From 698f8c2f01ea549d77d7dc3338a12e04c11057b9 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 17 Apr 2024 14:02:58 +0200 Subject: Adding upstream version 1.64.0+dfsg1. Signed-off-by: Daniel Baumann --- src/librustdoc/clean/auto_trait.rs | 742 +++++++++++++++++++++++++++++++++++++ 1 file changed, 742 insertions(+) create mode 100644 src/librustdoc/clean/auto_trait.rs (limited to 'src/librustdoc/clean/auto_trait.rs') diff --git a/src/librustdoc/clean/auto_trait.rs b/src/librustdoc/clean/auto_trait.rs new file mode 100644 index 000000000..af33c1a6a --- /dev/null +++ b/src/librustdoc/clean/auto_trait.rs @@ -0,0 +1,742 @@ +use rustc_data_structures::fx::FxHashSet; +use rustc_hir as hir; +use rustc_hir::lang_items::LangItem; +use rustc_middle::ty::{self, Region, RegionVid, TypeFoldable, TypeSuperFoldable}; +use rustc_trait_selection::traits::auto_trait::{self, AutoTraitResult}; + +use std::fmt::Debug; + +use super::*; + +#[derive(Eq, PartialEq, Hash, Copy, Clone, Debug)] +enum RegionTarget<'tcx> { + Region(Region<'tcx>), + RegionVid(RegionVid), +} + +#[derive(Default, Debug, Clone)] +struct RegionDeps<'tcx> { + larger: FxHashSet>, + smaller: FxHashSet>, +} + +pub(crate) struct AutoTraitFinder<'a, 'tcx> { + pub(crate) cx: &'a mut core::DocContext<'tcx>, +} + +impl<'a, 'tcx> AutoTraitFinder<'a, 'tcx> +where + 'tcx: 'a, // should be an implied bound; rustc bug #98852. +{ + pub(crate) fn new(cx: &'a mut core::DocContext<'tcx>) -> Self { + AutoTraitFinder { cx } + } + + fn generate_for_trait( + &mut self, + ty: Ty<'tcx>, + trait_def_id: DefId, + param_env: ty::ParamEnv<'tcx>, + item_def_id: DefId, + f: &auto_trait::AutoTraitFinder<'tcx>, + // If this is set, show only negative trait implementations, not positive ones. + discard_positive_impl: bool, + ) -> Option { + let tcx = self.cx.tcx; + let trait_ref = ty::TraitRef { def_id: trait_def_id, substs: tcx.mk_substs_trait(ty, &[]) }; + if !self.cx.generated_synthetics.insert((ty, trait_def_id)) { + debug!("get_auto_trait_impl_for({:?}): already generated, aborting", trait_ref); + return None; + } + + let result = f.find_auto_trait_generics(ty, param_env, trait_def_id, |info| { + let region_data = info.region_data; + + let names_map = tcx + .generics_of(item_def_id) + .params + .iter() + .filter_map(|param| match param.kind { + ty::GenericParamDefKind::Lifetime => Some(param.name), + _ => None, + }) + .map(|name| (name, Lifetime(name))) + .collect(); + let lifetime_predicates = Self::handle_lifetimes(®ion_data, &names_map); + let new_generics = self.param_env_to_generics( + item_def_id, + info.full_user_env, + lifetime_predicates, + info.vid_to_region, + ); + + debug!( + "find_auto_trait_generics(item_def_id={:?}, trait_def_id={:?}): \ + finished with {:?}", + item_def_id, trait_def_id, new_generics + ); + + new_generics + }); + + let polarity; + let new_generics = match result { + AutoTraitResult::PositiveImpl(new_generics) => { + polarity = ty::ImplPolarity::Positive; + if discard_positive_impl { + return None; + } + new_generics + } + AutoTraitResult::NegativeImpl => { + polarity = ty::ImplPolarity::Negative; + + // For negative impls, we use the generic params, but *not* the predicates, + // from the original type. Otherwise, the displayed impl appears to be a + // conditional negative impl, when it's really unconditional. + // + // For example, consider the struct Foo(*mut T). Using + // the original predicates in our impl would cause us to generate + // `impl !Send for Foo`, which makes it appear that Foo + // implements Send where T is not copy. + // + // Instead, we generate `impl !Send for Foo`, which better + // expresses the fact that `Foo` never implements `Send`, + // regardless of the choice of `T`. + let raw_generics = clean_ty_generics( + self.cx, + tcx.generics_of(item_def_id), + ty::GenericPredicates::default(), + ); + let params = raw_generics.params; + + Generics { params, where_predicates: Vec::new() } + } + AutoTraitResult::ExplicitImpl => return None, + }; + + Some(Item { + name: None, + attrs: Default::default(), + visibility: Inherited, + item_id: ItemId::Auto { trait_: trait_def_id, for_: item_def_id }, + kind: Box::new(ImplItem(Box::new(Impl { + unsafety: hir::Unsafety::Normal, + generics: new_generics, + trait_: Some(clean_trait_ref_with_bindings(self.cx, trait_ref, &[])), + for_: clean_middle_ty(ty, self.cx, None), + items: Vec::new(), + polarity, + kind: ImplKind::Auto, + }))), + cfg: None, + }) + } + + pub(crate) fn get_auto_trait_impls(&mut self, item_def_id: DefId) -> Vec { + let tcx = self.cx.tcx; + let param_env = tcx.param_env(item_def_id); + let ty = tcx.type_of(item_def_id); + let f = auto_trait::AutoTraitFinder::new(tcx); + + debug!("get_auto_trait_impls({:?})", ty); + let auto_traits: Vec<_> = self.cx.auto_traits.iter().copied().collect(); + let mut auto_traits: Vec = auto_traits + .into_iter() + .filter_map(|trait_def_id| { + self.generate_for_trait(ty, trait_def_id, param_env, item_def_id, &f, false) + }) + .collect(); + // We are only interested in case the type *doesn't* implement the Sized trait. + if !ty.is_sized(tcx.at(rustc_span::DUMMY_SP), param_env) { + // In case `#![no_core]` is used, `sized_trait` returns nothing. + if let Some(item) = tcx.lang_items().sized_trait().and_then(|sized_trait_did| { + self.generate_for_trait(ty, sized_trait_did, param_env, item_def_id, &f, true) + }) { + auto_traits.push(item); + } + } + auto_traits + } + + fn get_lifetime(region: Region<'_>, names_map: &FxHashMap) -> Lifetime { + region_name(region) + .map(|name| { + names_map.get(&name).unwrap_or_else(|| { + panic!("Missing lifetime with name {:?} for {:?}", name.as_str(), region) + }) + }) + .unwrap_or(&Lifetime::statik()) + .clone() + } + + /// This method calculates two things: Lifetime constraints of the form `'a: 'b`, + /// and region constraints of the form `RegionVid: '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>( + regions: &RegionConstraintData<'cx>, + names_map: &FxHashMap, + ) -> Vec { + // 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<_, Vec<_>> = Default::default(); + + let mut vid_map: FxHashMap, RegionDeps<'_>> = Default::default(); + + // 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_default(); + deps1.larger.insert(RegionTarget::RegionVid(r2)); + } + + let deps2 = vid_map.entry(RegionTarget::RegionVid(r2)).or_default(); + deps2.smaller.insert(RegionTarget::RegionVid(r1)); + } + Constraint::RegSubVar(region, vid) => { + let deps = vid_map.entry(RegionTarget::RegionVid(vid)).or_default(); + deps.smaller.insert(RegionTarget::Region(region)); + } + Constraint::VarSubReg(vid, region) => { + let deps = vid_map.entry(RegionTarget::RegionVid(vid)).or_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 region_name(r1) != region_name(r2) { + finished + .entry(region_name(r2).expect("no region_name found")) + .or_default() + .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"); + 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 region_name(r1) != region_name(r2) { + finished + .entry(region_name(r2).expect("no region name found")) + .or_default() + .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 = finished + .get(name) + .unwrap_or(&empty) + .iter() + .map(|region| GenericBound::Outlives(Self::get_lifetime(*region, names_map))) + .collect(); + + if bounds.is_empty() { + return None; + } + Some(WherePredicate::RegionPredicate { + lifetime: lifetime.clone(), + bounds: bounds.into_iter().collect(), + }) + }) + .collect(); + + lifetime_predicates + } + + fn extract_for_generics(&self, pred: ty::Predicate<'tcx>) -> FxHashSet { + let bound_predicate = pred.kind(); + let tcx = self.cx.tcx; + let regions = match bound_predicate.skip_binder() { + ty::PredicateKind::Trait(poly_trait_pred) => { + tcx.collect_referenced_late_bound_regions(&bound_predicate.rebind(poly_trait_pred)) + } + ty::PredicateKind::Projection(poly_proj_pred) => { + tcx.collect_referenced_late_bound_regions(&bound_predicate.rebind(poly_proj_pred)) + } + _ => return FxHashSet::default(), + }; + + regions + .into_iter() + .filter_map(|br| { + match br { + // We only care about named late bound regions, as we need to add them + // to the 'for<>' section + ty::BrNamed(_, name) => Some(GenericParamDef { + name, + kind: GenericParamDefKind::Lifetime { outlives: vec![] }, + }), + _ => None, + } + }) + .collect() + } + + fn make_final_bounds( + &self, + ty_to_bounds: FxHashMap>, + ty_to_fn: FxHashMap)>, + lifetime_to_bounds: FxHashMap>, + ) -> Vec { + ty_to_bounds + .into_iter() + .flat_map(|(ty, mut bounds)| { + if let Some((ref poly_trait, ref output)) = ty_to_fn.get(&ty) { + let mut new_path = poly_trait.trait_.clone(); + let last_segment = new_path.segments.pop().expect("segments were empty"); + + let (old_input, old_output) = match last_segment.args { + GenericArgs::AngleBracketed { args, .. } => { + let types = args + .iter() + .filter_map(|arg| match arg { + GenericArg::Type(ty) => Some(ty.clone()), + _ => None, + }) + .collect(); + (types, None) + } + GenericArgs::Parenthesized { inputs, output } => (inputs, output), + }; + + let output = output.as_ref().cloned().map(Box::new); + if old_output.is_some() && old_output != output { + panic!("Output mismatch for {:?} {:?} {:?}", ty, old_output, output); + } + + let new_params = GenericArgs::Parenthesized { inputs: old_input, output }; + + new_path + .segments + .push(PathSegment { name: last_segment.name, args: new_params }); + + bounds.insert(GenericBound::TraitBound( + PolyTrait { + trait_: new_path, + generic_params: poly_trait.generic_params.clone(), + }, + hir::TraitBoundModifier::None, + )); + } + if bounds.is_empty() { + return None; + } + + let mut bounds_vec = bounds.into_iter().collect(); + self.sort_where_bounds(&mut bounds_vec); + + Some(WherePredicate::BoundPredicate { + ty, + bounds: bounds_vec, + bound_params: Vec::new(), + }) + }) + .chain( + lifetime_to_bounds.into_iter().filter(|&(_, ref bounds)| !bounds.is_empty()).map( + |(lifetime, bounds)| { + let mut bounds_vec = bounds.into_iter().collect(); + self.sort_where_bounds(&mut bounds_vec); + WherePredicate::RegionPredicate { lifetime, bounds: bounds_vec } + }, + ), + ) + .collect() + } + + /// Converts the calculated `ParamEnv` and lifetime information to a [`clean::Generics`](Generics), suitable for + /// display on the docs page. Cleaning the `Predicates` produces sub-optimal [`WherePredicate`]s, + /// so we fix them up: + /// + /// * Multiple bounds for the same type are coalesced into one: e.g., `T: Copy`, `T: Debug` + /// becomes `T: Copy + Debug` + /// * `Fn` bounds are handled specially - instead of leaving it as `T: Fn(), = + /// K`, we use the dedicated syntax `T: Fn() -> K` + /// * We explicitly add a `?Sized` bound if we didn't find any `Sized` predicates for a type + fn param_env_to_generics( + &mut self, + item_def_id: DefId, + param_env: ty::ParamEnv<'tcx>, + mut existing_predicates: Vec, + vid_to_region: FxHashMap>, + ) -> Generics { + debug!( + "param_env_to_generics(item_def_id={:?}, param_env={:?}, \ + existing_predicates={:?})", + item_def_id, param_env, existing_predicates + ); + + let tcx = self.cx.tcx; + + // The `Sized` trait must be handled specially, since we only display it when + // it is *not* required (i.e., '?Sized') + let sized_trait = tcx.require_lang_item(LangItem::Sized, None); + + let mut replacer = RegionReplacer { vid_to_region: &vid_to_region, tcx }; + + let orig_bounds: FxHashSet<_> = tcx.param_env(item_def_id).caller_bounds().iter().collect(); + let clean_where_predicates = param_env + .caller_bounds() + .iter() + .filter(|p| { + !orig_bounds.contains(p) + || match p.kind().skip_binder() { + ty::PredicateKind::Trait(pred) => pred.def_id() == sized_trait, + _ => false, + } + }) + .map(|p| p.fold_with(&mut replacer)); + + let raw_generics = clean_ty_generics( + self.cx, + tcx.generics_of(item_def_id), + tcx.explicit_predicates_of(item_def_id), + ); + let mut generic_params = raw_generics.params; + + debug!("param_env_to_generics({:?}): generic_params={:?}", item_def_id, generic_params); + + let mut has_sized = FxHashSet::default(); + let mut ty_to_bounds: FxHashMap<_, FxHashSet<_>> = Default::default(); + let mut lifetime_to_bounds: FxHashMap<_, FxHashSet<_>> = Default::default(); + let mut ty_to_traits: FxHashMap> = Default::default(); + + let mut ty_to_fn: FxHashMap)> = Default::default(); + + for p in clean_where_predicates { + let (orig_p, p) = (p, p.clean(self.cx)); + if p.is_none() { + continue; + } + let p = p.unwrap(); + match p { + WherePredicate::BoundPredicate { ty, mut bounds, .. } => { + // Writing a projection trait bound of the form + // ::Name : ?Sized + // is illegal, because ?Sized bounds can only + // be written in the (here, nonexistent) definition + // of the type. + // Therefore, we make sure that we never add a ?Sized + // bound for projections + if let Type::QPath { .. } = ty { + has_sized.insert(ty.clone()); + } + + if bounds.is_empty() { + continue; + } + + let mut for_generics = self.extract_for_generics(orig_p); + + assert!(bounds.len() == 1); + let mut b = bounds.pop().expect("bounds were empty"); + + if b.is_sized_bound(self.cx) { + has_sized.insert(ty.clone()); + } else if !b + .get_trait_path() + .and_then(|trait_| { + ty_to_traits + .get(&ty) + .map(|bounds| bounds.contains(&strip_path_generics(trait_))) + }) + .unwrap_or(false) + { + // If we've already added a projection bound for the same type, don't add + // this, as it would be a duplicate + + // Handle any 'Fn/FnOnce/FnMut' bounds specially, + // as we want to combine them with any 'Output' qpaths + // later + + let is_fn = match b { + GenericBound::TraitBound(ref mut p, _) => { + // Insert regions into the for_generics hash map first, to ensure + // that we don't end up with duplicate bounds (e.g., for<'b, 'b>) + for_generics.extend(p.generic_params.clone()); + p.generic_params = for_generics.into_iter().collect(); + self.is_fn_trait(&p.trait_) + } + _ => false, + }; + + let poly_trait = b.get_poly_trait().expect("Cannot get poly trait"); + + if is_fn { + ty_to_fn + .entry(ty.clone()) + .and_modify(|e| *e = (poly_trait.clone(), e.1.clone())) + .or_insert(((poly_trait.clone()), None)); + + ty_to_bounds.entry(ty.clone()).or_default(); + } else { + ty_to_bounds.entry(ty.clone()).or_default().insert(b.clone()); + } + } + } + WherePredicate::RegionPredicate { lifetime, bounds } => { + lifetime_to_bounds.entry(lifetime).or_default().extend(bounds); + } + WherePredicate::EqPredicate { lhs, rhs } => { + match lhs { + Type::QPath { ref assoc, ref self_type, ref trait_, .. } => { + let ty = &*self_type; + let mut new_trait = trait_.clone(); + + if self.is_fn_trait(trait_) && assoc.name == sym::Output { + ty_to_fn + .entry(*ty.clone()) + .and_modify(|e| { + *e = (e.0.clone(), Some(rhs.ty().unwrap().clone())) + }) + .or_insert(( + PolyTrait { + trait_: trait_.clone(), + generic_params: Vec::new(), + }, + Some(rhs.ty().unwrap().clone()), + )); + continue; + } + + let args = &mut new_trait + .segments + .last_mut() + .expect("segments were empty") + .args; + + match args { + // Convert something like ' = u8' + // to 'T: Iterator' + GenericArgs::AngleBracketed { ref mut bindings, .. } => { + bindings.push(TypeBinding { + assoc: *assoc.clone(), + kind: TypeBindingKind::Equality { term: rhs }, + }); + } + GenericArgs::Parenthesized { .. } => { + existing_predicates.push(WherePredicate::EqPredicate { + lhs: lhs.clone(), + rhs, + }); + continue; // If something other than a Fn ends up + // with parentheses, leave it alone + } + } + + let bounds = ty_to_bounds.entry(*ty.clone()).or_default(); + + bounds.insert(GenericBound::TraitBound( + PolyTrait { trait_: new_trait, generic_params: Vec::new() }, + hir::TraitBoundModifier::None, + )); + + // Remove any existing 'plain' bound (e.g., 'T: Iterator`) so + // that we don't see a + // duplicate bound like `T: Iterator + Iterator` + // on the docs page. + bounds.remove(&GenericBound::TraitBound( + PolyTrait { trait_: trait_.clone(), generic_params: Vec::new() }, + hir::TraitBoundModifier::None, + )); + // Avoid creating any new duplicate bounds later in the outer + // loop + ty_to_traits.entry(*ty.clone()).or_default().insert(trait_.clone()); + } + _ => panic!("Unexpected LHS {:?} for {:?}", lhs, item_def_id), + } + } + }; + } + + let final_bounds = self.make_final_bounds(ty_to_bounds, ty_to_fn, lifetime_to_bounds); + + existing_predicates.extend(final_bounds); + + for param in generic_params.iter_mut() { + match param.kind { + GenericParamDefKind::Type { ref mut default, ref mut bounds, .. } => { + // We never want something like `impl`. + default.take(); + let generic_ty = Type::Generic(param.name); + if !has_sized.contains(&generic_ty) { + bounds.insert(0, GenericBound::maybe_sized(self.cx)); + } + } + GenericParamDefKind::Lifetime { .. } => {} + GenericParamDefKind::Const { ref mut default, .. } => { + // We never want something like `impl` + default.take(); + } + } + } + + self.sort_where_predicates(&mut existing_predicates); + + Generics { params: generic_params, where_predicates: existing_predicates } + } + + /// Ensure that the predicates are in a consistent order. The precise + /// ordering doesn't actually matter, but it's important that + /// a given set of predicates always appears in the same order - + /// both for visual consistency between 'rustdoc' runs, and to + /// make writing tests much easier + #[inline] + fn sort_where_predicates(&self, predicates: &mut Vec) { + // We should never have identical bounds - and if we do, + // they're visually identical as well. Therefore, using + // an unstable sort is fine. + self.unstable_debug_sort(predicates); + } + + /// Ensure that the bounds are in a consistent order. The precise + /// ordering doesn't actually matter, but it's important that + /// a given set of bounds always appears in the same order - + /// both for visual consistency between 'rustdoc' runs, and to + /// make writing tests much easier + #[inline] + fn sort_where_bounds(&self, bounds: &mut Vec) { + // We should never have identical bounds - and if we do, + // they're visually identical as well. Therefore, using + // an unstable sort is fine. + self.unstable_debug_sort(bounds); + } + + /// This might look horrendously hacky, but it's actually not that bad. + /// + /// For performance reasons, we use several different FxHashMaps + /// in the process of computing the final set of where predicates. + /// However, the iteration order of a HashMap is completely unspecified. + /// In fact, the iteration of an FxHashMap can even vary between platforms, + /// since FxHasher has different behavior for 32-bit and 64-bit platforms. + /// + /// Obviously, it's extremely undesirable for documentation rendering + /// to be dependent on the platform it's run on. Apart from being confusing + /// to end users, it makes writing tests much more difficult, as predicates + /// can appear in any order in the final result. + /// + /// To solve this problem, we sort WherePredicates and GenericBounds + /// by their Debug string. The thing to keep in mind is that we don't really + /// care what the final order is - we're synthesizing an impl or bound + /// ourselves, so any order can be considered equally valid. By sorting the + /// predicates and bounds, however, we ensure that for a given codebase, all + /// auto-trait impls always render in exactly the same way. + /// + /// Using the Debug implementation for sorting prevents us from needing to + /// write quite a bit of almost entirely useless code (e.g., how should two + /// Types be sorted relative to each other). It also allows us to solve the + /// problem for both WherePredicates and GenericBounds at the same time. This + /// approach is probably somewhat slower, but the small number of items + /// involved (impls rarely have more than a few bounds) means that it + /// shouldn't matter in practice. + fn unstable_debug_sort(&self, vec: &mut Vec) { + vec.sort_by_cached_key(|x| format!("{:?}", x)) + } + + fn is_fn_trait(&self, path: &Path) -> bool { + let tcx = self.cx.tcx; + let did = path.def_id(); + did == tcx.require_lang_item(LangItem::Fn, None) + || did == tcx.require_lang_item(LangItem::FnMut, None) + || did == tcx.require_lang_item(LangItem::FnOnce, None) + } +} + +fn region_name(region: Region<'_>) -> Option { + match *region { + ty::ReEarlyBound(r) => Some(r.name), + _ => None, + } +} + +/// Replaces all [`ty::RegionVid`]s in a type with [`ty::Region`]s, using the provided map. +struct RegionReplacer<'a, 'tcx> { + vid_to_region: &'a FxHashMap>, + tcx: TyCtxt<'tcx>, +} + +impl<'a, 'tcx> TypeFolder<'tcx> for RegionReplacer<'a, 'tcx> { + fn tcx<'b>(&'b self) -> TyCtxt<'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)) + } +} -- cgit v1.2.3