1 //! Name resolution for lifetimes: type declarations.
5 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
6 use rustc_hir::def_id::{DefId, LocalDefId};
7 use rustc_hir::{GenericParam, ItemLocalId};
8 use rustc_hir::{GenericParamKind, LifetimeParamKind};
9 use rustc_macros::HashStable;
11 /// The origin of a named lifetime definition.
13 /// This is used to prevent the usage of in-band lifetimes in `Fn`/`fn` syntax.
14 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Debug, HashStable)]
15 pub enum LifetimeDefOrigin {
16 // Explicit binders like `fn foo<'a>(x: &'a u8)` or elided like `impl Foo<&u32>`
18 // In-band declarations like `fn foo(x: &'a u8)`
20 // Some kind of erroneous origin
24 impl LifetimeDefOrigin {
25 pub fn from_param(param: &GenericParam<'_>) -> Self {
27 GenericParamKind::Lifetime { kind } => match kind {
28 LifetimeParamKind::InBand => LifetimeDefOrigin::InBand,
29 LifetimeParamKind::Explicit => LifetimeDefOrigin::ExplicitOrElided,
30 LifetimeParamKind::Elided => LifetimeDefOrigin::ExplicitOrElided,
31 LifetimeParamKind::Error => LifetimeDefOrigin::Error,
33 _ => bug!("expected a lifetime param"),
38 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Debug, HashStable)]
41 EarlyBound(/* index */ u32, /* lifetime decl */ DefId, LifetimeDefOrigin),
42 LateBound(ty::DebruijnIndex, /* lifetime decl */ DefId, LifetimeDefOrigin),
43 LateBoundAnon(ty::DebruijnIndex, /* anon index */ u32),
44 Free(DefId, /* lifetime decl */ DefId),
47 /// A set containing, at most, one known element.
48 /// If two distinct values are inserted into a set, then it
49 /// becomes `Many`, which can be used to detect ambiguities.
50 #[derive(Copy, Clone, PartialEq, Eq, TyEncodable, TyDecodable, Debug, HashStable)]
57 impl<T: PartialEq> Set1<T> {
58 pub fn insert(&mut self, value: T) {
60 Set1::Empty => Set1::One(value),
61 Set1::One(old) if *old == value => return,
67 pub type ObjectLifetimeDefault = Set1<Region>;
69 /// Maps the id of each lifetime reference to the lifetime decl
70 /// that it corresponds to.
71 #[derive(Default, HashStable)]
72 pub struct ResolveLifetimes {
73 /// Maps from every use of a named (not anonymous) lifetime to a
74 /// `Region` describing how that region is bound
75 pub defs: FxHashMap<LocalDefId, FxHashMap<ItemLocalId, Region>>,
77 /// Set of lifetime def ids that are late-bound; a region can
78 /// be late-bound if (a) it does NOT appear in a where-clause and
79 /// (b) it DOES appear in the arguments.
80 pub late_bound: FxHashMap<LocalDefId, FxHashSet<ItemLocalId>>,
82 /// For each type and trait definition, maps type parameters
83 /// to the trait object lifetime defaults computed from them.
84 pub object_lifetime_defaults:
85 FxHashMap<LocalDefId, FxHashMap<ItemLocalId, Vec<ObjectLifetimeDefault>>>,