| 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}; |
| use rustc_trait_selection::traits::auto_trait::{self, AutoTraitResult}; |
| use thin_vec::ThinVec; |
| |
| 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<RegionTarget<'tcx>>, |
| smaller: FxHashSet<RegionTarget<'tcx>>, |
| } |
| |
| 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<Item> { |
| let tcx = self.cx.tcx; |
| let trait_ref = ty::Binder::dummy(ty::TraitRef::new(tcx, trait_def_id, [ty])); |
| if !self.cx.generated_synthetics.insert((ty, trait_def_id)) { |
| debug!("get_auto_trait_impl_for({trait_ref:?}): already generated, aborting"); |
| 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<T: Copy>(*mut T). Using |
| // the original predicates in our impl would cause us to generate |
| // `impl !Send for Foo<T: Copy>`, which makes it appear that Foo |
| // implements Send where T is not copy. |
| // |
| // Instead, we generate `impl !Send for Foo<T>`, which better |
| // expresses the fact that `Foo<T>` 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: ThinVec::new() } |
| } |
| AutoTraitResult::ExplicitImpl => return None, |
| }; |
| |
| Some(Item { |
| name: None, |
| attrs: Default::default(), |
| 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, ThinVec::new())), |
| for_: clean_middle_ty(ty::Binder::dummy(ty), self.cx, None, None), |
| items: Vec::new(), |
| polarity, |
| kind: ImplKind::Auto, |
| }))), |
| cfg: None, |
| inline_stmt_id: None, |
| }) |
| } |
| |
| pub(crate) fn get_auto_trait_impls(&mut self, item_def_id: DefId) -> Vec<Item> { |
| let tcx = self.cx.tcx; |
| let param_env = tcx.param_env(item_def_id); |
| let ty = tcx.type_of(item_def_id).instantiate_identity(); |
| let f = auto_trait::AutoTraitFinder::new(tcx); |
| |
| debug!("get_auto_trait_impls({ty:?})"); |
| let auto_traits: Vec<_> = self.cx.auto_traits.to_vec(); |
| let mut auto_traits: Vec<Item> = 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, 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<Symbol, Lifetime>) -> Lifetime { |
| region_name(region) |
| .map(|name| { |
| names_map |
| .get(&name) |
| .unwrap_or_else(|| panic!("Missing lifetime with name {name:?} for {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<Symbol, Lifetime>, |
| ) -> ThinVec<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<_, Vec<_>> = Default::default(); |
| |
| let mut vid_map: FxHashMap<RegionTarget<'_>, 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<GenericBound> = 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::Clause<'tcx>) -> FxHashSet<GenericParamDef> { |
| let bound_predicate = pred.kind(); |
| let tcx = self.cx.tcx; |
| let regions = match bound_predicate.skip_binder() { |
| ty::ClauseKind::Trait(poly_trait_pred) => { |
| tcx.collect_referenced_late_bound_regions(&bound_predicate.rebind(poly_trait_pred)) |
| } |
| ty::ClauseKind::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::lifetime(name)), |
| _ => None, |
| } |
| }) |
| .collect() |
| } |
| |
| fn make_final_bounds( |
| &self, |
| ty_to_bounds: FxHashMap<Type, FxHashSet<GenericBound>>, |
| ty_to_fn: FxHashMap<Type, (PolyTrait, Option<Type>)>, |
| lifetime_to_bounds: FxHashMap<Lifetime, FxHashSet<GenericBound>>, |
| ) -> Vec<WherePredicate> { |
| 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(|(_, 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(), <T as Fn::Output> = |
| /// 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: ThinVec<WherePredicate>, |
| vid_to_region: FxHashMap<ty::RegionVid, ty::Region<'tcx>>, |
| ) -> 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::ClauseKind::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({item_def_id:?}): generic_params={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<Type, FxHashSet<Path>> = Default::default(); |
| |
| let mut ty_to_fn: FxHashMap<Type, (PolyTrait, Option<Type>)> = Default::default(); |
| |
| // FIXME: This code shares much of the logic found in `clean_ty_generics` and |
| // `simplify::where_clause`. Consider deduplicating it to avoid diverging |
| // implementations. |
| // Further, the code below does not merge (partially re-sugared) bounds like |
| // `Tr<A = T>` & `Tr<B = U>` and it does not render higher-ranked parameters |
| // originating from equality predicates. |
| for p in clean_where_predicates { |
| let (orig_p, p) = (p, clean_predicate(p, 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 |
| // <T as Trait>::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.drain(..)); |
| p.generic_params.extend(for_generics); |
| 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(box QPathData { |
| ref assoc, |
| ref self_type, |
| trait_: Some(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 '<T as Iterator::Item> = u8' |
| // to 'T: Iterator<Item=u8>' |
| 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<Item=u8>` |
| // 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 {lhs:?} for {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<T=Foo>`. |
| 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<const N: usize = 10>` |
| 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 [WherePredicate]) { |
| // 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<GenericBound>) { |
| // 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<T: Debug>(&self, vec: &mut [T]) { |
| 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<Symbol> { |
| 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<ty::RegionVid, ty::Region<'tcx>>, |
| tcx: TyCtxt<'tcx>, |
| } |
| |
| impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for RegionReplacer<'a, 'tcx> { |
| fn interner(&self) -> TyCtxt<'tcx> { |
| self.tcx |
| } |
| |
| fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> { |
| match *r { |
| // These are the regions that can be seen in the AST. |
| ty::ReVar(vid) => self.vid_to_region.get(&vid).cloned().unwrap_or(r), |
| ty::ReEarlyBound(_) | ty::ReStatic | ty::ReLateBound(..) | ty::ReError(_) => r, |
| r => bug!("unexpected region: {r:?}"), |
| } |
| } |
| } |
