-// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
+//! Name resolution for lifetimes: type declarations.
-//! 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.
+use crate::ty;
-use dep_graph::DepNode;
-use hir::map::Map;
-use session::Session;
-use hir::def::Def;
-use hir::def_id::DefId;
-use middle::region;
-use ty;
+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::cell::Cell;
-use std::mem::replace;
-use syntax::ast;
-use syntax::attr;
-use syntax::ptr::P;
-use syntax::symbol::keywords;
-use syntax_pos::Span;
-use errors::DiagnosticBuilder;
-use util::nodemap::{NodeMap, FxHashSet, FxHashMap, DefIdMap};
-use rustc_back::slice;
-
-use hir;
-use hir::intravisit::{self, Visitor, NestedVisitorMap};
-
-#[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Debug)]
-pub enum Region {
- Static,
- EarlyBound(/* index */ u32, /* lifetime decl */ ast::NodeId),
- LateBound(ty::DebruijnIndex, /* lifetime decl */ ast::NodeId),
- LateBoundAnon(ty::DebruijnIndex, /* anon index */ u32),
- Free(region::CallSiteScopeData, /* lifetime decl */ ast::NodeId),
+/// The origin of a named lifetime definition.
+///
+/// This is used to prevent the usage of in-band lifetimes in `Fn`/`fn` syntax.
+#[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Debug, HashStable)]
+pub enum LifetimeDefOrigin {
+ // Explicit binders like `fn foo<'a>(x: &'a u8)` or elided like `impl Foo<&u32>`
+ ExplicitOrElided,
+ // In-band declarations like `fn foo(x: &'a u8)`
+ InBand,
+ // Some kind of erroneous origin
+ Error,
}
-impl Region {
- fn early(index: &mut u32, def: &hir::LifetimeDef) -> (ast::Name, Region) {
- let i = *index;
- *index += 1;
- (def.lifetime.name, Region::EarlyBound(i, def.lifetime.id))
- }
-
- fn late(def: &hir::LifetimeDef) -> (ast::Name, Region) {
- let depth = ty::DebruijnIndex::new(1);
- (def.lifetime.name, Region::LateBound(depth, def.lifetime.id))
- }
-
- fn late_anon(index: &Cell<u32>) -> Region {
- let i = index.get();
- index.set(i + 1);
- let depth = ty::DebruijnIndex::new(1);
- Region::LateBoundAnon(depth, i)
- }
-
- fn id(&self) -> Option<ast::NodeId> {
- 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(depth, id) => {
- Region::LateBound(depth.shifted(amount), id)
- }
- Region::LateBoundAnon(depth, index) => {
- Region::LateBoundAnon(depth.shifted(amount), index)
- }
- _ => self
- }
- }
-
- fn from_depth(self, depth: u32) -> Region {
- match self {
- Region::LateBound(debruijn, id) => {
- Region::LateBound(ty::DebruijnIndex {
- depth: debruijn.depth - (depth - 1)
- }, id)
- }
- Region::LateBoundAnon(debruijn, index) => {
- Region::LateBoundAnon(ty::DebruijnIndex {
- depth: debruijn.depth - (depth - 1)
- }, index)
- }
- _ => self
+impl LifetimeDefOrigin {
+ pub fn from_param(param: &GenericParam<'_>) -> Self {
+ match param.kind {
+ GenericParamKind::Lifetime { kind } => match kind {
+ LifetimeParamKind::InBand => LifetimeDefOrigin::InBand,
+ LifetimeParamKind::Explicit => LifetimeDefOrigin::ExplicitOrElided,
+ LifetimeParamKind::Elided => LifetimeDefOrigin::ExplicitOrElided,
+ LifetimeParamKind::Error => LifetimeDefOrigin::Error,
+ },
+ _ => bug!("expected a lifetime param"),
}
}
+}
- fn subst(self, params: &[hir::Lifetime], map: &NamedRegionMap)
- -> Option<Region> {
- if let Region::EarlyBound(index, _) = self {
- params.get(index as usize).and_then(|lifetime| {
- map.defs.get(&lifetime.id).cloned()
- })
- } else {
- Some(self)
- }
- }
+#[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),
+ LateBoundAnon(ty::DebruijnIndex, /* anon index */ u32),
+ Free(DefId, /* lifetime decl */ DefId),
}
/// 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.
-#[derive(Copy, Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Debug)]
+#[derive(Copy, Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Debug, HashStable)]
pub enum Set1<T> {
Empty,
One(T),
- Many
+ Many,
}
impl<T: PartialEq> Set1<T> {
pub fn insert(&mut self, value: T) {
- if let Set1::Empty = *self {
- *self = Set1::One(value);
- return;
- }
- if let Set1::One(ref old) = *self {
- if *old == value {
- return;
- }
- }
- *self = Set1::Many;
- }
-}
-
-pub type ObjectLifetimeDefault = Set1<Region>;
-
-// Maps the id of each lifetime reference to the lifetime decl
-// that it corresponds to.
-pub struct NamedRegionMap {
- // maps from every use of a named (not anonymous) lifetime to a
- // `Region` describing how that region is bound
- pub defs: NodeMap<Region>,
-
- // the set of lifetime def ids that are late-bound; late-bound ids
- // are named regions appearing in fn arguments that do not appear
- // in where-clauses
- pub late_bound: NodeMap<ty::Issue32330>,
-
- // For each type and trait definition, maps type parameters
- // to the trait object lifetime defaults computed from them.
- pub object_lifetime_defaults: NodeMap<Vec<ObjectLifetimeDefault>>,
-}
-
-struct LifetimeContext<'a, 'tcx: 'a> {
- sess: &'a Session,
- hir_map: &'a Map<'tcx>,
- map: &'a mut NamedRegionMap,
- scope: ScopeRef<'a>,
- // Deep breath. 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.
-
- // I'm sorry.
- trait_ref_hack: bool,
-
- // List of labels in the function/method currently under analysis.
- labels_in_fn: Vec<(ast::Name, Span)>,
-
- // 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 {
- lifetimes: FxHashMap<ast::Name, Region>,
- 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),
- /// Like `Exact(Static)` but requires `#![feature(static_in_const)]`.
- Static,
- /// 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 krate(sess: &Session,
- hir_map: &Map)
- -> Result<NamedRegionMap, usize> {
- let _task = hir_map.dep_graph.in_task(DepNode::ResolveLifetimes);
- let krate = hir_map.krate();
- let mut map = NamedRegionMap {
- defs: NodeMap(),
- late_bound: NodeMap(),
- object_lifetime_defaults: compute_object_lifetime_defaults(sess, hir_map),
- };
- sess.track_errors(|| {
- let mut visitor = LifetimeContext {
- sess: sess,
- hir_map: hir_map,
- map: &mut map,
- scope: ROOT_SCOPE,
- trait_ref_hack: false,
- labels_in_fn: vec![],
- xcrate_object_lifetime_defaults: DefIdMap(),
- };
- for (_, item) in &krate.items {
- visitor.visit_item(item);
- }
- })?;
- Ok(map)
-}
-
-impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
- fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
- NestedVisitorMap::All(self.hir_map)
- }
-
- // 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 = replace(&mut self.labels_in_fn, vec![]);
- let body = self.hir_map.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::ItemFn(ref decl, _, _, _, ref generics, _) => {
- self.visit_early_late(item.id, None, decl, generics, |this| {
- intravisit::walk_item(this, item);
- });
- }
- hir::ItemExternCrate(_) |
- hir::ItemUse(..) |
- hir::ItemMod(..) |
- hir::ItemDefaultImpl(..) |
- hir::ItemForeignMod(..) => {
- // These sorts of items have no lifetime parameters at all.
- intravisit::walk_item(self, item);
- }
- hir::ItemStatic(..) |
- hir::ItemConst(..) => {
- // No lifetime parameters, but implied 'static.
- let scope = Scope::Elision {
- elide: Elide::Static,
- s: ROOT_SCOPE
- };
- self.with(scope, |_, this| intravisit::walk_item(this, item));
- }
- hir::ItemTy(_, ref generics) |
- hir::ItemEnum(_, ref generics) |
- hir::ItemStruct(_, ref generics) |
- hir::ItemUnion(_, ref generics) |
- hir::ItemTrait(_, ref generics, ..) |
- hir::ItemImpl(_, _, ref generics, ..) => {
- // These kinds of items have only early bound lifetime parameters.
- let mut index = if let hir::ItemTrait(..) = item.node {
- 1 // Self comes before lifetimes
- } else {
- 0
- };
- let lifetimes = generics.lifetimes.iter().map(|def| {
- Region::early(&mut index, def)
- }).collect();
- let scope = Scope::Binder {
- lifetimes: lifetimes,
- s: ROOT_SCOPE
- };
- self.with(scope, |old_scope, this| {
- this.check_lifetime_defs(old_scope, &generics.lifetimes);
- intravisit::walk_item(this, item);
- });
- }
- }
- }
-
- fn visit_foreign_item(&mut self, item: &'tcx hir::ForeignItem) {
- match item.node {
- hir::ForeignItemFn(ref decl, _, ref generics) => {
- self.visit_early_late(item.id, None, decl, generics, |this| {
- intravisit::walk_foreign_item(this, item);
- })
- }
- hir::ForeignItemStatic(..) => {
- intravisit::walk_foreign_item(self, item);
- }
- }
- }
-
- fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
- match ty.node {
- hir::TyBareFn(ref c) => {
- let scope = Scope::Binder {
- lifetimes: c.lifetimes.iter().map(Region::late).collect(),
- s: self.scope
- };
- self.with(scope, |old_scope, this| {
- // a bare fn has no bounds, so everything
- // contained within is scoped within its binder.
- this.check_lifetime_defs(old_scope, &c.lifetimes);
- intravisit::walk_ty(this, ty);
- });
- }
- hir::TyTraitObject(ref bounds, ref lifetime) => {
- for bound in bounds {
- self.visit_poly_trait_ref(bound, hir::TraitBoundModifier::None);
- }
- if lifetime.is_elided() {
- self.resolve_object_lifetime_default(lifetime)
- } else {
- self.visit_lifetime(lifetime);
- }
- }
- hir::TyRptr(ref lifetime_ref, ref mt) => {
- self.visit_lifetime(lifetime_ref);
- let scope = Scope::ObjectLifetimeDefault {
- lifetime: self.map.defs.get(&lifetime_ref.id).cloned(),
- s: self.scope
- };
- self.with(scope, |_, this| this.visit_ty(&mt.ty));
- }
- _ => {
- intravisit::walk_ty(self, ty)
- }
- }
- }
-
- fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem) {
- if let hir::TraitItemKind::Method(ref sig, _) = trait_item.node {
- self.visit_early_late(
- trait_item.id,
- Some(self.hir_map.get_parent(trait_item.id)),
- &sig.decl, &sig.generics,
- |this| intravisit::walk_trait_item(this, trait_item))
- } else {
- intravisit::walk_trait_item(self, trait_item);
- }
- }
-
- fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem) {
- if let hir::ImplItemKind::Method(ref sig, _) = impl_item.node {
- self.visit_early_late(
- impl_item.id,
- Some(self.hir_map.get_parent(impl_item.id)),
- &sig.decl, &sig.generics,
- |this| intravisit::walk_impl_item(this, impl_item))
- } else {
- intravisit::walk_impl_item(self, impl_item);
- }
- }
-
- fn visit_lifetime(&mut self, lifetime_ref: &'tcx hir::Lifetime) {
- if lifetime_ref.is_elided() {
- self.resolve_elided_lifetimes(slice::ref_slice(lifetime_ref));
- return;
- }
- if lifetime_ref.name == keywords::StaticLifetime.name() {
- self.insert_lifetime(lifetime_ref, Region::Static);
- return;
- }
- self.resolve_lifetime_ref(lifetime_ref);
- }
-
- fn visit_path(&mut self, path: &'tcx hir::Path, _: ast::NodeId) {
- for (i, segment) in path.segments.iter().enumerate() {
- let depth = path.segments.len() - i - 1;
- self.visit_segment_parameters(path.def, depth, &segment.parameters);
- }
- }
-
- 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) {
- for ty_param in generics.ty_params.iter() {
- walk_list!(self, visit_ty_param_bound, &ty_param.bounds);
- if let Some(ref ty) = ty_param.default {
- 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_lifetimes,
- .. }) => {
- if !bound_lifetimes.is_empty() {
- self.trait_ref_hack = true;
- let scope = Scope::Binder {
- lifetimes: bound_lifetimes.iter().map(Region::late).collect(),
- s: self.scope
- };
- let result = self.with(scope, |old_scope, this| {
- this.check_lifetime_defs(old_scope, bound_lifetimes);
- this.visit_ty(&bounded_ty);
- walk_list!(this, visit_ty_param_bound, bounds);
- });
- self.trait_ref_hack = false;
- result
- } else {
- self.visit_ty(&bounded_ty);
- walk_list!(self, visit_ty_param_bound, bounds);
- }
- }
- &hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate{ref lifetime,
- ref bounds,
- .. }) => {
-
- self.visit_lifetime(lifetime);
- for bound in bounds {
- self.visit_lifetime(bound);
- }
- }
- &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_lifetimes.is_empty() {
- if self.trait_ref_hack {
- span_err!(self.sess, trait_ref.span, E0316,
- "nested quantification of lifetimes");
- }
- let scope = Scope::Binder {
- lifetimes: trait_ref.bound_lifetimes.iter().map(Region::late).collect(),
- s: self.scope
- };
- self.with(scope, |old_scope, this| {
- this.check_lifetime_defs(old_scope, &trait_ref.bound_lifetimes);
- for lifetime in &trait_ref.bound_lifetimes {
- this.visit_lifetime_def(lifetime);
- }
- 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(l: &hir::Lifetime) -> Shadower {
- Shadower { kind: ShadowKind::Lifetime, span: l.span }
-}
-
-impl ShadowKind {
- fn desc(&self) -> &'static str {
- match *self {
- ShadowKind::Label => "label",
- ShadowKind::Lifetime => "lifetime",
- }
- }
-}
-
-fn signal_shadowing_problem(sess: &Session, 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!(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.
- 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: 'a> {
- sess: &'a Session,
- hir_map: &'a Map<'tcx>,
- scope: ScopeRef<'a>,
- labels_in_fn: &'a mut Vec<(ast::Name, Span)>,
- }
-
- let mut gather = GatherLabels {
- sess: ctxt.sess,
- hir_map: ctxt.hir_map,
- 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, label_span)) = expression_label(ex) {
- for &(prior, prior_span) in &self.labels_in_fn[..] {
- // FIXME (#24278): non-hygienic comparison
- if label == prior {
- signal_shadowing_problem(self.sess,
- label,
- original_label(prior_span),
- shadower_label(label_span));
- }
- }
-
- check_if_label_shadows_lifetime(self.sess,
- self.hir_map,
- self.scope,
- label,
- label_span);
-
- self.labels_in_fn.push((label, label_span));
- }
- intravisit::walk_expr(self, ex)
- }
- }
-
- fn expression_label(ex: &hir::Expr) -> Option<(ast::Name, Span)> {
- match ex.node {
- hir::ExprWhile(.., Some(label)) |
- hir::ExprLoop(_, Some(label), _) => Some((label.node, label.span)),
- _ => None,
- }
- }
-
- fn check_if_label_shadows_lifetime<'a>(sess: &'a Session,
- hir_map: &Map,
- mut scope: ScopeRef<'a>,
- label: ast::Name,
- label_span: Span) {
- 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(&label) {
- signal_shadowing_problem(
- sess,
- label,
- original_lifetime(hir_map.span(def.id().unwrap())),
- shadower_label(label_span));
- return;
- }
- scope = s;
- }
- }
- }
- }
-}
-
-fn compute_object_lifetime_defaults(sess: &Session, hir_map: &Map)
- -> NodeMap<Vec<ObjectLifetimeDefault>> {
- let mut map = NodeMap();
- for item in hir_map.krate().items.values() {
- match item.node {
- hir::ItemStruct(_, ref generics) |
- hir::ItemUnion(_, ref generics) |
- hir::ItemEnum(_, ref generics) |
- hir::ItemTy(_, ref generics) |
- hir::ItemTrait(_, ref generics, ..) => {
- let result = object_lifetime_defaults_for_item(hir_map, generics);
-
- // Debugging aid.
- if attr::contains_name(&item.attrs, "rustc_object_lifetime_default") {
- let object_lifetime_default_reprs: String =
- result.iter().map(|set| {
- match *set {
- Set1::Empty => "BaseDefault".to_string(),
- Set1::One(Region::Static) => "'static".to_string(),
- Set1::One(Region::EarlyBound(i, _)) => {
- generics.lifetimes[i as usize].lifetime.name.to_string()
- }
- Set1::One(_) => bug!(),
- Set1::Many => "Ambiguous".to_string(),
- }
- }).collect::<Vec<String>>().join(",");
- sess.span_err(item.span, &object_lifetime_default_reprs);
- }
-
- map.insert(item.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(hir_map: &Map, generics: &hir::Generics)
- -> Vec<ObjectLifetimeDefault> {
- fn add_bounds(set: &mut Set1<ast::Name>, bounds: &[hir::TyParamBound]) {
- for bound in bounds {
- if let hir::RegionTyParamBound(ref lifetime) = *bound {
- set.insert(lifetime.name);
- }
- }
- }
-
- generics.ty_params.iter().map(|param| {
- let mut set = Set1::Empty;
-
- add_bounds(&mut set, ¶m.bounds);
-
- let param_def_id = hir_map.local_def_id(param.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_lifetimes.is_empty() {
- continue;
- }
-
- let def = match data.bounded_ty.node {
- hir::TyPath(hir::QPath::Resolved(None, ref path)) => path.def,
- _ => continue
- };
-
- if def == Def::TyParam(param_def_id) {
- add_bounds(&mut set, &data.bounds);
- }
- }
-
- match set {
- Set1::Empty => Set1::Empty,
- Set1::One(name) => {
- if name == keywords::StaticLifetime.name() {
- Set1::One(Region::Static)
- } else {
- generics.lifetimes.iter().enumerate().find(|&(_, def)| {
- def.lifetime.name == name
- }).map_or(Set1::Many, |(i, def)| {
- Set1::One(Region::EarlyBound(i as u32, def.lifetime.id))
- })
- }
- }
- Set1::Many => Set1::Many
- }
- }).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 {sess, hir_map, ref mut map, ..} = *self;
- let labels_in_fn = replace(&mut self.labels_in_fn, vec![]);
- let xcrate_object_lifetime_defaults =
- replace(&mut self.xcrate_object_lifetime_defaults, DefIdMap());
- let mut this = LifetimeContext {
- sess: sess,
- hir_map: hir_map,
- map: *map,
- scope: &wrap_scope,
- trait_ref_hack: self.trait_ref_hack,
- labels_in_fn: labels_in_fn,
- xcrate_object_lifetime_defaults: xcrate_object_lifetime_defaults,
- };
- debug!("entering scope {:?}", this.scope);
- f(self.scope, &mut this);
- debug!("exiting scope {:?}", this.scope);
- self.labels_in_fn = this.labels_in_fn;
- 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,
- fn_id: ast::NodeId,
- parent_id: Option<ast::NodeId>,
- decl: &'tcx hir::FnDecl,
- generics: &'tcx hir::Generics,
- walk: F) where
- F: for<'b, 'c> FnOnce(&'b mut LifetimeContext<'c, 'tcx>),
- {
- let fn_def_id = self.hir_map.local_def_id(fn_id);
- insert_late_bound_lifetimes(self.map,
- fn_def_id,
- 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.hir_map.expect_item(parent_id);
- if let hir::ItemTrait(..) = parent.node {
- index += 1; // Self comes first.
- }
- match parent.node {
- hir::ItemTrait(_, ref generics, ..) |
- hir::ItemImpl(_, _, ref generics, ..) => {
- index += (generics.lifetimes.len() + generics.ty_params.len()) as u32;
- }
- _ => {}
- }
- }
-
- let lifetimes = generics.lifetimes.iter().map(|def| {
- if self.map.late_bound.contains_key(&def.lifetime.id) {
- Region::late(def)
- } else {
- Region::early(&mut index, def)
- }
- }).collect();
-
- let scope = Scope::Binder {
- lifetimes: lifetimes,
- s: self.scope
- };
- self.with(scope, move |old_scope, this| {
- this.check_lifetime_defs(old_scope, &generics.lifetimes);
- this.hack(walk); // FIXME(#37666) workaround in place of `walk(this)`
- });
- }
-
- fn resolve_lifetime_ref(&mut self, lifetime_ref: &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, s } => {
- if let Some(&def) = lifetimes.get(&lifetime_ref.name) {
- break Some(def.shifted(late_depth));
- } else {
- late_depth += 1;
- scope = s;
- }
- }
-
- Scope::Elision { s, .. } |
- Scope::ObjectLifetimeDefault { s, .. } => {
- scope = s;
- }
- }
- };
-
- if let Some(mut def) = result {
- if let Some(body_id) = outermost_body {
- let fn_id = self.hir_map.body_owner(body_id);
- let scope_data = region::CallSiteScopeData {
- fn_id: fn_id, body_id: body_id.node_id
- };
- match self.hir_map.get(fn_id) {
- hir::map::NodeItem(&hir::Item {
- node: hir::ItemFn(..), ..
- }) |
- hir::map::NodeTraitItem(&hir::TraitItem {
- node: hir::TraitItemKind::Method(..), ..
- }) |
- hir::map::NodeImplItem(&hir::ImplItem {
- node: hir::ImplItemKind::Method(..), ..
- }) => {
- def = Region::Free(scope_data, def.id().unwrap());
- }
- _ => {}
- }
- }
- self.insert_lifetime(lifetime_ref, def);
- } else {
- struct_span_err!(self.sess, lifetime_ref.span, E0261,
- "use of undeclared lifetime name `{}`", lifetime_ref.name)
- .span_label(lifetime_ref.span, &format!("undeclared lifetime"))
- .emit();
- }
- }
-
- fn visit_segment_parameters(&mut self,
- def: Def,
- depth: usize,
- params: &'tcx hir::PathParameters) {
- let data = match *params {
- hir::ParenthesizedParameters(ref data) => {
- self.visit_fn_like_elision(&data.inputs, data.output.as_ref());
- return;
- }
- hir::AngleBracketedParameters(ref data) => data
- };
-
- if data.lifetimes.iter().all(|l| l.is_elided()) {
- self.resolve_elided_lifetimes(&data.lifetimes);
- } else {
- for l in &data.lifetimes { self.visit_lifetime(l); }
- }
-
- // 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 = if def_id.is_local() {
- this.hir_map.def_key(def_id)
- } else {
- this.sess.cstore.def_key(def_id)
- };
- DefId {
- krate: def_id.krate,
- index: def_key.parent.expect("missing parent")
- }
- };
- let type_def_id = match def {
- Def::AssociatedTy(def_id) if depth == 1 => {
- Some(parent_def_id(self, def_id))
- }
- Def::Variant(def_id) if depth == 0 => {
- Some(parent_def_id(self, def_id))
- }
- Def::Struct(def_id) |
- Def::Union(def_id) |
- Def::Enum(def_id) |
- Def::TyAlias(def_id) |
- Def::Trait(def_id) if depth == 0 => Some(def_id),
- _ => None
- };
-
- 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.hir_map.as_local_node_id(def_id) {
- &map.object_lifetime_defaults[&id]
- } else {
- let cstore = &self.sess.cstore;
- self.xcrate_object_lifetime_defaults.entry(def_id).or_insert_with(|| {
- cstore.item_generics_object_lifetime_defaults(def_id)
- })
- };
- unsubst.iter().map(|set| {
- match *set {
- Set1::Empty => {
- if in_body {
- None
- } else {
- Some(Region::Static)
- }
- }
- Set1::One(r) => r.subst(&data.lifetimes, map),
- Set1::Many => None
- }
- }).collect()
- });
-
- for (i, ty) in data.types.iter().enumerate() {
- 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);
- }
- }
-
- for b in &data.bindings { self.visit_assoc_type_binding(b); }
- }
-
- fn visit_fn_like_elision(&mut self, inputs: &'tcx [P<hir::Ty>],
- output: Option<&'tcx P<hir::Ty>>) {
- 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
- };
-
- // 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.hir_map.get_parent_node(output.id);
- let body = match self.hir_map.get(parent) {
- // `fn` definitions and methods.
- hir::map::NodeItem(&hir::Item {
- node: hir::ItemFn(.., body), ..
- }) => Some(body),
-
- hir::map::NodeTraitItem(&hir::TraitItem {
- node: hir::TraitItemKind::Method(_, ref m), ..
- }) => {
- match self.hir_map.expect_item(self.hir_map.get_parent(parent)).node {
- hir::ItemTrait(.., ref trait_items) => {
- assoc_item_kind = trait_items.iter().find(|ti| ti.id.node_id == parent)
- .map(|ti| ti.kind);
- }
- _ => {}
- }
- match *m {
- hir::TraitMethod::Required(_) => None,
- hir::TraitMethod::Provided(body) => Some(body),
- }
- }
-
- hir::map::NodeImplItem(&hir::ImplItem {
- node: hir::ImplItemKind::Method(_, body), ..
- }) => {
- match self.hir_map.expect_item(self.hir_map.get_parent(parent)).node {
- hir::ItemImpl(.., ref self_ty, ref impl_items) => {
- impl_self = Some(self_ty);
- assoc_item_kind = impl_items.iter().find(|ii| ii.id.node_id == parent)
- .map(|ii| ii.kind);
- }
- _ => {}
- }
- Some(body)
- }
-
- // `fn(...) -> R` and `Trait(...) -> R` (both types and bounds).
- hir::map::NodeTy(_) | hir::map::NodeTraitRef(_) => None,
-
- // Foreign `fn` decls are terrible because we messed up,
- // and their return types get argument type elision.
- // And now too much code out there is abusing this rule.
- hir::map::NodeForeignItem(_) => {
- let arg_scope = Scope::Elision {
- elide: arg_elide,
- s: self.scope
- };
- self.with(arg_scope, |_, this| this.visit_ty(output));
- return;
- }
-
- // 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::AssociatedItemKind::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 {
- // Look for `self: &'a Self` - also desugared from `&'a self`,
- // and if that matches, use it for elision and return early.
- let is_self_ty = |def: Def| {
- if let Def::SelfTy(..) = def {
- return true;
- }
-
- // Can't always rely on literal (or implied) `Self` due
- // to the way elision rules were originally specified.
- let impl_self = impl_self.map(|ty| &ty.node);
- if let Some(&hir::TyPath(hir::QPath::Resolved(None, ref path))) = impl_self {
- match path.def {
- // Whitelist the types that unambiguously always
- // result in the same type constructor being used
- // (it can't differ between `Self` and `self`).
- Def::Struct(_) |
- Def::Union(_) |
- Def::Enum(_) |
- Def::PrimTy(_) => return def == path.def,
- _ => {}
- }
- }
-
- false
- };
-
- if let hir::TyRptr(lifetime_ref, ref mt) = inputs[0].node {
- if let hir::TyPath(hir::QPath::Resolved(None, ref path)) = mt.ty.node {
- if is_self_ty(path.def) {
- if let Some(&lifetime) = self.map.defs.get(&lifetime_ref.id) {
- 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,
- binder_depth: 1,
- have_bound_regions: false,
- lifetimes: FxHashSet()
- };
- 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)
+ *self = match self {
+ Set1::Empty => Set1::One(value),
+ Set1::One(old) if *old == value => return,
+ _ => Set1::Many,
};
-
- let scope = Scope::Elision {
- elide: elide,
- s: self.scope
- };
- self.with(scope, |_, this| this.visit_ty(output));
-
- struct GatherLifetimes<'a> {
- map: &'a NamedRegionMap,
- binder_depth: u32,
- 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::TyBareFn(_) = ty.node {
- self.binder_depth += 1;
- }
- if let hir::TyTraitObject(ref bounds, ref lifetime) = ty.node {
- 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);
- }
- } else {
- intravisit::walk_ty(self, ty);
- }
- if let hir::TyBareFn(_) = ty.node {
- self.binder_depth -= 1;
- }
- }
-
- fn visit_poly_trait_ref(&mut self,
- trait_ref: &hir::PolyTraitRef,
- modifier: hir::TraitBoundModifier) {
- self.binder_depth += 1;
- intravisit::walk_poly_trait_ref(self, trait_ref, modifier);
- self.binder_depth -= 1;
- }
-
- fn visit_lifetime_def(&mut self, lifetime_def: &hir::LifetimeDef) {
- for l in &lifetime_def.bounds { self.visit_lifetime(l); }
- }
-
- fn visit_lifetime(&mut self, lifetime_ref: &hir::Lifetime) {
- if let Some(&lifetime) = self.map.defs.get(&lifetime_ref.id) {
- match lifetime {
- Region::LateBound(debruijn, _) |
- Region::LateBoundAnon(debruijn, _)
- if debruijn.depth < self.binder_depth => {
- self.have_bound_regions = true;
- }
- _ => {
- self.lifetimes.insert(lifetime.from_depth(self.binder_depth));
- }
- }
- }
- }
- }
-
- }
-
- fn resolve_elided_lifetimes(&mut self, lifetime_refs: &[hir::Lifetime]) {
- if lifetime_refs.is_empty() {
- return;
- }
-
- let span = lifetime_refs[0].span;
- let mut late_depth = 0;
- let mut scope = self.scope;
- let error = loop {
- match *scope {
- // Do not assign any resolution, it will be inferred.
- Scope::Body { .. } => return,
-
- Scope::Root => break None,
-
- Scope::Binder { s, .. } => {
- late_depth += 1;
- scope = s;
- }
-
- Scope::Elision { ref elide, .. } => {
- 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::Static => {
- if !self.sess.features.borrow().static_in_const {
- self.sess
- .struct_span_err(span,
- "this needs a `'static` lifetime or the \
- `static_in_const` feature, see #35897")
- .emit();
- }
- Region::Static
- }
- Elide::Error(ref e) => break Some(e)
- };
- for lifetime_ref in lifetime_refs {
- self.insert_lifetime(lifetime_ref, lifetime);
- }
- return;
- }
-
- Scope::ObjectLifetimeDefault { s, .. } => {
- scope = s;
- }
- }
- };
-
- let mut err = struct_span_err!(self.sess, span, E0106,
- "missing lifetime specifier{}",
- if lifetime_refs.len() > 1 { "s" } else { "" });
- let msg = if lifetime_refs.len() > 1 {
- format!("expected {} lifetime parameters", lifetime_refs.len())
- } else {
- format!("expected lifetime parameter")
- };
- err.span_label(span, &msg);
-
- if let Some(params) = error {
- if lifetime_refs.len() == 1 {
- self.report_elision_failure(&mut err, params);
- }
- }
- err.emit();
- }
-
- fn report_elision_failure(&mut self,
- db: &mut DiagnosticBuilder,
- params: &[ElisionFailureInfo]) {
- 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(body) = parent {
- let arg = &self.hir_map.body(body).arguments[index];
- format!("`{}`", self.hir_map.node_to_pretty_string(arg.pat.id))
- } else {
- format!("argument {}", index + 1)
- };
-
- m.push_str(&(if n == 1 {
- help_name
- } else {
- format!("one of {}'s {} elided {}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");
- help!(db,
- "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");
- help!(db,
- "consider giving it an explicit bounded or 'static \
- lifetime");
- } 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);
- } else {
- help!(db,
- "this function's return type contains a borrowed value, but \
- the signature does not say whether it is borrowed from {}",
- m);
- }
- }
-
- fn resolve_object_lifetime_default(&mut self, lifetime_ref: &hir::Lifetime) {
- 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_defs(&mut self, old_scope: ScopeRef, lifetimes: &[hir::LifetimeDef]) {
- for i in 0..lifetimes.len() {
- let lifetime_i = &lifetimes[i];
-
- for lifetime in lifetimes {
- if lifetime.lifetime.name == keywords::StaticLifetime.name() {
- let lifetime = lifetime.lifetime;
- let mut err = struct_span_err!(self.sess, lifetime.span, E0262,
- "invalid lifetime parameter name: `{}`", lifetime.name);
- err.span_label(lifetime.span,
- &format!("{} is a reserved lifetime name", lifetime.name));
- err.emit();
- }
- }
-
- // It is a hard error to shadow a lifetime within the same scope.
- for j in i + 1..lifetimes.len() {
- let lifetime_j = &lifetimes[j];
-
- if lifetime_i.lifetime.name == lifetime_j.lifetime.name {
- struct_span_err!(self.sess, lifetime_j.lifetime.span, E0263,
- "lifetime name `{}` declared twice in the same scope",
- lifetime_j.lifetime.name)
- .span_label(lifetime_j.lifetime.span,
- &format!("declared twice"))
- .span_label(lifetime_i.lifetime.span,
- &format!("previous declaration here"))
- .emit();
- }
- }
-
- // It is a soft error to shadow a lifetime within a parent scope.
- self.check_lifetime_def_for_shadowing(old_scope, &lifetime_i.lifetime);
-
- for bound in &lifetime_i.bounds {
- self.resolve_lifetime_ref(bound);
- }
- }
- }
-
- fn check_lifetime_def_for_shadowing(&self,
- mut old_scope: ScopeRef,
- lifetime: &hir::Lifetime)
- {
- for &(label, label_span) in &self.labels_in_fn {
- // FIXME (#24278): non-hygienic comparison
- if lifetime.name == label {
- signal_shadowing_problem(self.sess,
- lifetime.name,
- original_label(label_span),
- shadower_lifetime(&lifetime));
- 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(&lifetime.name) {
- signal_shadowing_problem(
- self.sess,
- lifetime.name,
- original_lifetime(self.hir_map.span(def.id().unwrap())),
- shadower_lifetime(&lifetime));
- return;
- }
-
- old_scope = s;
- }
- }
- }
- }
-
- fn insert_lifetime(&mut self,
- lifetime_ref: &hir::Lifetime,
- def: Region) {
- if lifetime_ref.id == ast::DUMMY_NODE_ID {
- span_bug!(lifetime_ref.span,
- "lifetime reference not renumbered, \
- probably a bug in syntax::fold");
- }
-
- debug!("{} resolved to {:?} span={:?}",
- self.hir_map.node_to_string(lifetime_ref.id),
- def,
- self.sess.codemap().span_to_string(lifetime_ref.span));
- self.map.defs.insert(lifetime_ref.id, 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,
- fn_def_id: DefId,
- decl: &hir::FnDecl,
- generics: &hir::Generics) {
- debug!("insert_late_bound_lifetimes(decl={:?}, generics={:?})", decl, generics);
-
- let mut constrained_by_input = ConstrainedCollector { regions: FxHashSet() };
- for arg_ty in &decl.inputs {
- constrained_by_input.visit_ty(arg_ty);
- }
-
- let mut appears_in_output = AllCollector {
- regions: FxHashSet(),
- impl_trait: false
- };
- 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 {
- regions: FxHashSet(),
- impl_trait: false
- };
- for ty_param in generics.ty_params.iter() {
- walk_list!(&mut appears_in_where_clause,
- visit_ty_param_bound,
- &ty_param.bounds);
- }
- walk_list!(&mut appears_in_where_clause,
- visit_where_predicate,
- &generics.where_clause.predicates);
- for lifetime_def in &generics.lifetimes {
- if !lifetime_def.bounds.is_empty() {
- // `'a: 'b` means both `'a` and `'b` are referenced
- appears_in_where_clause.visit_lifetime_def(lifetime_def);
- }
- }
-
- 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 lifetime in &generics.lifetimes {
- let name = lifetime.lifetime.name;
-
- // appears in the where clauses? early-bound.
- if appears_in_where_clause.regions.contains(&name) { continue; }
-
- // any `impl Trait` in the return type? early-bound.
- if appears_in_output.impl_trait { continue; }
-
- // does not appear in the inputs, but appears in the return
- // type? eventually this will be early-bound, but for now we
- // just mark it so we can issue warnings.
- let constrained_by_input = constrained_by_input.regions.contains(&name);
- let appears_in_output = appears_in_output.regions.contains(&name);
- let will_change = !constrained_by_input && appears_in_output;
- let issue_32330 = if will_change {
- ty::Issue32330::WillChange {
- fn_def_id: fn_def_id,
- region_name: name,
- }
- } else {
- ty::Issue32330::WontChange
- };
-
- debug!("insert_late_bound_lifetimes: \
- lifetime {:?} with id {:?} is late-bound ({:?}",
- lifetime.lifetime.name, lifetime.lifetime.id, issue_32330);
-
- let prev = map.late_bound.insert(lifetime.lifetime.id, issue_32330);
- assert!(prev.is_none(), "visited lifetime {:?} twice", lifetime.lifetime.id);
- }
-
- return;
-
- struct ConstrainedCollector {
- regions: FxHashSet<ast::Name>,
- }
-
- 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::TyPath(hir::QPath::Resolved(Some(_), _)) |
- hir::TyPath(hir::QPath::TypeRelative(..)) => {
- // ignore lifetimes appearing in associated type
- // projections, as they are not *constrained*
- // (defined above)
- }
-
- hir::TyPath(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);
- }
- }
-
- struct AllCollector {
- regions: FxHashSet<ast::Name>,
- impl_trait: bool
- }
-
- 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);
- }
+pub type ObjectLifetimeDefault = Set1<Region>;
- fn visit_ty(&mut self, ty: &hir::Ty) {
- if let hir::TyImplTrait(_) = ty.node {
- self.impl_trait = true;
- }
- intravisit::walk_ty(self, ty);
- }
- }
+/// Maps the id of each lifetime reference to the lifetime decl
+/// that it corresponds to.
+#[derive(Default, HashStable)]
+pub struct ResolveLifetimes {
+ /// 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>>>,
}
projects / rustc.git / blobdiff