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Diffstat (limited to '')
| -rw-r--r-- | compiler/rustc_resolve/src/late/lifetimes.rs | 2144 |
1 files changed, 0 insertions, 2144 deletions
diff --git a/compiler/rustc_resolve/src/late/lifetimes.rs b/compiler/rustc_resolve/src/late/lifetimes.rs deleted file mode 100644 index 94460e33d..000000000 --- a/compiler/rustc_resolve/src/late/lifetimes.rs +++ /dev/null @@ -1,2144 +0,0 @@ -//! 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); - } - } - } -} |