{InferCtxt, RegionObligation}; +use infer::region_constraints::{Constraint, RegionConstraintData}; + +use ty::{Region, RegionVid}; +use ty::fold::TypeFolder; + +// TODO(twk): this is obviously not nice to duplicate like that +#[derive(Eq, PartialEq, Hash, Copy, Clone, Debug)] +enum RegionTarget<'tcx> { + Region(Region<'tcx>), + RegionVid(RegionVid) +} + +#[derive(Default, Debug, Clone)] +struct RegionDeps<'tcx> { + larger: FxHashSet<RegionTarget<'tcx>>, + smaller: FxHashSet<RegionTarget<'tcx>> +} + +enum AutoTraitResult { + ExplicitImpl, + PositiveImpl, /*(ty::Generics), TODO(twk)*/ + NegativeImpl, +} + +impl AutoTraitResult { + fn is_auto(&self) -> bool { + match *self { + AutoTraitResult::PositiveImpl | AutoTraitResult::NegativeImpl => true, + _ => false, + } + } +} + +pub struct AutoTraitFinder<'a, 'tcx: 'a> { + pub tcx: &'a TyCtxt<'a, 'tcx, 'tcx>, +} + +impl<'a, 'tcx> AutoTraitFinder<'a, 'tcx> { + fn find_auto_trait_generics( + &self, + did: DefId, + trait_did: DefId, + generics: &ty::Generics, + ) -> AutoTraitResult { + let tcx = self.tcx; + let ty = self.tcx.type_of(did); + + let orig_params = tcx.param_env(did); + + let trait_ref = ty::TraitRef { + def_id: trait_did, + substs: tcx.mk_substs_trait(ty, &[]), + }; + + let trait_pred = ty::Binder(trait_ref); + + let bail_out = tcx.infer_ctxt().enter(|infcx| { + let mut selcx = SelectionContext::with_negative(&infcx, true); + let result = selcx.select(&Obligation::new( + ObligationCause::dummy(), + orig_params, + trait_pred.to_poly_trait_predicate(), + )); + match result { + Ok(Some(Vtable::VtableImpl(_))) => { + debug!( + "find_auto_trait_generics(did={:?}, trait_did={:?}, generics={:?}): \ + manual impl found, bailing out", + did, trait_did, generics + ); + return true; + } + _ => return false, + }; + }); + + // If an explicit impl exists, it always takes priority over an auto impl + if bail_out { + return AutoTraitResult::ExplicitImpl; + } + + return tcx.infer_ctxt().enter(|mut infcx| { + let mut fresh_preds = FxHashSet(); + + // Due to the way projections are handled by SelectionContext, we need to run + // evaluate_predicates twice: once on the original param env, and once on the result of + // the first evaluate_predicates call. + // + // The problem is this: most of rustc, including SelectionContext and traits::project, + // are designed to work with a concrete usage of a type (e.g. Vec<u8> + // fn<T>() { Vec<T> }. This information will generally never change - given + // the 'T' in fn<T>() { ... }, we'll never know anything else about 'T'. + // If we're unable to prove that 'T' implements a particular trait, we're done - + // there's nothing left to do but error out. + // + // However, synthesizing an auto trait impl works differently. Here, we start out with + // a set of initial conditions - the ParamEnv of the struct/enum/union we're dealing + // with - and progressively discover the conditions we need to fulfill for it to + // implement a certain auto trait. This ends up breaking two assumptions made by trait + // selection and projection: + // + // * We can always cache the result of a particular trait selection for the lifetime of + // an InfCtxt + // * Given a projection bound such as '<T as SomeTrait>::SomeItem = K', if 'T: + // SomeTrait' doesn't hold, then we don't need to care about the 'SomeItem = K' + // + // We fix the first assumption by manually clearing out all of the InferCtxt's caches + // in between calls to SelectionContext.select. This allows us to keep all of the + // intermediate types we create bound to the 'tcx lifetime, rather than needing to lift + // them between calls. + // + // We fix the second assumption by reprocessing the result of our first call to + // evaluate_predicates. Using the example of '<T as SomeTrait>::SomeItem = K', our first + // pass will pick up 'T: SomeTrait', but not 'SomeItem = K'. On our second pass, + // traits::project will see that 'T: SomeTrait' is in our ParamEnv, allowing + // SelectionContext to return it back to us. + + let (new_env, user_env) = match self.evaluate_predicates( + &mut infcx, + did, + trait_did, + ty, + orig_params.clone(), + orig_params, + &mut fresh_preds, + false, + ) { + Some(e) => e, + None => return AutoTraitResult::NegativeImpl, + }; + + let (full_env, _full_user_env) = self.evaluate_predicates( + &mut infcx, + did, + trait_did, + ty, + new_env.clone(), + user_env, + &mut fresh_preds, + true, + ).unwrap_or_else(|| { + panic!( + "Failed to fully process: {:?} {:?} {:?}", + ty, trait_did, orig_params + ) + }); + + debug!( + "find_auto_trait_generics(did={:?}, trait_did={:?}, generics={:?}): fulfilling \ + with {:?}", + did, trait_did, generics, full_env + ); + infcx.clear_caches(); + + // At this point, we already have all of the bounds we need. FulfillmentContext is used + // to store all of the necessary region/lifetime bounds in the InferContext, as well as + // an additional sanity check. + let mut fulfill = FulfillmentContext::new(); + fulfill.register_bound( + &infcx, + full_env, + ty, + trait_did, + ObligationCause::misc(DUMMY_SP, ast::DUMMY_NODE_ID), + ); + fulfill.select_all_or_error(&infcx).unwrap_or_else(|e| { + panic!( + "Unable to fulfill trait {:?} for '{:?}': {:?}", + trait_did, ty, e + ) + }); + + let names_map: FxHashMap<String, String> = generics + .regions + .iter() + .map(|l| (l.name.as_str().to_string(), l.name.to_string())) + // TODO(twk): Lifetime branding + .collect(); + + let body_ids: FxHashSet<_> = infcx + .region_obligations + .borrow() + .iter() + .map(|&(id, _)| id) + .collect(); + + for id in body_ids { + infcx.process_registered_region_obligations(&[], None, full_env.clone(), id); + } + + let region_data = infcx + .borrow_region_constraints() + .region_constraint_data() + .clone(); + + let lifetime_predicates = self.handle_lifetimes(®ion_data, &names_map); + let vid_to_region = self.map_vid_to_region(®ion_data); + + debug!( + "find_auto_trait_generics(did={:?}, trait_did={:?}, generics={:?}): computed \ + lifetime information '{:?}' '{:?}'", + did, trait_did, generics, lifetime_predicates, vid_to_region + ); + + /* let new_generics = self.param_env_to_generics( + infcx.tcx, + did, + full_user_env, + generics.clone(), + lifetime_predicates, + vid_to_region, + ); */ + + debug!( + "find_auto_trait_generics(did={:?}, trait_did={:?}, generics={:?}): finished with \ + <generics placeholder here>", + did, trait_did, generics /* , new_generics */ + ); + return AutoTraitResult::PositiveImpl; + }); + } + + // The core logic responsible for computing the bounds for our synthesized impl. + // + // To calculate the bounds, we call SelectionContext.select in a loop. Like FulfillmentContext, + // we recursively select the nested obligations of predicates we encounter. However, whenver we + // encounter an UnimplementedError involving a type parameter, we add it to our ParamEnv. Since + // our goal is to determine when a particular type implements an auto trait, Unimplemented + // errors tell us what conditions need to be met. + // + // This method ends up working somewhat similary to FulfillmentContext, but with a few key + // differences. FulfillmentContext works under the assumption that it's dealing with concrete + // user code. According, it considers all possible ways that a Predicate could be met - which + // isn't always what we want for a synthesized impl. For example, given the predicate 'T: + // Iterator', FulfillmentContext can end up reporting an Unimplemented error for T: + // IntoIterator - since there's an implementation of Iteratpr where T: IntoIterator, + // FulfillmentContext will drive SelectionContext to consider that impl before giving up. If we + // were to rely on FulfillmentContext's decision, we might end up synthesizing an impl like + // this: + // 'impl<T> Send for Foo<T> where T: IntoIterator' + // + // While it might be technically true that Foo implements Send where T: IntoIterator, + // the bound is overly restrictive - it's really only necessary that T: Iterator. + // + // For this reason, evaluate_predicates handles predicates with type variables specially. When + // we encounter an Unimplemented error for a bound such as 'T: Iterator', we immediately add it + // to our ParamEnv, and add it to our stack for recursive evaluation. When we later select it, + // we'll pick up any nested bounds, without ever inferring that 'T: IntoIterator' needs to + // hold. + // + // One additonal consideration is supertrait bounds. Normally, a ParamEnv is only ever + // consutrcted once for a given type. As part of the construction process, the ParamEnv will + // have any supertrait bounds normalized - e.g. if we have a type 'struct Foo<T: Copy>', the + // ParamEnv will contain 'T: Copy' and 'T: Clone', since 'Copy: Clone'. When we construct our + // own ParamEnv, we need to do this outselves, through traits::elaborate_predicates, or else + // SelectionContext will choke on the missing predicates. However, this should never show up in + // the final synthesized generics: we don't want our generated docs page to contain something + // like 'T: Copy + Clone', as that's redundant. Therefore, we keep track of a separate + // 'user_env', which only holds the predicates that will actually be displayed to the user. + fn evaluate_predicates<'b, 'gcx, 'c>( + &self, + infcx: &mut InferCtxt<'b, 'tcx, 'c>, + ty_did: DefId, + trait_did: DefId, + ty: ty::Ty<'c>, + param_env: ty::ParamEnv<'c>, + user_env: ty::ParamEnv<'c>, + fresh_preds: &mut FxHashSet<ty::Predicate<'c>>, + only_projections: bool, + ) -> Option<(ty::ParamEnv<'c>, ty::ParamEnv<'c>)> { + let tcx = infcx.tcx; + + let mut select = SelectionContext::new(&infcx); + + let mut already_visited = FxHashSet(); + let mut predicates = VecDeque::new(); + predicates.push_back(ty::Binder(ty::TraitPredicate { + trait_ref: ty::TraitRef { + def_id: trait_did, + substs: infcx.tcx.mk_substs_trait(ty, &[]), + }, + })); + + let mut computed_preds: FxHashSet<_> = param_env.caller_bounds.iter().cloned().collect(); + let mut user_computed_preds: FxHashSet<_> = + user_env.caller_bounds.iter().cloned().collect(); + + let mut new_env = param_env.clone(); + let dummy_cause = ObligationCause::misc(DUMMY_SP, ast::DUMMY_NODE_ID); + + while let Some(pred) = predicates.pop_front() { + infcx.clear_caches(); + + if !already_visited.insert(pred.clone()) { + continue; + } + + let result = select.select(&Obligation::new(dummy_cause.clone(), new_env, pred)); + + match &result { + &Ok(Some(ref vtable)) => { + let obligations = vtable.clone().nested_obligations().into_iter(); + + if !self.evaluate_nested_obligations( + ty, + obligations, + &mut user_computed_preds, + fresh_preds, + &mut predicates, + &mut select, + only_projections, + ) { + return None; + } + } + &Ok(None) => {} + &Err(SelectionError::Unimplemented) => { + if self.is_of_param(pred.skip_binder().trait_ref.substs) { + already_visited.remove(&pred); + user_computed_preds.insert(ty::Predicate::Trait(pred.clone())); + predicates.push_back(pred); + } else { + debug!( + "evaluate_nested_obligations: Unimplemented found, bailing: {:?} {:?} \ + {:?}", + ty, + pred, + pred.skip_binder().trait_ref.substs + ); + return None; + } + } + _ => panic!("Unexpected error for '{:?}': {:?}", ty, result), + }; + + computed_preds.extend(user_computed_preds.iter().cloned()); + let normalized_preds = + elaborate_predicates(tcx, computed_preds.clone().into_iter().collect()); + new_env = ty::ParamEnv::new( + tcx.mk_predicates(normalized_preds), + param_env.reveal, + ty::UniverseIndex::ROOT, + ); + } + + let final_user_env = ty::ParamEnv::new( + tcx.mk_predicates(user_computed_preds.into_iter()), + user_env.reveal, + ty::UniverseIndex::ROOT, + ); + debug!( + "evaluate_nested_obligations(ty_did={:?}, trait_did={:?}): succeeded with '{:?}' \ + '{:?}'", + ty_did, trait_did, new_env, final_user_env + ); + + return Some((new_env, final_user_env)); + } + + // This method calculates two things: Lifetime constraints of the form 'a: 'b, + // and region constraints of the form ReVar: 'a + // + // This is essentially a simplified version of lexical_region_resolve. However, + // handle_lifetimes determines what *needs be* true in order for an impl to hold. + // lexical_region_resolve, along with much of the rest of the compiler, is concerned + // with determining if a given set up constraints/predicates *are* met, given some + // starting conditions (e.g. user-provided code). For this reason, it's easier + // to perform the calculations we need on our own, rather than trying to make + // existing inference/solver code do what we want. + fn handle_lifetimes<'cx>( + &self, + regions: &RegionConstraintData<'cx>, + names_map: &FxHashMap<String, String>, // TODO(twk): lifetime branding + ) -> Vec<WherePredicate> { + // Our goal is to 'flatten' the list of constraints by eliminating + // all intermediate RegionVids. At the end, all constraints should + // be between Regions (aka region variables). This gives us the information + // we need to create the Generics. + let mut finished = FxHashMap(); + + let mut vid_map: FxHashMap<RegionTarget, RegionDeps> = FxHashMap(); + + // Flattening is done in two parts. First, we insert all of the constraints + // into a map. Each RegionTarget (either a RegionVid or a Region) maps + // to its smaller and larger regions. Note that 'larger' regions correspond + // to sub-regions in Rust code (e.g. in 'a: 'b, 'a is the larger region). + for constraint in regions.constraints.keys() { + match constraint { + &Constraint::VarSubVar(r1, r2) => { + { + let deps1 = vid_map + .entry(RegionTarget::RegionVid(r1)) + .or_insert_with(|| Default::default()); + deps1.larger.insert(RegionTarget::RegionVid(r2)); + } + + let deps2 = vid_map + .entry(RegionTarget::RegionVid(r2)) + .or_insert_with(|| Default::default()); + deps2.smaller.insert(RegionTarget::RegionVid(r1)); + } + &Constraint::RegSubVar(region, vid) => { + let deps = vid_map + .entry(RegionTarget::RegionVid(vid)) + .or_insert_with(|| Default::default()); + deps.smaller.insert(RegionTarget::Region(region)); + } + &Constraint::VarSubReg(vid, region) => { + let deps = vid_map + .entry(RegionTarget::RegionVid(vid)) + .or_insert_with(|| Default::default()); + deps.larger.insert(RegionTarget::Region(region)); + } + &Constraint::RegSubReg(r1, r2) => { + // The constraint is already in the form that we want, so we're done with it + // Desired order is 'larger, smaller', so flip then + if self.region_name(r1) != self.region_name(r2) { + finished + .entry(self.region_name(r2).unwrap()) + .or_insert_with(|| Vec::new()) + .push(r1); + } + } + } + } + + // Here, we 'flatten' the map one element at a time. + // All of the element's sub and super regions are connected + // to each other. For example, if we have a graph that looks like this: + // + // (A, B) - C - (D, E) + // Where (A, B) are subregions, and (D,E) are super-regions + // + // then after deleting 'C', the graph will look like this: + // ... - A - (D, E ...) + // ... - B - (D, E, ...) + // (A, B, ...) - D - ... + // (A, B, ...) - E - ... + // + // where '...' signifies the existing sub and super regions of an entry + // When two adjacent ty::Regions are encountered, we've computed a final + // constraint, and add it to our list. Since we make sure to never re-add + // deleted items, this process will always finish. + while !vid_map.is_empty() { + let target = vid_map.keys().next().expect("Keys somehow empty").clone(); + let deps = vid_map.remove(&target).expect("Entry somehow missing"); + + for smaller in deps.smaller.iter() { + for larger in deps.larger.iter() { + match (smaller, larger) { + (&RegionTarget::Region(r1), &RegionTarget::Region(r2)) => { + if self.region_name(r1) != self.region_name(r2) { + finished + .entry(self.region_name(r2).unwrap()) + .or_insert_with(|| Vec::new()) + .push(r1) // Larger, smaller + } + } + (&RegionTarget::RegionVid(_), &RegionTarget::Region(_)) => { + if let Entry::Occupied(v) = vid_map.entry(*smaller) { + let smaller_deps = v.into_mut(); + smaller_deps.larger.insert(*larger); + smaller_deps.larger.remove(&target); + } + } + (&RegionTarget::Region(_), &RegionTarget::RegionVid(_)) => { + if let Entry::Occupied(v) = vid_map.entry(*larger) { + let deps = v.into_mut(); + deps.smaller.insert(*smaller); + deps.smaller.remove(&target); + } + } + (&RegionTarget::RegionVid(_), &RegionTarget::RegionVid(_)) => { + if let Entry::Occupied(v) = vid_map.entry(*smaller) { + let smaller_deps = v.into_mut(); + smaller_deps.larger.insert(*larger); + smaller_deps.larger.remove(&target); + } + + if let Entry::Occupied(v) = vid_map.entry(*larger) { + let larger_deps = v.into_mut(); + larger_deps.smaller.insert(*smaller); + larger_deps.smaller.remove(&target); + } + } + } + } + } + } + + let lifetime_predicates = names_map + .iter() + .flat_map(|(name, _lifetime)| { + let empty = Vec::new(); + let bounds: FxHashSet<String> = finished // TODO(twk): lifetime branding + .get(name) + .unwrap_or(&empty) + .iter() + .map(|region| self.get_lifetime(region, names_map)) + .collect(); + + if bounds.is_empty() { + return None; + } + /* Some(WherePredicate::RegionPredicate { + lifetime: lifetime.clone(), + bounds: bounds.into_iter().collect(), + }) */ + None // TODO(twk): use the correct WherePredicate and rebuild the code above + }) + .collect(); + + lifetime_predicates + } + + fn region_name(&self, region: Region) -> Option<String> { + match region { + &ty::ReEarlyBound(r) => Some(r.name.as_str().to_string()), + _ => None, + } + } + + // TODO(twk): lifetime branding + fn get_lifetime(&self, region: Region, names_map: &FxHashMap<String, String>) -> String { + self.region_name(region) + .map(|name| { + names_map.get(&name).unwrap_or_else(|| { + panic!("Missing lifetime with name {:?} for {:?}", name, region) + }) + }) + // TODO(twk): .unwrap_or(&Lifetime::statik()) + .unwrap_or(&"'static".to_string()) + .clone() + } + + // This is very similar to handle_lifetimes. However, instead of matching ty::Region's + // to each other, we match ty::RegionVid's to ty::Region's + fn map_vid_to_region<'cx>( + &self, + regions: &RegionConstraintData<'cx>, + ) -> FxHashMap<ty::RegionVid, ty::Region<'cx>> { + let mut vid_map: FxHashMap<RegionTarget<'cx>, RegionDeps<'cx>> = FxHashMap(); + let mut finished_map = FxHashMap(); + + for constraint in regions.constraints.keys() { + match constraint { + &Constraint::VarSubVar(r1, r2) => { + { + let deps1 = vid_map + .entry(RegionTarget::RegionVid(r1)) + .or_insert_with(|| Default::default()); + deps1.larger.insert(RegionTarget::RegionVid(r2)); + } + + let deps2 = vid_map + .entry(RegionTarget::RegionVid(r2)) + .or_insert_with(|| Default::default()); + deps2.smaller.insert(RegionTarget::RegionVid(r1)); + } + &Constraint::RegSubVar(region, vid) => { + { + let deps1 = vid_map + .entry(RegionTarget::Region(region)) + .or_insert_with(|| Default::default()); + deps1.larger.insert(RegionTarget::RegionVid(vid)); + } + + let deps2 = vid_map + .entry(RegionTarget::RegionVid(vid)) + .or_insert_with(|| Default::default()); + deps2.smaller.insert(RegionTarget::Region(region)); + } + &Constraint::VarSubReg(vid, region) => { + finished_map.insert(vid, region); + } + &Constraint::RegSubReg(r1, r2) => { + { + let deps1 = vid_map + .entry(RegionTarget::Region(r1)) + .or_insert_with(|| Default::default()); + deps1.larger.insert(RegionTarget::Region(r2)); + } + + let deps2 = vid_map + .entry(RegionTarget::Region(r2)) + .or_insert_with(|| Default::default()); + deps2.smaller.insert(RegionTarget::Region(r1)); + } + } + } + + while !vid_map.is_empty() { + let target = vid_map.keys().next().expect("Keys somehow empty").clone(); + let deps = vid_map.remove(&target).expect("Entry somehow missing"); + + for smaller in deps.smaller.iter() { + for larger in deps.larger.iter() { + match (smaller, larger) { + (&RegionTarget::Region(_), &RegionTarget::Region(_)) => { + if let Entry::Occupied(v) = vid_map.entry(*smaller) { + let smaller_deps = v.into_mut(); + smaller_deps.larger.insert(*larger); + smaller_deps.larger.remove(&target); + } + + if let Entry::Occupied(v) = vid_map.entry(*larger) { + let larger_deps = v.into_mut(); + larger_deps.smaller.insert(*smaller); + larger_deps.smaller.remove(&target); + } + } + (&RegionTarget::RegionVid(v1), &RegionTarget::Region(r1)) => { + finished_map.insert(v1, r1); + } + (&RegionTarget::Region(_), &RegionTarget::RegionVid(_)) => { + // Do nothing - we don't care about regions that are smaller than vids + } + (&RegionTarget::RegionVid(_), &RegionTarget::RegionVid(_)) => { + if let Entry::Occupied(v) = vid_map.entry(*smaller) { + let smaller_deps = v.into_mut(); + smaller_deps.larger.insert(*larger); + smaller_deps.larger.remove(&target); + } + + if let Entry::Occupied(v) = vid_map.entry(*larger) { + let larger_deps = v.into_mut(); + larger_deps.smaller.insert(*smaller); + larger_deps.smaller.remove(&target); + } + } + } + } + } + } + finished_map + } + + fn is_of_param(&self, substs: &Substs) -> bool { + if substs.is_noop() { + return false; + } + + return match substs.type_at(0).sty { + ty::TyParam(_) => true, + ty::TyProjection(p) => self.is_of_param(p.substs), + _ => false, + }; + } + + fn evaluate_nested_obligations<'b, 'c, 'd, 'cx, + T: Iterator<Item = Obligation<'cx, ty::Predicate<'cx>>>>( + &self, + ty: ty::Ty, + nested: T, + computed_preds: &'b mut FxHashSet<ty::Predicate<'cx>>, + fresh_preds: &'b mut FxHashSet<ty::Predicate<'cx>>, + predicates: &'b mut VecDeque<ty::PolyTraitPredicate<'cx>>, + select: &mut SelectionContext<'c, 'd, 'cx>, + only_projections: bool, + ) -> bool { + let dummy_cause = ObligationCause::misc(DUMMY_SP, ast::DUMMY_NODE_ID); + + for (obligation, predicate) in nested + .filter(|o| o.recursion_depth == 1) + .map(|o| (o.clone(), o.predicate.clone())) + { + let is_new_pred = + fresh_preds.insert(self.clean_pred(select.infcx(), predicate.clone())); + + match &predicate { + &ty::Predicate::Trait(ref p) => { + let substs = &p.skip_binder().trait_ref.substs; + + if self.is_of_param(substs) && !only_projections && is_new_pred { + computed_preds.insert(predicate); + } + predicates.push_back(p.clone()); + } + &ty::Predicate::Projection(p) => { + // If the projection isn't all type vars, then + // we don't want to add it as a bound + if self.is_of_param(p.skip_binder().projection_ty.substs) && is_new_pred { + computed_preds.insert(predicate); + } else { + match poly_project_and_unify_type( + select, + &obligation.with(p.clone()), + ) { + Err(e) => { + debug!( + "evaluate_nested_obligations: Unable to unify predicate \ + '{:?}' '{:?}', bailing out", + ty, e + ); + return false; + } + Ok(Some(v)) => { + if !self.evaluate_nested_obligations( + ty, + v.clone().iter().cloned(), + computed_preds, + fresh_preds, + predicates, + select, + only_projections, + ) { + return false; + } + } + Ok(None) => { + panic!("Unexpected result when selecting {:?} {:?}", ty, obligation) + } + } + } + } + &ty::Predicate::RegionOutlives(ref binder) => { + if let Err(_) = select + .infcx() + .region_outlives_predicate(&dummy_cause, binder) + { + return false; + } + } + &ty::Predicate::TypeOutlives(ref binder) => { + match ( + binder.no_late_bound_regions(), + binder.map_bound_ref(|pred| pred.0).no_late_bound_regions(), + ) { + (None, Some(t_a)) => { + select.infcx().register_region_obligation( + ast::DUMMY_NODE_ID, + RegionObligation { + sup_type: t_a, + sub_region: select.infcx().tcx.types.re_static, + cause: dummy_cause.clone(), + }, + ); + } + (Some(ty::OutlivesPredicate(t_a, r_b)), _) => { + select.infcx().register_region_obligation( + ast::DUMMY_NODE_ID, + RegionObligation { + sup_type: t_a, + sub_region: r_b, + cause: dummy_cause.clone(), + }, + ); + } + _ => {} + }; + } + _ => panic!("Unexpected predicate {:?} {:?}", ty, predicate), + }; + } + return true; + } + + fn clean_pred<'c, 'd, 'cx>( + &self, + infcx: &InferCtxt<'c, 'd, 'cx>, + p: ty::Predicate<'cx>, + ) -> ty::Predicate<'cx> { + infcx.freshen(p) + } +} + +// Replaces all ReVars in a type with ty::Region's, using the provided map +struct RegionReplacer<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> { + vid_to_region: &'a FxHashMap<ty::RegionVid, ty::Region<'tcx>>, + tcx: TyCtxt<'a, 'gcx, 'tcx>, +} + +impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for RegionReplacer<'a, 'gcx, 'tcx> { + fn tcx<'b>(&'b self) -> TyCtxt<'b, 'gcx, 'tcx> { + self.tcx + } + + fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> { + (match r { + &ty::ReVar(vid) => self.vid_to_region.get(&vid).cloned(), + _ => None, + }).unwrap_or_else(|| r.super_fold_with(self)) + } +} diff --git a/src/librustc/traits/mod.rs b/src/librustc/traits/mod.rs index 728d9f1a027..b6b0b91fc53 100644 --- a/src/librustc/traits/mod.rs +++ b/src/librustc/traits/mod.rs @@ -52,6 +52,8 @@ pub use self::util::supertrait_def_ids; pub use self::util::SupertraitDefIds; pub use self::util::transitive_bounds; +#[allow(dead_code)] +pub mod auto_trait; mod coherence; pub mod error_reporting; mod engine; |