| //! Resolution of early vs late bound lifetimes. |
| //! |
| //! Name resolution for lifetimes is performed on the AST and embedded into HIR. From this |
| //! information, typechecking needs to transform the lifetime parameters into bound lifetimes. |
| //! Lifetimes can be early-bound or late-bound. Construction of typechecking terms needs to visit |
| //! the types in HIR to identify late-bound lifetimes and assign their Debruijn indices. This file |
| //! is also responsible for assigning their semantics to implicit lifetimes in trait objects. |
| |
| use rustc_ast::walk_list; |
| use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet}; |
| use rustc_errors::struct_span_err; |
| use rustc_hir as hir; |
| use rustc_hir::def::{DefKind, Res}; |
| use rustc_hir::def_id::{DefIdMap, LocalDefId}; |
| use rustc_hir::intravisit::{self, Visitor}; |
| use rustc_hir::{GenericArg, GenericParam, GenericParamKind, HirIdMap, LifetimeName, Node}; |
| use rustc_middle::bug; |
| use rustc_middle::hir::map::Map; |
| use rustc_middle::hir::nested_filter; |
| use rustc_middle::middle::resolve_lifetime::*; |
| use rustc_middle::ty::{self, GenericParamDefKind, TyCtxt}; |
| use rustc_span::def_id::DefId; |
| use rustc_span::symbol::{sym, Ident}; |
| use rustc_span::Span; |
| use std::borrow::Cow; |
| use std::fmt; |
| use std::mem::take; |
| |
| trait RegionExt { |
| fn early(hir_map: Map<'_>, index: &mut u32, param: &GenericParam<'_>) -> (LocalDefId, Region); |
| |
| fn late(index: u32, hir_map: Map<'_>, param: &GenericParam<'_>) -> (LocalDefId, Region); |
| |
| fn id(&self) -> Option<DefId>; |
| |
| fn shifted(self, amount: u32) -> Region; |
| |
| fn shifted_out_to_binder(self, binder: ty::DebruijnIndex) -> Region; |
| |
| fn subst<'a, L>(self, params: L, map: &NamedRegionMap) -> Option<Region> |
| where |
| L: Iterator<Item = &'a hir::Lifetime>; |
| } |
| |
| impl RegionExt for Region { |
| fn early(hir_map: Map<'_>, index: &mut u32, param: &GenericParam<'_>) -> (LocalDefId, Region) { |
| let i = *index; |
| *index += 1; |
| let def_id = hir_map.local_def_id(param.hir_id); |
| debug!("Region::early: index={} def_id={:?}", i, def_id); |
| (def_id, Region::EarlyBound(i, def_id.to_def_id())) |
| } |
| |
| fn late(idx: u32, hir_map: Map<'_>, param: &GenericParam<'_>) -> (LocalDefId, Region) { |
| let depth = ty::INNERMOST; |
| let def_id = hir_map.local_def_id(param.hir_id); |
| debug!( |
| "Region::late: idx={:?}, param={:?} depth={:?} def_id={:?}", |
| idx, param, depth, def_id, |
| ); |
| (def_id, Region::LateBound(depth, idx, def_id.to_def_id())) |
| } |
| |
| fn id(&self) -> Option<DefId> { |
| match *self { |
| Region::Static => None, |
| |
| Region::EarlyBound(_, id) | Region::LateBound(_, _, id) | Region::Free(_, id) => { |
| Some(id) |
| } |
| } |
| } |
| |
| fn shifted(self, amount: u32) -> Region { |
| match self { |
| Region::LateBound(debruijn, idx, id) => { |
| Region::LateBound(debruijn.shifted_in(amount), idx, id) |
| } |
| _ => self, |
| } |
| } |
| |
| fn shifted_out_to_binder(self, binder: ty::DebruijnIndex) -> Region { |
| match self { |
| Region::LateBound(debruijn, index, id) => { |
| Region::LateBound(debruijn.shifted_out_to_binder(binder), index, id) |
| } |
| _ => self, |
| } |
| } |
| |
| fn subst<'a, L>(self, mut params: L, map: &NamedRegionMap) -> Option<Region> |
| where |
| L: Iterator<Item = &'a hir::Lifetime>, |
| { |
| if let Region::EarlyBound(index, _) = self { |
| params.nth(index as usize).and_then(|lifetime| map.defs.get(&lifetime.hir_id).cloned()) |
| } else { |
| Some(self) |
| } |
| } |
| } |
| |
| /// Maps the id of each lifetime reference to the lifetime decl |
| /// that it corresponds to. |
| /// |
| /// FIXME. This struct gets converted to a `ResolveLifetimes` for |
| /// actual use. It has the same data, but indexed by `LocalDefId`. This |
| /// is silly. |
| #[derive(Debug, Default)] |
| struct NamedRegionMap { |
| // maps from every use of a named (not anonymous) lifetime to a |
| // `Region` describing how that region is bound |
| defs: HirIdMap<Region>, |
| |
| // Maps relevant hir items to the bound vars on them. These include: |
| // - function defs |
| // - function pointers |
| // - closures |
| // - trait refs |
| // - bound types (like `T` in `for<'a> T<'a>: Foo`) |
| late_bound_vars: HirIdMap<Vec<ty::BoundVariableKind>>, |
| } |
| |
| pub(crate) struct LifetimeContext<'a, 'tcx> { |
| pub(crate) tcx: TyCtxt<'tcx>, |
| map: &'a mut NamedRegionMap, |
| scope: ScopeRef<'a>, |
| |
| /// Indicates that we only care about the definition of a trait. This should |
| /// be false if the `Item` we are resolving lifetimes for is not a trait or |
| /// we eventually need lifetimes resolve for trait items. |
| trait_definition_only: bool, |
| |
| /// Cache for cross-crate per-definition object lifetime defaults. |
| xcrate_object_lifetime_defaults: DefIdMap<Vec<ObjectLifetimeDefault>>, |
| } |
| |
| #[derive(Debug)] |
| enum Scope<'a> { |
| /// Declares lifetimes, and each can be early-bound or late-bound. |
| /// The `DebruijnIndex` of late-bound lifetimes starts at `1` and |
| /// it should be shifted by the number of `Binder`s in between the |
| /// declaration `Binder` and the location it's referenced from. |
| Binder { |
| /// We use an IndexMap here because we want these lifetimes in order |
| /// for diagnostics. |
| lifetimes: FxIndexMap<LocalDefId, Region>, |
| |
| /// if we extend this scope with another scope, what is the next index |
| /// we should use for an early-bound region? |
| next_early_index: u32, |
| |
| /// Whether or not this binder would serve as the parent |
| /// binder for opaque types introduced within. For example: |
| /// |
| /// ```text |
| /// fn foo<'a>() -> impl for<'b> Trait<Item = impl Trait2<'a>> |
| /// ``` |
| /// |
| /// Here, the opaque types we create for the `impl Trait` |
| /// and `impl Trait2` references will both have the `foo` item |
| /// as their parent. When we get to `impl Trait2`, we find |
| /// that it is nested within the `for<>` binder -- this flag |
| /// allows us to skip that when looking for the parent binder |
| /// of the resulting opaque type. |
| opaque_type_parent: bool, |
| |
| scope_type: BinderScopeType, |
| |
| /// The late bound vars for a given item are stored by `HirId` to be |
| /// queried later. However, if we enter an elision scope, we have to |
| /// later append the elided bound vars to the list and need to know what |
| /// to append to. |
| hir_id: hir::HirId, |
| |
| s: ScopeRef<'a>, |
| |
| /// If this binder comes from a where clause, specify how it was created. |
| /// This is used to diagnose inaccessible lifetimes in APIT: |
| /// ```ignore (illustrative) |
| /// fn foo(x: impl for<'a> Trait<'a, Assoc = impl Copy + 'a>) {} |
| /// ``` |
| where_bound_origin: Option<hir::PredicateOrigin>, |
| }, |
| |
| /// Lifetimes introduced by a fn are scoped to the call-site for that fn, |
| /// if this is a fn body, otherwise the original definitions are used. |
| /// Unspecified lifetimes are inferred, unless an elision scope is nested, |
| /// e.g., `(&T, fn(&T) -> &T);` becomes `(&'_ T, for<'a> fn(&'a T) -> &'a T)`. |
| Body { |
| id: hir::BodyId, |
| s: ScopeRef<'a>, |
| }, |
| |
| /// A scope which either determines unspecified lifetimes or errors |
| /// on them (e.g., due to ambiguity). |
| Elision { |
| s: ScopeRef<'a>, |
| }, |
| |
| /// Use a specific lifetime (if `Some`) or leave it unset (to be |
| /// inferred in a function body or potentially error outside one), |
| /// for the default choice of lifetime in a trait object type. |
| ObjectLifetimeDefault { |
| lifetime: Option<Region>, |
| s: ScopeRef<'a>, |
| }, |
| |
| /// When we have nested trait refs, we concatenate late bound vars for inner |
| /// trait refs from outer ones. But we also need to include any HRTB |
| /// lifetimes encountered when identifying the trait that an associated type |
| /// is declared on. |
| Supertrait { |
| lifetimes: Vec<ty::BoundVariableKind>, |
| s: ScopeRef<'a>, |
| }, |
| |
| TraitRefBoundary { |
| s: ScopeRef<'a>, |
| }, |
| |
| Root, |
| } |
| |
| #[derive(Copy, Clone, Debug)] |
| enum BinderScopeType { |
| /// Any non-concatenating binder scopes. |
| Normal, |
| /// Within a syntactic trait ref, there may be multiple poly trait refs that |
| /// are nested (under the `associated_type_bounds` feature). The binders of |
| /// the inner poly trait refs are extended from the outer poly trait refs |
| /// and don't increase the late bound depth. If you had |
| /// `T: for<'a> Foo<Bar: for<'b> Baz<'a, 'b>>`, then the `for<'b>` scope |
| /// would be `Concatenating`. This also used in trait refs in where clauses |
| /// where we have two binders `for<> T: for<> Foo` (I've intentionally left |
| /// out any lifetimes because they aren't needed to show the two scopes). |
| /// The inner `for<>` has a scope of `Concatenating`. |
| Concatenating, |
| } |
| |
| // A helper struct for debugging scopes without printing parent scopes |
| struct TruncatedScopeDebug<'a>(&'a Scope<'a>); |
| |
| impl<'a> fmt::Debug for TruncatedScopeDebug<'a> { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| match self.0 { |
| Scope::Binder { |
| lifetimes, |
| next_early_index, |
| opaque_type_parent, |
| scope_type, |
| hir_id, |
| where_bound_origin, |
| s: _, |
| } => f |
| .debug_struct("Binder") |
| .field("lifetimes", lifetimes) |
| .field("next_early_index", next_early_index) |
| .field("opaque_type_parent", opaque_type_parent) |
| .field("scope_type", scope_type) |
| .field("hir_id", hir_id) |
| .field("where_bound_origin", where_bound_origin) |
| .field("s", &"..") |
| .finish(), |
| Scope::Body { id, s: _ } => { |
| f.debug_struct("Body").field("id", id).field("s", &"..").finish() |
| } |
| Scope::Elision { s: _ } => f.debug_struct("Elision").field("s", &"..").finish(), |
| Scope::ObjectLifetimeDefault { lifetime, s: _ } => f |
| .debug_struct("ObjectLifetimeDefault") |
| .field("lifetime", lifetime) |
| .field("s", &"..") |
| .finish(), |
| Scope::Supertrait { lifetimes, s: _ } => f |
| .debug_struct("Supertrait") |
| .field("lifetimes", lifetimes) |
| .field("s", &"..") |
| .finish(), |
| Scope::TraitRefBoundary { s: _ } => f.debug_struct("TraitRefBoundary").finish(), |
| Scope::Root => f.debug_struct("Root").finish(), |
| } |
| } |
| } |
| |
| type ScopeRef<'a> = &'a Scope<'a>; |
| |
| const ROOT_SCOPE: ScopeRef<'static> = &Scope::Root; |
| |
| pub fn provide(providers: &mut ty::query::Providers) { |
| *providers = ty::query::Providers { |
| resolve_lifetimes_trait_definition, |
| resolve_lifetimes, |
| |
| named_region_map: |tcx, id| resolve_lifetimes_for(tcx, id).defs.get(&id), |
| is_late_bound_map, |
| object_lifetime_defaults: |tcx, id| match tcx.hir().find_by_def_id(id) { |
| Some(Node::Item(item)) => compute_object_lifetime_defaults(tcx, item), |
| _ => None, |
| }, |
| late_bound_vars_map: |tcx, id| resolve_lifetimes_for(tcx, id).late_bound_vars.get(&id), |
| |
| ..*providers |
| }; |
| } |
| |
| /// Like `resolve_lifetimes`, but does not resolve lifetimes for trait items. |
| /// Also does not generate any diagnostics. |
| /// |
| /// This is ultimately a subset of the `resolve_lifetimes` work. It effectively |
| /// resolves lifetimes only within the trait "header" -- that is, the trait |
| /// and supertrait list. In contrast, `resolve_lifetimes` resolves all the |
| /// lifetimes within the trait and its items. There is room to refactor this, |
| /// for example to resolve lifetimes for each trait item in separate queries, |
| /// but it's convenient to do the entire trait at once because the lifetimes |
| /// from the trait definition are in scope within the trait items as well. |
| /// |
| /// The reason for this separate call is to resolve what would otherwise |
| /// be a cycle. Consider this example: |
| /// |
| /// ```ignore UNSOLVED (maybe @jackh726 knows what lifetime parameter to give Sub) |
| /// trait Base<'a> { |
| /// type BaseItem; |
| /// } |
| /// trait Sub<'b>: for<'a> Base<'a> { |
| /// type SubItem: Sub<BaseItem = &'b u32>; |
| /// } |
| /// ``` |
| /// |
| /// When we resolve `Sub` and all its items, we also have to resolve `Sub<BaseItem = &'b u32>`. |
| /// To figure out the index of `'b`, we have to know about the supertraits |
| /// of `Sub` so that we can determine that the `for<'a>` will be in scope. |
| /// (This is because we -- currently at least -- flatten all the late-bound |
| /// lifetimes into a single binder.) This requires us to resolve the |
| /// *trait definition* of `Sub`; basically just enough lifetime information |
| /// to look at the supertraits. |
| #[tracing::instrument(level = "debug", skip(tcx))] |
| fn resolve_lifetimes_trait_definition( |
| tcx: TyCtxt<'_>, |
| local_def_id: LocalDefId, |
| ) -> ResolveLifetimes { |
| convert_named_region_map(do_resolve(tcx, local_def_id, true)) |
| } |
| |
| /// Computes the `ResolveLifetimes` map that contains data for an entire `Item`. |
| /// You should not read the result of this query directly, but rather use |
| /// `named_region_map`, `is_late_bound_map`, etc. |
| #[tracing::instrument(level = "debug", skip(tcx))] |
| fn resolve_lifetimes(tcx: TyCtxt<'_>, local_def_id: LocalDefId) -> ResolveLifetimes { |
| convert_named_region_map(do_resolve(tcx, local_def_id, false)) |
| } |
| |
| fn do_resolve( |
| tcx: TyCtxt<'_>, |
| local_def_id: LocalDefId, |
| trait_definition_only: bool, |
| ) -> NamedRegionMap { |
| let item = tcx.hir().expect_item(local_def_id); |
| let mut named_region_map = |
| NamedRegionMap { defs: Default::default(), late_bound_vars: Default::default() }; |
| let mut visitor = LifetimeContext { |
| tcx, |
| map: &mut named_region_map, |
| scope: ROOT_SCOPE, |
| trait_definition_only, |
| xcrate_object_lifetime_defaults: Default::default(), |
| }; |
| visitor.visit_item(item); |
| |
| named_region_map |
| } |
| |
| fn convert_named_region_map(named_region_map: NamedRegionMap) -> ResolveLifetimes { |
| let mut rl = ResolveLifetimes::default(); |
| |
| for (hir_id, v) in named_region_map.defs { |
| let map = rl.defs.entry(hir_id.owner).or_default(); |
| map.insert(hir_id.local_id, v); |
| } |
| for (hir_id, v) in named_region_map.late_bound_vars { |
| let map = rl.late_bound_vars.entry(hir_id.owner).or_default(); |
| map.insert(hir_id.local_id, v); |
| } |
| |
| debug!(?rl.defs); |
| rl |
| } |
| |
| /// Given `any` owner (structs, traits, trait methods, etc.), does lifetime resolution. |
| /// There are two important things this does. |
| /// First, we have to resolve lifetimes for |
| /// the entire *`Item`* that contains this owner, because that's the largest "scope" |
| /// where we can have relevant lifetimes. |
| /// Second, if we are asking for lifetimes in a trait *definition*, we use `resolve_lifetimes_trait_definition` |
| /// instead of `resolve_lifetimes`, which does not descend into the trait items and does not emit diagnostics. |
| /// This allows us to avoid cycles. Importantly, if we ask for lifetimes for lifetimes that have an owner |
| /// other than the trait itself (like the trait methods or associated types), then we just use the regular |
| /// `resolve_lifetimes`. |
| fn resolve_lifetimes_for<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &'tcx ResolveLifetimes { |
| let item_id = item_for(tcx, def_id); |
| if item_id == def_id { |
| let item = tcx.hir().item(hir::ItemId { def_id: item_id }); |
| match item.kind { |
| hir::ItemKind::Trait(..) => tcx.resolve_lifetimes_trait_definition(item_id), |
| _ => tcx.resolve_lifetimes(item_id), |
| } |
| } else { |
| tcx.resolve_lifetimes(item_id) |
| } |
| } |
| |
| /// Finds the `Item` that contains the given `LocalDefId` |
| fn item_for(tcx: TyCtxt<'_>, local_def_id: LocalDefId) -> LocalDefId { |
| match tcx.hir().find_by_def_id(local_def_id) { |
| Some(Node::Item(item)) => { |
| return item.def_id; |
| } |
| _ => {} |
| } |
| let item = { |
| let hir_id = tcx.hir().local_def_id_to_hir_id(local_def_id); |
| let mut parent_iter = tcx.hir().parent_iter(hir_id); |
| loop { |
| let node = parent_iter.next().map(|n| n.1); |
| match node { |
| Some(hir::Node::Item(item)) => break item.def_id, |
| Some(hir::Node::Crate(_)) | None => bug!("Called `item_for` on an Item."), |
| _ => {} |
| } |
| } |
| }; |
| item |
| } |
| |
| /// In traits, there is an implicit `Self` type parameter which comes before the generics. |
| /// We have to account for this when computing the index of the other generic parameters. |
| /// This function returns whether there is such an implicit parameter defined on the given item. |
| fn sub_items_have_self_param(node: &hir::ItemKind<'_>) -> bool { |
| matches!(*node, hir::ItemKind::Trait(..) | hir::ItemKind::TraitAlias(..)) |
| } |
| |
| fn late_region_as_bound_region<'tcx>(tcx: TyCtxt<'tcx>, region: &Region) -> ty::BoundVariableKind { |
| match region { |
| Region::LateBound(_, _, def_id) => { |
| let name = tcx.hir().name(tcx.hir().local_def_id_to_hir_id(def_id.expect_local())); |
| ty::BoundVariableKind::Region(ty::BrNamed(*def_id, name)) |
| } |
| _ => bug!("{:?} is not a late region", region), |
| } |
| } |
| |
| impl<'a, 'tcx> LifetimeContext<'a, 'tcx> { |
| /// Returns the binders in scope and the type of `Binder` that should be created for a poly trait ref. |
| fn poly_trait_ref_binder_info(&mut self) -> (Vec<ty::BoundVariableKind>, BinderScopeType) { |
| let mut scope = self.scope; |
| let mut supertrait_lifetimes = vec![]; |
| loop { |
| match scope { |
| Scope::Body { .. } | Scope::Root => { |
| break (vec![], BinderScopeType::Normal); |
| } |
| |
| Scope::Elision { s, .. } | Scope::ObjectLifetimeDefault { s, .. } => { |
| scope = s; |
| } |
| |
| Scope::Supertrait { s, lifetimes } => { |
| supertrait_lifetimes = lifetimes.clone(); |
| scope = s; |
| } |
| |
| Scope::TraitRefBoundary { .. } => { |
| // We should only see super trait lifetimes if there is a `Binder` above |
| assert!(supertrait_lifetimes.is_empty()); |
| break (vec![], BinderScopeType::Normal); |
| } |
| |
| Scope::Binder { hir_id, .. } => { |
| // Nested poly trait refs have the binders concatenated |
| let mut full_binders = |
| self.map.late_bound_vars.entry(*hir_id).or_default().clone(); |
| full_binders.extend(supertrait_lifetimes.into_iter()); |
| break (full_binders, BinderScopeType::Concatenating); |
| } |
| } |
| } |
| } |
| } |
| impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> { |
| type NestedFilter = nested_filter::All; |
| |
| fn nested_visit_map(&mut self) -> Self::Map { |
| self.tcx.hir() |
| } |
| |
| // We want to nest trait/impl items in their parent, but nothing else. |
| fn visit_nested_item(&mut self, _: hir::ItemId) {} |
| |
| fn visit_trait_item_ref(&mut self, ii: &'tcx hir::TraitItemRef) { |
| if !self.trait_definition_only { |
| intravisit::walk_trait_item_ref(self, ii) |
| } |
| } |
| |
| fn visit_nested_body(&mut self, body: hir::BodyId) { |
| let body = self.tcx.hir().body(body); |
| self.with(Scope::Body { id: body.id(), s: self.scope }, |this| { |
| this.visit_body(body); |
| }); |
| } |
| |
| fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) { |
| if let hir::ExprKind::Closure(hir::Closure { |
| binder, bound_generic_params, fn_decl, .. |
| }) = e.kind |
| { |
| if let &hir::ClosureBinder::For { span: for_sp, .. } = binder { |
| fn span_of_infer(ty: &hir::Ty<'_>) -> Option<Span> { |
| struct V(Option<Span>); |
| |
| impl<'v> Visitor<'v> for V { |
| fn visit_ty(&mut self, t: &'v hir::Ty<'v>) { |
| match t.kind { |
| _ if self.0.is_some() => (), |
| hir::TyKind::Infer => { |
| self.0 = Some(t.span); |
| } |
| _ => intravisit::walk_ty(self, t), |
| } |
| } |
| } |
| |
| let mut v = V(None); |
| v.visit_ty(ty); |
| v.0 |
| } |
| |
| let infer_in_rt_sp = match fn_decl.output { |
| hir::FnRetTy::DefaultReturn(sp) => Some(sp), |
| hir::FnRetTy::Return(ty) => span_of_infer(ty), |
| }; |
| |
| let infer_spans = fn_decl |
| .inputs |
| .into_iter() |
| .filter_map(span_of_infer) |
| .chain(infer_in_rt_sp) |
| .collect::<Vec<_>>(); |
| |
| if !infer_spans.is_empty() { |
| self.tcx.sess |
| .struct_span_err( |
| infer_spans, |
| "implicit types in closure signatures are forbidden when `for<...>` is present", |
| ) |
| .span_label(for_sp, "`for<...>` is here") |
| .emit(); |
| } |
| } |
| |
| let next_early_index = self.next_early_index(); |
| let (lifetimes, binders): (FxIndexMap<LocalDefId, Region>, Vec<_>) = |
| bound_generic_params |
| .iter() |
| .filter(|param| matches!(param.kind, GenericParamKind::Lifetime { .. })) |
| .enumerate() |
| .map(|(late_bound_idx, param)| { |
| let pair = Region::late(late_bound_idx as u32, self.tcx.hir(), param); |
| let r = late_region_as_bound_region(self.tcx, &pair.1); |
| (pair, r) |
| }) |
| .unzip(); |
| |
| self.map.late_bound_vars.insert(e.hir_id, binders); |
| let scope = Scope::Binder { |
| hir_id: e.hir_id, |
| lifetimes, |
| s: self.scope, |
| next_early_index, |
| opaque_type_parent: false, |
| scope_type: BinderScopeType::Normal, |
| where_bound_origin: None, |
| }; |
| |
| self.with(scope, |this| { |
| // a closure has no bounds, so everything |
| // contained within is scoped within its binder. |
| intravisit::walk_expr(this, e) |
| }); |
| } else { |
| intravisit::walk_expr(self, e) |
| } |
| } |
| |
| fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) { |
| match &item.kind { |
| hir::ItemKind::Impl(hir::Impl { of_trait, .. }) => { |
| if let Some(of_trait) = of_trait { |
| self.map.late_bound_vars.insert(of_trait.hir_ref_id, Vec::default()); |
| } |
| } |
| _ => {} |
| } |
| match item.kind { |
| hir::ItemKind::Fn(_, ref generics, _) => { |
| self.visit_early_late(None, item.hir_id(), generics, |this| { |
| intravisit::walk_item(this, item); |
| }); |
| } |
| |
| hir::ItemKind::ExternCrate(_) |
| | hir::ItemKind::Use(..) |
| | hir::ItemKind::Macro(..) |
| | hir::ItemKind::Mod(..) |
| | hir::ItemKind::ForeignMod { .. } |
| | hir::ItemKind::GlobalAsm(..) => { |
| // These sorts of items have no lifetime parameters at all. |
| intravisit::walk_item(self, item); |
| } |
| hir::ItemKind::Static(..) | hir::ItemKind::Const(..) => { |
| // No lifetime parameters, but implied 'static. |
| self.with(Scope::Elision { s: self.scope }, |this| { |
| intravisit::walk_item(this, item) |
| }); |
| } |
| hir::ItemKind::OpaqueTy(hir::OpaqueTy { .. }) => { |
| // Opaque types are visited when we visit the |
| // `TyKind::OpaqueDef`, so that they have the lifetimes from |
| // their parent opaque_ty in scope. |
| // |
| // The core idea here is that since OpaqueTys are generated with the impl Trait as |
| // their owner, we can keep going until we find the Item that owns that. We then |
| // conservatively add all resolved lifetimes. Otherwise we run into problems in |
| // cases like `type Foo<'a> = impl Bar<As = impl Baz + 'a>`. |
| for (_hir_id, node) in |
| self.tcx.hir().parent_iter(self.tcx.hir().local_def_id_to_hir_id(item.def_id)) |
| { |
| match node { |
| hir::Node::Item(parent_item) => { |
| let resolved_lifetimes: &ResolveLifetimes = |
| self.tcx.resolve_lifetimes(item_for(self.tcx, parent_item.def_id)); |
| // We need to add *all* deps, since opaque tys may want them from *us* |
| for (&owner, defs) in resolved_lifetimes.defs.iter() { |
| defs.iter().for_each(|(&local_id, region)| { |
| self.map.defs.insert(hir::HirId { owner, local_id }, *region); |
| }); |
| } |
| for (&owner, late_bound_vars) in |
| resolved_lifetimes.late_bound_vars.iter() |
| { |
| late_bound_vars.iter().for_each(|(&local_id, late_bound_vars)| { |
| self.map.late_bound_vars.insert( |
| hir::HirId { owner, local_id }, |
| late_bound_vars.clone(), |
| ); |
| }); |
| } |
| break; |
| } |
| hir::Node::Crate(_) => bug!("No Item about an OpaqueTy"), |
| _ => {} |
| } |
| } |
| } |
| hir::ItemKind::TyAlias(_, ref generics) |
| | hir::ItemKind::Enum(_, ref generics) |
| | hir::ItemKind::Struct(_, ref generics) |
| | hir::ItemKind::Union(_, ref generics) |
| | hir::ItemKind::Trait(_, _, ref generics, ..) |
| | hir::ItemKind::TraitAlias(ref generics, ..) |
| | hir::ItemKind::Impl(hir::Impl { ref generics, .. }) => { |
| // These kinds of items have only early-bound lifetime parameters. |
| let mut index = if sub_items_have_self_param(&item.kind) { |
| 1 // Self comes before lifetimes |
| } else { |
| 0 |
| }; |
| let mut non_lifetime_count = 0; |
| let lifetimes = generics |
| .params |
| .iter() |
| .filter_map(|param| match param.kind { |
| GenericParamKind::Lifetime { .. } => { |
| Some(Region::early(self.tcx.hir(), &mut index, param)) |
| } |
| GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => { |
| non_lifetime_count += 1; |
| None |
| } |
| }) |
| .collect(); |
| self.map.late_bound_vars.insert(item.hir_id(), vec![]); |
| let scope = Scope::Binder { |
| hir_id: item.hir_id(), |
| lifetimes, |
| next_early_index: index + non_lifetime_count, |
| opaque_type_parent: true, |
| scope_type: BinderScopeType::Normal, |
| s: ROOT_SCOPE, |
| where_bound_origin: None, |
| }; |
| self.with(scope, |this| { |
| let scope = Scope::TraitRefBoundary { s: this.scope }; |
| this.with(scope, |this| { |
| intravisit::walk_item(this, item); |
| }); |
| }); |
| } |
| } |
| } |
| |
| fn visit_foreign_item(&mut self, item: &'tcx hir::ForeignItem<'tcx>) { |
| match item.kind { |
| hir::ForeignItemKind::Fn(_, _, ref generics) => { |
| self.visit_early_late(None, item.hir_id(), generics, |this| { |
| intravisit::walk_foreign_item(this, item); |
| }) |
| } |
| hir::ForeignItemKind::Static(..) => { |
| intravisit::walk_foreign_item(self, item); |
| } |
| hir::ForeignItemKind::Type => { |
| intravisit::walk_foreign_item(self, item); |
| } |
| } |
| } |
| |
| #[tracing::instrument(level = "debug", skip(self))] |
| fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) { |
| match ty.kind { |
| hir::TyKind::BareFn(ref c) => { |
| let next_early_index = self.next_early_index(); |
| let (lifetimes, binders): (FxIndexMap<LocalDefId, Region>, Vec<_>) = c |
| .generic_params |
| .iter() |
| .filter(|param| matches!(param.kind, GenericParamKind::Lifetime { .. })) |
| .enumerate() |
| .map(|(late_bound_idx, param)| { |
| let pair = Region::late(late_bound_idx as u32, self.tcx.hir(), param); |
| let r = late_region_as_bound_region(self.tcx, &pair.1); |
| (pair, r) |
| }) |
| .unzip(); |
| self.map.late_bound_vars.insert(ty.hir_id, binders); |
| let scope = Scope::Binder { |
| hir_id: ty.hir_id, |
| lifetimes, |
| s: self.scope, |
| next_early_index, |
| opaque_type_parent: false, |
| scope_type: BinderScopeType::Normal, |
| where_bound_origin: None, |
| }; |
| self.with(scope, |this| { |
| // a bare fn has no bounds, so everything |
| // contained within is scoped within its binder. |
| intravisit::walk_ty(this, ty); |
| }); |
| } |
| hir::TyKind::TraitObject(bounds, ref lifetime, _) => { |
| debug!(?bounds, ?lifetime, "TraitObject"); |
| let scope = Scope::TraitRefBoundary { s: self.scope }; |
| self.with(scope, |this| { |
| for bound in bounds { |
| this.visit_poly_trait_ref(bound, hir::TraitBoundModifier::None); |
| } |
| }); |
| match lifetime.name { |
| LifetimeName::ImplicitObjectLifetimeDefault => { |
| // If the user does not write *anything*, we |
| // use the object lifetime defaulting |
| // rules. So e.g., `Box<dyn Debug>` becomes |
| // `Box<dyn Debug + 'static>`. |
| self.resolve_object_lifetime_default(lifetime) |
| } |
| LifetimeName::Infer => { |
| // If the user writes `'_`, we use the *ordinary* elision |
| // rules. So the `'_` in e.g., `Box<dyn Debug + '_>` will be |
| // resolved the same as the `'_` in `&'_ Foo`. |
| // |
| // cc #48468 |
| } |
| LifetimeName::Param(..) | LifetimeName::Static => { |
| // If the user wrote an explicit name, use that. |
| self.visit_lifetime(lifetime); |
| } |
| LifetimeName::Error => {} |
| } |
| } |
| hir::TyKind::Rptr(ref lifetime_ref, ref mt) => { |
| self.visit_lifetime(lifetime_ref); |
| let scope = Scope::ObjectLifetimeDefault { |
| lifetime: self.map.defs.get(&lifetime_ref.hir_id).cloned(), |
| s: self.scope, |
| }; |
| self.with(scope, |this| this.visit_ty(&mt.ty)); |
| } |
| hir::TyKind::OpaqueDef(item_id, lifetimes) => { |
| // Resolve the lifetimes in the bounds to the lifetime defs in the generics. |
| // `fn foo<'a>() -> impl MyTrait<'a> { ... }` desugars to |
| // `type MyAnonTy<'b> = impl MyTrait<'b>;` |
| // ^ ^ this gets resolved in the scope of |
| // the opaque_ty generics |
| let opaque_ty = self.tcx.hir().item(item_id); |
| let (generics, bounds) = match opaque_ty.kind { |
| hir::ItemKind::OpaqueTy(hir::OpaqueTy { |
| origin: hir::OpaqueTyOrigin::TyAlias, |
| .. |
| }) => { |
| intravisit::walk_ty(self, ty); |
| |
| // Elided lifetimes are not allowed in non-return |
| // position impl Trait |
| let scope = Scope::TraitRefBoundary { s: self.scope }; |
| self.with(scope, |this| { |
| let scope = Scope::Elision { s: this.scope }; |
| this.with(scope, |this| { |
| intravisit::walk_item(this, opaque_ty); |
| }) |
| }); |
| |
| return; |
| } |
| hir::ItemKind::OpaqueTy(hir::OpaqueTy { |
| origin: hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..), |
| ref generics, |
| bounds, |
| .. |
| }) => (generics, bounds), |
| ref i => bug!("`impl Trait` pointed to non-opaque type?? {:#?}", i), |
| }; |
| |
| // Resolve the lifetimes that are applied to the opaque type. |
| // These are resolved in the current scope. |
| // `fn foo<'a>() -> impl MyTrait<'a> { ... }` desugars to |
| // `fn foo<'a>() -> MyAnonTy<'a> { ... }` |
| // ^ ^this gets resolved in the current scope |
| for lifetime in lifetimes { |
| let hir::GenericArg::Lifetime(lifetime) = lifetime else { |
| continue |
| }; |
| self.visit_lifetime(lifetime); |
| |
| // Check for predicates like `impl for<'a> Trait<impl OtherTrait<'a>>` |
| // and ban them. Type variables instantiated inside binders aren't |
| // well-supported at the moment, so this doesn't work. |
| // In the future, this should be fixed and this error should be removed. |
| let def = self.map.defs.get(&lifetime.hir_id).cloned(); |
| let Some(Region::LateBound(_, _, def_id)) = def else { |
| continue |
| }; |
| let Some(def_id) = def_id.as_local() else { |
| continue |
| }; |
| let hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id); |
| // Ensure that the parent of the def is an item, not HRTB |
| let parent_id = self.tcx.hir().get_parent_node(hir_id); |
| if !parent_id.is_owner() { |
| if !self.trait_definition_only { |
| struct_span_err!( |
| self.tcx.sess, |
| lifetime.span, |
| E0657, |
| "`impl Trait` can only capture lifetimes \ |
| bound at the fn or impl level" |
| ) |
| .emit(); |
| } |
| self.uninsert_lifetime_on_error(lifetime, def.unwrap()); |
| } |
| if let hir::Node::Item(hir::Item { |
| kind: hir::ItemKind::OpaqueTy { .. }, .. |
| }) = self.tcx.hir().get(parent_id) |
| { |
| if !self.trait_definition_only { |
| let mut err = self.tcx.sess.struct_span_err( |
| lifetime.span, |
| "higher kinded lifetime bounds on nested opaque types are not supported yet", |
| ); |
| err.span_note(self.tcx.def_span(def_id), "lifetime declared here"); |
| err.emit(); |
| } |
| self.uninsert_lifetime_on_error(lifetime, def.unwrap()); |
| } |
| } |
| |
| // We want to start our early-bound indices at the end of the parent scope, |
| // not including any parent `impl Trait`s. |
| let mut index = self.next_early_index_for_opaque_type(); |
| debug!(?index); |
| |
| let mut lifetimes = FxIndexMap::default(); |
| let mut non_lifetime_count = 0; |
| debug!(?generics.params); |
| for param in generics.params { |
| match param.kind { |
| GenericParamKind::Lifetime { .. } => { |
| let (def_id, reg) = Region::early(self.tcx.hir(), &mut index, ¶m); |
| lifetimes.insert(def_id, reg); |
| } |
| GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => { |
| non_lifetime_count += 1; |
| } |
| } |
| } |
| let next_early_index = index + non_lifetime_count; |
| self.map.late_bound_vars.insert(ty.hir_id, vec![]); |
| |
| let scope = Scope::Binder { |
| hir_id: ty.hir_id, |
| lifetimes, |
| next_early_index, |
| s: self.scope, |
| opaque_type_parent: false, |
| scope_type: BinderScopeType::Normal, |
| where_bound_origin: None, |
| }; |
| self.with(scope, |this| { |
| let scope = Scope::TraitRefBoundary { s: this.scope }; |
| this.with(scope, |this| { |
| this.visit_generics(generics); |
| for bound in bounds { |
| this.visit_param_bound(bound); |
| } |
| }) |
| }); |
| } |
| _ => intravisit::walk_ty(self, ty), |
| } |
| } |
| |
| fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) { |
| use self::hir::TraitItemKind::*; |
| match trait_item.kind { |
| Fn(_, _) => { |
| let tcx = self.tcx; |
| self.visit_early_late( |
| Some(tcx.hir().get_parent_item(trait_item.hir_id())), |
| trait_item.hir_id(), |
| &trait_item.generics, |
| |this| intravisit::walk_trait_item(this, trait_item), |
| ); |
| } |
| Type(bounds, ref ty) => { |
| let generics = &trait_item.generics; |
| let mut index = self.next_early_index(); |
| debug!("visit_ty: index = {}", index); |
| let mut non_lifetime_count = 0; |
| let lifetimes = generics |
| .params |
| .iter() |
| .filter_map(|param| match param.kind { |
| GenericParamKind::Lifetime { .. } => { |
| Some(Region::early(self.tcx.hir(), &mut index, param)) |
| } |
| GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => { |
| non_lifetime_count += 1; |
| None |
| } |
| }) |
| .collect(); |
| self.map.late_bound_vars.insert(trait_item.hir_id(), vec![]); |
| let scope = Scope::Binder { |
| hir_id: trait_item.hir_id(), |
| lifetimes, |
| next_early_index: index + non_lifetime_count, |
| s: self.scope, |
| opaque_type_parent: true, |
| scope_type: BinderScopeType::Normal, |
| where_bound_origin: None, |
| }; |
| self.with(scope, |this| { |
| let scope = Scope::TraitRefBoundary { s: this.scope }; |
| this.with(scope, |this| { |
| this.visit_generics(generics); |
| for bound in bounds { |
| this.visit_param_bound(bound); |
| } |
| if let Some(ty) = ty { |
| this.visit_ty(ty); |
| } |
| }) |
| }); |
| } |
| Const(_, _) => { |
| // Only methods and types support generics. |
| assert!(trait_item.generics.params.is_empty()); |
| intravisit::walk_trait_item(self, trait_item); |
| } |
| } |
| } |
| |
| fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) { |
| use self::hir::ImplItemKind::*; |
| match impl_item.kind { |
| Fn(..) => { |
| let tcx = self.tcx; |
| self.visit_early_late( |
| Some(tcx.hir().get_parent_item(impl_item.hir_id())), |
| impl_item.hir_id(), |
| &impl_item.generics, |
| |this| intravisit::walk_impl_item(this, impl_item), |
| ); |
| } |
| TyAlias(ref ty) => { |
| let generics = &impl_item.generics; |
| let mut index = self.next_early_index(); |
| let mut non_lifetime_count = 0; |
| debug!("visit_ty: index = {}", index); |
| let lifetimes: FxIndexMap<LocalDefId, Region> = generics |
| .params |
| .iter() |
| .filter_map(|param| match param.kind { |
| GenericParamKind::Lifetime { .. } => { |
| Some(Region::early(self.tcx.hir(), &mut index, param)) |
| } |
| GenericParamKind::Const { .. } | GenericParamKind::Type { .. } => { |
| non_lifetime_count += 1; |
| None |
| } |
| }) |
| .collect(); |
| self.map.late_bound_vars.insert(ty.hir_id, vec![]); |
| let scope = Scope::Binder { |
| hir_id: ty.hir_id, |
| lifetimes, |
| next_early_index: index + non_lifetime_count, |
| s: self.scope, |
| opaque_type_parent: true, |
| scope_type: BinderScopeType::Normal, |
| where_bound_origin: None, |
| }; |
| self.with(scope, |this| { |
| let scope = Scope::TraitRefBoundary { s: this.scope }; |
| this.with(scope, |this| { |
| this.visit_generics(generics); |
| this.visit_ty(ty); |
| }) |
| }); |
| } |
| Const(_, _) => { |
| // Only methods and types support generics. |
| assert!(impl_item.generics.params.is_empty()); |
| intravisit::walk_impl_item(self, impl_item); |
| } |
| } |
| } |
| |
| #[tracing::instrument(level = "debug", skip(self))] |
| fn visit_lifetime(&mut self, lifetime_ref: &'tcx hir::Lifetime) { |
| match lifetime_ref.name { |
| hir::LifetimeName::Static => self.insert_lifetime(lifetime_ref, Region::Static), |
| hir::LifetimeName::Param(param_def_id, _) => { |
| self.resolve_lifetime_ref(param_def_id, lifetime_ref) |
| } |
| // If we've already reported an error, just ignore `lifetime_ref`. |
| hir::LifetimeName::Error => {} |
| // Those will be resolved by typechecking. |
| hir::LifetimeName::ImplicitObjectLifetimeDefault | hir::LifetimeName::Infer => {} |
| } |
| } |
| |
| fn visit_path(&mut self, path: &'tcx hir::Path<'tcx>, _: hir::HirId) { |
| for (i, segment) in path.segments.iter().enumerate() { |
| let depth = path.segments.len() - i - 1; |
| if let Some(ref args) = segment.args { |
| self.visit_segment_args(path.res, depth, args); |
| } |
| } |
| } |
| |
| fn visit_fn( |
| &mut self, |
| fk: intravisit::FnKind<'tcx>, |
| fd: &'tcx hir::FnDecl<'tcx>, |
| body_id: hir::BodyId, |
| _: Span, |
| _: hir::HirId, |
| ) { |
| let output = match fd.output { |
| hir::FnRetTy::DefaultReturn(_) => None, |
| hir::FnRetTy::Return(ref ty) => Some(&**ty), |
| }; |
| self.visit_fn_like_elision(&fd.inputs, output, matches!(fk, intravisit::FnKind::Closure)); |
| intravisit::walk_fn_kind(self, fk); |
| self.visit_nested_body(body_id) |
| } |
| |
| fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) { |
| let scope = Scope::TraitRefBoundary { s: self.scope }; |
| self.with(scope, |this| { |
| for param in generics.params { |
| match param.kind { |
| GenericParamKind::Lifetime { .. } => {} |
| GenericParamKind::Type { ref default, .. } => { |
| if let Some(ref ty) = default { |
| this.visit_ty(&ty); |
| } |
| } |
| GenericParamKind::Const { ref ty, default } => { |
| this.visit_ty(&ty); |
| if let Some(default) = default { |
| this.visit_body(this.tcx.hir().body(default.body)); |
| } |
| } |
| } |
| } |
| for predicate in generics.predicates { |
| match predicate { |
| &hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate { |
| ref bounded_ty, |
| bounds, |
| ref bound_generic_params, |
| origin, |
| .. |
| }) => { |
| let (lifetimes, binders): (FxIndexMap<LocalDefId, Region>, Vec<_>) = |
| bound_generic_params |
| .iter() |
| .filter(|param| { |
| matches!(param.kind, GenericParamKind::Lifetime { .. }) |
| }) |
| .enumerate() |
| .map(|(late_bound_idx, param)| { |
| let pair = |
| Region::late(late_bound_idx as u32, this.tcx.hir(), param); |
| let r = late_region_as_bound_region(this.tcx, &pair.1); |
| (pair, r) |
| }) |
| .unzip(); |
| this.map.late_bound_vars.insert(bounded_ty.hir_id, binders.clone()); |
| let next_early_index = this.next_early_index(); |
| // Even if there are no lifetimes defined here, we still wrap it in a binder |
| // scope. If there happens to be a nested poly trait ref (an error), that |
| // will be `Concatenating` anyways, so we don't have to worry about the depth |
| // being wrong. |
| let scope = Scope::Binder { |
| hir_id: bounded_ty.hir_id, |
| lifetimes, |
| s: this.scope, |
| next_early_index, |
| opaque_type_parent: false, |
| scope_type: BinderScopeType::Normal, |
| where_bound_origin: Some(origin), |
| }; |
| this.with(scope, |this| { |
| this.visit_ty(&bounded_ty); |
| walk_list!(this, visit_param_bound, bounds); |
| }) |
| } |
| &hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate { |
| ref lifetime, |
| bounds, |
| .. |
| }) => { |
| this.visit_lifetime(lifetime); |
| walk_list!(this, visit_param_bound, bounds); |
| |
| if lifetime.name != hir::LifetimeName::Static { |
| for bound in bounds { |
| let hir::GenericBound::Outlives(ref lt) = bound else { |
| continue; |
| }; |
| if lt.name != hir::LifetimeName::Static { |
| continue; |
| } |
| this.insert_lifetime(lt, Region::Static); |
| this.tcx |
| .sess |
| .struct_span_warn( |
| lifetime.span, |
| &format!( |
| "unnecessary lifetime parameter `{}`", |
| lifetime.name.ident(), |
| ), |
| ) |
| .help(&format!( |
| "you can use the `'static` lifetime directly, in place of `{}`", |
| lifetime.name.ident(), |
| )) |
| .emit(); |
| } |
| } |
| } |
| &hir::WherePredicate::EqPredicate(hir::WhereEqPredicate { |
| ref lhs_ty, |
| ref rhs_ty, |
| .. |
| }) => { |
| this.visit_ty(lhs_ty); |
| this.visit_ty(rhs_ty); |
| } |
| } |
| } |
| }) |
| } |
| |
| fn visit_param_bound(&mut self, bound: &'tcx hir::GenericBound<'tcx>) { |
| match bound { |
| hir::GenericBound::LangItemTrait(_, _, hir_id, _) => { |
| // FIXME(jackh726): This is pretty weird. `LangItemTrait` doesn't go |
| // through the regular poly trait ref code, so we don't get another |
| // chance to introduce a binder. For now, I'm keeping the existing logic |
| // of "if there isn't a Binder scope above us, add one", but I |
| // imagine there's a better way to go about this. |
| let (binders, scope_type) = self.poly_trait_ref_binder_info(); |
| |
| self.map.late_bound_vars.insert(*hir_id, binders); |
| let scope = Scope::Binder { |
| hir_id: *hir_id, |
| lifetimes: FxIndexMap::default(), |
| s: self.scope, |
| next_early_index: self.next_early_index(), |
| opaque_type_parent: false, |
| scope_type, |
| where_bound_origin: None, |
| }; |
| self.with(scope, |this| { |
| intravisit::walk_param_bound(this, bound); |
| }); |
| } |
| _ => intravisit::walk_param_bound(self, bound), |
| } |
| } |
| |
| fn visit_poly_trait_ref( |
| &mut self, |
| trait_ref: &'tcx hir::PolyTraitRef<'tcx>, |
| _modifier: hir::TraitBoundModifier, |
| ) { |
| debug!("visit_poly_trait_ref(trait_ref={:?})", trait_ref); |
| |
| let next_early_index = self.next_early_index(); |
| let (mut binders, scope_type) = self.poly_trait_ref_binder_info(); |
| |
| let initial_bound_vars = binders.len() as u32; |
| let mut lifetimes: FxIndexMap<LocalDefId, Region> = FxIndexMap::default(); |
| let binders_iter = trait_ref |
| .bound_generic_params |
| .iter() |
| .filter(|param| matches!(param.kind, GenericParamKind::Lifetime { .. })) |
| .enumerate() |
| .map(|(late_bound_idx, param)| { |
| let pair = |
| Region::late(initial_bound_vars + late_bound_idx as u32, self.tcx.hir(), param); |
| let r = late_region_as_bound_region(self.tcx, &pair.1); |
| lifetimes.insert(pair.0, pair.1); |
| r |
| }); |
| binders.extend(binders_iter); |
| |
| debug!(?binders); |
| self.map.late_bound_vars.insert(trait_ref.trait_ref.hir_ref_id, binders); |
| |
| // Always introduce a scope here, even if this is in a where clause and |
| // we introduced the binders around the bounded Ty. In that case, we |
| // just reuse the concatenation functionality also present in nested trait |
| // refs. |
| let scope = Scope::Binder { |
| hir_id: trait_ref.trait_ref.hir_ref_id, |
| lifetimes, |
| s: self.scope, |
| next_early_index, |
| opaque_type_parent: false, |
| scope_type, |
| where_bound_origin: None, |
| }; |
| self.with(scope, |this| { |
| walk_list!(this, visit_generic_param, trait_ref.bound_generic_params); |
| this.visit_trait_ref(&trait_ref.trait_ref); |
| }); |
| } |
| } |
| |
| fn compute_object_lifetime_defaults<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| item: &hir::Item<'_>, |
| ) -> Option<&'tcx [ObjectLifetimeDefault]> { |
| match item.kind { |
| hir::ItemKind::Struct(_, ref generics) |
| | hir::ItemKind::Union(_, ref generics) |
| | hir::ItemKind::Enum(_, ref generics) |
| | hir::ItemKind::OpaqueTy(hir::OpaqueTy { |
| ref generics, |
| origin: hir::OpaqueTyOrigin::TyAlias, |
| .. |
| }) |
| | hir::ItemKind::TyAlias(_, ref generics) |
| | hir::ItemKind::Trait(_, _, ref generics, ..) => { |
| let result = object_lifetime_defaults_for_item(tcx, generics); |
| |
| // Debugging aid. |
| let attrs = tcx.hir().attrs(item.hir_id()); |
| if tcx.sess.contains_name(attrs, sym::rustc_object_lifetime_default) { |
| let object_lifetime_default_reprs: String = result |
| .iter() |
| .map(|set| match *set { |
| Set1::Empty => "BaseDefault".into(), |
| Set1::One(Region::Static) => "'static".into(), |
| Set1::One(Region::EarlyBound(mut i, _)) => generics |
| .params |
| .iter() |
| .find_map(|param| match param.kind { |
| GenericParamKind::Lifetime { .. } => { |
| if i == 0 { |
| return Some(param.name.ident().to_string().into()); |
| } |
| i -= 1; |
| None |
| } |
| _ => None, |
| }) |
| .unwrap(), |
| Set1::One(_) => bug!(), |
| Set1::Many => "Ambiguous".into(), |
| }) |
| .collect::<Vec<Cow<'static, str>>>() |
| .join(","); |
| tcx.sess.span_err(item.span, &object_lifetime_default_reprs); |
| } |
| |
| Some(result) |
| } |
| _ => None, |
| } |
| } |
| |
| /// Scan the bounds and where-clauses on parameters to extract bounds |
| /// of the form `T:'a` so as to determine the `ObjectLifetimeDefault` |
| /// for each type parameter. |
| fn object_lifetime_defaults_for_item<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| generics: &hir::Generics<'_>, |
| ) -> &'tcx [ObjectLifetimeDefault] { |
| fn add_bounds(set: &mut Set1<hir::LifetimeName>, bounds: &[hir::GenericBound<'_>]) { |
| for bound in bounds { |
| if let hir::GenericBound::Outlives(ref lifetime) = *bound { |
| set.insert(lifetime.name.normalize_to_macros_2_0()); |
| } |
| } |
| } |
| |
| let process_param = |param: &hir::GenericParam<'_>| match param.kind { |
| GenericParamKind::Lifetime { .. } => None, |
| GenericParamKind::Type { .. } => { |
| let mut set = Set1::Empty; |
| |
| let param_def_id = tcx.hir().local_def_id(param.hir_id); |
| for predicate in generics.predicates { |
| // Look for `type: ...` where clauses. |
| let hir::WherePredicate::BoundPredicate(ref data) = *predicate else { continue }; |
| |
| // Ignore `for<'a> type: ...` as they can change what |
| // lifetimes mean (although we could "just" handle it). |
| if !data.bound_generic_params.is_empty() { |
| continue; |
| } |
| |
| let res = match data.bounded_ty.kind { |
| hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => path.res, |
| _ => continue, |
| }; |
| |
| if res == Res::Def(DefKind::TyParam, param_def_id.to_def_id()) { |
| add_bounds(&mut set, &data.bounds); |
| } |
| } |
| |
| Some(match set { |
| Set1::Empty => Set1::Empty, |
| Set1::One(name) => { |
| if name == hir::LifetimeName::Static { |
| Set1::One(Region::Static) |
| } else { |
| generics |
| .params |
| .iter() |
| .filter_map(|param| match param.kind { |
| GenericParamKind::Lifetime { .. } => { |
| let param_def_id = tcx.hir().local_def_id(param.hir_id); |
| Some(( |
| param_def_id, |
| hir::LifetimeName::Param(param_def_id, param.name), |
| )) |
| } |
| _ => None, |
| }) |
| .enumerate() |
| .find(|&(_, (_, lt_name))| lt_name == name) |
| .map_or(Set1::Many, |(i, (def_id, _))| { |
| Set1::One(Region::EarlyBound(i as u32, def_id.to_def_id())) |
| }) |
| } |
| } |
| Set1::Many => Set1::Many, |
| }) |
| } |
| GenericParamKind::Const { .. } => { |
| // Generic consts don't impose any constraints. |
| // |
| // We still store a dummy value here to allow generic parameters |
| // in an arbitrary order. |
| Some(Set1::Empty) |
| } |
| }; |
| |
| tcx.arena.alloc_from_iter(generics.params.iter().filter_map(process_param)) |
| } |
| |
| impl<'a, 'tcx> LifetimeContext<'a, 'tcx> { |
| fn with<F>(&mut self, wrap_scope: Scope<'_>, f: F) |
| where |
| F: for<'b> FnOnce(&mut LifetimeContext<'b, 'tcx>), |
| { |
| let LifetimeContext { tcx, map, .. } = self; |
| let xcrate_object_lifetime_defaults = take(&mut self.xcrate_object_lifetime_defaults); |
| let mut this = LifetimeContext { |
| tcx: *tcx, |
| map, |
| scope: &wrap_scope, |
| trait_definition_only: self.trait_definition_only, |
| xcrate_object_lifetime_defaults, |
| }; |
| let span = tracing::debug_span!("scope", scope = ?TruncatedScopeDebug(&this.scope)); |
| { |
| let _enter = span.enter(); |
| f(&mut this); |
| } |
| self.xcrate_object_lifetime_defaults = this.xcrate_object_lifetime_defaults; |
| } |
| |
| /// Visits self by adding a scope and handling recursive walk over the contents with `walk`. |
| /// |
| /// Handles visiting fns and methods. These are a bit complicated because we must distinguish |
| /// early- vs late-bound lifetime parameters. We do this by checking which lifetimes appear |
| /// within type bounds; those are early bound lifetimes, and the rest are late bound. |
| /// |
| /// For example: |
| /// |
| /// fn foo<'a,'b,'c,T:Trait<'b>>(...) |
| /// |
| /// Here `'a` and `'c` are late bound but `'b` is early bound. Note that early- and late-bound |
| /// lifetimes may be interspersed together. |
| /// |
| /// If early bound lifetimes are present, we separate them into their own list (and likewise |
| /// for late bound). They will be numbered sequentially, starting from the lowest index that is |
| /// already in scope (for a fn item, that will be 0, but for a method it might not be). Late |
| /// bound lifetimes are resolved by name and associated with a binder ID (`binder_id`), so the |
| /// ordering is not important there. |
| fn visit_early_late<F>( |
| &mut self, |
| parent_id: Option<LocalDefId>, |
| hir_id: hir::HirId, |
| generics: &'tcx hir::Generics<'tcx>, |
| walk: F, |
| ) where |
| F: for<'b, 'c> FnOnce(&'b mut LifetimeContext<'c, 'tcx>), |
| { |
| // Find the start of nested early scopes, e.g., in methods. |
| let mut next_early_index = 0; |
| if let Some(parent_id) = parent_id { |
| let parent = self.tcx.hir().expect_item(parent_id); |
| if sub_items_have_self_param(&parent.kind) { |
| next_early_index += 1; // Self comes before lifetimes |
| } |
| match parent.kind { |
| hir::ItemKind::Trait(_, _, ref generics, ..) |
| | hir::ItemKind::Impl(hir::Impl { ref generics, .. }) => { |
| next_early_index += generics.params.len() as u32; |
| } |
| _ => {} |
| } |
| } |
| |
| let mut non_lifetime_count = 0; |
| let mut named_late_bound_vars = 0; |
| let lifetimes: FxIndexMap<LocalDefId, Region> = generics |
| .params |
| .iter() |
| .filter_map(|param| match param.kind { |
| GenericParamKind::Lifetime { .. } => { |
| if self.tcx.is_late_bound(param.hir_id) { |
| let late_bound_idx = named_late_bound_vars; |
| named_late_bound_vars += 1; |
| Some(Region::late(late_bound_idx, self.tcx.hir(), param)) |
| } else { |
| Some(Region::early(self.tcx.hir(), &mut next_early_index, param)) |
| } |
| } |
| GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => { |
| non_lifetime_count += 1; |
| None |
| } |
| }) |
| .collect(); |
| let next_early_index = next_early_index + non_lifetime_count; |
| |
| let binders: Vec<_> = generics |
| .params |
| .iter() |
| .filter(|param| { |
| matches!(param.kind, GenericParamKind::Lifetime { .. }) |
| && self.tcx.is_late_bound(param.hir_id) |
| }) |
| .enumerate() |
| .map(|(late_bound_idx, param)| { |
| let pair = Region::late(late_bound_idx as u32, self.tcx.hir(), param); |
| late_region_as_bound_region(self.tcx, &pair.1) |
| }) |
| .collect(); |
| self.map.late_bound_vars.insert(hir_id, binders); |
| let scope = Scope::Binder { |
| hir_id, |
| lifetimes, |
| next_early_index, |
| s: self.scope, |
| opaque_type_parent: true, |
| scope_type: BinderScopeType::Normal, |
| where_bound_origin: None, |
| }; |
| self.with(scope, walk); |
| } |
| |
| fn next_early_index_helper(&self, only_opaque_type_parent: bool) -> u32 { |
| let mut scope = self.scope; |
| loop { |
| match *scope { |
| Scope::Root => return 0, |
| |
| Scope::Binder { next_early_index, opaque_type_parent, .. } |
| if (!only_opaque_type_parent || opaque_type_parent) => |
| { |
| return next_early_index; |
| } |
| |
| Scope::Binder { s, .. } |
| | Scope::Body { s, .. } |
| | Scope::Elision { s, .. } |
| | Scope::ObjectLifetimeDefault { s, .. } |
| | Scope::Supertrait { s, .. } |
| | Scope::TraitRefBoundary { s, .. } => scope = s, |
| } |
| } |
| } |
| |
| /// Returns the next index one would use for an early-bound-region |
| /// if extending the current scope. |
| fn next_early_index(&self) -> u32 { |
| self.next_early_index_helper(true) |
| } |
| |
| /// Returns the next index one would use for an `impl Trait` that |
| /// is being converted into an opaque type alias `impl Trait`. This will be the |
| /// next early index from the enclosing item, for the most |
| /// part. See the `opaque_type_parent` field for more info. |
| fn next_early_index_for_opaque_type(&self) -> u32 { |
| self.next_early_index_helper(false) |
| } |
| |
| #[tracing::instrument(level = "debug", skip(self))] |
| fn resolve_lifetime_ref( |
| &mut self, |
| region_def_id: LocalDefId, |
| lifetime_ref: &'tcx hir::Lifetime, |
| ) { |
| // Walk up the scope chain, tracking the number of fn scopes |
| // that we pass through, until we find a lifetime with the |
| // given name or we run out of scopes. |
| // search. |
| let mut late_depth = 0; |
| let mut scope = self.scope; |
| let mut outermost_body = None; |
| let result = loop { |
| match *scope { |
| Scope::Body { id, s } => { |
| outermost_body = Some(id); |
| scope = s; |
| } |
| |
| Scope::Root => { |
| break None; |
| } |
| |
| Scope::Binder { ref lifetimes, scope_type, s, where_bound_origin, .. } => { |
| if let Some(&def) = lifetimes.get(®ion_def_id) { |
| break Some(def.shifted(late_depth)); |
| } |
| match scope_type { |
| BinderScopeType::Normal => late_depth += 1, |
| BinderScopeType::Concatenating => {} |
| } |
| // Fresh lifetimes in APIT used to be allowed in async fns and forbidden in |
| // regular fns. |
| if let Some(hir::PredicateOrigin::ImplTrait) = where_bound_origin |
| && let hir::LifetimeName::Param(_, hir::ParamName::Fresh) = lifetime_ref.name |
| && let hir::IsAsync::NotAsync = self.tcx.asyncness(lifetime_ref.hir_id.owner) |
| && !self.tcx.features().anonymous_lifetime_in_impl_trait |
| { |
| rustc_session::parse::feature_err( |
| &self.tcx.sess.parse_sess, |
| sym::anonymous_lifetime_in_impl_trait, |
| lifetime_ref.span, |
| "anonymous lifetimes in `impl Trait` are unstable", |
| ).emit(); |
| return; |
| } |
| scope = s; |
| } |
| |
| Scope::Elision { s, .. } |
| | Scope::ObjectLifetimeDefault { s, .. } |
| | Scope::Supertrait { s, .. } |
| | Scope::TraitRefBoundary { s, .. } => { |
| scope = s; |
| } |
| } |
| }; |
| |
| if let Some(mut def) = result { |
| if let Region::EarlyBound(..) = def { |
| // Do not free early-bound regions, only late-bound ones. |
| } else if let Some(body_id) = outermost_body { |
| let fn_id = self.tcx.hir().body_owner(body_id); |
| match self.tcx.hir().get(fn_id) { |
| Node::Item(&hir::Item { kind: hir::ItemKind::Fn(..), .. }) |
| | Node::TraitItem(&hir::TraitItem { |
| kind: hir::TraitItemKind::Fn(..), .. |
| }) |
| | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) => { |
| let scope = self.tcx.hir().local_def_id(fn_id); |
| def = Region::Free(scope.to_def_id(), def.id().unwrap()); |
| } |
| _ => {} |
| } |
| } |
| |
| self.insert_lifetime(lifetime_ref, def); |
| return; |
| } |
| |
| // We may fail to resolve higher-ranked lifetimes that are mentionned by APIT. |
| // AST-based resolution does not care for impl-trait desugaring, which are the |
| // responibility of lowering. This may create a mismatch between the resolution |
| // AST found (`region_def_id`) which points to HRTB, and what HIR allows. |
| // ``` |
| // fn foo(x: impl for<'a> Trait<'a, Assoc = impl Copy + 'a>) {} |
| // ``` |
| // |
| // In such case, walk back the binders to diagnose it properly. |
| let mut scope = self.scope; |
| loop { |
| match *scope { |
| Scope::Binder { |
| where_bound_origin: Some(hir::PredicateOrigin::ImplTrait), .. |
| } => { |
| let mut err = self.tcx.sess.struct_span_err( |
| lifetime_ref.span, |
| "`impl Trait` can only mention lifetimes bound at the fn or impl level", |
| ); |
| err.span_note(self.tcx.def_span(region_def_id), "lifetime declared here"); |
| err.emit(); |
| return; |
| } |
| Scope::Root => break, |
| Scope::Binder { s, .. } |
| | Scope::Body { s, .. } |
| | Scope::Elision { s, .. } |
| | Scope::ObjectLifetimeDefault { s, .. } |
| | Scope::Supertrait { s, .. } |
| | Scope::TraitRefBoundary { s, .. } => { |
| scope = s; |
| } |
| } |
| } |
| |
| self.tcx.sess.delay_span_bug( |
| lifetime_ref.span, |
| &format!("Could not resolve {:?} in scope {:#?}", lifetime_ref, self.scope,), |
| ); |
| } |
| |
| fn visit_segment_args( |
| &mut self, |
| res: Res, |
| depth: usize, |
| generic_args: &'tcx hir::GenericArgs<'tcx>, |
| ) { |
| debug!( |
| "visit_segment_args(res={:?}, depth={:?}, generic_args={:?})", |
| res, depth, generic_args, |
| ); |
| |
| if generic_args.parenthesized { |
| self.visit_fn_like_elision( |
| generic_args.inputs(), |
| Some(generic_args.bindings[0].ty()), |
| false, |
| ); |
| return; |
| } |
| |
| for arg in generic_args.args { |
| if let hir::GenericArg::Lifetime(lt) = arg { |
| self.visit_lifetime(lt); |
| } |
| } |
| |
| // Figure out if this is a type/trait segment, |
| // which requires object lifetime defaults. |
| let parent_def_id = |this: &mut Self, def_id: DefId| { |
| let def_key = this.tcx.def_key(def_id); |
| DefId { krate: def_id.krate, index: def_key.parent.expect("missing parent") } |
| }; |
| let type_def_id = match res { |
| Res::Def(DefKind::AssocTy, def_id) if depth == 1 => Some(parent_def_id(self, def_id)), |
| Res::Def(DefKind::Variant, def_id) if depth == 0 => Some(parent_def_id(self, def_id)), |
| Res::Def( |
| DefKind::Struct |
| | DefKind::Union |
| | DefKind::Enum |
| | DefKind::TyAlias |
| | DefKind::Trait, |
| def_id, |
| ) if depth == 0 => Some(def_id), |
| _ => None, |
| }; |
| |
| debug!("visit_segment_args: type_def_id={:?}", type_def_id); |
| |
| // Compute a vector of defaults, one for each type parameter, |
| // per the rules given in RFCs 599 and 1156. Example: |
| // |
| // ```rust |
| // struct Foo<'a, T: 'a, U> { } |
| // ``` |
| // |
| // If you have `Foo<'x, dyn Bar, dyn Baz>`, we want to default |
| // `dyn Bar` to `dyn Bar + 'x` (because of the `T: 'a` bound) |
| // and `dyn Baz` to `dyn Baz + 'static` (because there is no |
| // such bound). |
| // |
| // Therefore, we would compute `object_lifetime_defaults` to a |
| // vector like `['x, 'static]`. Note that the vector only |
| // includes type parameters. |
| let object_lifetime_defaults = type_def_id.map_or_else(Vec::new, |def_id| { |
| let in_body = { |
| let mut scope = self.scope; |
| loop { |
| match *scope { |
| Scope::Root => break false, |
| |
| Scope::Body { .. } => break true, |
| |
| Scope::Binder { s, .. } |
| | Scope::Elision { s, .. } |
| | Scope::ObjectLifetimeDefault { s, .. } |
| | Scope::Supertrait { s, .. } |
| | Scope::TraitRefBoundary { s, .. } => { |
| scope = s; |
| } |
| } |
| } |
| }; |
| |
| let map = &self.map; |
| let set_to_region = |set: &ObjectLifetimeDefault| match *set { |
| Set1::Empty => { |
| if in_body { |
| None |
| } else { |
| Some(Region::Static) |
| } |
| } |
| Set1::One(r) => { |
| let lifetimes = generic_args.args.iter().filter_map(|arg| match arg { |
| GenericArg::Lifetime(lt) => Some(lt), |
| _ => None, |
| }); |
| r.subst(lifetimes, map) |
| } |
| Set1::Many => None, |
| }; |
| if let Some(def_id) = def_id.as_local() { |
| let id = self.tcx.hir().local_def_id_to_hir_id(def_id); |
| self.tcx |
| .object_lifetime_defaults(id.owner) |
| .unwrap() |
| .iter() |
| .map(set_to_region) |
| .collect() |
| } else { |
| let tcx = self.tcx; |
| self.xcrate_object_lifetime_defaults |
| .entry(def_id) |
| .or_insert_with(|| { |
| tcx.generics_of(def_id) |
| .params |
| .iter() |
| .filter_map(|param| match param.kind { |
| GenericParamDefKind::Type { object_lifetime_default, .. } => { |
| Some(object_lifetime_default) |
| } |
| GenericParamDefKind::Const { .. } => Some(Set1::Empty), |
| GenericParamDefKind::Lifetime => None, |
| }) |
| .collect() |
| }) |
| .iter() |
| .map(set_to_region) |
| .collect() |
| } |
| }); |
| |
| debug!("visit_segment_args: object_lifetime_defaults={:?}", object_lifetime_defaults); |
| |
| let mut i = 0; |
| for arg in generic_args.args { |
| match arg { |
| GenericArg::Lifetime(_) => {} |
| GenericArg::Type(ty) => { |
| if let Some(<) = object_lifetime_defaults.get(i) { |
| let scope = Scope::ObjectLifetimeDefault { lifetime: lt, s: self.scope }; |
| self.with(scope, |this| this.visit_ty(ty)); |
| } else { |
| self.visit_ty(ty); |
| } |
| i += 1; |
| } |
| GenericArg::Const(ct) => { |
| self.visit_anon_const(&ct.value); |
| i += 1; |
| } |
| GenericArg::Infer(inf) => { |
| self.visit_id(inf.hir_id); |
| i += 1; |
| } |
| } |
| } |
| |
| // Hack: when resolving the type `XX` in binding like `dyn |
| // Foo<'b, Item = XX>`, the current object-lifetime default |
| // would be to examine the trait `Foo` to check whether it has |
| // a lifetime bound declared on `Item`. e.g., if `Foo` is |
| // declared like so, then the default object lifetime bound in |
| // `XX` should be `'b`: |
| // |
| // ```rust |
| // trait Foo<'a> { |
| // type Item: 'a; |
| // } |
| // ``` |
| // |
| // but if we just have `type Item;`, then it would be |
| // `'static`. However, we don't get all of this logic correct. |
| // |
| // Instead, we do something hacky: if there are no lifetime parameters |
| // to the trait, then we simply use a default object lifetime |
| // bound of `'static`, because there is no other possibility. On the other hand, |
| // if there ARE lifetime parameters, then we require the user to give an |
| // explicit bound for now. |
| // |
| // This is intended to leave room for us to implement the |
| // correct behavior in the future. |
| let has_lifetime_parameter = |
| generic_args.args.iter().any(|arg| matches!(arg, GenericArg::Lifetime(_))); |
| |
| // Resolve lifetimes found in the bindings, so either in the type `XX` in `Item = XX` or |
| // in the trait ref `YY<...>` in `Item: YY<...>`. |
| for binding in generic_args.bindings { |
| let scope = Scope::ObjectLifetimeDefault { |
| lifetime: if has_lifetime_parameter { None } else { Some(Region::Static) }, |
| s: self.scope, |
| }; |
| if let Some(type_def_id) = type_def_id { |
| let lifetimes = LifetimeContext::supertrait_hrtb_lifetimes( |
| self.tcx, |
| type_def_id, |
| binding.ident, |
| ); |
| self.with(scope, |this| { |
| let scope = Scope::Supertrait { |
| lifetimes: lifetimes.unwrap_or_default(), |
| s: this.scope, |
| }; |
| this.with(scope, |this| this.visit_assoc_type_binding(binding)); |
| }); |
| } else { |
| self.with(scope, |this| this.visit_assoc_type_binding(binding)); |
| } |
| } |
| } |
| |
| /// Returns all the late-bound vars that come into scope from supertrait HRTBs, based on the |
| /// associated type name and starting trait. |
| /// For example, imagine we have |
| /// ```ignore (illustrative) |
| /// trait Foo<'a, 'b> { |
| /// type As; |
| /// } |
| /// trait Bar<'b>: for<'a> Foo<'a, 'b> {} |
| /// trait Bar: for<'b> Bar<'b> {} |
| /// ``` |
| /// In this case, if we wanted to the supertrait HRTB lifetimes for `As` on |
| /// the starting trait `Bar`, we would return `Some(['b, 'a])`. |
| fn supertrait_hrtb_lifetimes( |
| tcx: TyCtxt<'tcx>, |
| def_id: DefId, |
| assoc_name: Ident, |
| ) -> Option<Vec<ty::BoundVariableKind>> { |
| let trait_defines_associated_type_named = |trait_def_id: DefId| { |
| tcx.associated_items(trait_def_id) |
| .find_by_name_and_kind(tcx, assoc_name, ty::AssocKind::Type, trait_def_id) |
| .is_some() |
| }; |
| |
| use smallvec::{smallvec, SmallVec}; |
| let mut stack: SmallVec<[(DefId, SmallVec<[ty::BoundVariableKind; 8]>); 8]> = |
| smallvec![(def_id, smallvec![])]; |
| let mut visited: FxHashSet<DefId> = FxHashSet::default(); |
| loop { |
| let Some((def_id, bound_vars)) = stack.pop() else { |
| break None; |
| }; |
| // See issue #83753. If someone writes an associated type on a non-trait, just treat it as |
| // there being no supertrait HRTBs. |
| match tcx.def_kind(def_id) { |
| DefKind::Trait | DefKind::TraitAlias | DefKind::Impl => {} |
| _ => break None, |
| } |
| |
| if trait_defines_associated_type_named(def_id) { |
| break Some(bound_vars.into_iter().collect()); |
| } |
| let predicates = |
| tcx.super_predicates_that_define_assoc_type((def_id, Some(assoc_name))); |
| let obligations = predicates.predicates.iter().filter_map(|&(pred, _)| { |
| let bound_predicate = pred.kind(); |
| match bound_predicate.skip_binder() { |
| ty::PredicateKind::Trait(data) => { |
| // The order here needs to match what we would get from `subst_supertrait` |
| let pred_bound_vars = bound_predicate.bound_vars(); |
| let mut all_bound_vars = bound_vars.clone(); |
| all_bound_vars.extend(pred_bound_vars.iter()); |
| let super_def_id = data.trait_ref.def_id; |
| Some((super_def_id, all_bound_vars)) |
| } |
| _ => None, |
| } |
| }); |
| |
| let obligations = obligations.filter(|o| visited.insert(o.0)); |
| stack.extend(obligations); |
| } |
| } |
| |
| #[tracing::instrument(level = "debug", skip(self))] |
| fn visit_fn_like_elision( |
| &mut self, |
| inputs: &'tcx [hir::Ty<'tcx>], |
| output: Option<&'tcx hir::Ty<'tcx>>, |
| in_closure: bool, |
| ) { |
| self.with(Scope::Elision { s: self.scope }, |this| { |
| for input in inputs { |
| this.visit_ty(input); |
| } |
| if !in_closure && let Some(output) = output { |
| this.visit_ty(output); |
| } |
| }); |
| if in_closure && let Some(output) = output { |
| self.visit_ty(output); |
| } |
| } |
| |
| fn resolve_object_lifetime_default(&mut self, lifetime_ref: &'tcx hir::Lifetime) { |
| debug!("resolve_object_lifetime_default(lifetime_ref={:?})", lifetime_ref); |
| let mut late_depth = 0; |
| let mut scope = self.scope; |
| let lifetime = loop { |
| match *scope { |
| Scope::Binder { s, scope_type, .. } => { |
| match scope_type { |
| BinderScopeType::Normal => late_depth += 1, |
| BinderScopeType::Concatenating => {} |
| } |
| scope = s; |
| } |
| |
| Scope::Root | Scope::Elision { .. } => break Region::Static, |
| |
| Scope::Body { .. } | Scope::ObjectLifetimeDefault { lifetime: None, .. } => return, |
| |
| Scope::ObjectLifetimeDefault { lifetime: Some(l), .. } => break l, |
| |
| Scope::Supertrait { s, .. } | Scope::TraitRefBoundary { s, .. } => { |
| scope = s; |
| } |
| } |
| }; |
| self.insert_lifetime(lifetime_ref, lifetime.shifted(late_depth)); |
| } |
| |
| #[tracing::instrument(level = "debug", skip(self))] |
| fn insert_lifetime(&mut self, lifetime_ref: &'tcx hir::Lifetime, def: Region) { |
| debug!( |
| node = ?self.tcx.hir().node_to_string(lifetime_ref.hir_id), |
| span = ?self.tcx.sess.source_map().span_to_diagnostic_string(lifetime_ref.span) |
| ); |
| self.map.defs.insert(lifetime_ref.hir_id, def); |
| } |
| |
| /// Sometimes we resolve a lifetime, but later find that it is an |
| /// error (esp. around impl trait). In that case, we remove the |
| /// entry into `map.defs` so as not to confuse later code. |
| fn uninsert_lifetime_on_error(&mut self, lifetime_ref: &'tcx hir::Lifetime, bad_def: Region) { |
| let old_value = self.map.defs.remove(&lifetime_ref.hir_id); |
| assert_eq!(old_value, Some(bad_def)); |
| } |
| } |
| |
| /// Detects late-bound lifetimes and inserts them into |
| /// `late_bound`. |
| /// |
| /// A region declared on a fn is **late-bound** if: |
| /// - it is constrained by an argument type; |
| /// - it does not appear in a where-clause. |
| /// |
| /// "Constrained" basically means that it appears in any type but |
| /// not amongst the inputs to a projection. In other words, `<&'a |
| /// T as Trait<''b>>::Foo` does not constrain `'a` or `'b`. |
| fn is_late_bound_map(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<&FxIndexSet<LocalDefId>> { |
| let hir_id = tcx.hir().local_def_id_to_hir_id(def_id); |
| let decl = tcx.hir().fn_decl_by_hir_id(hir_id)?; |
| let generics = tcx.hir().get_generics(def_id)?; |
| |
| let mut late_bound = FxIndexSet::default(); |
| |
| let mut constrained_by_input = ConstrainedCollector::default(); |
| for arg_ty in decl.inputs { |
| constrained_by_input.visit_ty(arg_ty); |
| } |
| |
| let mut appears_in_output = AllCollector::default(); |
| intravisit::walk_fn_ret_ty(&mut appears_in_output, &decl.output); |
| |
| debug!(?constrained_by_input.regions); |
| |
| // Walk the lifetimes that appear in where clauses. |
| // |
| // Subtle point: because we disallow nested bindings, we can just |
| // ignore binders here and scrape up all names we see. |
| let mut appears_in_where_clause = AllCollector::default(); |
| appears_in_where_clause.visit_generics(generics); |
| debug!(?appears_in_where_clause.regions); |
| |
| // Late bound regions are those that: |
| // - appear in the inputs |
| // - do not appear in the where-clauses |
| // - are not implicitly captured by `impl Trait` |
| for param in generics.params { |
| match param.kind { |
| hir::GenericParamKind::Lifetime { .. } => { /* fall through */ } |
| |
| // Neither types nor consts are late-bound. |
| hir::GenericParamKind::Type { .. } | hir::GenericParamKind::Const { .. } => continue, |
| } |
| |
| let param_def_id = tcx.hir().local_def_id(param.hir_id); |
| |
| // appears in the where clauses? early-bound. |
| if appears_in_where_clause.regions.contains(¶m_def_id) { |
| continue; |
| } |
| |
| // does not appear in the inputs, but appears in the return type? early-bound. |
| if !constrained_by_input.regions.contains(¶m_def_id) |
| && appears_in_output.regions.contains(¶m_def_id) |
| { |
| continue; |
| } |
| |
| debug!("lifetime {:?} with id {:?} is late-bound", param.name.ident(), param.hir_id); |
| |
| let inserted = late_bound.insert(param_def_id); |
| assert!(inserted, "visited lifetime {:?} twice", param.hir_id); |
| } |
| |
| debug!(?late_bound); |
| return Some(tcx.arena.alloc(late_bound)); |
| |
| #[derive(Default)] |
| struct ConstrainedCollector { |
| regions: FxHashSet<LocalDefId>, |
| } |
| |
| impl<'v> Visitor<'v> for ConstrainedCollector { |
| fn visit_ty(&mut self, ty: &'v hir::Ty<'v>) { |
| match ty.kind { |
| hir::TyKind::Path( |
| hir::QPath::Resolved(Some(_), _) | hir::QPath::TypeRelative(..), |
| ) => { |
| // ignore lifetimes appearing in associated type |
| // projections, as they are not *constrained* |
| // (defined above) |
| } |
| |
| hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => { |
| // consider only the lifetimes on the final |
| // segment; I am not sure it's even currently |
| // valid to have them elsewhere, but even if it |
| // is, those would be potentially inputs to |
| // projections |
| if let Some(last_segment) = path.segments.last() { |
| self.visit_path_segment(path.span, last_segment); |
| } |
| } |
| |
| _ => { |
| intravisit::walk_ty(self, ty); |
| } |
| } |
| } |
| |
| fn visit_lifetime(&mut self, lifetime_ref: &'v hir::Lifetime) { |
| if let hir::LifetimeName::Param(def_id, _) = lifetime_ref.name { |
| self.regions.insert(def_id); |
| } |
| } |
| } |
| |
| #[derive(Default)] |
| struct AllCollector { |
| regions: FxHashSet<LocalDefId>, |
| } |
| |
| impl<'v> Visitor<'v> for AllCollector { |
| fn visit_lifetime(&mut self, lifetime_ref: &'v hir::Lifetime) { |
| if let hir::LifetimeName::Param(def_id, _) = lifetime_ref.name { |
| self.regions.insert(def_id); |
| } |
| } |
| } |
| } |
