-//! Name resolution for lifetimes.
-//!
-//! Name resolution for lifetimes follows *much* simpler rules than the
-//! full resolve. For example, lifetime names are never exported or
-//! used between functions, and they operate in a purely top-down
-//! way. Therefore, we break lifetime name resolution into a separate pass.
+//! Name resolution for lifetimes: type declarations.
-// ignore-tidy-filelength
+use crate::ty;
-use crate::hir::def::{Res, DefKind};
-use crate::hir::def_id::{CrateNum, DefId, LocalDefId, LOCAL_CRATE};
-use crate::hir::map::Map;
-use crate::hir::ptr::P;
-use crate::hir::{GenericArg, GenericParam, ItemLocalId, LifetimeName, Node, ParamName, QPath};
-use crate::ty::{self, DefIdTree, GenericParamDefKind, TyCtxt};
-
-use crate::rustc::lint;
-use crate::session::Session;
-use crate::util::nodemap::{DefIdMap, FxHashMap, FxHashSet, HirIdMap, HirIdSet};
-use errors::{Applicability, DiagnosticBuilder, pluralise};
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_hir::def_id::{DefId, LocalDefId};
+use rustc_hir::{GenericParam, ItemLocalId};
+use rustc_hir::{GenericParamKind, LifetimeParamKind};
use rustc_macros::HashStable;
-use std::borrow::Cow;
-use std::cell::Cell;
-use std::mem::{replace, take};
-use syntax::ast;
-use syntax::attr;
-use syntax::symbol::{kw, sym};
-use syntax_pos::Span;
-
-use crate::hir::intravisit::{self, NestedVisitorMap, Visitor};
-use crate::hir::{self, GenericParamKind, LifetimeParamKind};
/// The origin of a named lifetime definition.
///
}
impl LifetimeDefOrigin {
- fn from_param(param: &GenericParam) -> Self {
+ pub fn from_param(param: &GenericParam<'_>) -> Self {
match param.kind {
GenericParamKind::Lifetime { kind } => match kind {
LifetimeParamKind::InBand => LifetimeDefOrigin::InBand,
}
}
-// This counts the no of times a lifetime is used
-#[derive(Clone, Copy, Debug)]
-pub enum LifetimeUseSet<'tcx> {
- One(&'tcx hir::Lifetime),
- Many,
-}
-
#[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Debug, HashStable)]
pub enum Region {
Static,
- EarlyBound(
- /* index */ u32,
- /* lifetime decl */ DefId,
- LifetimeDefOrigin,
- ),
- LateBound(
- ty::DebruijnIndex,
- /* lifetime decl */ DefId,
- LifetimeDefOrigin,
- ),
+ EarlyBound(/* index */ u32, /* lifetime decl */ DefId, LifetimeDefOrigin),
+ LateBound(ty::DebruijnIndex, /* lifetime decl */ DefId, LifetimeDefOrigin),
LateBoundAnon(ty::DebruijnIndex, /* anon index */ u32),
Free(DefId, /* lifetime decl */ DefId),
}
-impl Region {
- fn early(hir_map: &Map<'_>, index: &mut u32, param: &GenericParam) -> (ParamName, Region) {
- let i = *index;
- *index += 1;
- let def_id = hir_map.local_def_id(param.hir_id);
- let origin = LifetimeDefOrigin::from_param(param);
- debug!("Region::early: index={} def_id={:?}", i, def_id);
- (param.name.modern(), Region::EarlyBound(i, def_id, origin))
- }
-
- fn late(hir_map: &Map<'_>, param: &GenericParam) -> (ParamName, Region) {
- let depth = ty::INNERMOST;
- let def_id = hir_map.local_def_id(param.hir_id);
- let origin = LifetimeDefOrigin::from_param(param);
- debug!(
- "Region::late: param={:?} depth={:?} def_id={:?} origin={:?}",
- param, depth, def_id, origin,
- );
- (
- param.name.modern(),
- Region::LateBound(depth, def_id, origin),
- )
- }
-
- fn late_anon(index: &Cell<u32>) -> Region {
- let i = index.get();
- index.set(i + 1);
- let depth = ty::INNERMOST;
- Region::LateBoundAnon(depth, i)
- }
-
- fn id(&self) -> Option<DefId> {
- match *self {
- Region::Static | Region::LateBoundAnon(..) => None,
-
- Region::EarlyBound(_, id, _) | Region::LateBound(_, id, _) | Region::Free(_, id) => {
- Some(id)
- }
- }
- }
-
- fn shifted(self, amount: u32) -> Region {
- match self {
- Region::LateBound(debruijn, id, origin) => {
- Region::LateBound(debruijn.shifted_in(amount), id, origin)
- }
- Region::LateBoundAnon(debruijn, index) => {
- Region::LateBoundAnon(debruijn.shifted_in(amount), index)
- }
- _ => self,
- }
- }
-
- fn shifted_out_to_binder(self, binder: ty::DebruijnIndex) -> Region {
- match self {
- Region::LateBound(debruijn, id, origin) => {
- Region::LateBound(debruijn.shifted_out_to_binder(binder), id, origin)
- }
- Region::LateBoundAnon(debruijn, index) => {
- Region::LateBoundAnon(debruijn.shifted_out_to_binder(binder), index)
- }
- _ => 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)
- }
- }
-}
-
/// A set containing, at most, one known element.
/// If two distinct values are inserted into a set, then it
/// becomes `Many`, which can be used to detect ambiguities.
/// 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 `DefIndex`. This
-/// is silly.
-#[derive(Default)]
-struct NamedRegionMap {
- // maps from every use of a named (not anonymous) lifetime to a
- // `Region` describing how that region is bound
- pub defs: HirIdMap<Region>,
-
- // the set of lifetime def ids that are late-bound; a region can
- // be late-bound if (a) it does NOT appear in a where-clause and
- // (b) it DOES appear in the arguments.
- pub late_bound: HirIdSet,
-
- // For each type and trait definition, maps type parameters
- // to the trait object lifetime defaults computed from them.
- pub object_lifetime_defaults: HirIdMap<Vec<ObjectLifetimeDefault>>,
-}
-
-/// See [`NamedRegionMap`].
-#[derive(Default)]
+#[derive(Default, HashStable)]
pub struct ResolveLifetimes {
- defs: FxHashMap<LocalDefId, FxHashMap<ItemLocalId, Region>>,
- late_bound: FxHashMap<LocalDefId, FxHashSet<ItemLocalId>>,
- object_lifetime_defaults:
+ /// Maps from every use of a named (not anonymous) lifetime to a
+ /// `Region` describing how that region is bound
+ pub defs: FxHashMap<LocalDefId, FxHashMap<ItemLocalId, Region>>,
+
+ /// Set of lifetime def ids that are late-bound; a region can
+ /// be late-bound if (a) it does NOT appear in a where-clause and
+ /// (b) it DOES appear in the arguments.
+ pub late_bound: FxHashMap<LocalDefId, FxHashSet<ItemLocalId>>,
+
+ /// For each type and trait definition, maps type parameters
+ /// to the trait object lifetime defaults computed from them.
+ pub object_lifetime_defaults:
FxHashMap<LocalDefId, FxHashMap<ItemLocalId, Vec<ObjectLifetimeDefault>>>,
}
-
-impl_stable_hash_for!(struct crate::middle::resolve_lifetime::ResolveLifetimes {
- defs,
- late_bound,
- object_lifetime_defaults
-});
-
-struct LifetimeContext<'a, 'tcx> {
- tcx: TyCtxt<'tcx>,
- map: &'a mut NamedRegionMap,
- scope: ScopeRef<'a>,
-
- /// This is slightly complicated. Our representation for poly-trait-refs contains a single
- /// binder and thus we only allow a single level of quantification. However,
- /// the syntax of Rust permits quantification in two places, e.g., `T: for <'a> Foo<'a>`
- /// and `for <'a, 'b> &'b T: Foo<'a>`. In order to get the De Bruijn indices
- /// correct when representing these constraints, we should only introduce one
- /// scope. However, we want to support both locations for the quantifier and
- /// during lifetime resolution we want precise information (so we can't
- /// desugar in an earlier phase).
- ///
- /// So, if we encounter a quantifier at the outer scope, we set
- /// `trait_ref_hack` to `true` (and introduce a scope), and then if we encounter
- /// a quantifier at the inner scope, we error. If `trait_ref_hack` is `false`,
- /// then we introduce the scope at the inner quantifier.
- trait_ref_hack: bool,
-
- /// Used to disallow the use of in-band lifetimes in `fn` or `Fn` syntax.
- is_in_fn_syntax: bool,
-
- /// List of labels in the function/method currently under analysis.
- labels_in_fn: Vec<ast::Ident>,
-
- /// Cache for cross-crate per-definition object lifetime defaults.
- xcrate_object_lifetime_defaults: DefIdMap<Vec<ObjectLifetimeDefault>>,
-
- lifetime_uses: &'a mut DefIdMap<LifetimeUseSet<'tcx>>,
-}
-
-#[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 {
- lifetimes: FxHashMap<hir::ParamName, 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,
-
- /// Flag is set to true if, in this binder, `'_` would be
- /// equivalent to a "single-use region". This is true on
- /// impls, but not other kinds of items.
- track_lifetime_uses: bool,
-
- /// Whether or not this binder would serve as the parent
- /// binder for opaque types introduced within. For example:
- ///
- /// 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,
-
- s: ScopeRef<'a>,
- },
-
- /// 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). For more details, see `Elide`.
- Elision {
- elide: Elide,
- 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>,
- },
-
- Root,
-}
-
-#[derive(Clone, Debug)]
-enum Elide {
- /// Use a fresh anonymous late-bound lifetime each time, by
- /// incrementing the counter to generate sequential indices.
- FreshLateAnon(Cell<u32>),
- /// Always use this one lifetime.
- Exact(Region),
- /// Less or more than one lifetime were found, error on unspecified.
- Error(Vec<ElisionFailureInfo>),
-}
-
-#[derive(Clone, Debug)]
-struct ElisionFailureInfo {
- /// Where we can find the argument pattern.
- parent: Option<hir::BodyId>,
- /// The index of the argument in the original definition.
- index: usize,
- lifetime_count: usize,
- have_bound_regions: bool,
-}
-
-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,
-
- named_region_map: |tcx, id| {
- let id = LocalDefId::from_def_id(DefId::local(id)); // (*)
- tcx.resolve_lifetimes(LOCAL_CRATE).defs.get(&id)
- },
-
- is_late_bound_map: |tcx, id| {
- let id = LocalDefId::from_def_id(DefId::local(id)); // (*)
- tcx.resolve_lifetimes(LOCAL_CRATE)
- .late_bound
- .get(&id)
- },
-
- object_lifetime_defaults_map: |tcx, id| {
- let id = LocalDefId::from_def_id(DefId::local(id)); // (*)
- tcx.resolve_lifetimes(LOCAL_CRATE)
- .object_lifetime_defaults
- .get(&id)
- },
-
- ..*providers
- };
-
- // (*) FIXME the query should be defined to take a LocalDefId
-}
-
-/// Computes the `ResolveLifetimes` map that contains data for the
-/// entire crate. You should not read the result of this query
-/// directly, but rather use `named_region_map`, `is_late_bound_map`,
-/// etc.
-fn resolve_lifetimes(tcx: TyCtxt<'_>, for_krate: CrateNum) -> &ResolveLifetimes {
- assert_eq!(for_krate, LOCAL_CRATE);
-
- let named_region_map = krate(tcx);
-
- let mut rl = ResolveLifetimes::default();
-
- for (hir_id, v) in named_region_map.defs {
- let map = rl.defs.entry(hir_id.owner_local_def_id()).or_default();
- map.insert(hir_id.local_id, v);
- }
- for hir_id in named_region_map.late_bound {
- let map = rl.late_bound
- .entry(hir_id.owner_local_def_id())
- .or_default();
- map.insert(hir_id.local_id);
- }
- for (hir_id, v) in named_region_map.object_lifetime_defaults {
- let map = rl.object_lifetime_defaults
- .entry(hir_id.owner_local_def_id())
- .or_default();
- map.insert(hir_id.local_id, v);
- }
-
- tcx.arena.alloc(rl)
-}
-
-fn krate(tcx: TyCtxt<'_>) -> NamedRegionMap {
- let krate = tcx.hir().krate();
- let mut map = NamedRegionMap {
- defs: Default::default(),
- late_bound: Default::default(),
- object_lifetime_defaults: compute_object_lifetime_defaults(tcx),
- };
- {
- let mut visitor = LifetimeContext {
- tcx,
- map: &mut map,
- scope: ROOT_SCOPE,
- trait_ref_hack: false,
- is_in_fn_syntax: false,
- labels_in_fn: vec![],
- xcrate_object_lifetime_defaults: Default::default(),
- lifetime_uses: &mut Default::default(),
- };
- for (_, item) in &krate.items {
- visitor.visit_item(item);
- }
- }
- map
-}
-
-/// 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 {
- match *node {
- hir::ItemKind::Trait(..) |
- hir::ItemKind::TraitAlias(..) => true,
- _ => false,
- }
-}
-
-impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
- fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
- NestedVisitorMap::All(&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_nested_body(&mut self, body: hir::BodyId) {
- // Each body has their own set of labels, save labels.
- let saved = take(&mut self.labels_in_fn);
- let body = self.tcx.hir().body(body);
- extract_labels(self, body);
- self.with(
- Scope::Body {
- id: body.id(),
- s: self.scope,
- },
- |_, this| {
- this.visit_body(body);
- },
- );
- replace(&mut self.labels_in_fn, saved);
- }
-
- fn visit_item(&mut self, item: &'tcx hir::Item) {
- match item.node {
- hir::ItemKind::Fn(ref decl, _, ref generics, _) => {
- self.visit_early_late(None, decl, generics, |this| {
- intravisit::walk_item(this, item);
- });
- }
-
- hir::ItemKind::ExternCrate(_)
- | hir::ItemKind::Use(..)
- | 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.
- let scope = Scope::Elision {
- elide: Elide::Exact(Region::Static),
- s: ROOT_SCOPE,
- };
- self.with(scope, |_, this| intravisit::walk_item(this, item));
- }
- hir::ItemKind::OpaqueTy(hir::OpaqueTy {
- impl_trait_fn: Some(_),
- ..
- }) => {
- // Currently opaque type declarations are just generated from `impl Trait`
- // items. Doing anything on this node is irrelevant, as we currently don't need
- // it.
- }
- hir::ItemKind::TyAlias(_, ref generics)
- | hir::ItemKind::OpaqueTy(hir::OpaqueTy {
- impl_trait_fn: None,
- 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(_, _, _, ref generics, ..) => {
- // Impls permit `'_` to be used and it is equivalent to "some fresh lifetime name".
- // This is not true for other kinds of items.x
- let track_lifetime_uses = match item.node {
- hir::ItemKind::Impl(..) => true,
- _ => false,
- };
- // These kinds of items have only early-bound lifetime parameters.
- let mut index = if sub_items_have_self_param(&item.node) {
- 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();
- let scope = Scope::Binder {
- lifetimes,
- next_early_index: index + non_lifetime_count,
- opaque_type_parent: true,
- track_lifetime_uses,
- s: ROOT_SCOPE,
- };
- self.with(scope, |old_scope, this| {
- this.check_lifetime_params(old_scope, &generics.params);
- intravisit::walk_item(this, item);
- });
- }
- }
- }
-
- fn visit_foreign_item(&mut self, item: &'tcx hir::ForeignItem) {
- match item.node {
- hir::ForeignItemKind::Fn(ref decl, _, ref generics) => {
- self.visit_early_late(None, decl, 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);
- }
- }
- }
-
- fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
- debug!("visit_ty: id={:?} ty={:?}", ty.hir_id, ty);
- debug!("visit_ty: ty.node={:?}", ty.node);
- match ty.node {
- hir::TyKind::BareFn(ref c) => {
- let next_early_index = self.next_early_index();
- let was_in_fn_syntax = self.is_in_fn_syntax;
- self.is_in_fn_syntax = true;
- let scope = Scope::Binder {
- lifetimes: c.generic_params
- .iter()
- .filter_map(|param| match param.kind {
- GenericParamKind::Lifetime { .. } => {
- Some(Region::late(&self.tcx.hir(), param))
- }
- _ => None,
- })
- .collect(),
- s: self.scope,
- next_early_index,
- track_lifetime_uses: true,
- opaque_type_parent: false,
- };
- self.with(scope, |old_scope, this| {
- // a bare fn has no bounds, so everything
- // contained within is scoped within its binder.
- this.check_lifetime_params(old_scope, &c.generic_params);
- intravisit::walk_ty(this, ty);
- });
- self.is_in_fn_syntax = was_in_fn_syntax;
- }
- hir::TyKind::TraitObject(ref bounds, ref lifetime) => {
- debug!("visit_ty: TraitObject(bounds={:?}, lifetime={:?})", bounds, lifetime);
- for bound in bounds {
- self.visit_poly_trait_ref(bound, hir::TraitBoundModifier::None);
- }
- match lifetime.name {
- LifetimeName::Implicit => {
- // For types like `dyn Foo`, we should
- // generate a special form of elided.
- span_bug!(
- ty.span,
- "object-lifetime-default expected, not implict",
- );
- }
- 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::Underscore => {
- // 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
- self.resolve_elided_lifetimes(vec![lifetime])
- }
- 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::Def(item_id, ref 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 (generics, bounds) = match self.tcx.hir().expect_item(item_id.id).node
- {
- // Named opaque `impl Trait` types are reached via `TyKind::Path`.
- // This arm is for `impl Trait` in the types of statics, constants and locals.
- hir::ItemKind::OpaqueTy(hir::OpaqueTy {
- impl_trait_fn: None,
- ..
- }) => {
- intravisit::walk_ty(self, ty);
- return;
- }
- // RPIT (return position impl trait)
- hir::ItemKind::OpaqueTy(hir::OpaqueTy {
- ref generics,
- ref 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 {
- if let hir::GenericArg::Lifetime(lifetime) = lifetime {
- 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();
- if let Some(Region::LateBound(_, def_id, _)) = def {
- if let Some(hir_id) = self.tcx.hir().as_local_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);
- let parent_impl_id = hir::ImplItemId { hir_id: parent_id };
- let parent_trait_id = hir::TraitItemId { hir_id: parent_id };
- let krate = self.tcx.hir().forest.krate();
-
- if !(krate.items.contains_key(&parent_id)
- || krate.impl_items.contains_key(&parent_impl_id)
- || krate.trait_items.contains_key(&parent_trait_id))
- {
- span_err!(
- self.tcx.sess,
- lifetime.span,
- E0657,
- "`impl Trait` can only capture lifetimes \
- bound at the fn or impl level"
- );
- 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!("visit_ty: index = {}", index);
-
- let mut elision = None;
- let mut lifetimes = FxHashMap::default();
- let mut non_lifetime_count = 0;
- for param in &generics.params {
- match param.kind {
- GenericParamKind::Lifetime { .. } => {
- let (name, reg) = Region::early(&self.tcx.hir(), &mut index, ¶m);
- if let hir::ParamName::Plain(param_name) = name {
- if param_name.name == kw::UnderscoreLifetime {
- // Pick the elided lifetime "definition" if one exists
- // and use it to make an elision scope.
- elision = Some(reg);
- } else {
- lifetimes.insert(name, reg);
- }
- } else {
- lifetimes.insert(name, reg);
- }
- }
- GenericParamKind::Type { .. } |
- GenericParamKind::Const { .. } => {
- non_lifetime_count += 1;
- }
- }
- }
- let next_early_index = index + non_lifetime_count;
-
- if let Some(elision_region) = elision {
- let scope = Scope::Elision {
- elide: Elide::Exact(elision_region),
- s: self.scope,
- };
- self.with(scope, |_old_scope, this| {
- let scope = Scope::Binder {
- lifetimes,
- next_early_index,
- s: this.scope,
- track_lifetime_uses: true,
- opaque_type_parent: false,
- };
- this.with(scope, |_old_scope, this| {
- this.visit_generics(generics);
- for bound in bounds {
- this.visit_param_bound(bound);
- }
- });
- });
- } else {
- let scope = Scope::Binder {
- lifetimes,
- next_early_index,
- s: self.scope,
- track_lifetime_uses: true,
- opaque_type_parent: false,
- };
- self.with(scope, |_old_scope, this| {
- this.visit_generics(generics);
- for bound in bounds {
- this.visit_param_bound(bound);
- }
- });
- }
- }
- hir::TyKind::CVarArgs(ref lt) => {
- // Resolve the generated lifetime for the C-variadic arguments.
- // The lifetime is generated in AST -> HIR lowering.
- if lt.name.is_elided() {
- self.resolve_elided_lifetimes(vec![lt])
- }
- }
- _ => intravisit::walk_ty(self, ty),
- }
- }
-
- fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem) {
- use self::hir::TraitItemKind::*;
- match trait_item.node {
- Method(ref sig, _) => {
- let tcx = self.tcx;
- self.visit_early_late(
- Some(tcx.hir().get_parent_item(trait_item.hir_id)),
- &sig.decl,
- &trait_item.generics,
- |this| intravisit::walk_trait_item(this, trait_item),
- );
- }
- Type(ref 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();
- let scope = Scope::Binder {
- lifetimes,
- next_early_index: index + non_lifetime_count,
- s: self.scope,
- track_lifetime_uses: true,
- opaque_type_parent: true,
- };
- self.with(scope, |_old_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) {
- use self::hir::ImplItemKind::*;
- match impl_item.node {
- Method(ref sig, _) => {
- let tcx = self.tcx;
- self.visit_early_late(
- Some(tcx.hir().get_parent_item(impl_item.hir_id)),
- &sig.decl,
- &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 = 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();
- let scope = Scope::Binder {
- lifetimes,
- next_early_index: index + non_lifetime_count,
- s: self.scope,
- track_lifetime_uses: true,
- opaque_type_parent: true,
- };
- self.with(scope, |_old_scope, this| {
- this.visit_generics(generics);
- this.visit_ty(ty);
- });
- }
- OpaqueTy(ref bounds) => {
- let generics = &impl_item.generics;
- let mut index = self.next_early_index();
- let mut next_early_index = index;
- debug!("visit_ty: index = {}", index);
- let lifetimes = generics.params.iter().filter_map(|param| match param.kind {
- GenericParamKind::Lifetime { .. } => {
- Some(Region::early(&self.tcx.hir(), &mut index, param))
- }
- GenericParamKind::Type { .. } => {
- next_early_index += 1;
- None
- }
- GenericParamKind::Const { .. } => {
- next_early_index += 1;
- None
- }
- }).collect();
-
- let scope = Scope::Binder {
- lifetimes,
- next_early_index,
- s: self.scope,
- track_lifetime_uses: true,
- opaque_type_parent: true,
- };
- self.with(scope, |_old_scope, this| {
- this.visit_generics(generics);
- for bound in bounds {
- this.visit_param_bound(bound);
- }
- });
- }
- Const(_, _) => {
- // Only methods and types support generics.
- assert!(impl_item.generics.params.is_empty());
- intravisit::walk_impl_item(self, impl_item);
- }
- }
- }
-
- fn visit_lifetime(&mut self, lifetime_ref: &'tcx hir::Lifetime) {
- debug!("visit_lifetime(lifetime_ref={:?})", lifetime_ref);
- if lifetime_ref.is_elided() {
- self.resolve_elided_lifetimes(vec![lifetime_ref]);
- return;
- }
- if lifetime_ref.is_static() {
- self.insert_lifetime(lifetime_ref, Region::Static);
- return;
- }
- self.resolve_lifetime_ref(lifetime_ref);
- }
-
- fn visit_path(&mut self, path: &'tcx hir::Path, _: 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_decl(&mut self, fd: &'tcx hir::FnDecl) {
- let output = match fd.output {
- hir::DefaultReturn(_) => None,
- hir::Return(ref ty) => Some(&**ty),
- };
- self.visit_fn_like_elision(&fd.inputs, output);
- }
-
- fn visit_generics(&mut self, generics: &'tcx hir::Generics) {
- check_mixed_explicit_and_in_band_defs(self.tcx, &generics.params);
- for param in &generics.params {
- match param.kind {
- GenericParamKind::Lifetime { .. } => {}
- GenericParamKind::Type { ref default, .. } => {
- walk_list!(self, visit_param_bound, ¶m.bounds);
- if let Some(ref ty) = default {
- self.visit_ty(&ty);
- }
- }
- GenericParamKind::Const { ref ty, .. } => {
- walk_list!(self, visit_param_bound, ¶m.bounds);
- self.visit_ty(&ty);
- }
- }
- }
- for predicate in &generics.where_clause.predicates {
- match predicate {
- &hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
- ref bounded_ty,
- ref bounds,
- ref bound_generic_params,
- ..
- }) => {
- let lifetimes: FxHashMap<_, _> = bound_generic_params
- .iter()
- .filter_map(|param| match param.kind {
- GenericParamKind::Lifetime { .. } => {
- Some(Region::late(&self.tcx.hir(), param))
- }
- _ => None,
- })
- .collect();
- if !lifetimes.is_empty() {
- self.trait_ref_hack = true;
- let next_early_index = self.next_early_index();
- let scope = Scope::Binder {
- lifetimes,
- s: self.scope,
- next_early_index,
- track_lifetime_uses: true,
- opaque_type_parent: false,
- };
- let result = self.with(scope, |old_scope, this| {
- this.check_lifetime_params(old_scope, &bound_generic_params);
- this.visit_ty(&bounded_ty);
- walk_list!(this, visit_param_bound, bounds);
- });
- self.trait_ref_hack = false;
- result
- } else {
- self.visit_ty(&bounded_ty);
- walk_list!(self, visit_param_bound, bounds);
- }
- }
- &hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
- ref lifetime,
- ref bounds,
- ..
- }) => {
- self.visit_lifetime(lifetime);
- walk_list!(self, visit_param_bound, bounds);
- }
- &hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
- ref lhs_ty,
- ref rhs_ty,
- ..
- }) => {
- self.visit_ty(lhs_ty);
- self.visit_ty(rhs_ty);
- }
- }
- }
- }
-
- fn visit_poly_trait_ref(
- &mut self,
- trait_ref: &'tcx hir::PolyTraitRef,
- _modifier: hir::TraitBoundModifier,
- ) {
- debug!("visit_poly_trait_ref(trait_ref={:?})", trait_ref);
-
- if !self.trait_ref_hack || trait_ref.bound_generic_params.iter().any(|param| {
- match param.kind {
- GenericParamKind::Lifetime { .. } => true,
- _ => false,
- }
- }) {
- if self.trait_ref_hack {
- span_err!(
- self.tcx.sess,
- trait_ref.span,
- E0316,
- "nested quantification of lifetimes"
- );
- }
- let next_early_index = self.next_early_index();
- let scope = Scope::Binder {
- lifetimes: trait_ref
- .bound_generic_params
- .iter()
- .filter_map(|param| match param.kind {
- GenericParamKind::Lifetime { .. } => {
- Some(Region::late(&self.tcx.hir(), param))
- }
- _ => None,
- })
- .collect(),
- s: self.scope,
- next_early_index,
- track_lifetime_uses: true,
- opaque_type_parent: false,
- };
- self.with(scope, |old_scope, this| {
- this.check_lifetime_params(old_scope, &trait_ref.bound_generic_params);
- walk_list!(this, visit_generic_param, &trait_ref.bound_generic_params);
- this.visit_trait_ref(&trait_ref.trait_ref)
- })
- } else {
- self.visit_trait_ref(&trait_ref.trait_ref)
- }
- }
-}
-
-#[derive(Copy, Clone, PartialEq)]
-enum ShadowKind {
- Label,
- Lifetime,
-}
-struct Original {
- kind: ShadowKind,
- span: Span,
-}
-struct Shadower {
- kind: ShadowKind,
- span: Span,
-}
-
-fn original_label(span: Span) -> Original {
- Original {
- kind: ShadowKind::Label,
- span: span,
- }
-}
-fn shadower_label(span: Span) -> Shadower {
- Shadower {
- kind: ShadowKind::Label,
- span: span,
- }
-}
-fn original_lifetime(span: Span) -> Original {
- Original {
- kind: ShadowKind::Lifetime,
- span: span,
- }
-}
-fn shadower_lifetime(param: &hir::GenericParam) -> Shadower {
- Shadower {
- kind: ShadowKind::Lifetime,
- span: param.span,
- }
-}
-
-impl ShadowKind {
- fn desc(&self) -> &'static str {
- match *self {
- ShadowKind::Label => "label",
- ShadowKind::Lifetime => "lifetime",
- }
- }
-}
-
-fn check_mixed_explicit_and_in_band_defs(tcx: TyCtxt<'_>, params: &P<[hir::GenericParam]>) {
- let lifetime_params: Vec<_> = params
- .iter()
- .filter_map(|param| match param.kind {
- GenericParamKind::Lifetime { kind, .. } => Some((kind, param.span)),
- _ => None,
- })
- .collect();
- let explicit = lifetime_params
- .iter()
- .find(|(kind, _)| *kind == LifetimeParamKind::Explicit);
- let in_band = lifetime_params
- .iter()
- .find(|(kind, _)| *kind == LifetimeParamKind::InBand);
-
- if let (Some((_, explicit_span)), Some((_, in_band_span))) = (explicit, in_band) {
- struct_span_err!(
- tcx.sess,
- *in_band_span,
- E0688,
- "cannot mix in-band and explicit lifetime definitions"
- ).span_label(*in_band_span, "in-band lifetime definition here")
- .span_label(*explicit_span, "explicit lifetime definition here")
- .emit();
- }
-}
-
-fn signal_shadowing_problem(tcx: TyCtxt<'_>, name: ast::Name, orig: Original, shadower: Shadower) {
- let mut err = if let (ShadowKind::Lifetime, ShadowKind::Lifetime) = (orig.kind, shadower.kind) {
- // lifetime/lifetime shadowing is an error
- struct_span_err!(
- tcx.sess,
- shadower.span,
- E0496,
- "{} name `{}` shadows a \
- {} name that is already in scope",
- shadower.kind.desc(),
- name,
- orig.kind.desc()
- )
- } else {
- // shadowing involving a label is only a warning, due to issues with
- // labels and lifetimes not being macro-hygienic.
- tcx.sess.struct_span_warn(
- shadower.span,
- &format!(
- "{} name `{}` shadows a \
- {} name that is already in scope",
- shadower.kind.desc(),
- name,
- orig.kind.desc()
- ),
- )
- };
- err.span_label(orig.span, "first declared here");
- err.span_label(shadower.span, format!("lifetime {} already in scope", name));
- err.emit();
-}
-
-// Adds all labels in `b` to `ctxt.labels_in_fn`, signalling a warning
-// if one of the label shadows a lifetime or another label.
-fn extract_labels(ctxt: &mut LifetimeContext<'_, '_>, body: &hir::Body) {
- struct GatherLabels<'a, 'tcx> {
- tcx: TyCtxt<'tcx>,
- scope: ScopeRef<'a>,
- labels_in_fn: &'a mut Vec<ast::Ident>,
- }
-
- let mut gather = GatherLabels {
- tcx: ctxt.tcx,
- scope: ctxt.scope,
- labels_in_fn: &mut ctxt.labels_in_fn,
- };
- gather.visit_body(body);
-
- impl<'v, 'a, 'tcx> Visitor<'v> for GatherLabels<'a, 'tcx> {
- fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
- NestedVisitorMap::None
- }
-
- fn visit_expr(&mut self, ex: &hir::Expr) {
- if let Some(label) = expression_label(ex) {
- for prior_label in &self.labels_in_fn[..] {
- // FIXME (#24278): non-hygienic comparison
- if label.name == prior_label.name {
- signal_shadowing_problem(
- self.tcx,
- label.name,
- original_label(prior_label.span),
- shadower_label(label.span),
- );
- }
- }
-
- check_if_label_shadows_lifetime(self.tcx, self.scope, label);
-
- self.labels_in_fn.push(label);
- }
- intravisit::walk_expr(self, ex)
- }
- }
-
- fn expression_label(ex: &hir::Expr) -> Option<ast::Ident> {
- if let hir::ExprKind::Loop(_, Some(label), _) = ex.node {
- Some(label.ident)
- } else {
- None
- }
- }
-
- fn check_if_label_shadows_lifetime(
- tcx: TyCtxt<'_>,
- mut scope: ScopeRef<'_>,
- label: ast::Ident,
- ) {
- loop {
- match *scope {
- Scope::Body { s, .. }
- | Scope::Elision { s, .. }
- | Scope::ObjectLifetimeDefault { s, .. } => {
- scope = s;
- }
-
- Scope::Root => {
- return;
- }
-
- Scope::Binder {
- ref lifetimes, s, ..
- } => {
- // FIXME (#24278): non-hygienic comparison
- if let Some(def) = lifetimes.get(&hir::ParamName::Plain(label.modern())) {
- let hir_id = tcx.hir().as_local_hir_id(def.id().unwrap()).unwrap();
-
- signal_shadowing_problem(
- tcx,
- label.name,
- original_lifetime(tcx.hir().span(hir_id)),
- shadower_label(label.span),
- );
- return;
- }
- scope = s;
- }
- }
- }
- }
-}
-
-fn compute_object_lifetime_defaults(tcx: TyCtxt<'_>) -> HirIdMap<Vec<ObjectLifetimeDefault>> {
- let mut map = HirIdMap::default();
- for item in tcx.hir().krate().items.values() {
- match item.node {
- hir::ItemKind::Struct(_, ref generics)
- | hir::ItemKind::Union(_, ref generics)
- | hir::ItemKind::Enum(_, ref generics)
- | hir::ItemKind::OpaqueTy(hir::OpaqueTy {
- ref generics,
- impl_trait_fn: None,
- ..
- })
- | hir::ItemKind::TyAlias(_, ref generics)
- | hir::ItemKind::Trait(_, _, ref generics, ..) => {
- let result = object_lifetime_defaults_for_item(tcx, generics);
-
- // Debugging aid.
- if attr::contains_name(&item.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);
- }
-
- map.insert(item.hir_id, result);
- }
- _ => {}
- }
- }
- map
-}
-
-/// 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: TyCtxt<'_>,
- generics: &hir::Generics,
-) -> Vec<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.modern());
- }
- }
- }
-
- generics
- .params
- .iter()
- .filter_map(|param| match param.kind {
- GenericParamKind::Lifetime { .. } => None,
- GenericParamKind::Type { .. } => {
- let mut set = Set1::Empty;
-
- add_bounds(&mut set, ¶m.bounds);
-
- let param_def_id = tcx.hir().local_def_id(param.hir_id);
- for predicate in &generics.where_clause.predicates {
- // Look for `type: ...` where clauses.
- let data = match *predicate {
- hir::WherePredicate::BoundPredicate(ref data) => data,
- _ => 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.node {
- hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => path.res,
- _ => continue,
- };
-
- if res == Res::Def(DefKind::TyParam, param_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 { .. } => Some((
- param.hir_id,
- hir::LifetimeName::Param(param.name),
- LifetimeDefOrigin::from_param(param),
- )),
- _ => None,
- })
- .enumerate()
- .find(|&(_, (_, lt_name, _))| lt_name == name)
- .map_or(Set1::Many, |(i, (id, _, origin))| {
- let def_id = tcx.hir().local_def_id(id);
- Set1::One(Region::EarlyBound(i as u32, def_id, origin))
- })
- }
- }
- Set1::Many => Set1::Many,
- })
- }
- GenericParamKind::Const { .. } => {
- // Generic consts don't impose any constraints.
- None
- }
- })
- .collect()
-}
-
-impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
- // FIXME(#37666) this works around a limitation in the region inferencer
- fn hack<F>(&mut self, f: F)
- where
- F: for<'b> FnOnce(&mut LifetimeContext<'b, 'tcx>),
- {
- f(self)
- }
-
- fn with<F>(&mut self, wrap_scope: Scope<'_>, f: F)
- where
- F: for<'b> FnOnce(ScopeRef<'_>, &mut LifetimeContext<'b, 'tcx>),
- {
- let LifetimeContext {
- tcx,
- map,
- lifetime_uses,
- ..
- } = self;
- let labels_in_fn = take(&mut self.labels_in_fn);
- let xcrate_object_lifetime_defaults = take(&mut self.xcrate_object_lifetime_defaults);
- let mut this = LifetimeContext {
- tcx: *tcx,
- map: map,
- scope: &wrap_scope,
- trait_ref_hack: self.trait_ref_hack,
- is_in_fn_syntax: self.is_in_fn_syntax,
- labels_in_fn,
- xcrate_object_lifetime_defaults,
- lifetime_uses: lifetime_uses,
- };
- debug!("entering scope {:?}", this.scope);
- f(self.scope, &mut this);
- this.check_uses_for_lifetimes_defined_by_scope();
- debug!("exiting scope {:?}", this.scope);
- self.labels_in_fn = this.labels_in_fn;
- self.xcrate_object_lifetime_defaults = this.xcrate_object_lifetime_defaults;
- }
-
- /// helper method to determine the span to remove when suggesting the
- /// deletion of a lifetime
- fn lifetime_deletion_span(&self, name: ast::Ident, generics: &hir::Generics) -> Option<Span> {
- generics.params.iter().enumerate().find_map(|(i, param)| {
- if param.name.ident() == name {
- let mut in_band = false;
- if let hir::GenericParamKind::Lifetime { kind } = param.kind {
- if let hir::LifetimeParamKind::InBand = kind {
- in_band = true;
- }
- }
- if in_band {
- Some(param.span)
- } else {
- if generics.params.len() == 1 {
- // if sole lifetime, remove the entire `<>` brackets
- Some(generics.span)
- } else {
- // if removing within `<>` brackets, we also want to
- // delete a leading or trailing comma as appropriate
- if i >= generics.params.len() - 1 {
- Some(generics.params[i - 1].span.shrink_to_hi().to(param.span))
- } else {
- Some(param.span.to(generics.params[i + 1].span.shrink_to_lo()))
- }
- }
- }
- } else {
- None
- }
- })
- }
-
- // helper method to issue suggestions from `fn rah<'a>(&'a T)` to `fn rah(&T)`
- // or from `fn rah<'a>(T<'a>)` to `fn rah(T<'_>)`
- fn suggest_eliding_single_use_lifetime(
- &self, err: &mut DiagnosticBuilder<'_>, def_id: DefId, lifetime: &hir::Lifetime
- ) {
- let name = lifetime.name.ident();
- let mut remove_decl = None;
- if let Some(parent_def_id) = self.tcx.parent(def_id) {
- if let Some(generics) = self.tcx.hir().get_generics(parent_def_id) {
- remove_decl = self.lifetime_deletion_span(name, generics);
- }
- }
-
- let mut remove_use = None;
- let mut elide_use = None;
- let mut find_arg_use_span = |inputs: &hir::HirVec<hir::Ty>| {
- for input in inputs {
- match input.node {
- hir::TyKind::Rptr(lt, _) => {
- if lt.name.ident() == name {
- // include the trailing whitespace between the lifetime and type names
- let lt_through_ty_span = lifetime.span.to(input.span.shrink_to_hi());
- remove_use = Some(
- self.tcx.sess.source_map()
- .span_until_non_whitespace(lt_through_ty_span)
- );
- break;
- }
- }
- hir::TyKind::Path(ref qpath) => {
- if let QPath::Resolved(_, path) = qpath {
-
- let last_segment = &path.segments[path.segments.len()-1];
- let generics = last_segment.generic_args();
- for arg in generics.args.iter() {
- if let GenericArg::Lifetime(lt) = arg {
- if lt.name.ident() == name {
- elide_use = Some(lt.span);
- break;
- }
- }
- }
- break;
- }
- },
- _ => {}
- }
- }
- };
- if let Node::Lifetime(hir_lifetime) = self.tcx.hir().get(lifetime.hir_id) {
- if let Some(parent) = self.tcx.hir().find(
- self.tcx.hir().get_parent_item(hir_lifetime.hir_id))
- {
- match parent {
- Node::Item(item) => {
- if let hir::ItemKind::Fn(decl, _, _, _) = &item.node {
- find_arg_use_span(&decl.inputs);
- }
- },
- Node::ImplItem(impl_item) => {
- if let hir::ImplItemKind::Method(sig, _) = &impl_item.node {
- find_arg_use_span(&sig.decl.inputs);
- }
- }
- _ => {}
- }
- }
- }
-
- let msg = "elide the single-use lifetime";
- match (remove_decl, remove_use, elide_use) {
- (Some(decl_span), Some(use_span), None) => {
- // if both declaration and use deletion spans start at the same
- // place ("start at" because the latter includes trailing
- // whitespace), then this is an in-band lifetime
- if decl_span.shrink_to_lo() == use_span.shrink_to_lo() {
- err.span_suggestion(
- use_span,
- msg,
- String::new(),
- Applicability::MachineApplicable,
- );
- } else {
- err.multipart_suggestion(
- msg,
- vec![(decl_span, String::new()), (use_span, String::new())],
- Applicability::MachineApplicable,
- );
- }
- }
- (Some(decl_span), None, Some(use_span)) => {
- err.multipart_suggestion(
- msg,
- vec![(decl_span, String::new()), (use_span, "'_".to_owned())],
- Applicability::MachineApplicable,
- );
- }
- _ => {}
- }
- }
-
- fn check_uses_for_lifetimes_defined_by_scope(&mut self) {
- let defined_by = match self.scope {
- Scope::Binder { lifetimes, .. } => lifetimes,
- _ => {
- debug!("check_uses_for_lifetimes_defined_by_scope: not in a binder scope");
- return;
- }
- };
-
- let mut def_ids: Vec<_> = defined_by
- .values()
- .flat_map(|region| match region {
- Region::EarlyBound(_, def_id, _)
- | Region::LateBound(_, def_id, _)
- | Region::Free(_, def_id) => Some(*def_id),
-
- Region::LateBoundAnon(..) | Region::Static => None,
- })
- .collect();
-
- // ensure that we issue lints in a repeatable order
- def_ids.sort_by_cached_key(|&def_id| self.tcx.def_path_hash(def_id));
-
- for def_id in def_ids {
- debug!(
- "check_uses_for_lifetimes_defined_by_scope: def_id = {:?}",
- def_id
- );
-
- let lifetimeuseset = self.lifetime_uses.remove(&def_id);
-
- debug!(
- "check_uses_for_lifetimes_defined_by_scope: lifetimeuseset = {:?}",
- lifetimeuseset
- );
-
- match lifetimeuseset {
- Some(LifetimeUseSet::One(lifetime)) => {
- let hir_id = self.tcx.hir().as_local_hir_id(def_id).unwrap();
- debug!("hir id first={:?}", hir_id);
- if let Some((id, span, name)) = match self.tcx.hir().get(hir_id) {
- Node::Lifetime(hir_lifetime) => Some((
- hir_lifetime.hir_id,
- hir_lifetime.span,
- hir_lifetime.name.ident(),
- )),
- Node::GenericParam(param) => {
- Some((param.hir_id, param.span, param.name.ident()))
- }
- _ => None,
- } {
- debug!("id = {:?} span = {:?} name = {:?}", id, span, name);
-
- if name.name == kw::UnderscoreLifetime {
- continue;
- }
-
- if let Some(parent_def_id) = self.tcx.parent(def_id) {
- if let Some(parent_hir_id) = self.tcx.hir()
- .as_local_hir_id(parent_def_id) {
- // lifetimes in `derive` expansions don't count (Issue #53738)
- if self.tcx.hir().attrs(parent_hir_id).iter()
- .any(|attr| attr.check_name(sym::automatically_derived)) {
- continue;
- }
- }
- }
-
- let mut err = self.tcx.struct_span_lint_hir(
- lint::builtin::SINGLE_USE_LIFETIMES,
- id,
- span,
- &format!("lifetime parameter `{}` only used once", name),
- );
-
- if span == lifetime.span {
- // spans are the same for in-band lifetime declarations
- err.span_label(span, "this lifetime is only used here");
- } else {
- err.span_label(span, "this lifetime...");
- err.span_label(lifetime.span, "...is used only here");
- }
- self.suggest_eliding_single_use_lifetime(&mut err, def_id, lifetime);
- err.emit();
- }
- }
- Some(LifetimeUseSet::Many) => {
- debug!("not one use lifetime");
- }
- None => {
- let hir_id = self.tcx.hir().as_local_hir_id(def_id).unwrap();
- if let Some((id, span, name)) = match self.tcx.hir().get(hir_id) {
- Node::Lifetime(hir_lifetime) => Some((
- hir_lifetime.hir_id,
- hir_lifetime.span,
- hir_lifetime.name.ident(),
- )),
- Node::GenericParam(param) => {
- Some((param.hir_id, param.span, param.name.ident()))
- }
- _ => None,
- } {
- debug!("id ={:?} span = {:?} name = {:?}", id, span, name);
- let mut err = self.tcx.struct_span_lint_hir(
- lint::builtin::UNUSED_LIFETIMES,
- id,
- span,
- &format!("lifetime parameter `{}` never used", name),
- );
- if let Some(parent_def_id) = self.tcx.parent(def_id) {
- if let Some(generics) = self.tcx.hir().get_generics(parent_def_id) {
- let unused_lt_span = self.lifetime_deletion_span(name, generics);
- if let Some(span) = unused_lt_span {
- err.span_suggestion(
- span,
- "elide the unused lifetime",
- String::new(),
- Applicability::MachineApplicable,
- );
- }
- }
- }
- err.emit();
- }
- }
- }
- }
- }
-
- /// 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<hir::HirId>,
- decl: &'tcx hir::FnDecl,
- generics: &'tcx hir::Generics,
- walk: F,
- ) where
- F: for<'b, 'c> FnOnce(&'b mut LifetimeContext<'c, 'tcx>),
- {
- insert_late_bound_lifetimes(self.map, decl, generics);
-
- // Find the start of nested early scopes, e.g., in methods.
- let mut 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.node) {
- index += 1; // Self comes before lifetimes
- }
- match parent.node {
- hir::ItemKind::Trait(_, _, ref generics, ..)
- | hir::ItemKind::Impl(_, _, _, ref generics, ..) => {
- index += generics.params.len() as u32;
- }
- _ => {}
- }
- }
-
- let mut non_lifetime_count = 0;
- let lifetimes = generics.params.iter().filter_map(|param| match param.kind {
- GenericParamKind::Lifetime { .. } => {
- if self.map.late_bound.contains(¶m.hir_id) {
- Some(Region::late(&self.tcx.hir(), param))
- } else {
- Some(Region::early(&self.tcx.hir(), &mut index, param))
- }
- }
- GenericParamKind::Type { .. } |
- GenericParamKind::Const { .. } => {
- non_lifetime_count += 1;
- None
- }
- }).collect();
- let next_early_index = index + non_lifetime_count;
-
- let scope = Scope::Binder {
- lifetimes,
- next_early_index,
- s: self.scope,
- opaque_type_parent: true,
- track_lifetime_uses: false,
- };
- self.with(scope, move |old_scope, this| {
- this.check_lifetime_params(old_scope, &generics.params);
- this.hack(walk); // FIXME(#37666) workaround in place of `walk(this)`
- });
- }
-
- 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 = 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)
- }
-
- fn resolve_lifetime_ref(&mut self, lifetime_ref: &'tcx hir::Lifetime) {
- debug!("resolve_lifetime_ref(lifetime_ref={:?})", lifetime_ref);
-
- // If we've already reported an error, just ignore `lifetime_ref`.
- if let LifetimeName::Error = lifetime_ref.name {
- return;
- }
-
- // 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, s, ..
- } => {
- match lifetime_ref.name {
- LifetimeName::Param(param_name) => {
- if let Some(&def) = lifetimes.get(¶m_name.modern()) {
- break Some(def.shifted(late_depth));
- }
- }
- _ => bug!("expected LifetimeName::Param"),
- }
-
- late_depth += 1;
- scope = s;
- }
-
- Scope::Elision { s, .. } | Scope::ObjectLifetimeDefault { 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 {
- node: hir::ItemKind::Fn(..),
- ..
- })
- | Node::TraitItem(&hir::TraitItem {
- node: hir::TraitItemKind::Method(..),
- ..
- })
- | Node::ImplItem(&hir::ImplItem {
- node: hir::ImplItemKind::Method(..),
- ..
- }) => {
- let scope = self.tcx.hir().local_def_id(fn_id);
- def = Region::Free(scope, def.id().unwrap());
- }
- _ => {}
- }
- }
-
- // Check for fn-syntax conflicts with in-band lifetime definitions
- if self.is_in_fn_syntax {
- match def {
- Region::EarlyBound(_, _, LifetimeDefOrigin::InBand)
- | Region::LateBound(_, _, LifetimeDefOrigin::InBand) => {
- struct_span_err!(
- self.tcx.sess,
- lifetime_ref.span,
- E0687,
- "lifetimes used in `fn` or `Fn` syntax must be \
- explicitly declared using `<...>` binders"
- ).span_label(lifetime_ref.span, "in-band lifetime definition")
- .emit();
- }
-
- Region::Static
- | Region::EarlyBound(_, _, LifetimeDefOrigin::ExplicitOrElided)
- | Region::LateBound(_, _, LifetimeDefOrigin::ExplicitOrElided)
- | Region::EarlyBound(_, _, LifetimeDefOrigin::Error)
- | Region::LateBound(_, _, LifetimeDefOrigin::Error)
- | Region::LateBoundAnon(..)
- | Region::Free(..) => {}
- }
- }
-
- self.insert_lifetime(lifetime_ref, def);
- } else {
- struct_span_err!(
- self.tcx.sess,
- lifetime_ref.span,
- E0261,
- "use of undeclared lifetime name `{}`",
- lifetime_ref
- ).span_label(lifetime_ref.span, "undeclared lifetime")
- .emit();
- }
- }
-
- fn visit_segment_args(&mut self, res: Res, depth: usize, generic_args: &'tcx hir::GenericArgs) {
- debug!(
- "visit_segment_args(res={:?}, depth={:?}, generic_args={:?})",
- res,
- depth,
- generic_args,
- );
-
- if generic_args.parenthesized {
- let was_in_fn_syntax = self.is_in_fn_syntax;
- self.is_in_fn_syntax = true;
- self.visit_fn_like_elision(generic_args.inputs(), Some(generic_args.bindings[0].ty()));
- self.is_in_fn_syntax = was_in_fn_syntax;
- return;
- }
-
- let mut elide_lifetimes = true;
- let lifetimes = generic_args
- .args
- .iter()
- .filter_map(|arg| match arg {
- hir::GenericArg::Lifetime(lt) => {
- if !lt.is_elided() {
- elide_lifetimes = false;
- }
- Some(lt)
- }
- _ => None,
- })
- .collect();
- if elide_lifetimes {
- self.resolve_elided_lifetimes(lifetimes);
- } else {
- lifetimes.iter().for_each(|lt| 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, def_id)
- | Res::Def(DefKind::Union, def_id)
- | Res::Def(DefKind::Enum, def_id)
- | Res::Def(DefKind::TyAlias, def_id)
- | Res::Def(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(vec![], |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 = s;
- }
- }
- }
- };
-
- let map = &self.map;
- let unsubst = if let Some(id) = self.tcx.hir().as_local_hir_id(def_id) {
- &map.object_lifetime_defaults[&id]
- } 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::Lifetime | GenericParamDefKind::Const => None,
- })
- .collect()
- })
- };
- debug!("visit_segment_args: unsubst={:?}", unsubst);
- unsubst
- .iter()
- .map(|set| 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,
- })
- .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);
- }
- }
- }
-
- // 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| match arg {
- GenericArg::Lifetime(_) => true,
- _ => false,
- });
-
- // Resolve lifetimes found in the type `XX` from `Item = XX` bindings.
- for b in &generic_args.bindings {
- let scope = Scope::ObjectLifetimeDefault {
- lifetime: if has_lifetime_parameter {
- None
- } else {
- Some(Region::Static)
- },
- s: self.scope,
- };
- self.with(scope, |_, this| this.visit_assoc_type_binding(b));
- }
- }
-
- fn visit_fn_like_elision(&mut self, inputs: &'tcx [hir::Ty], output: Option<&'tcx hir::Ty>) {
- debug!("visit_fn_like_elision: enter");
- let mut arg_elide = Elide::FreshLateAnon(Cell::new(0));
- let arg_scope = Scope::Elision {
- elide: arg_elide.clone(),
- s: self.scope,
- };
- self.with(arg_scope, |_, this| {
- for input in inputs {
- this.visit_ty(input);
- }
- match *this.scope {
- Scope::Elision { ref elide, .. } => {
- arg_elide = elide.clone();
- }
- _ => bug!(),
- }
- });
-
- let output = match output {
- Some(ty) => ty,
- None => return,
- };
-
- debug!("visit_fn_like_elision: determine output");
-
- // Figure out if there's a body we can get argument names from,
- // and whether there's a `self` argument (treated specially).
- let mut assoc_item_kind = None;
- let mut impl_self = None;
- let parent = self.tcx.hir().get_parent_node(output.hir_id);
- let body = match self.tcx.hir().get(parent) {
- // `fn` definitions and methods.
- Node::Item(&hir::Item {
- node: hir::ItemKind::Fn(.., body),
- ..
- }) => Some(body),
-
- Node::TraitItem(&hir::TraitItem {
- node: hir::TraitItemKind::Method(_, ref m),
- ..
- }) => {
- if let hir::ItemKind::Trait(.., ref trait_items) = self.tcx
- .hir()
- .expect_item(self.tcx.hir().get_parent_item(parent))
- .node
- {
- assoc_item_kind = trait_items
- .iter()
- .find(|ti| ti.id.hir_id == parent)
- .map(|ti| ti.kind);
- }
- match *m {
- hir::TraitMethod::Required(_) => None,
- hir::TraitMethod::Provided(body) => Some(body),
- }
- }
-
- Node::ImplItem(&hir::ImplItem {
- node: hir::ImplItemKind::Method(_, body),
- ..
- }) => {
- if let hir::ItemKind::Impl(.., ref self_ty, ref impl_items) = self.tcx
- .hir()
- .expect_item(self.tcx.hir().get_parent_item(parent))
- .node
- {
- impl_self = Some(self_ty);
- assoc_item_kind = impl_items
- .iter()
- .find(|ii| ii.id.hir_id == parent)
- .map(|ii| ii.kind);
- }
- Some(body)
- }
-
- // Foreign functions, `fn(...) -> R` and `Trait(...) -> R` (both types and bounds).
- Node::ForeignItem(_) | Node::Ty(_) | Node::TraitRef(_) => None,
- // Everything else (only closures?) doesn't
- // actually enjoy elision in return types.
- _ => {
- self.visit_ty(output);
- return;
- }
- };
-
- let has_self = match assoc_item_kind {
- Some(hir::AssocItemKind::Method { has_self }) => has_self,
- _ => false,
- };
-
- // In accordance with the rules for lifetime elision, we can determine
- // what region to use for elision in the output type in two ways.
- // First (determined here), if `self` is by-reference, then the
- // implied output region is the region of the self parameter.
- if has_self {
- struct SelfVisitor<'a> {
- map: &'a NamedRegionMap,
- impl_self: Option<&'a hir::TyKind>,
- lifetime: Set1<Region>,
- }
-
- impl SelfVisitor<'_> {
- // Look for `self: &'a Self` - also desugared from `&'a self`,
- // and if that matches, use it for elision and return early.
- fn is_self_ty(&self, res: Res) -> bool {
- if let Res::SelfTy(..) = res {
- return true;
- }
-
- // Can't always rely on literal (or implied) `Self` due
- // to the way elision rules were originally specified.
- if let Some(&hir::TyKind::Path(hir::QPath::Resolved(None, ref path))) =
- self.impl_self
- {
- match path.res {
- // Whitelist the types that unambiguously always
- // result in the same type constructor being used
- // (it can't differ between `Self` and `self`).
- Res::Def(DefKind::Struct, _)
- | Res::Def(DefKind::Union, _)
- | Res::Def(DefKind::Enum, _)
- | Res::PrimTy(_) => {
- return res == path.res
- }
- _ => {}
- }
- }
-
- false
- }
- }
-
- impl<'a> Visitor<'a> for SelfVisitor<'a> {
- fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'a> {
- NestedVisitorMap::None
- }
-
- fn visit_ty(&mut self, ty: &'a hir::Ty) {
- if let hir::TyKind::Rptr(lifetime_ref, ref mt) = ty.node {
- if let hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) = mt.ty.node
- {
- if self.is_self_ty(path.res) {
- if let Some(lifetime) = self.map.defs.get(&lifetime_ref.hir_id) {
- self.lifetime.insert(*lifetime);
- }
- }
- }
- }
- intravisit::walk_ty(self, ty)
- }
- }
-
- let mut visitor = SelfVisitor {
- map: self.map,
- impl_self: impl_self.map(|ty| &ty.node),
- lifetime: Set1::Empty,
- };
- visitor.visit_ty(&inputs[0]);
- if let Set1::One(lifetime) = visitor.lifetime {
- let scope = Scope::Elision {
- elide: Elide::Exact(lifetime),
- s: self.scope,
- };
- self.with(scope, |_, this| this.visit_ty(output));
- return;
- }
- }
-
- // Second, if there was exactly one lifetime (either a substitution or a
- // reference) in the arguments, then any anonymous regions in the output
- // have that lifetime.
- let mut possible_implied_output_region = None;
- let mut lifetime_count = 0;
- let arg_lifetimes = inputs
- .iter()
- .enumerate()
- .skip(has_self as usize)
- .map(|(i, input)| {
- let mut gather = GatherLifetimes {
- map: self.map,
- outer_index: ty::INNERMOST,
- have_bound_regions: false,
- lifetimes: Default::default(),
- };
- gather.visit_ty(input);
-
- lifetime_count += gather.lifetimes.len();
-
- if lifetime_count == 1 && gather.lifetimes.len() == 1 {
- // there's a chance that the unique lifetime of this
- // iteration will be the appropriate lifetime for output
- // parameters, so lets store it.
- possible_implied_output_region = gather.lifetimes.iter().cloned().next();
- }
-
- ElisionFailureInfo {
- parent: body,
- index: i,
- lifetime_count: gather.lifetimes.len(),
- have_bound_regions: gather.have_bound_regions,
- }
- })
- .collect();
-
- let elide = if lifetime_count == 1 {
- Elide::Exact(possible_implied_output_region.unwrap())
- } else {
- Elide::Error(arg_lifetimes)
- };
-
- debug!("visit_fn_like_elision: elide={:?}", elide);
-
- let scope = Scope::Elision {
- elide,
- s: self.scope,
- };
- self.with(scope, |_, this| this.visit_ty(output));
- debug!("visit_fn_like_elision: exit");
-
- struct GatherLifetimes<'a> {
- map: &'a NamedRegionMap,
- outer_index: ty::DebruijnIndex,
- have_bound_regions: bool,
- lifetimes: FxHashSet<Region>,
- }
-
- impl<'v, 'a> Visitor<'v> for GatherLifetimes<'a> {
- fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
- NestedVisitorMap::None
- }
-
- fn visit_ty(&mut self, ty: &hir::Ty) {
- if let hir::TyKind::BareFn(_) = ty.node {
- self.outer_index.shift_in(1);
- }
- match ty.node {
- hir::TyKind::TraitObject(ref bounds, ref lifetime) => {
- for bound in bounds {
- self.visit_poly_trait_ref(bound, hir::TraitBoundModifier::None);
- }
-
- // Stay on the safe side and don't include the object
- // lifetime default (which may not end up being used).
- if !lifetime.is_elided() {
- self.visit_lifetime(lifetime);
- }
- }
- hir::TyKind::CVarArgs(_) => {}
- _ => {
- intravisit::walk_ty(self, ty);
- }
- }
- if let hir::TyKind::BareFn(_) = ty.node {
- self.outer_index.shift_out(1);
- }
- }
-
- fn visit_generic_param(&mut self, param: &hir::GenericParam) {
- if let hir::GenericParamKind::Lifetime { .. } = param.kind {
- // FIXME(eddyb) Do we want this? It only makes a difference
- // if this `for<'a>` lifetime parameter is never used.
- self.have_bound_regions = true;
- }
-
- intravisit::walk_generic_param(self, param);
- }
-
- fn visit_poly_trait_ref(
- &mut self,
- trait_ref: &hir::PolyTraitRef,
- modifier: hir::TraitBoundModifier,
- ) {
- self.outer_index.shift_in(1);
- intravisit::walk_poly_trait_ref(self, trait_ref, modifier);
- self.outer_index.shift_out(1);
- }
-
- fn visit_lifetime(&mut self, lifetime_ref: &hir::Lifetime) {
- if let Some(&lifetime) = self.map.defs.get(&lifetime_ref.hir_id) {
- match lifetime {
- Region::LateBound(debruijn, _, _) | Region::LateBoundAnon(debruijn, _)
- if debruijn < self.outer_index =>
- {
- self.have_bound_regions = true;
- }
- _ => {
- self.lifetimes
- .insert(lifetime.shifted_out_to_binder(self.outer_index));
- }
- }
- }
- }
- }
- }
-
- fn resolve_elided_lifetimes(&mut self, lifetime_refs: Vec<&'tcx hir::Lifetime>) {
- debug!("resolve_elided_lifetimes(lifetime_refs={:?})", lifetime_refs);
-
- if lifetime_refs.is_empty() {
- return;
- }
-
- let span = lifetime_refs[0].span;
- let mut late_depth = 0;
- let mut scope = self.scope;
- let mut lifetime_names = FxHashSet::default();
- let error = loop {
- match *scope {
- // Do not assign any resolution, it will be inferred.
- Scope::Body { .. } => return,
-
- Scope::Root => break None,
-
- Scope::Binder { s, ref lifetimes, .. } => {
- // collect named lifetimes for suggestions
- for name in lifetimes.keys() {
- if let hir::ParamName::Plain(name) = name {
- lifetime_names.insert(*name);
- }
- }
- late_depth += 1;
- scope = s;
- }
-
- Scope::Elision { ref elide, ref s, .. } => {
- let lifetime = match *elide {
- Elide::FreshLateAnon(ref counter) => {
- for lifetime_ref in lifetime_refs {
- let lifetime = Region::late_anon(counter).shifted(late_depth);
- self.insert_lifetime(lifetime_ref, lifetime);
- }
- return;
- }
- Elide::Exact(l) => l.shifted(late_depth),
- Elide::Error(ref e) => {
- if let Scope::Binder { ref lifetimes, .. } = s {
- // collect named lifetimes for suggestions
- for name in lifetimes.keys() {
- if let hir::ParamName::Plain(name) = name {
- lifetime_names.insert(*name);
- }
- }
- }
- break Some(e);
- }
- };
- for lifetime_ref in lifetime_refs {
- self.insert_lifetime(lifetime_ref, lifetime);
- }
- return;
- }
-
- Scope::ObjectLifetimeDefault { s, .. } => {
- scope = s;
- }
- }
- };
-
- let mut err = report_missing_lifetime_specifiers(self.tcx.sess, span, lifetime_refs.len());
- let mut add_label = true;
-
- if let Some(params) = error {
- if lifetime_refs.len() == 1 {
- add_label = add_label && self.report_elision_failure(&mut err, params, span);
- }
- }
- if add_label {
- add_missing_lifetime_specifiers_label(
- &mut err,
- span,
- lifetime_refs.len(),
- &lifetime_names,
- self.tcx.sess.source_map().span_to_snippet(span).ok().as_ref().map(|s| s.as_str()),
- );
- }
-
- err.emit();
- }
-
- fn suggest_lifetime(&self, db: &mut DiagnosticBuilder<'_>, span: Span, msg: &str) -> bool {
- match self.tcx.sess.source_map().span_to_snippet(span) {
- Ok(ref snippet) => {
- let (sugg, applicability) = if snippet == "&" {
- ("&'static ".to_owned(), Applicability::MachineApplicable)
- } else if snippet == "'_" {
- ("'static".to_owned(), Applicability::MachineApplicable)
- } else {
- (format!("{} + 'static", snippet), Applicability::MaybeIncorrect)
- };
- db.span_suggestion(span, msg, sugg, applicability);
- false
- }
- Err(_) => {
- db.help(msg);
- true
- }
- }
- }
-
- fn report_elision_failure(
- &mut self,
- db: &mut DiagnosticBuilder<'_>,
- params: &[ElisionFailureInfo],
- span: Span,
- ) -> bool {
- let mut m = String::new();
- let len = params.len();
-
- let elided_params: Vec<_> = params
- .iter()
- .cloned()
- .filter(|info| info.lifetime_count > 0)
- .collect();
-
- let elided_len = elided_params.len();
-
- for (i, info) in elided_params.into_iter().enumerate() {
- let ElisionFailureInfo {
- parent,
- index,
- lifetime_count: n,
- have_bound_regions,
- } = info;
-
- let help_name = if let Some(ident) = parent.and_then(|body| {
- self.tcx.hir().body(body).params[index].pat.simple_ident()
- }) {
- format!("`{}`", ident)
- } else {
- format!("argument {}", index + 1)
- };
-
- m.push_str(
- &(if n == 1 {
- help_name
- } else {
- format!(
- "one of {}'s {} {}lifetimes",
- help_name,
- n,
- if have_bound_regions { "free " } else { "" }
- )
- })[..],
- );
-
- if elided_len == 2 && i == 0 {
- m.push_str(" or ");
- } else if i + 2 == elided_len {
- m.push_str(", or ");
- } else if i != elided_len - 1 {
- m.push_str(", ");
- }
- }
-
- if len == 0 {
- help!(
- db,
- "this function's return type contains a borrowed value, but \
- there is no value for it to be borrowed from"
- );
- self.suggest_lifetime(db, span, "consider giving it a 'static lifetime")
- } else if elided_len == 0 {
- help!(
- db,
- "this function's return type contains a borrowed value with \
- an elided lifetime, but the lifetime cannot be derived from \
- the arguments"
- );
- let msg = "consider giving it an explicit bounded or 'static lifetime";
- self.suggest_lifetime(db, span, msg)
- } else if elided_len == 1 {
- help!(
- db,
- "this function's return type contains a borrowed value, but \
- the signature does not say which {} it is borrowed from",
- m
- );
- true
- } else {
- help!(
- db,
- "this function's return type contains a borrowed value, but \
- the signature does not say whether it is borrowed from {}",
- m
- );
- true
- }
- }
-
- 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, .. } => {
- late_depth += 1;
- scope = s;
- }
-
- Scope::Root | Scope::Elision { .. } => break Region::Static,
-
- Scope::Body { .. } | Scope::ObjectLifetimeDefault { lifetime: None, .. } => return,
-
- Scope::ObjectLifetimeDefault {
- lifetime: Some(l), ..
- } => break l,
- }
- };
- self.insert_lifetime(lifetime_ref, lifetime.shifted(late_depth));
- }
-
- fn check_lifetime_params(
- &mut self,
- old_scope: ScopeRef<'_>,
- params: &'tcx [hir::GenericParam],
- ) {
- let lifetimes: Vec<_> = params
- .iter()
- .filter_map(|param| match param.kind {
- GenericParamKind::Lifetime { .. } => Some((param, param.name.modern())),
- _ => None,
- })
- .collect();
- for (i, (lifetime_i, lifetime_i_name)) in lifetimes.iter().enumerate() {
- if let hir::ParamName::Plain(_) = lifetime_i_name {
- let name = lifetime_i_name.ident().name;
- if name == kw::UnderscoreLifetime
- || name == kw::StaticLifetime
- {
- let mut err = struct_span_err!(
- self.tcx.sess,
- lifetime_i.span,
- E0262,
- "invalid lifetime parameter name: `{}`",
- lifetime_i.name.ident(),
- );
- err.span_label(
- lifetime_i.span,
- format!("{} is a reserved lifetime name", name),
- );
- err.emit();
- }
- }
-
- // It is a hard error to shadow a lifetime within the same scope.
- for (lifetime_j, lifetime_j_name) in lifetimes.iter().skip(i + 1) {
- if lifetime_i_name == lifetime_j_name {
- struct_span_err!(
- self.tcx.sess,
- lifetime_j.span,
- E0263,
- "lifetime name `{}` declared twice in the same scope",
- lifetime_j.name.ident()
- ).span_label(lifetime_j.span, "declared twice")
- .span_label(lifetime_i.span, "previous declaration here")
- .emit();
- }
- }
-
- // It is a soft error to shadow a lifetime within a parent scope.
- self.check_lifetime_param_for_shadowing(old_scope, &lifetime_i);
-
- for bound in &lifetime_i.bounds {
- match bound {
- hir::GenericBound::Outlives(lt) => match lt.name {
- hir::LifetimeName::Underscore => self.tcx.sess.delay_span_bug(
- lt.span,
- "use of `'_` in illegal place, but not caught by lowering",
- ),
- hir::LifetimeName::Static => {
- self.insert_lifetime(lt, Region::Static);
- self.tcx
- .sess
- .struct_span_warn(
- lifetime_i.span.to(lt.span),
- &format!(
- "unnecessary lifetime parameter `{}`",
- lifetime_i.name.ident(),
- ),
- )
- .help(&format!(
- "you can use the `'static` lifetime directly, in place of `{}`",
- lifetime_i.name.ident(),
- ))
- .emit();
- }
- hir::LifetimeName::Param(_) | hir::LifetimeName::Implicit => {
- self.resolve_lifetime_ref(lt);
- }
- hir::LifetimeName::ImplicitObjectLifetimeDefault => {
- self.tcx.sess.delay_span_bug(
- lt.span,
- "lowering generated `ImplicitObjectLifetimeDefault` \
- outside of an object type",
- )
- }
- hir::LifetimeName::Error => {
- // No need to do anything, error already reported.
- }
- },
- _ => bug!(),
- }
- }
- }
- }
-
- fn check_lifetime_param_for_shadowing(
- &self,
- mut old_scope: ScopeRef<'_>,
- param: &'tcx hir::GenericParam,
- ) {
- for label in &self.labels_in_fn {
- // FIXME (#24278): non-hygienic comparison
- if param.name.ident().name == label.name {
- signal_shadowing_problem(
- self.tcx,
- label.name,
- original_label(label.span),
- shadower_lifetime(¶m),
- );
- return;
- }
- }
-
- loop {
- match *old_scope {
- Scope::Body { s, .. }
- | Scope::Elision { s, .. }
- | Scope::ObjectLifetimeDefault { s, .. } => {
- old_scope = s;
- }
-
- Scope::Root => {
- return;
- }
-
- Scope::Binder {
- ref lifetimes, s, ..
- } => {
- if let Some(&def) = lifetimes.get(¶m.name.modern()) {
- let hir_id = self.tcx.hir().as_local_hir_id(def.id().unwrap()).unwrap();
-
- signal_shadowing_problem(
- self.tcx,
- param.name.ident().name,
- original_lifetime(self.tcx.hir().span(hir_id)),
- shadower_lifetime(¶m),
- );
- return;
- }
-
- old_scope = s;
- }
- }
- }
- }
-
- /// Returns `true` if, in the current scope, replacing `'_` would be
- /// equivalent to a single-use lifetime.
- fn track_lifetime_uses(&self) -> bool {
- let mut scope = self.scope;
- loop {
- match *scope {
- Scope::Root => break false,
-
- // Inside of items, it depends on the kind of item.
- Scope::Binder {
- track_lifetime_uses,
- ..
- } => break track_lifetime_uses,
-
- // Inside a body, `'_` will use an inference variable,
- // should be fine.
- Scope::Body { .. } => break true,
-
- // A lifetime only used in a fn argument could as well
- // be replaced with `'_`, as that would generate a
- // fresh name, too.
- Scope::Elision {
- elide: Elide::FreshLateAnon(_),
- ..
- } => break true,
-
- // In the return type or other such place, `'_` is not
- // going to make a fresh name, so we cannot
- // necessarily replace a single-use lifetime with
- // `'_`.
- Scope::Elision {
- elide: Elide::Exact(_),
- ..
- } => break false,
- Scope::Elision {
- elide: Elide::Error(_),
- ..
- } => break false,
-
- Scope::ObjectLifetimeDefault { s, .. } => scope = s,
- }
- }
- }
-
- fn insert_lifetime(&mut self, lifetime_ref: &'tcx hir::Lifetime, def: Region) {
- if lifetime_ref.hir_id == hir::DUMMY_HIR_ID {
- span_bug!(
- lifetime_ref.span,
- "lifetime reference not renumbered, \
- probably a bug in syntax::fold"
- );
- }
-
- debug!(
- "insert_lifetime: {} resolved to {:?} span={:?}",
- self.tcx.hir().node_to_string(lifetime_ref.hir_id),
- def,
- self.tcx.sess.source_map().span_to_string(lifetime_ref.span)
- );
- self.map.defs.insert(lifetime_ref.hir_id, def);
-
- match def {
- Region::LateBoundAnon(..) | Region::Static => {
- // These are anonymous lifetimes or lifetimes that are not declared.
- }
-
- Region::Free(_, def_id)
- | Region::LateBound(_, def_id, _)
- | Region::EarlyBound(_, def_id, _) => {
- // A lifetime declared by the user.
- let track_lifetime_uses = self.track_lifetime_uses();
- debug!(
- "insert_lifetime: track_lifetime_uses={}",
- track_lifetime_uses
- );
- if track_lifetime_uses && !self.lifetime_uses.contains_key(&def_id) {
- debug!("insert_lifetime: first use of {:?}", def_id);
- self.lifetime_uses
- .insert(def_id, LifetimeUseSet::One(lifetime_ref));
- } else {
- debug!("insert_lifetime: many uses of {:?}", def_id);
- self.lifetime_uses.insert(def_id, LifetimeUseSet::Many);
- }
- }
- }
- }
-
- /// 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
-/// `map.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 insert_late_bound_lifetimes(
- map: &mut NamedRegionMap,
- decl: &hir::FnDecl,
- generics: &hir::Generics,
-) {
- debug!(
- "insert_late_bound_lifetimes(decl={:?}, generics={:?})",
- decl, generics
- );
-
- 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!(
- "insert_late_bound_lifetimes: constrained_by_input={:?}",
- 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);
-
- for param in &generics.params {
- if let hir::GenericParamKind::Lifetime { .. } = param.kind {
- if !param.bounds.is_empty() {
- // `'a: 'b` means both `'a` and `'b` are referenced
- appears_in_where_clause
- .regions
- .insert(hir::LifetimeName::Param(param.name.modern()));
- }
- }
- }
-
- debug!(
- "insert_late_bound_lifetimes: appears_in_where_clause={:?}",
- 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 lt_name = hir::LifetimeName::Param(param.name.modern());
- // appears in the where clauses? early-bound.
- if appears_in_where_clause.regions.contains(<_name) {
- continue;
- }
-
- // does not appear in the inputs, but appears in the return type? early-bound.
- if !constrained_by_input.regions.contains(<_name)
- && appears_in_output.regions.contains(<_name)
- {
- continue;
- }
-
- debug!(
- "insert_late_bound_lifetimes: lifetime {:?} with id {:?} is late-bound",
- param.name.ident(),
- param.hir_id
- );
-
- let inserted = map.late_bound.insert(param.hir_id);
- assert!(inserted, "visited lifetime {:?} twice", param.hir_id);
- }
-
- return;
-
- #[derive(Default)]
- struct ConstrainedCollector {
- regions: FxHashSet<hir::LifetimeName>,
- }
-
- impl<'v> Visitor<'v> for ConstrainedCollector {
- fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
- NestedVisitorMap::None
- }
-
- fn visit_ty(&mut self, ty: &'v hir::Ty) {
- match ty.node {
- hir::TyKind::Path(hir::QPath::Resolved(Some(_), _))
- | hir::TyKind::Path(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) {
- self.regions.insert(lifetime_ref.name.modern());
- }
- }
-
- #[derive(Default)]
- struct AllCollector {
- regions: FxHashSet<hir::LifetimeName>,
- }
-
- impl<'v> Visitor<'v> for AllCollector {
- fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
- NestedVisitorMap::None
- }
-
- fn visit_lifetime(&mut self, lifetime_ref: &'v hir::Lifetime) {
- self.regions.insert(lifetime_ref.name.modern());
- }
- }
-}
-
-pub fn report_missing_lifetime_specifiers(
- sess: &Session,
- span: Span,
- count: usize,
-) -> DiagnosticBuilder<'_> {
- struct_span_err!(
- sess,
- span,
- E0106,
- "missing lifetime specifier{}",
- pluralise!(count)
- )
-}
-
-fn add_missing_lifetime_specifiers_label(
- err: &mut DiagnosticBuilder<'_>,
- span: Span,
- count: usize,
- lifetime_names: &FxHashSet<ast::Ident>,
- snippet: Option<&str>,
-) {
- if count > 1 {
- err.span_label(span, format!("expected {} lifetime parameters", count));
- } else if let (1, Some(name), Some("&")) = (
- lifetime_names.len(),
- lifetime_names.iter().next(),
- snippet,
- ) {
- err.span_suggestion(
- span,
- "consider using the named lifetime",
- format!("&{} ", name),
- Applicability::MaybeIncorrect,
- );
- } else {
- err.span_label(span, "expected lifetime parameter");
- }
-}
projects / rustc.git / blobdiff