45940fe6d8
Qualifier tweaking Adding and removing qualifiers in some cases that make things nicer. Details in individual commits. r? `@compiler-errors`
2109 lines
86 KiB
Rust
2109 lines
86 KiB
Rust
//! Resolution of early vs late bound lifetimes.
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//!
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//! Name resolution for lifetimes is performed on the AST and embedded into HIR. From this
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//! information, typechecking needs to transform the lifetime parameters into bound lifetimes.
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//! Lifetimes can be early-bound or late-bound. Construction of typechecking terms needs to visit
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//! the types in HIR to identify late-bound lifetimes and assign their Debruijn indices. This file
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//! is also responsible for assigning their semantics to implicit lifetimes in trait objects.
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use core::ops::ControlFlow;
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use rustc_ast::visit::walk_list;
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use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
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use rustc_hir as hir;
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use rustc_hir::def::{DefKind, Res};
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use rustc_hir::def_id::LocalDefId;
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use rustc_hir::intravisit::{self, Visitor};
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use rustc_hir::{GenericArg, GenericParam, GenericParamKind, HirId, HirIdMap, LifetimeName, Node};
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use rustc_macros::extension;
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use rustc_middle::bug;
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use rustc_middle::hir::nested_filter;
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use rustc_middle::middle::resolve_bound_vars::*;
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use rustc_middle::query::Providers;
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use rustc_middle::ty::{self, TyCtxt, TypeSuperVisitable, TypeVisitor};
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use rustc_span::def_id::DefId;
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use rustc_span::symbol::{sym, Ident};
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use rustc_span::Span;
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use std::fmt;
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use crate::errors;
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#[extension(trait RegionExt)]
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impl ResolvedArg {
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fn early(param: &GenericParam<'_>) -> (LocalDefId, ResolvedArg) {
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debug!("ResolvedArg::early: def_id={:?}", param.def_id);
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(param.def_id, ResolvedArg::EarlyBound(param.def_id.to_def_id()))
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}
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fn late(idx: u32, param: &GenericParam<'_>) -> (LocalDefId, ResolvedArg) {
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let depth = ty::INNERMOST;
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debug!(
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"ResolvedArg::late: idx={:?}, param={:?} depth={:?} def_id={:?}",
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idx, param, depth, param.def_id,
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);
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(param.def_id, ResolvedArg::LateBound(depth, idx, param.def_id.to_def_id()))
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}
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fn id(&self) -> Option<DefId> {
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match *self {
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ResolvedArg::StaticLifetime | ResolvedArg::Error(_) => None,
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ResolvedArg::EarlyBound(id)
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| ResolvedArg::LateBound(_, _, id)
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| ResolvedArg::Free(_, id) => Some(id),
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}
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}
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fn shifted(self, amount: u32) -> ResolvedArg {
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match self {
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ResolvedArg::LateBound(debruijn, idx, id) => {
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ResolvedArg::LateBound(debruijn.shifted_in(amount), idx, id)
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}
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_ => self,
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}
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}
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}
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/// Maps the id of each bound variable reference to the variable decl
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/// that it corresponds to.
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///
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/// FIXME. This struct gets converted to a `ResolveBoundVars` for
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/// actual use. It has the same data, but indexed by `LocalDefId`. This
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/// is silly.
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#[derive(Debug, Default)]
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struct NamedVarMap {
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// maps from every use of a named (not anonymous) bound var to a
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// `ResolvedArg` describing how that variable is bound
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defs: HirIdMap<ResolvedArg>,
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// Maps relevant hir items to the bound vars on them. These include:
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// - function defs
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// - function pointers
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// - closures
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// - trait refs
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// - bound types (like `T` in `for<'a> T<'a>: Foo`)
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late_bound_vars: HirIdMap<Vec<ty::BoundVariableKind>>,
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}
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struct BoundVarContext<'a, 'tcx> {
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tcx: TyCtxt<'tcx>,
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map: &'a mut NamedVarMap,
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scope: ScopeRef<'a>,
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}
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#[derive(Debug)]
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enum Scope<'a> {
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/// Declares lifetimes, and each can be early-bound or late-bound.
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/// The `DebruijnIndex` of late-bound lifetimes starts at `1` and
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/// it should be shifted by the number of `Binder`s in between the
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/// declaration `Binder` and the location it's referenced from.
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Binder {
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/// We use an IndexMap here because we want these lifetimes in order
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/// for diagnostics.
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bound_vars: FxIndexMap<LocalDefId, ResolvedArg>,
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scope_type: BinderScopeType,
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/// The late bound vars for a given item are stored by `HirId` to be
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/// queried later. However, if we enter an elision scope, we have to
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/// later append the elided bound vars to the list and need to know what
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/// to append to.
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hir_id: HirId,
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s: ScopeRef<'a>,
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/// If this binder comes from a where clause, specify how it was created.
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/// This is used to diagnose inaccessible lifetimes in APIT:
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/// ```ignore (illustrative)
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/// fn foo(x: impl for<'a> Trait<'a, Assoc = impl Copy + 'a>) {}
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/// ```
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where_bound_origin: Option<hir::PredicateOrigin>,
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},
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/// Lifetimes introduced by a fn are scoped to the call-site for that fn,
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/// if this is a fn body, otherwise the original definitions are used.
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/// Unspecified lifetimes are inferred, unless an elision scope is nested,
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/// e.g., `(&T, fn(&T) -> &T);` becomes `(&'_ T, for<'a> fn(&'a T) -> &'a T)`.
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Body {
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id: hir::BodyId,
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s: ScopeRef<'a>,
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},
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/// Use a specific lifetime (if `Some`) or leave it unset (to be
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/// inferred in a function body or potentially error outside one),
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/// for the default choice of lifetime in a trait object type.
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ObjectLifetimeDefault {
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lifetime: Option<ResolvedArg>,
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s: ScopeRef<'a>,
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},
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/// When we have nested trait refs, we concatenate late bound vars for inner
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/// trait refs from outer ones. But we also need to include any HRTB
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/// lifetimes encountered when identifying the trait that an associated type
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/// is declared on.
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Supertrait {
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bound_vars: Vec<ty::BoundVariableKind>,
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s: ScopeRef<'a>,
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},
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TraitRefBoundary {
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s: ScopeRef<'a>,
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},
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/// Disallows capturing late-bound vars from parent scopes.
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///
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/// This is necessary for something like `for<T> [(); { /* references T */ }]:`,
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/// since we don't do something more correct like replacing any captured
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/// late-bound vars with early-bound params in the const's own generics.
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LateBoundary {
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s: ScopeRef<'a>,
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what: &'static str,
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},
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Root {
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opt_parent_item: Option<LocalDefId>,
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},
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}
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#[derive(Copy, Clone, Debug)]
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enum BinderScopeType {
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/// Any non-concatenating binder scopes.
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Normal,
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/// Within a syntactic trait ref, there may be multiple poly trait refs that
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/// are nested (under the `associated_type_bounds` feature). The binders of
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/// the inner poly trait refs are extended from the outer poly trait refs
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/// and don't increase the late bound depth. If you had
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/// `T: for<'a> Foo<Bar: for<'b> Baz<'a, 'b>>`, then the `for<'b>` scope
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/// would be `Concatenating`. This also used in trait refs in where clauses
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/// where we have two binders `for<> T: for<> Foo` (I've intentionally left
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/// out any lifetimes because they aren't needed to show the two scopes).
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/// The inner `for<>` has a scope of `Concatenating`.
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Concatenating,
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}
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// A helper struct for debugging scopes without printing parent scopes
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struct TruncatedScopeDebug<'a>(&'a Scope<'a>);
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impl<'a> fmt::Debug for TruncatedScopeDebug<'a> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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match self.0 {
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Scope::Binder { bound_vars, scope_type, hir_id, where_bound_origin, s: _ } => f
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.debug_struct("Binder")
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.field("bound_vars", bound_vars)
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.field("scope_type", scope_type)
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.field("hir_id", hir_id)
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.field("where_bound_origin", where_bound_origin)
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.field("s", &"..")
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.finish(),
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Scope::Body { id, s: _ } => {
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f.debug_struct("Body").field("id", id).field("s", &"..").finish()
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}
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Scope::ObjectLifetimeDefault { lifetime, s: _ } => f
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.debug_struct("ObjectLifetimeDefault")
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.field("lifetime", lifetime)
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.field("s", &"..")
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.finish(),
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Scope::Supertrait { bound_vars, s: _ } => f
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.debug_struct("Supertrait")
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.field("bound_vars", bound_vars)
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.field("s", &"..")
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.finish(),
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Scope::TraitRefBoundary { s: _ } => f.debug_struct("TraitRefBoundary").finish(),
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Scope::LateBoundary { s: _, what } => {
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f.debug_struct("LateBoundary").field("what", what).finish()
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}
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Scope::Root { opt_parent_item } => {
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f.debug_struct("Root").field("opt_parent_item", &opt_parent_item).finish()
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}
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}
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}
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}
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type ScopeRef<'a> = &'a Scope<'a>;
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pub(crate) fn provide(providers: &mut Providers) {
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*providers = Providers {
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resolve_bound_vars,
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named_variable_map: |tcx, id| tcx.resolve_bound_vars(id).defs.get(&id),
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is_late_bound_map,
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object_lifetime_default,
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late_bound_vars_map: |tcx, id| tcx.resolve_bound_vars(id).late_bound_vars.get(&id),
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..*providers
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};
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}
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/// Computes the `ResolveBoundVars` map that contains data for an entire `Item`.
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/// You should not read the result of this query directly, but rather use
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/// `named_variable_map`, `is_late_bound_map`, etc.
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#[instrument(level = "debug", skip(tcx))]
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fn resolve_bound_vars(tcx: TyCtxt<'_>, local_def_id: hir::OwnerId) -> ResolveBoundVars {
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let mut named_variable_map =
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NamedVarMap { defs: Default::default(), late_bound_vars: Default::default() };
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let mut visitor = BoundVarContext {
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tcx,
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map: &mut named_variable_map,
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scope: &Scope::Root { opt_parent_item: None },
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};
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match tcx.hir_owner_node(local_def_id) {
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hir::OwnerNode::Item(item) => visitor.visit_item(item),
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hir::OwnerNode::ForeignItem(item) => visitor.visit_foreign_item(item),
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hir::OwnerNode::TraitItem(item) => {
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let scope =
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Scope::Root { opt_parent_item: Some(tcx.local_parent(item.owner_id.def_id)) };
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visitor.scope = &scope;
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visitor.visit_trait_item(item)
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}
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hir::OwnerNode::ImplItem(item) => {
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let scope =
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Scope::Root { opt_parent_item: Some(tcx.local_parent(item.owner_id.def_id)) };
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visitor.scope = &scope;
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visitor.visit_impl_item(item)
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}
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hir::OwnerNode::Crate(_) => {}
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hir::OwnerNode::Synthetic => unreachable!(),
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}
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let mut rl = ResolveBoundVars::default();
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for (hir_id, v) in named_variable_map.defs {
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let map = rl.defs.entry(hir_id.owner).or_default();
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map.insert(hir_id.local_id, v);
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}
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for (hir_id, v) in named_variable_map.late_bound_vars {
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let map = rl.late_bound_vars.entry(hir_id.owner).or_default();
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map.insert(hir_id.local_id, v);
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}
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debug!(?rl.defs);
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debug!(?rl.late_bound_vars);
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rl
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}
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fn late_arg_as_bound_arg<'tcx>(
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tcx: TyCtxt<'tcx>,
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arg: &ResolvedArg,
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param: &GenericParam<'tcx>,
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) -> ty::BoundVariableKind {
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match arg {
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ResolvedArg::LateBound(_, _, def_id) => {
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let name = tcx.hir().name(tcx.local_def_id_to_hir_id(def_id.expect_local()));
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match param.kind {
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GenericParamKind::Lifetime { .. } => {
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ty::BoundVariableKind::Region(ty::BrNamed(*def_id, name))
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}
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GenericParamKind::Type { .. } => {
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ty::BoundVariableKind::Ty(ty::BoundTyKind::Param(*def_id, name))
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}
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GenericParamKind::Const { .. } => ty::BoundVariableKind::Const,
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}
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}
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_ => bug!("{:?} is not a late argument", arg),
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}
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}
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impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
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/// Returns the binders in scope and the type of `Binder` that should be created for a poly trait ref.
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fn poly_trait_ref_binder_info(&mut self) -> (Vec<ty::BoundVariableKind>, BinderScopeType) {
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let mut scope = self.scope;
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let mut supertrait_bound_vars = vec![];
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loop {
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match scope {
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Scope::Body { .. } | Scope::Root { .. } => {
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break (vec![], BinderScopeType::Normal);
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}
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Scope::ObjectLifetimeDefault { s, .. } | Scope::LateBoundary { s, .. } => {
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scope = s;
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}
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Scope::Supertrait { s, bound_vars } => {
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supertrait_bound_vars = bound_vars.clone();
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scope = s;
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}
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Scope::TraitRefBoundary { .. } => {
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// We should only see super trait lifetimes if there is a `Binder` above
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// though this may happen when we call `poly_trait_ref_binder_info` with
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// an (erroneous, #113423) associated return type bound in an impl header.
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if !supertrait_bound_vars.is_empty() {
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self.tcx.dcx().delayed_bug(format!(
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"found supertrait lifetimes without a binder to append \
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them to: {supertrait_bound_vars:?}"
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));
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}
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break (vec![], BinderScopeType::Normal);
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}
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Scope::Binder { hir_id, .. } => {
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// Nested poly trait refs have the binders concatenated
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let mut full_binders =
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self.map.late_bound_vars.entry(*hir_id).or_default().clone();
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full_binders.extend(supertrait_bound_vars);
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break (full_binders, BinderScopeType::Concatenating);
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}
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}
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}
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}
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fn visit_poly_trait_ref_inner(
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&mut self,
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trait_ref: &'tcx hir::PolyTraitRef<'tcx>,
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non_lifetime_binder_allowed: NonLifetimeBinderAllowed,
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) {
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debug!("visit_poly_trait_ref(trait_ref={:?})", trait_ref);
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let (mut binders, scope_type) = self.poly_trait_ref_binder_info();
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let initial_bound_vars = binders.len() as u32;
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let mut bound_vars: FxIndexMap<LocalDefId, ResolvedArg> = FxIndexMap::default();
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let binders_iter =
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trait_ref.bound_generic_params.iter().enumerate().map(|(late_bound_idx, param)| {
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let pair = ResolvedArg::late(initial_bound_vars + late_bound_idx as u32, param);
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let r = late_arg_as_bound_arg(self.tcx, &pair.1, param);
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bound_vars.insert(pair.0, pair.1);
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r
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});
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binders.extend(binders_iter);
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if let NonLifetimeBinderAllowed::Deny(where_) = non_lifetime_binder_allowed {
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deny_non_region_late_bound(self.tcx, &mut bound_vars, where_);
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}
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debug!(?binders);
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self.record_late_bound_vars(trait_ref.trait_ref.hir_ref_id, binders);
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// Always introduce a scope here, even if this is in a where clause and
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// we introduced the binders around the bounded Ty. In that case, we
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// just reuse the concatenation functionality also present in nested trait
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// refs.
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let scope = Scope::Binder {
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hir_id: trait_ref.trait_ref.hir_ref_id,
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bound_vars,
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s: self.scope,
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scope_type,
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where_bound_origin: None,
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};
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self.with(scope, |this| {
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walk_list!(this, visit_generic_param, trait_ref.bound_generic_params);
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this.visit_trait_ref(&trait_ref.trait_ref);
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});
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}
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}
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enum NonLifetimeBinderAllowed {
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Deny(&'static str),
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Allow,
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}
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impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
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type NestedFilter = nested_filter::OnlyBodies;
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fn nested_visit_map(&mut self) -> Self::Map {
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self.tcx.hir()
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}
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fn visit_nested_body(&mut self, body: hir::BodyId) {
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let body = self.tcx.hir().body(body);
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self.with(Scope::Body { id: body.id(), s: self.scope }, |this| {
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this.visit_body(body);
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});
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}
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fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
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if let hir::ExprKind::Closure(hir::Closure {
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binder, bound_generic_params, fn_decl, ..
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}) = e.kind
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{
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if let &hir::ClosureBinder::For { span: for_sp, .. } = binder {
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fn span_of_infer(ty: &hir::Ty<'_>) -> Option<Span> {
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/// Look for `_` anywhere in the signature of a `for<> ||` closure.
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/// This is currently disallowed.
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struct FindInferInClosureWithBinder;
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impl<'v> Visitor<'v> for FindInferInClosureWithBinder {
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type Result = ControlFlow<Span>;
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fn visit_ty(&mut self, t: &'v hir::Ty<'v>) -> Self::Result {
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if matches!(t.kind, hir::TyKind::Infer) {
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ControlFlow::Break(t.span)
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} else {
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intravisit::walk_ty(self, t)
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}
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}
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}
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FindInferInClosureWithBinder.visit_ty(ty).break_value()
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}
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let infer_in_rt_sp = match fn_decl.output {
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hir::FnRetTy::DefaultReturn(sp) => Some(sp),
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hir::FnRetTy::Return(ty) => span_of_infer(ty),
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};
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let infer_spans = fn_decl
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.inputs
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.into_iter()
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.filter_map(span_of_infer)
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.chain(infer_in_rt_sp)
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.collect::<Vec<_>>();
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if !infer_spans.is_empty() {
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self.tcx
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.dcx()
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.emit_err(errors::ClosureImplicitHrtb { spans: infer_spans, for_sp });
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}
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}
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|
|
let (mut bound_vars, binders): (FxIndexMap<LocalDefId, ResolvedArg>, Vec<_>) =
|
|
bound_generic_params
|
|
.iter()
|
|
.enumerate()
|
|
.map(|(late_bound_idx, param)| {
|
|
let pair = ResolvedArg::late(late_bound_idx as u32, param);
|
|
let r = late_arg_as_bound_arg(self.tcx, &pair.1, param);
|
|
(pair, r)
|
|
})
|
|
.unzip();
|
|
|
|
deny_non_region_late_bound(self.tcx, &mut bound_vars, "closures");
|
|
|
|
self.record_late_bound_vars(e.hir_id, binders);
|
|
let scope = Scope::Binder {
|
|
hir_id: e.hir_id,
|
|
bound_vars,
|
|
s: self.scope,
|
|
scope_type: BinderScopeType::Normal,
|
|
where_bound_origin: None,
|
|
};
|
|
|
|
self.with(scope, |this| {
|
|
// a closure has no bounds, so everything
|
|
// contained within is scoped within its binder.
|
|
intravisit::walk_expr(this, e)
|
|
});
|
|
} else {
|
|
intravisit::walk_expr(self, e)
|
|
}
|
|
}
|
|
|
|
#[instrument(level = "debug", skip(self))]
|
|
fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
|
|
match &item.kind {
|
|
hir::ItemKind::Impl(hir::Impl { of_trait, .. }) => {
|
|
if let Some(of_trait) = of_trait {
|
|
self.record_late_bound_vars(of_trait.hir_ref_id, Vec::default());
|
|
}
|
|
}
|
|
_ => {}
|
|
}
|
|
match item.kind {
|
|
hir::ItemKind::Fn(_, generics, _) => {
|
|
self.visit_early_late(item.hir_id(), generics, |this| {
|
|
intravisit::walk_item(this, item);
|
|
});
|
|
}
|
|
|
|
hir::ItemKind::ExternCrate(_)
|
|
| hir::ItemKind::Use(..)
|
|
| hir::ItemKind::Macro(..)
|
|
| hir::ItemKind::Mod(..)
|
|
| hir::ItemKind::ForeignMod { .. }
|
|
| hir::ItemKind::Static(..)
|
|
| hir::ItemKind::GlobalAsm(..) => {
|
|
// These sorts of items have no lifetime parameters at all.
|
|
intravisit::walk_item(self, item);
|
|
}
|
|
hir::ItemKind::OpaqueTy(&hir::OpaqueTy {
|
|
origin:
|
|
hir::OpaqueTyOrigin::FnReturn(parent)
|
|
| hir::OpaqueTyOrigin::AsyncFn(parent)
|
|
| hir::OpaqueTyOrigin::TyAlias { parent, .. },
|
|
generics,
|
|
..
|
|
}) => {
|
|
// We want to start our early-bound indices at the end of the parent scope,
|
|
// not including any parent `impl Trait`s.
|
|
let mut bound_vars = FxIndexMap::default();
|
|
debug!(?generics.params);
|
|
for param in generics.params {
|
|
let (def_id, reg) = ResolvedArg::early(param);
|
|
bound_vars.insert(def_id, reg);
|
|
}
|
|
|
|
let scope = Scope::Root { opt_parent_item: Some(parent) };
|
|
self.with(scope, |this| {
|
|
let scope = Scope::Binder {
|
|
hir_id: item.hir_id(),
|
|
bound_vars,
|
|
s: this.scope,
|
|
scope_type: BinderScopeType::Normal,
|
|
where_bound_origin: None,
|
|
};
|
|
this.with(scope, |this| {
|
|
let scope = Scope::TraitRefBoundary { s: this.scope };
|
|
this.with(scope, |this| intravisit::walk_item(this, item))
|
|
});
|
|
})
|
|
}
|
|
hir::ItemKind::TyAlias(_, generics)
|
|
| hir::ItemKind::Const(_, generics, _)
|
|
| hir::ItemKind::Enum(_, generics)
|
|
| hir::ItemKind::Struct(_, generics)
|
|
| hir::ItemKind::Union(_, generics)
|
|
| hir::ItemKind::Trait(_, _, generics, ..)
|
|
| hir::ItemKind::TraitAlias(generics, ..)
|
|
| hir::ItemKind::Impl(&hir::Impl { generics, .. }) => {
|
|
// These kinds of items have only early-bound lifetime parameters.
|
|
self.visit_early(item.hir_id(), generics, |this| intravisit::walk_item(this, item));
|
|
}
|
|
}
|
|
}
|
|
|
|
fn visit_precise_capturing_arg(
|
|
&mut self,
|
|
arg: &'tcx hir::PreciseCapturingArg<'tcx>,
|
|
) -> Self::Result {
|
|
match *arg {
|
|
hir::PreciseCapturingArg::Lifetime(lt) => match lt.res {
|
|
LifetimeName::Param(def_id) => {
|
|
self.resolve_lifetime_ref(def_id, lt);
|
|
}
|
|
LifetimeName::Error => {}
|
|
LifetimeName::ImplicitObjectLifetimeDefault
|
|
| LifetimeName::Infer
|
|
| LifetimeName::Static => {
|
|
self.tcx.dcx().emit_err(errors::BadPreciseCapture {
|
|
span: lt.ident.span,
|
|
kind: "lifetime",
|
|
found: format!("`{}`", lt.ident.name),
|
|
});
|
|
}
|
|
},
|
|
hir::PreciseCapturingArg::Param(param) => match param.res {
|
|
Res::Def(DefKind::TyParam | DefKind::ConstParam, def_id)
|
|
| Res::SelfTyParam { trait_: def_id } => {
|
|
self.resolve_type_ref(def_id.expect_local(), param.hir_id);
|
|
}
|
|
Res::Err => {}
|
|
Res::SelfTyAlias { alias_to, .. } => {
|
|
self.tcx.dcx().emit_err(errors::PreciseCaptureSelfAlias {
|
|
span: param.ident.span,
|
|
self_span: self.tcx.def_span(alias_to),
|
|
what: self.tcx.def_descr(alias_to),
|
|
});
|
|
}
|
|
res => {
|
|
self.tcx.dcx().emit_err(errors::BadPreciseCapture {
|
|
span: param.ident.span,
|
|
kind: "type or const",
|
|
found: res.descr().to_string(),
|
|
});
|
|
}
|
|
},
|
|
}
|
|
}
|
|
|
|
fn visit_foreign_item(&mut self, item: &'tcx hir::ForeignItem<'tcx>) {
|
|
match item.kind {
|
|
hir::ForeignItemKind::Fn(_, _, generics) => {
|
|
self.visit_early_late(item.hir_id(), generics, |this| {
|
|
intravisit::walk_foreign_item(this, item);
|
|
})
|
|
}
|
|
hir::ForeignItemKind::Static(..) => {
|
|
intravisit::walk_foreign_item(self, item);
|
|
}
|
|
hir::ForeignItemKind::Type => {
|
|
intravisit::walk_foreign_item(self, item);
|
|
}
|
|
}
|
|
}
|
|
|
|
#[instrument(level = "debug", skip(self))]
|
|
fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
|
|
match ty.kind {
|
|
hir::TyKind::BareFn(c) => {
|
|
let (mut bound_vars, binders): (FxIndexMap<LocalDefId, ResolvedArg>, Vec<_>) = c
|
|
.generic_params
|
|
.iter()
|
|
.enumerate()
|
|
.map(|(late_bound_idx, param)| {
|
|
let pair = ResolvedArg::late(late_bound_idx as u32, param);
|
|
let r = late_arg_as_bound_arg(self.tcx, &pair.1, param);
|
|
(pair, r)
|
|
})
|
|
.unzip();
|
|
|
|
deny_non_region_late_bound(self.tcx, &mut bound_vars, "function pointer types");
|
|
|
|
self.record_late_bound_vars(ty.hir_id, binders);
|
|
let scope = Scope::Binder {
|
|
hir_id: ty.hir_id,
|
|
bound_vars,
|
|
s: self.scope,
|
|
scope_type: BinderScopeType::Normal,
|
|
where_bound_origin: None,
|
|
};
|
|
self.with(scope, |this| {
|
|
// a bare fn has no bounds, so everything
|
|
// contained within is scoped within its binder.
|
|
intravisit::walk_ty(this, ty);
|
|
});
|
|
}
|
|
hir::TyKind::TraitObject(bounds, lifetime, _) => {
|
|
debug!(?bounds, ?lifetime, "TraitObject");
|
|
let scope = Scope::TraitRefBoundary { s: self.scope };
|
|
self.with(scope, |this| {
|
|
for bound in bounds {
|
|
this.visit_poly_trait_ref_inner(
|
|
bound,
|
|
NonLifetimeBinderAllowed::Deny("trait object types"),
|
|
);
|
|
}
|
|
});
|
|
match lifetime.res {
|
|
LifetimeName::ImplicitObjectLifetimeDefault => {
|
|
// If the user does not write *anything*, we
|
|
// use the object lifetime defaulting
|
|
// rules. So e.g., `Box<dyn Debug>` becomes
|
|
// `Box<dyn Debug + 'static>`.
|
|
self.resolve_object_lifetime_default(lifetime)
|
|
}
|
|
LifetimeName::Infer => {
|
|
// If the user writes `'_`, we use the *ordinary* elision
|
|
// rules. So the `'_` in e.g., `Box<dyn Debug + '_>` will be
|
|
// resolved the same as the `'_` in `&'_ Foo`.
|
|
//
|
|
// cc #48468
|
|
}
|
|
LifetimeName::Param(..) | LifetimeName::Static => {
|
|
// If the user wrote an explicit name, use that.
|
|
self.visit_lifetime(lifetime);
|
|
}
|
|
LifetimeName::Error => {}
|
|
}
|
|
}
|
|
hir::TyKind::Ref(lifetime_ref, ref mt) => {
|
|
self.visit_lifetime(lifetime_ref);
|
|
let scope = Scope::ObjectLifetimeDefault {
|
|
lifetime: self.map.defs.get(&lifetime_ref.hir_id).cloned(),
|
|
s: self.scope,
|
|
};
|
|
self.with(scope, |this| this.visit_ty(mt.ty));
|
|
}
|
|
hir::TyKind::OpaqueDef(item_id, lifetimes, _in_trait) => {
|
|
// Resolve the lifetimes in the bounds to the lifetime defs in the generics.
|
|
// `fn foo<'a>() -> impl MyTrait<'a> { ... }` desugars to
|
|
// `type MyAnonTy<'b> = impl MyTrait<'b>;`
|
|
// ^ ^ this gets resolved in the scope of
|
|
// the opaque_ty generics
|
|
let opaque_ty = self.tcx.hir().item(item_id);
|
|
match &opaque_ty.kind {
|
|
hir::ItemKind::OpaqueTy(hir::OpaqueTy { origin: _, .. }) => {}
|
|
i => bug!("`impl Trait` pointed to non-opaque type?? {:#?}", i),
|
|
};
|
|
|
|
// Resolve the lifetimes that are applied to the opaque type.
|
|
// These are resolved in the current scope.
|
|
// `fn foo<'a>() -> impl MyTrait<'a> { ... }` desugars to
|
|
// `fn foo<'a>() -> MyAnonTy<'a> { ... }`
|
|
// ^ ^this gets resolved in the current scope
|
|
for lifetime in lifetimes {
|
|
let hir::GenericArg::Lifetime(lifetime) = lifetime else { continue };
|
|
self.visit_lifetime(lifetime);
|
|
|
|
// Check for predicates like `impl for<'a> Trait<impl OtherTrait<'a>>`
|
|
// and ban them. Type variables instantiated inside binders aren't
|
|
// well-supported at the moment, so this doesn't work.
|
|
// In the future, this should be fixed and this error should be removed.
|
|
let def = self.map.defs.get(&lifetime.hir_id).copied();
|
|
let Some(ResolvedArg::LateBound(_, _, lifetime_def_id)) = def else { continue };
|
|
let Some(lifetime_def_id) = lifetime_def_id.as_local() else { continue };
|
|
let lifetime_hir_id = self.tcx.local_def_id_to_hir_id(lifetime_def_id);
|
|
|
|
let bad_place = match self.tcx.hir_node(self.tcx.parent_hir_id(lifetime_hir_id))
|
|
{
|
|
// Opaques do not declare their own lifetimes, so if a lifetime comes from an opaque
|
|
// it must be a reified late-bound lifetime from a trait goal.
|
|
hir::Node::Item(hir::Item {
|
|
kind: hir::ItemKind::OpaqueTy { .. }, ..
|
|
}) => "higher-ranked lifetime from outer `impl Trait`",
|
|
// Other items are fine.
|
|
hir::Node::Item(_) | hir::Node::TraitItem(_) | hir::Node::ImplItem(_) => {
|
|
continue;
|
|
}
|
|
hir::Node::Ty(hir::Ty { kind: hir::TyKind::BareFn(_), .. }) => {
|
|
"higher-ranked lifetime from function pointer"
|
|
}
|
|
hir::Node::Ty(hir::Ty { kind: hir::TyKind::TraitObject(..), .. }) => {
|
|
"higher-ranked lifetime from `dyn` type"
|
|
}
|
|
_ => "higher-ranked lifetime",
|
|
};
|
|
|
|
let (span, label) = if lifetime.ident.span == self.tcx.def_span(lifetime_def_id)
|
|
{
|
|
let opaque_span = self.tcx.def_span(item_id.owner_id);
|
|
(opaque_span, Some(opaque_span))
|
|
} else {
|
|
(lifetime.ident.span, None)
|
|
};
|
|
|
|
// Ensure that the parent of the def is an item, not HRTB
|
|
self.tcx.dcx().emit_err(errors::OpaqueCapturesHigherRankedLifetime {
|
|
span,
|
|
label,
|
|
decl_span: self.tcx.def_span(lifetime_def_id),
|
|
bad_place,
|
|
});
|
|
self.uninsert_lifetime_on_error(lifetime, def.unwrap());
|
|
}
|
|
}
|
|
_ => intravisit::walk_ty(self, ty),
|
|
}
|
|
}
|
|
|
|
#[instrument(level = "debug", skip(self))]
|
|
fn visit_pattern_type_pattern(&mut self, p: &'tcx hir::Pat<'tcx>) {
|
|
intravisit::walk_pat(self, p)
|
|
}
|
|
|
|
#[instrument(level = "debug", skip(self))]
|
|
fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
|
|
use self::hir::TraitItemKind::*;
|
|
match trait_item.kind {
|
|
Fn(_, _) => {
|
|
self.visit_early_late(trait_item.hir_id(), trait_item.generics, |this| {
|
|
intravisit::walk_trait_item(this, trait_item)
|
|
});
|
|
}
|
|
Type(bounds, ty) => {
|
|
self.visit_early(trait_item.hir_id(), trait_item.generics, |this| {
|
|
this.visit_generics(trait_item.generics);
|
|
for bound in bounds {
|
|
this.visit_param_bound(bound);
|
|
}
|
|
if let Some(ty) = ty {
|
|
this.visit_ty(ty);
|
|
}
|
|
})
|
|
}
|
|
Const(_, _) => self.visit_early(trait_item.hir_id(), trait_item.generics, |this| {
|
|
intravisit::walk_trait_item(this, trait_item)
|
|
}),
|
|
}
|
|
}
|
|
|
|
#[instrument(level = "debug", skip(self))]
|
|
fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
|
|
use self::hir::ImplItemKind::*;
|
|
match impl_item.kind {
|
|
Fn(..) => self.visit_early_late(impl_item.hir_id(), impl_item.generics, |this| {
|
|
intravisit::walk_impl_item(this, impl_item)
|
|
}),
|
|
Type(ty) => self.visit_early(impl_item.hir_id(), impl_item.generics, |this| {
|
|
this.visit_generics(impl_item.generics);
|
|
this.visit_ty(ty);
|
|
}),
|
|
Const(_, _) => self.visit_early(impl_item.hir_id(), impl_item.generics, |this| {
|
|
intravisit::walk_impl_item(this, impl_item)
|
|
}),
|
|
}
|
|
}
|
|
|
|
#[instrument(level = "debug", skip(self))]
|
|
fn visit_lifetime(&mut self, lifetime_ref: &'tcx hir::Lifetime) {
|
|
match lifetime_ref.res {
|
|
hir::LifetimeName::Static => {
|
|
self.insert_lifetime(lifetime_ref, ResolvedArg::StaticLifetime)
|
|
}
|
|
hir::LifetimeName::Param(param_def_id) => {
|
|
self.resolve_lifetime_ref(param_def_id, lifetime_ref)
|
|
}
|
|
// If we've already reported an error, just ignore `lifetime_ref`.
|
|
hir::LifetimeName::Error => {}
|
|
// Those will be resolved by typechecking.
|
|
hir::LifetimeName::ImplicitObjectLifetimeDefault | hir::LifetimeName::Infer => {}
|
|
}
|
|
}
|
|
|
|
fn visit_path(&mut self, path: &hir::Path<'tcx>, hir_id: HirId) {
|
|
for (i, segment) in path.segments.iter().enumerate() {
|
|
let depth = path.segments.len() - i - 1;
|
|
if let Some(args) = segment.args {
|
|
self.visit_segment_args(path.res, depth, args);
|
|
}
|
|
}
|
|
if let Res::Def(DefKind::TyParam | DefKind::ConstParam, param_def_id) = path.res {
|
|
self.resolve_type_ref(param_def_id.expect_local(), hir_id);
|
|
}
|
|
}
|
|
|
|
fn visit_fn(
|
|
&mut self,
|
|
fk: intravisit::FnKind<'tcx>,
|
|
fd: &'tcx hir::FnDecl<'tcx>,
|
|
body_id: hir::BodyId,
|
|
_: Span,
|
|
def_id: LocalDefId,
|
|
) {
|
|
let output = match fd.output {
|
|
hir::FnRetTy::DefaultReturn(_) => None,
|
|
hir::FnRetTy::Return(ty) => Some(ty),
|
|
};
|
|
if let Some(ty) = output
|
|
&& let hir::TyKind::InferDelegation(sig_id, _) = ty.kind
|
|
{
|
|
let bound_vars: Vec<_> =
|
|
self.tcx.fn_sig(sig_id).skip_binder().bound_vars().iter().collect();
|
|
let hir_id = self.tcx.local_def_id_to_hir_id(def_id);
|
|
self.map.late_bound_vars.insert(hir_id, bound_vars);
|
|
}
|
|
self.visit_fn_like_elision(fd.inputs, output, matches!(fk, intravisit::FnKind::Closure));
|
|
intravisit::walk_fn_kind(self, fk);
|
|
self.visit_nested_body(body_id)
|
|
}
|
|
|
|
fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
|
|
let scope = Scope::TraitRefBoundary { s: self.scope };
|
|
self.with(scope, |this| {
|
|
walk_list!(this, visit_generic_param, generics.params);
|
|
walk_list!(this, visit_where_predicate, generics.predicates);
|
|
})
|
|
}
|
|
|
|
fn visit_where_predicate(&mut self, predicate: &'tcx hir::WherePredicate<'tcx>) {
|
|
match predicate {
|
|
&hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
|
|
hir_id,
|
|
bounded_ty,
|
|
bounds,
|
|
bound_generic_params,
|
|
origin,
|
|
..
|
|
}) => {
|
|
let (bound_vars, binders): (FxIndexMap<LocalDefId, ResolvedArg>, Vec<_>) =
|
|
bound_generic_params
|
|
.iter()
|
|
.enumerate()
|
|
.map(|(late_bound_idx, param)| {
|
|
let pair = ResolvedArg::late(late_bound_idx as u32, param);
|
|
let r = late_arg_as_bound_arg(self.tcx, &pair.1, param);
|
|
(pair, r)
|
|
})
|
|
.unzip();
|
|
self.record_late_bound_vars(hir_id, binders);
|
|
// Even if there are no lifetimes defined here, we still wrap it in a binder
|
|
// scope. If there happens to be a nested poly trait ref (an error), that
|
|
// will be `Concatenating` anyways, so we don't have to worry about the depth
|
|
// being wrong.
|
|
let scope = Scope::Binder {
|
|
hir_id,
|
|
bound_vars,
|
|
s: self.scope,
|
|
scope_type: BinderScopeType::Normal,
|
|
where_bound_origin: Some(origin),
|
|
};
|
|
self.with(scope, |this| {
|
|
walk_list!(this, visit_generic_param, bound_generic_params);
|
|
this.visit_ty(bounded_ty);
|
|
walk_list!(this, visit_param_bound, bounds);
|
|
})
|
|
}
|
|
&hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
|
|
lifetime,
|
|
bounds,
|
|
..
|
|
}) => {
|
|
self.visit_lifetime(lifetime);
|
|
walk_list!(self, visit_param_bound, bounds);
|
|
}
|
|
&hir::WherePredicate::EqPredicate(hir::WhereEqPredicate { lhs_ty, rhs_ty, .. }) => {
|
|
self.visit_ty(lhs_ty);
|
|
self.visit_ty(rhs_ty);
|
|
}
|
|
}
|
|
}
|
|
|
|
fn visit_poly_trait_ref(&mut self, trait_ref: &'tcx hir::PolyTraitRef<'tcx>) {
|
|
self.visit_poly_trait_ref_inner(trait_ref, NonLifetimeBinderAllowed::Allow);
|
|
}
|
|
|
|
fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
|
|
self.with(Scope::LateBoundary { s: self.scope, what: "constant" }, |this| {
|
|
intravisit::walk_anon_const(this, c);
|
|
});
|
|
}
|
|
|
|
fn visit_generic_param(&mut self, p: &'tcx GenericParam<'tcx>) {
|
|
match p.kind {
|
|
GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
|
|
self.resolve_type_ref(p.def_id, p.hir_id);
|
|
}
|
|
GenericParamKind::Lifetime { .. } => {
|
|
// No need to resolve lifetime params, we don't use them for things
|
|
// like implicit `?Sized` or const-param-has-ty predicates.
|
|
}
|
|
}
|
|
|
|
match p.kind {
|
|
GenericParamKind::Lifetime { .. } => {}
|
|
GenericParamKind::Type { default, .. } => {
|
|
if let Some(ty) = default {
|
|
self.visit_ty(ty);
|
|
}
|
|
}
|
|
GenericParamKind::Const { ty, default, is_host_effect: _ } => {
|
|
self.visit_ty(ty);
|
|
if let Some(default) = default {
|
|
self.visit_body(self.tcx.hir().body(default.body));
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
fn object_lifetime_default(tcx: TyCtxt<'_>, param_def_id: LocalDefId) -> ObjectLifetimeDefault {
|
|
debug_assert_eq!(tcx.def_kind(param_def_id), DefKind::TyParam);
|
|
let hir::Node::GenericParam(param) = tcx.hir_node_by_def_id(param_def_id) else {
|
|
bug!("expected GenericParam for object_lifetime_default");
|
|
};
|
|
match param.source {
|
|
hir::GenericParamSource::Generics => {
|
|
let parent_def_id = tcx.local_parent(param_def_id);
|
|
let generics = tcx.hir().get_generics(parent_def_id).unwrap();
|
|
let param_hir_id = tcx.local_def_id_to_hir_id(param_def_id);
|
|
let param = generics.params.iter().find(|p| p.hir_id == param_hir_id).unwrap();
|
|
|
|
// 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.
|
|
match param.kind {
|
|
GenericParamKind::Type { .. } => {
|
|
let mut set = Set1::Empty;
|
|
|
|
// Look for `type: ...` where clauses.
|
|
for bound in generics.bounds_for_param(param_def_id) {
|
|
// Ignore `for<'a> type: ...` as they can change what
|
|
// lifetimes mean (although we could "just" handle it).
|
|
if !bound.bound_generic_params.is_empty() {
|
|
continue;
|
|
}
|
|
|
|
for bound in bound.bounds {
|
|
if let hir::GenericBound::Outlives(lifetime) = bound {
|
|
set.insert(lifetime.res);
|
|
}
|
|
}
|
|
}
|
|
|
|
match set {
|
|
Set1::Empty => ObjectLifetimeDefault::Empty,
|
|
Set1::One(hir::LifetimeName::Static) => ObjectLifetimeDefault::Static,
|
|
Set1::One(hir::LifetimeName::Param(param_def_id)) => {
|
|
ObjectLifetimeDefault::Param(param_def_id.to_def_id())
|
|
}
|
|
_ => ObjectLifetimeDefault::Ambiguous,
|
|
}
|
|
}
|
|
_ => {
|
|
bug!("object_lifetime_default_raw must only be called on a type parameter")
|
|
}
|
|
}
|
|
}
|
|
hir::GenericParamSource::Binder => ObjectLifetimeDefault::Empty,
|
|
}
|
|
}
|
|
|
|
impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
|
|
fn with<F>(&mut self, wrap_scope: Scope<'_>, f: F)
|
|
where
|
|
F: for<'b> FnOnce(&mut BoundVarContext<'b, 'tcx>),
|
|
{
|
|
let BoundVarContext { tcx, map, .. } = self;
|
|
let mut this = BoundVarContext { tcx: *tcx, map, scope: &wrap_scope };
|
|
let span = debug_span!("scope", scope = ?TruncatedScopeDebug(this.scope));
|
|
{
|
|
let _enter = span.enter();
|
|
f(&mut this);
|
|
}
|
|
}
|
|
|
|
fn record_late_bound_vars(&mut self, hir_id: HirId, binder: Vec<ty::BoundVariableKind>) {
|
|
if let Some(old) = self.map.late_bound_vars.insert(hir_id, binder) {
|
|
bug!(
|
|
"overwrote bound vars for {hir_id:?}:\nold={old:?}\nnew={:?}",
|
|
self.map.late_bound_vars[&hir_id]
|
|
)
|
|
}
|
|
}
|
|
|
|
/// 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, hir_id: HirId, generics: &'tcx hir::Generics<'tcx>, walk: F)
|
|
where
|
|
F: for<'b, 'c> FnOnce(&'b mut BoundVarContext<'c, 'tcx>),
|
|
{
|
|
let mut named_late_bound_vars = 0;
|
|
let bound_vars: FxIndexMap<LocalDefId, ResolvedArg> = generics
|
|
.params
|
|
.iter()
|
|
.map(|param| match param.kind {
|
|
GenericParamKind::Lifetime { .. } => {
|
|
if self.tcx.is_late_bound(param.hir_id) {
|
|
let late_bound_idx = named_late_bound_vars;
|
|
named_late_bound_vars += 1;
|
|
ResolvedArg::late(late_bound_idx, param)
|
|
} else {
|
|
ResolvedArg::early(param)
|
|
}
|
|
}
|
|
GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
|
|
ResolvedArg::early(param)
|
|
}
|
|
})
|
|
.collect();
|
|
|
|
let binders: Vec<_> = generics
|
|
.params
|
|
.iter()
|
|
.filter(|param| {
|
|
matches!(param.kind, GenericParamKind::Lifetime { .. })
|
|
&& self.tcx.is_late_bound(param.hir_id)
|
|
})
|
|
.enumerate()
|
|
.map(|(late_bound_idx, param)| {
|
|
let pair = ResolvedArg::late(late_bound_idx as u32, param);
|
|
late_arg_as_bound_arg(self.tcx, &pair.1, param)
|
|
})
|
|
.collect();
|
|
self.record_late_bound_vars(hir_id, binders);
|
|
let scope = Scope::Binder {
|
|
hir_id,
|
|
bound_vars,
|
|
s: self.scope,
|
|
scope_type: BinderScopeType::Normal,
|
|
where_bound_origin: None,
|
|
};
|
|
self.with(scope, walk);
|
|
}
|
|
|
|
fn visit_early<F>(&mut self, hir_id: HirId, generics: &'tcx hir::Generics<'tcx>, walk: F)
|
|
where
|
|
F: for<'b, 'c> FnOnce(&'b mut BoundVarContext<'c, 'tcx>),
|
|
{
|
|
let bound_vars = generics.params.iter().map(ResolvedArg::early).collect();
|
|
self.record_late_bound_vars(hir_id, vec![]);
|
|
let scope = Scope::Binder {
|
|
hir_id,
|
|
bound_vars,
|
|
s: self.scope,
|
|
scope_type: BinderScopeType::Normal,
|
|
where_bound_origin: None,
|
|
};
|
|
self.with(scope, |this| {
|
|
let scope = Scope::TraitRefBoundary { s: this.scope };
|
|
this.with(scope, walk)
|
|
});
|
|
}
|
|
|
|
#[instrument(level = "debug", skip(self))]
|
|
fn resolve_lifetime_ref(
|
|
&mut self,
|
|
region_def_id: LocalDefId,
|
|
lifetime_ref: &'tcx hir::Lifetime,
|
|
) {
|
|
// Walk up the scope chain, tracking the number of fn scopes
|
|
// that we pass through, until we find a lifetime with the
|
|
// given name or we run out of scopes.
|
|
// search.
|
|
let mut late_depth = 0;
|
|
let mut scope = self.scope;
|
|
let mut outermost_body = None;
|
|
let mut crossed_late_boundary = None;
|
|
let result = loop {
|
|
match *scope {
|
|
Scope::Body { id, s } => {
|
|
outermost_body = Some(id);
|
|
scope = s;
|
|
}
|
|
|
|
Scope::Root { opt_parent_item } => {
|
|
if let Some(parent_item) = opt_parent_item
|
|
&& let parent_generics = self.tcx.generics_of(parent_item)
|
|
&& parent_generics
|
|
.param_def_id_to_index(self.tcx, region_def_id.to_def_id())
|
|
.is_some()
|
|
{
|
|
break Some(ResolvedArg::EarlyBound(region_def_id.to_def_id()));
|
|
}
|
|
break None;
|
|
}
|
|
|
|
Scope::Binder { ref bound_vars, scope_type, s, where_bound_origin, .. } => {
|
|
if let Some(&def) = bound_vars.get(®ion_def_id) {
|
|
break Some(def.shifted(late_depth));
|
|
}
|
|
match scope_type {
|
|
BinderScopeType::Normal => late_depth += 1,
|
|
BinderScopeType::Concatenating => {}
|
|
}
|
|
// Fresh lifetimes in APIT used to be allowed in async fns and forbidden in
|
|
// regular fns.
|
|
if let Some(hir::PredicateOrigin::ImplTrait) = where_bound_origin
|
|
&& let hir::LifetimeName::Param(param_id) = lifetime_ref.res
|
|
&& let Some(generics) =
|
|
self.tcx.hir().get_generics(self.tcx.local_parent(param_id))
|
|
&& let Some(param) = generics.params.iter().find(|p| p.def_id == param_id)
|
|
&& param.is_elided_lifetime()
|
|
&& !self.tcx.asyncness(lifetime_ref.hir_id.owner.def_id).is_async()
|
|
&& !self.tcx.features().anonymous_lifetime_in_impl_trait
|
|
{
|
|
let mut diag: rustc_errors::Diag<'_> = rustc_session::parse::feature_err(
|
|
&self.tcx.sess,
|
|
sym::anonymous_lifetime_in_impl_trait,
|
|
lifetime_ref.ident.span,
|
|
"anonymous lifetimes in `impl Trait` are unstable",
|
|
);
|
|
|
|
if let Some(generics) =
|
|
self.tcx.hir().get_generics(lifetime_ref.hir_id.owner.def_id)
|
|
{
|
|
let new_param_sugg =
|
|
if let Some(span) = generics.span_for_lifetime_suggestion() {
|
|
(span, "'a, ".to_owned())
|
|
} else {
|
|
(generics.span, "<'a>".to_owned())
|
|
};
|
|
|
|
let lifetime_sugg = match lifetime_ref.suggestion_position() {
|
|
(hir::LifetimeSuggestionPosition::Normal, span) => {
|
|
(span, "'a".to_owned())
|
|
}
|
|
(hir::LifetimeSuggestionPosition::Ampersand, span) => {
|
|
(span, "'a ".to_owned())
|
|
}
|
|
(hir::LifetimeSuggestionPosition::ElidedPath, span) => {
|
|
(span, "<'a>".to_owned())
|
|
}
|
|
(hir::LifetimeSuggestionPosition::ElidedPathArgument, span) => {
|
|
(span, "'a, ".to_owned())
|
|
}
|
|
(hir::LifetimeSuggestionPosition::ObjectDefault, span) => {
|
|
(span, "+ 'a".to_owned())
|
|
}
|
|
};
|
|
let suggestions = vec![lifetime_sugg, new_param_sugg];
|
|
|
|
diag.span_label(
|
|
lifetime_ref.ident.span,
|
|
"expected named lifetime parameter",
|
|
);
|
|
diag.multipart_suggestion(
|
|
"consider introducing a named lifetime parameter",
|
|
suggestions,
|
|
rustc_errors::Applicability::MaybeIncorrect,
|
|
);
|
|
}
|
|
|
|
diag.emit();
|
|
return;
|
|
}
|
|
scope = s;
|
|
}
|
|
|
|
Scope::ObjectLifetimeDefault { s, .. }
|
|
| Scope::Supertrait { s, .. }
|
|
| Scope::TraitRefBoundary { s, .. } => {
|
|
scope = s;
|
|
}
|
|
|
|
Scope::LateBoundary { s, what } => {
|
|
crossed_late_boundary = Some(what);
|
|
scope = s;
|
|
}
|
|
}
|
|
};
|
|
|
|
if let Some(mut def) = result {
|
|
if let ResolvedArg::EarlyBound(..) = def {
|
|
// Do not free early-bound regions, only late-bound ones.
|
|
} else if let ResolvedArg::LateBound(_, _, param_def_id) = def
|
|
&& let Some(what) = crossed_late_boundary
|
|
{
|
|
let use_span = lifetime_ref.ident.span;
|
|
let def_span = self.tcx.def_span(param_def_id);
|
|
let guar = match self.tcx.def_kind(param_def_id) {
|
|
DefKind::LifetimeParam => {
|
|
self.tcx.dcx().emit_err(errors::CannotCaptureLateBound::Lifetime {
|
|
use_span,
|
|
def_span,
|
|
what,
|
|
})
|
|
}
|
|
kind => span_bug!(
|
|
use_span,
|
|
"did not expect to resolve lifetime to {}",
|
|
kind.descr(param_def_id)
|
|
),
|
|
};
|
|
def = ResolvedArg::Error(guar);
|
|
} else if let Some(body_id) = outermost_body {
|
|
let fn_id = self.tcx.hir().body_owner(body_id);
|
|
match self.tcx.hir_node(fn_id) {
|
|
Node::Item(hir::Item { owner_id, kind: hir::ItemKind::Fn(..), .. })
|
|
| Node::TraitItem(hir::TraitItem {
|
|
owner_id,
|
|
kind: hir::TraitItemKind::Fn(..),
|
|
..
|
|
})
|
|
| Node::ImplItem(hir::ImplItem {
|
|
owner_id,
|
|
kind: hir::ImplItemKind::Fn(..),
|
|
..
|
|
}) => {
|
|
def = ResolvedArg::Free(owner_id.to_def_id(), def.id().unwrap());
|
|
}
|
|
Node::Expr(hir::Expr { kind: hir::ExprKind::Closure(closure), .. }) => {
|
|
def = ResolvedArg::Free(closure.def_id.to_def_id(), def.id().unwrap());
|
|
}
|
|
_ => {}
|
|
}
|
|
}
|
|
|
|
self.insert_lifetime(lifetime_ref, def);
|
|
return;
|
|
}
|
|
|
|
// We may fail to resolve higher-ranked lifetimes that are mentioned by APIT.
|
|
// AST-based resolution does not care for impl-trait desugaring, which are the
|
|
// responsibility of lowering. This may create a mismatch between the resolution
|
|
// AST found (`region_def_id`) which points to HRTB, and what HIR allows.
|
|
// ```
|
|
// fn foo(x: impl for<'a> Trait<'a, Assoc = impl Copy + 'a>) {}
|
|
// ```
|
|
//
|
|
// In such case, walk back the binders to diagnose it properly.
|
|
let mut scope = self.scope;
|
|
loop {
|
|
match *scope {
|
|
Scope::Binder {
|
|
where_bound_origin: Some(hir::PredicateOrigin::ImplTrait), ..
|
|
} => {
|
|
self.tcx.dcx().emit_err(errors::LateBoundInApit::Lifetime {
|
|
span: lifetime_ref.ident.span,
|
|
param_span: self.tcx.def_span(region_def_id),
|
|
});
|
|
return;
|
|
}
|
|
Scope::Root { .. } => break,
|
|
Scope::Binder { s, .. }
|
|
| Scope::Body { s, .. }
|
|
| Scope::ObjectLifetimeDefault { s, .. }
|
|
| Scope::Supertrait { s, .. }
|
|
| Scope::TraitRefBoundary { s, .. }
|
|
| Scope::LateBoundary { s, .. } => {
|
|
scope = s;
|
|
}
|
|
}
|
|
}
|
|
|
|
self.tcx.dcx().span_delayed_bug(
|
|
lifetime_ref.ident.span,
|
|
format!("Could not resolve {:?} in scope {:#?}", lifetime_ref, self.scope,),
|
|
);
|
|
}
|
|
|
|
fn resolve_type_ref(&mut self, param_def_id: LocalDefId, hir_id: HirId) {
|
|
// 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 crossed_late_boundary = None;
|
|
|
|
let result = loop {
|
|
match *scope {
|
|
Scope::Body { s, .. } => {
|
|
scope = s;
|
|
}
|
|
|
|
Scope::Root { opt_parent_item } => {
|
|
if let Some(parent_item) = opt_parent_item
|
|
&& let parent_generics = self.tcx.generics_of(parent_item)
|
|
&& parent_generics
|
|
.param_def_id_to_index(self.tcx, param_def_id.to_def_id())
|
|
.is_some()
|
|
{
|
|
break Some(ResolvedArg::EarlyBound(param_def_id.to_def_id()));
|
|
}
|
|
break None;
|
|
}
|
|
|
|
Scope::Binder { ref bound_vars, scope_type, s, .. } => {
|
|
if let Some(&def) = bound_vars.get(¶m_def_id) {
|
|
break Some(def.shifted(late_depth));
|
|
}
|
|
match scope_type {
|
|
BinderScopeType::Normal => late_depth += 1,
|
|
BinderScopeType::Concatenating => {}
|
|
}
|
|
scope = s;
|
|
}
|
|
|
|
Scope::ObjectLifetimeDefault { s, .. }
|
|
| Scope::Supertrait { s, .. }
|
|
| Scope::TraitRefBoundary { s, .. } => {
|
|
scope = s;
|
|
}
|
|
|
|
Scope::LateBoundary { s, what } => {
|
|
crossed_late_boundary = Some(what);
|
|
scope = s;
|
|
}
|
|
}
|
|
};
|
|
|
|
if let Some(def) = result {
|
|
if let ResolvedArg::LateBound(..) = def
|
|
&& let Some(what) = crossed_late_boundary
|
|
{
|
|
let use_span = self.tcx.hir().span(hir_id);
|
|
let def_span = self.tcx.def_span(param_def_id);
|
|
let guar = match self.tcx.def_kind(param_def_id) {
|
|
DefKind::ConstParam => {
|
|
self.tcx.dcx().emit_err(errors::CannotCaptureLateBound::Const {
|
|
use_span,
|
|
def_span,
|
|
what,
|
|
})
|
|
}
|
|
DefKind::TyParam => {
|
|
self.tcx.dcx().emit_err(errors::CannotCaptureLateBound::Type {
|
|
use_span,
|
|
def_span,
|
|
what,
|
|
})
|
|
}
|
|
kind => span_bug!(
|
|
use_span,
|
|
"did not expect to resolve non-lifetime param to {}",
|
|
kind.descr(param_def_id.to_def_id())
|
|
),
|
|
};
|
|
self.map.defs.insert(hir_id, ResolvedArg::Error(guar));
|
|
} else {
|
|
self.map.defs.insert(hir_id, def);
|
|
}
|
|
return;
|
|
}
|
|
|
|
// We may fail to resolve higher-ranked ty/const vars that are mentioned by APIT.
|
|
// AST-based resolution does not care for impl-trait desugaring, which are the
|
|
// responsibility of lowering. This may create a mismatch between the resolution
|
|
// AST found (`param_def_id`) which points to HRTB, and what HIR allows.
|
|
// ```
|
|
// fn foo(x: impl for<T> Trait<Assoc = impl Trait2<T>>) {}
|
|
// ```
|
|
//
|
|
// In such case, walk back the binders to diagnose it properly.
|
|
let mut scope = self.scope;
|
|
loop {
|
|
match *scope {
|
|
Scope::Binder {
|
|
where_bound_origin: Some(hir::PredicateOrigin::ImplTrait), ..
|
|
} => {
|
|
let guar = self.tcx.dcx().emit_err(match self.tcx.def_kind(param_def_id) {
|
|
DefKind::TyParam => errors::LateBoundInApit::Type {
|
|
span: self.tcx.hir().span(hir_id),
|
|
param_span: self.tcx.def_span(param_def_id),
|
|
},
|
|
DefKind::ConstParam => errors::LateBoundInApit::Const {
|
|
span: self.tcx.hir().span(hir_id),
|
|
param_span: self.tcx.def_span(param_def_id),
|
|
},
|
|
kind => {
|
|
bug!("unexpected def-kind: {}", kind.descr(param_def_id.to_def_id()))
|
|
}
|
|
});
|
|
self.map.defs.insert(hir_id, ResolvedArg::Error(guar));
|
|
return;
|
|
}
|
|
Scope::Root { .. } => break,
|
|
Scope::Binder { s, .. }
|
|
| Scope::Body { s, .. }
|
|
| Scope::ObjectLifetimeDefault { s, .. }
|
|
| Scope::Supertrait { s, .. }
|
|
| Scope::TraitRefBoundary { s, .. }
|
|
| Scope::LateBoundary { s, .. } => {
|
|
scope = s;
|
|
}
|
|
}
|
|
}
|
|
|
|
self.tcx
|
|
.dcx()
|
|
.span_bug(self.tcx.hir().span(hir_id), format!("could not resolve {param_def_id:?}"));
|
|
}
|
|
|
|
#[instrument(level = "debug", skip(self))]
|
|
fn visit_segment_args(
|
|
&mut self,
|
|
res: Res,
|
|
depth: usize,
|
|
generic_args: &'tcx hir::GenericArgs<'tcx>,
|
|
) {
|
|
if generic_args.parenthesized == hir::GenericArgsParentheses::ParenSugar {
|
|
self.visit_fn_like_elision(
|
|
generic_args.inputs(),
|
|
Some(generic_args.bindings[0].ty()),
|
|
false,
|
|
);
|
|
return;
|
|
}
|
|
|
|
for arg in generic_args.args {
|
|
if let hir::GenericArg::Lifetime(lt) = arg {
|
|
self.visit_lifetime(lt);
|
|
}
|
|
}
|
|
|
|
// Figure out if this is a type/trait segment,
|
|
// which requires object lifetime defaults.
|
|
let type_def_id = match res {
|
|
Res::Def(DefKind::AssocTy, def_id) if depth == 1 => Some(self.tcx.parent(def_id)),
|
|
Res::Def(DefKind::Variant, def_id) if depth == 0 => Some(self.tcx.parent(def_id)),
|
|
Res::Def(
|
|
DefKind::Struct
|
|
| DefKind::Union
|
|
| DefKind::Enum
|
|
| DefKind::TyAlias
|
|
| DefKind::Trait,
|
|
def_id,
|
|
) if depth == 0 => Some(def_id),
|
|
_ => None,
|
|
};
|
|
|
|
debug!(?type_def_id);
|
|
|
|
// Compute a vector of defaults, one for each type parameter,
|
|
// per the rules given in RFCs 599 and 1156. Example:
|
|
//
|
|
// ```rust
|
|
// struct Foo<'a, T: 'a, U> { }
|
|
// ```
|
|
//
|
|
// If you have `Foo<'x, dyn Bar, dyn Baz>`, we want to default
|
|
// `dyn Bar` to `dyn Bar + 'x` (because of the `T: 'a` bound)
|
|
// and `dyn Baz` to `dyn Baz + 'static` (because there is no
|
|
// such bound).
|
|
//
|
|
// Therefore, we would compute `object_lifetime_defaults` to a
|
|
// vector like `['x, 'static]`. Note that the vector only
|
|
// includes type parameters.
|
|
let object_lifetime_defaults = type_def_id.map_or_else(Vec::new, |def_id| {
|
|
let in_body = {
|
|
let mut scope = self.scope;
|
|
loop {
|
|
match *scope {
|
|
Scope::Root { .. } => break false,
|
|
|
|
Scope::Body { .. } => break true,
|
|
|
|
Scope::Binder { s, .. }
|
|
| Scope::ObjectLifetimeDefault { s, .. }
|
|
| Scope::Supertrait { s, .. }
|
|
| Scope::TraitRefBoundary { s, .. }
|
|
| Scope::LateBoundary { s, .. } => {
|
|
scope = s;
|
|
}
|
|
}
|
|
}
|
|
};
|
|
|
|
let map = &self.map;
|
|
let generics = self.tcx.generics_of(def_id);
|
|
|
|
// `type_def_id` points to an item, so there is nothing to inherit generics from.
|
|
debug_assert_eq!(generics.parent_count, 0);
|
|
|
|
let set_to_region = |set: ObjectLifetimeDefault| match set {
|
|
ObjectLifetimeDefault::Empty => {
|
|
if in_body {
|
|
None
|
|
} else {
|
|
Some(ResolvedArg::StaticLifetime)
|
|
}
|
|
}
|
|
ObjectLifetimeDefault::Static => Some(ResolvedArg::StaticLifetime),
|
|
ObjectLifetimeDefault::Param(param_def_id) => {
|
|
// This index can be used with `generic_args` since `parent_count == 0`.
|
|
let index = generics.param_def_id_to_index[¶m_def_id] as usize;
|
|
generic_args.args.get(index).and_then(|arg| match arg {
|
|
GenericArg::Lifetime(lt) => map.defs.get(<.hir_id).copied(),
|
|
_ => None,
|
|
})
|
|
}
|
|
ObjectLifetimeDefault::Ambiguous => None,
|
|
};
|
|
generics
|
|
.params
|
|
.iter()
|
|
.filter_map(|param| {
|
|
match self.tcx.def_kind(param.def_id) {
|
|
// Generic consts don't impose any constraints.
|
|
//
|
|
// We still store a dummy value here to allow generic parameters
|
|
// in an arbitrary order.
|
|
DefKind::ConstParam => Some(ObjectLifetimeDefault::Empty),
|
|
DefKind::TyParam => Some(self.tcx.object_lifetime_default(param.def_id)),
|
|
// We may also get a `Trait` or `TraitAlias` because of how generics `Self` parameter
|
|
// works. Ignore it because it can't have a meaningful lifetime default.
|
|
DefKind::LifetimeParam | DefKind::Trait | DefKind::TraitAlias => None,
|
|
dk => bug!("unexpected def_kind {:?}", dk),
|
|
}
|
|
})
|
|
.map(set_to_region)
|
|
.collect()
|
|
});
|
|
|
|
debug!(?object_lifetime_defaults);
|
|
|
|
let mut i = 0;
|
|
for arg in generic_args.args {
|
|
match arg {
|
|
GenericArg::Lifetime(_) => {}
|
|
GenericArg::Type(ty) => {
|
|
if let Some(<) = object_lifetime_defaults.get(i) {
|
|
let scope = Scope::ObjectLifetimeDefault { lifetime: lt, s: self.scope };
|
|
self.with(scope, |this| this.visit_ty(ty));
|
|
} else {
|
|
self.visit_ty(ty);
|
|
}
|
|
i += 1;
|
|
}
|
|
GenericArg::Const(ct) => {
|
|
self.visit_anon_const(&ct.value);
|
|
i += 1;
|
|
}
|
|
GenericArg::Infer(inf) => {
|
|
self.visit_id(inf.hir_id);
|
|
i += 1;
|
|
}
|
|
}
|
|
}
|
|
|
|
// Hack: when resolving the type `XX` in binding like `dyn
|
|
// Foo<'b, Item = XX>`, the current object-lifetime default
|
|
// would be to examine the trait `Foo` to check whether it has
|
|
// a lifetime bound declared on `Item`. e.g., if `Foo` is
|
|
// declared like so, then the default object lifetime bound in
|
|
// `XX` should be `'b`:
|
|
//
|
|
// ```rust
|
|
// trait Foo<'a> {
|
|
// type Item: 'a;
|
|
// }
|
|
// ```
|
|
//
|
|
// but if we just have `type Item;`, then it would be
|
|
// `'static`. However, we don't get all of this logic correct.
|
|
//
|
|
// Instead, we do something hacky: if there are no lifetime parameters
|
|
// to the trait, then we simply use a default object lifetime
|
|
// bound of `'static`, because there is no other possibility. On the other hand,
|
|
// if there ARE lifetime parameters, then we require the user to give an
|
|
// explicit bound for now.
|
|
//
|
|
// This is intended to leave room for us to implement the
|
|
// correct behavior in the future.
|
|
let has_lifetime_parameter =
|
|
generic_args.args.iter().any(|arg| matches!(arg, GenericArg::Lifetime(_)));
|
|
|
|
// Resolve lifetimes found in the bindings, so either in the type `XX` in `Item = XX` or
|
|
// in the trait ref `YY<...>` in `Item: YY<...>`.
|
|
for binding in generic_args.bindings {
|
|
let scope = Scope::ObjectLifetimeDefault {
|
|
lifetime: if has_lifetime_parameter {
|
|
None
|
|
} else {
|
|
Some(ResolvedArg::StaticLifetime)
|
|
},
|
|
s: self.scope,
|
|
};
|
|
// If the binding is parenthesized, then this must be `feature(return_type_notation)`.
|
|
// In that case, introduce a binder over all of the function's early and late bound vars.
|
|
//
|
|
// For example, given
|
|
// ```
|
|
// trait Foo {
|
|
// async fn x<'r, T>();
|
|
// }
|
|
// ```
|
|
// and a bound that looks like:
|
|
// `for<'a> T::Trait<'a, x(): for<'b> Other<'b>>`
|
|
// this is going to expand to something like:
|
|
// `for<'a> for<'r, T> <T as Trait<'a>>::x::<'r, T>::{opaque#0}: for<'b> Other<'b>`.
|
|
if binding.gen_args.parenthesized == hir::GenericArgsParentheses::ReturnTypeNotation {
|
|
let bound_vars = if let Some(type_def_id) = type_def_id
|
|
&& self.tcx.def_kind(type_def_id) == DefKind::Trait
|
|
&& let Some((mut bound_vars, assoc_fn)) = BoundVarContext::supertrait_hrtb_vars(
|
|
self.tcx,
|
|
type_def_id,
|
|
binding.ident,
|
|
ty::AssocKind::Fn,
|
|
) {
|
|
bound_vars.extend(self.tcx.generics_of(assoc_fn.def_id).params.iter().map(
|
|
|param| match param.kind {
|
|
ty::GenericParamDefKind::Lifetime => ty::BoundVariableKind::Region(
|
|
ty::BoundRegionKind::BrNamed(param.def_id, param.name),
|
|
),
|
|
ty::GenericParamDefKind::Type { .. } => ty::BoundVariableKind::Ty(
|
|
ty::BoundTyKind::Param(param.def_id, param.name),
|
|
),
|
|
ty::GenericParamDefKind::Const { .. } => ty::BoundVariableKind::Const,
|
|
},
|
|
));
|
|
bound_vars.extend(
|
|
self.tcx.fn_sig(assoc_fn.def_id).instantiate_identity().bound_vars(),
|
|
);
|
|
bound_vars
|
|
} else {
|
|
self.tcx
|
|
.dcx()
|
|
.span_delayed_bug(binding.ident.span, "bad return type notation here");
|
|
vec![]
|
|
};
|
|
self.with(scope, |this| {
|
|
let scope = Scope::Supertrait { bound_vars, s: this.scope };
|
|
this.with(scope, |this| {
|
|
let (bound_vars, _) = this.poly_trait_ref_binder_info();
|
|
this.record_late_bound_vars(binding.hir_id, bound_vars);
|
|
this.visit_assoc_type_binding(binding)
|
|
});
|
|
});
|
|
} else if let Some(type_def_id) = type_def_id {
|
|
let bound_vars = BoundVarContext::supertrait_hrtb_vars(
|
|
self.tcx,
|
|
type_def_id,
|
|
binding.ident,
|
|
ty::AssocKind::Type,
|
|
)
|
|
.map(|(bound_vars, _)| bound_vars);
|
|
self.with(scope, |this| {
|
|
let scope = Scope::Supertrait {
|
|
bound_vars: bound_vars.unwrap_or_default(),
|
|
s: this.scope,
|
|
};
|
|
this.with(scope, |this| this.visit_assoc_type_binding(binding));
|
|
});
|
|
} else {
|
|
self.with(scope, |this| this.visit_assoc_type_binding(binding));
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Returns all the late-bound vars that come into scope from supertrait HRTBs, based on the
|
|
/// associated type name and starting trait.
|
|
/// For example, imagine we have
|
|
/// ```ignore (illustrative)
|
|
/// trait Foo<'a, 'b> {
|
|
/// type As;
|
|
/// }
|
|
/// trait Bar<'b>: for<'a> Foo<'a, 'b> {}
|
|
/// trait Bar: for<'b> Bar<'b> {}
|
|
/// ```
|
|
/// In this case, if we wanted to the supertrait HRTB lifetimes for `As` on
|
|
/// the starting trait `Bar`, we would return `Some(['b, 'a])`.
|
|
fn supertrait_hrtb_vars(
|
|
tcx: TyCtxt<'tcx>,
|
|
def_id: DefId,
|
|
assoc_name: Ident,
|
|
assoc_kind: ty::AssocKind,
|
|
) -> Option<(Vec<ty::BoundVariableKind>, &'tcx ty::AssocItem)> {
|
|
let trait_defines_associated_item_named = |trait_def_id: DefId| {
|
|
tcx.associated_items(trait_def_id).find_by_name_and_kind(
|
|
tcx,
|
|
assoc_name,
|
|
assoc_kind,
|
|
trait_def_id,
|
|
)
|
|
};
|
|
|
|
use smallvec::{smallvec, SmallVec};
|
|
let mut stack: SmallVec<[(DefId, SmallVec<[ty::BoundVariableKind; 8]>); 8]> =
|
|
smallvec![(def_id, smallvec![])];
|
|
let mut visited: FxHashSet<DefId> = FxHashSet::default();
|
|
loop {
|
|
let Some((def_id, bound_vars)) = stack.pop() else {
|
|
break None;
|
|
};
|
|
// See issue #83753. If someone writes an associated type on a non-trait, just treat it as
|
|
// there being no supertrait HRTBs.
|
|
match tcx.def_kind(def_id) {
|
|
DefKind::Trait | DefKind::TraitAlias | DefKind::Impl { .. } => {}
|
|
_ => break None,
|
|
}
|
|
|
|
if let Some(assoc_item) = trait_defines_associated_item_named(def_id) {
|
|
break Some((bound_vars.into_iter().collect(), assoc_item));
|
|
}
|
|
let predicates = tcx.super_predicates_that_define_assoc_item((def_id, assoc_name));
|
|
let obligations = predicates.predicates.iter().filter_map(|&(pred, _)| {
|
|
let bound_predicate = pred.kind();
|
|
match bound_predicate.skip_binder() {
|
|
ty::ClauseKind::Trait(data) => {
|
|
// The order here needs to match what we would get from
|
|
// `rustc_middle::ty::predicate::Clause::instantiate_supertrait`
|
|
let pred_bound_vars = bound_predicate.bound_vars();
|
|
let mut all_bound_vars = bound_vars.clone();
|
|
all_bound_vars.extend(pred_bound_vars.iter());
|
|
let super_def_id = data.trait_ref.def_id;
|
|
Some((super_def_id, all_bound_vars))
|
|
}
|
|
_ => None,
|
|
}
|
|
});
|
|
|
|
let obligations = obligations.filter(|o| visited.insert(o.0));
|
|
stack.extend(obligations);
|
|
}
|
|
}
|
|
|
|
#[instrument(level = "debug", skip(self))]
|
|
fn visit_fn_like_elision(
|
|
&mut self,
|
|
inputs: &'tcx [hir::Ty<'tcx>],
|
|
output: Option<&'tcx hir::Ty<'tcx>>,
|
|
in_closure: bool,
|
|
) {
|
|
self.with(
|
|
Scope::ObjectLifetimeDefault {
|
|
lifetime: Some(ResolvedArg::StaticLifetime),
|
|
s: self.scope,
|
|
},
|
|
|this| {
|
|
for input in inputs {
|
|
this.visit_ty(input);
|
|
}
|
|
if !in_closure && let Some(output) = output {
|
|
this.visit_ty(output);
|
|
}
|
|
},
|
|
);
|
|
if in_closure && let Some(output) = output {
|
|
self.visit_ty(output);
|
|
}
|
|
}
|
|
|
|
#[instrument(level = "debug", skip(self))]
|
|
fn resolve_object_lifetime_default(&mut self, lifetime_ref: &'tcx hir::Lifetime) {
|
|
let mut late_depth = 0;
|
|
let mut scope = self.scope;
|
|
let lifetime = loop {
|
|
match *scope {
|
|
Scope::Binder { s, scope_type, .. } => {
|
|
match scope_type {
|
|
BinderScopeType::Normal => late_depth += 1,
|
|
BinderScopeType::Concatenating => {}
|
|
}
|
|
scope = s;
|
|
}
|
|
|
|
Scope::Root { .. } => break ResolvedArg::StaticLifetime,
|
|
|
|
Scope::Body { .. } | Scope::ObjectLifetimeDefault { lifetime: None, .. } => return,
|
|
|
|
Scope::ObjectLifetimeDefault { lifetime: Some(l), .. } => break l,
|
|
|
|
Scope::Supertrait { s, .. }
|
|
| Scope::TraitRefBoundary { s, .. }
|
|
| Scope::LateBoundary { s, .. } => {
|
|
scope = s;
|
|
}
|
|
}
|
|
};
|
|
self.insert_lifetime(lifetime_ref, lifetime.shifted(late_depth));
|
|
}
|
|
|
|
#[instrument(level = "debug", skip(self))]
|
|
fn insert_lifetime(&mut self, lifetime_ref: &'tcx hir::Lifetime, def: ResolvedArg) {
|
|
debug!(span = ?lifetime_ref.ident.span);
|
|
self.map.defs.insert(lifetime_ref.hir_id, def);
|
|
}
|
|
|
|
/// Sometimes we resolve a lifetime, but later find that it is an
|
|
/// error (esp. around impl trait). In that case, we remove the
|
|
/// entry into `map.defs` so as not to confuse later code.
|
|
fn uninsert_lifetime_on_error(
|
|
&mut self,
|
|
lifetime_ref: &'tcx hir::Lifetime,
|
|
bad_def: ResolvedArg,
|
|
) {
|
|
// FIXME(#120456) - is `swap_remove` correct?
|
|
let old_value = self.map.defs.swap_remove(&lifetime_ref.hir_id);
|
|
assert_eq!(old_value, Some(bad_def));
|
|
}
|
|
}
|
|
|
|
/// Detects late-bound lifetimes and inserts them into
|
|
/// `late_bound`.
|
|
///
|
|
/// A region declared on a fn is **late-bound** if:
|
|
/// - it is constrained by an argument type;
|
|
/// - it does not appear in a where-clause.
|
|
///
|
|
/// "Constrained" basically means that it appears in any type but
|
|
/// not amongst the inputs to a projection. In other words, `<&'a
|
|
/// T as Trait<''b>>::Foo` does not constrain `'a` or `'b`.
|
|
fn is_late_bound_map(
|
|
tcx: TyCtxt<'_>,
|
|
owner_id: hir::OwnerId,
|
|
) -> Option<&FxIndexSet<hir::ItemLocalId>> {
|
|
let decl = tcx.hir().fn_decl_by_hir_id(owner_id.into())?;
|
|
let generics = tcx.hir().get_generics(owner_id.def_id)?;
|
|
|
|
let mut late_bound = FxIndexSet::default();
|
|
|
|
let mut constrained_by_input = ConstrainedCollector { regions: Default::default(), tcx };
|
|
for arg_ty in decl.inputs {
|
|
constrained_by_input.visit_ty(arg_ty);
|
|
}
|
|
|
|
let mut appears_in_output = AllCollector::default();
|
|
intravisit::walk_fn_ret_ty(&mut appears_in_output, &decl.output);
|
|
|
|
debug!(?constrained_by_input.regions);
|
|
|
|
// Walk the lifetimes that appear in where clauses.
|
|
//
|
|
// Subtle point: because we disallow nested bindings, we can just
|
|
// ignore binders here and scrape up all names we see.
|
|
let mut appears_in_where_clause = AllCollector::default();
|
|
appears_in_where_clause.visit_generics(generics);
|
|
debug!(?appears_in_where_clause.regions);
|
|
|
|
// Late bound regions are those that:
|
|
// - appear in the inputs
|
|
// - do not appear in the where-clauses
|
|
// - are not implicitly captured by `impl Trait`
|
|
for param in generics.params {
|
|
match param.kind {
|
|
hir::GenericParamKind::Lifetime { .. } => { /* fall through */ }
|
|
|
|
// Neither types nor consts are late-bound.
|
|
hir::GenericParamKind::Type { .. } | hir::GenericParamKind::Const { .. } => continue,
|
|
}
|
|
|
|
// appears in the where clauses? early-bound.
|
|
if appears_in_where_clause.regions.contains(¶m.def_id) {
|
|
continue;
|
|
}
|
|
|
|
// does not appear in the inputs, but appears in the return type? early-bound.
|
|
if !constrained_by_input.regions.contains(¶m.def_id)
|
|
&& appears_in_output.regions.contains(¶m.def_id)
|
|
{
|
|
continue;
|
|
}
|
|
|
|
debug!("lifetime {:?} with id {:?} is late-bound", param.name.ident(), param.def_id);
|
|
|
|
let inserted = late_bound.insert(param.hir_id.local_id);
|
|
assert!(inserted, "visited lifetime {:?} twice", param.def_id);
|
|
}
|
|
|
|
debug!(?late_bound);
|
|
return Some(tcx.arena.alloc(late_bound));
|
|
|
|
/// Visits a `ty::Ty` collecting information about what generic parameters are constrained.
|
|
///
|
|
/// The visitor does not operate on `hir::Ty` so that it can be called on the rhs of a `type Alias<...> = ...;`
|
|
/// which may live in a separate crate so there would not be any hir available. Instead we use the `type_of`
|
|
/// query to obtain a `ty::Ty` which will be present even in cross crate scenarios. It also naturally
|
|
/// handles cycle detection as we go through the query system.
|
|
///
|
|
/// This is necessary in the first place for the following case:
|
|
/// ```rust,ignore (pseudo-Rust)
|
|
/// type Alias<'a, T> = <T as Trait<'a>>::Assoc;
|
|
/// fn foo<'a>(_: Alias<'a, ()>) -> Alias<'a, ()> { ... }
|
|
/// ```
|
|
///
|
|
/// If we conservatively considered `'a` unconstrained then we could break users who had written code before
|
|
/// we started correctly handling aliases. If we considered `'a` constrained then it would become late bound
|
|
/// causing an error during HIR ty lowering as the `'a` is not constrained by the input type `<() as Trait<'a>>::Assoc`
|
|
/// but appears in the output type `<() as Trait<'a>>::Assoc`.
|
|
///
|
|
/// We must therefore "look into" the `Alias` to see whether we should consider `'a` constrained or not.
|
|
///
|
|
/// See #100508 #85533 #47511 for additional context
|
|
struct ConstrainedCollectorPostHirTyLowering {
|
|
arg_is_constrained: Box<[bool]>,
|
|
}
|
|
|
|
use ty::Ty;
|
|
impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ConstrainedCollectorPostHirTyLowering {
|
|
fn visit_ty(&mut self, t: Ty<'tcx>) {
|
|
match t.kind() {
|
|
ty::Param(param_ty) => {
|
|
self.arg_is_constrained[param_ty.index as usize] = true;
|
|
}
|
|
ty::Alias(ty::Projection | ty::Inherent, _) => return,
|
|
_ => (),
|
|
}
|
|
t.super_visit_with(self)
|
|
}
|
|
|
|
fn visit_const(&mut self, _: ty::Const<'tcx>) {}
|
|
|
|
fn visit_region(&mut self, r: ty::Region<'tcx>) {
|
|
debug!("r={:?}", r.kind());
|
|
if let ty::RegionKind::ReEarlyParam(region) = r.kind() {
|
|
self.arg_is_constrained[region.index as usize] = true;
|
|
}
|
|
}
|
|
}
|
|
|
|
struct ConstrainedCollector<'tcx> {
|
|
tcx: TyCtxt<'tcx>,
|
|
regions: FxHashSet<LocalDefId>,
|
|
}
|
|
|
|
impl<'v> Visitor<'v> for ConstrainedCollector<'_> {
|
|
fn visit_ty(&mut self, ty: &'v hir::Ty<'v>) {
|
|
match ty.kind {
|
|
hir::TyKind::Path(
|
|
hir::QPath::Resolved(Some(_), _) | hir::QPath::TypeRelative(..),
|
|
) => {
|
|
// ignore lifetimes appearing in associated type
|
|
// projections, as they are not *constrained*
|
|
// (defined above)
|
|
}
|
|
|
|
hir::TyKind::Path(hir::QPath::Resolved(
|
|
None,
|
|
hir::Path { res: Res::Def(DefKind::TyAlias, alias_def), segments, span },
|
|
)) => {
|
|
// See comments on `ConstrainedCollectorPostHirTyLowering` for why this arm does not
|
|
// just consider args to be unconstrained.
|
|
let generics = self.tcx.generics_of(alias_def);
|
|
let mut walker = ConstrainedCollectorPostHirTyLowering {
|
|
arg_is_constrained: vec![false; generics.params.len()].into_boxed_slice(),
|
|
};
|
|
walker.visit_ty(self.tcx.type_of(alias_def).instantiate_identity());
|
|
|
|
match segments.last() {
|
|
Some(hir::PathSegment { args: Some(args), .. }) => {
|
|
let tcx = self.tcx;
|
|
for constrained_arg in
|
|
args.args.iter().enumerate().flat_map(|(n, arg)| {
|
|
match walker.arg_is_constrained.get(n) {
|
|
Some(true) => Some(arg),
|
|
Some(false) => None,
|
|
None => {
|
|
tcx.dcx().span_delayed_bug(
|
|
*span,
|
|
format!(
|
|
"Incorrect generic arg count for alias {alias_def:?}"
|
|
),
|
|
);
|
|
None
|
|
}
|
|
}
|
|
})
|
|
{
|
|
self.visit_generic_arg(constrained_arg);
|
|
}
|
|
}
|
|
Some(_) => (),
|
|
None => bug!("Path with no segments or self type"),
|
|
}
|
|
}
|
|
|
|
hir::TyKind::Path(hir::QPath::Resolved(None, 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(last_segment);
|
|
}
|
|
}
|
|
|
|
_ => {
|
|
intravisit::walk_ty(self, ty);
|
|
}
|
|
}
|
|
}
|
|
|
|
fn visit_lifetime(&mut self, lifetime_ref: &'v hir::Lifetime) {
|
|
if let hir::LifetimeName::Param(def_id) = lifetime_ref.res {
|
|
self.regions.insert(def_id);
|
|
}
|
|
}
|
|
}
|
|
|
|
#[derive(Default)]
|
|
struct AllCollector {
|
|
regions: FxHashSet<LocalDefId>,
|
|
}
|
|
|
|
impl<'v> Visitor<'v> for AllCollector {
|
|
fn visit_lifetime(&mut self, lifetime_ref: &'v hir::Lifetime) {
|
|
if let hir::LifetimeName::Param(def_id) = lifetime_ref.res {
|
|
self.regions.insert(def_id);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
pub fn deny_non_region_late_bound(
|
|
tcx: TyCtxt<'_>,
|
|
bound_vars: &mut FxIndexMap<LocalDefId, ResolvedArg>,
|
|
where_: &str,
|
|
) {
|
|
let mut first = true;
|
|
|
|
for (var, arg) in bound_vars {
|
|
let Node::GenericParam(param) = tcx.hir_node_by_def_id(*var) else {
|
|
span_bug!(tcx.def_span(*var), "expected bound-var def-id to resolve to param");
|
|
};
|
|
|
|
let what = match param.kind {
|
|
hir::GenericParamKind::Type { .. } => "type",
|
|
hir::GenericParamKind::Const { .. } => "const",
|
|
hir::GenericParamKind::Lifetime { .. } => continue,
|
|
};
|
|
|
|
let diag = tcx.dcx().struct_span_err(
|
|
param.span,
|
|
format!("late-bound {what} parameter not allowed on {where_}"),
|
|
);
|
|
|
|
let guar = if tcx.features().non_lifetime_binders && first {
|
|
diag.emit()
|
|
} else {
|
|
diag.delay_as_bug()
|
|
};
|
|
|
|
first = false;
|
|
*arg = ResolvedArg::Error(guar);
|
|
}
|
|
}
|