rustc_middle/hir/

mod.rs

//! HIR datatypes. See the [rustc dev guide] for more info.
//!
//! [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/hir.html

pub mod map;
pub mod nested_filter;
pub mod place;

use std::sync::Arc;

use rustc_ast::{self as ast};
use rustc_data_structures::fingerprint::Fingerprint;
use rustc_data_structures::fx::FxIndexSet;
use rustc_data_structures::sorted_map::SortedMap;
use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
use rustc_data_structures::steal::Steal;
use rustc_data_structures::sync::{DynSend, DynSync, spawn, try_par_for_each_in};
use rustc_hir::def::{DefKind, Res};
use rustc_hir::def_id::{DefId, LocalDefId, LocalModDefId};
use rustc_hir::lints::DelayedLint;
use rustc_hir::*;
use rustc_index::IndexVec;
use rustc_macros::{Decodable, Encodable, HashStable};
use rustc_span::{ErrorGuaranteed, ExpnId, HashStableContext, Span};

use crate::query::Providers;
use crate::ty::{ResolverAstLowering, TyCtxt};

/// The top-level data structure that stores the entire contents of
/// the crate currently being compiled.
///
/// For more details, see the [rustc dev guide].
///
/// [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/hir.html
#[derive(Debug)]
pub struct Crate<'hir> {
    // This field is private by intention, access it through `owner` method.
    owners: IndexVec<LocalDefId, MaybeOwner<'hir>>,
    // Ids of delayed AST owners which are lowered through `lower_delayed_owner` query.
    pub delayed_ids: FxIndexSet<LocalDefId>,
    // The resolver and AST crate which are set in the end of the `hir_crate` query
    // and then stolen and dropped in `force_delayed_owners_lowering`.
    pub delayed_resolver: Steal<(ResolverAstLowering<'hir>, Arc<ast::Crate>)>,
    // Only present when incr. comp. is enabled.
    pub opt_hir_hash: Option<Fingerprint>,
}

impl<'hir> Crate<'hir> {
    pub fn new(
        owners: IndexVec<LocalDefId, MaybeOwner<'hir>>,
        delayed_ids: FxIndexSet<LocalDefId>,
        delayed_resolver: Steal<(ResolverAstLowering<'hir>, Arc<ast::Crate>)>,
        opt_hir_hash: Option<Fingerprint>,
    ) -> Crate<'hir> {
        Crate { owners, delayed_ids, delayed_resolver, opt_hir_hash }
    }

    /// Serves as an entry point for getting `MaybeOwner`. As owner can either be in
    /// `owners` of `hir_crate` or it can be delayed AST owner (i.e., delegations)
    /// we need to firstly check in `hir_crate` and then delayed AST owners.
    /// This method can be invoked when not all delayed AST owners are lowered.
    pub fn owner(&self, tcx: TyCtxt<'hir>, def_id: LocalDefId) -> MaybeOwner<'hir> {
        // Delayed LocalDefId can be in `self.owners` if there exists non-delayed LocalDefId
        // which is greater than delayed LocalDefId, we use IndexVec for owners,
        // so we will call ensure_contains_elem which will grow it.
        if let Some(owner) = self.owners.get(def_id)
            && (self.delayed_ids.is_empty()
                || !matches!(owner, MaybeOwner::Phantom | MaybeOwner::Delayed(_)))
        {
            return *owner;
        }

        if self.delayed_ids.contains(&def_id) {
            tcx.ensure_done().lower_delayed_owner(def_id);
        }

        tcx.delayed_owner(def_id)
    }
}

impl<Hcx: HashStableContext> HashStable<Hcx> for Crate<'_> {
    fn hash_stable(&self, hcx: &mut Hcx, hasher: &mut StableHasher) {
        let Crate { opt_hir_hash, .. } = self;
        opt_hir_hash.unwrap().hash_stable(hcx, hasher)
    }
}

/// Gather the LocalDefId for each item-like within a module, including items contained within
/// bodies. The Ids are in visitor order. This is used to partition a pass between modules.
#[derive(Debug, HashStable, Encodable, Decodable)]
pub struct ModuleItems {
    /// Whether this represents the whole crate, in which case we need to add `CRATE_OWNER_ID` to
    /// the iterators if we want to account for the crate root.
    add_root: bool,
    submodules: Box<[OwnerId]>,
    free_items: Box<[ItemId]>,
    trait_items: Box<[TraitItemId]>,
    impl_items: Box<[ImplItemId]>,
    foreign_items: Box<[ForeignItemId]>,
    opaques: Box<[LocalDefId]>,
    body_owners: Box<[LocalDefId]>,
    nested_bodies: Box<[LocalDefId]>,
    // only filled with hir_crate_items, not with hir_module_items
    delayed_lint_items: Box<[OwnerId]>,

    /// Statics and functions with an `EiiImpls` or `EiiExternTarget` attribute
    eiis: Box<[LocalDefId]>,
}

impl ModuleItems {
    /// Returns all non-associated locally defined items in all modules.
    ///
    /// Note that this does *not* include associated items of `impl` blocks! It also does not
    /// include foreign items. If you want to e.g. get all functions, use `definitions()` below.
    ///
    /// However, this does include the `impl` blocks themselves.
    pub fn free_items(&self) -> impl Iterator<Item = ItemId> {
        self.free_items.iter().copied()
    }

    pub fn trait_items(&self) -> impl Iterator<Item = TraitItemId> {
        self.trait_items.iter().copied()
    }

    pub fn delayed_lint_items(&self) -> impl Iterator<Item = OwnerId> {
        self.delayed_lint_items.iter().copied()
    }

    pub fn eiis(&self) -> impl Iterator<Item = LocalDefId> {
        self.eiis.iter().copied()
    }

    /// Returns all items that are associated with some `impl` block (both inherent and trait impl
    /// blocks).
    pub fn impl_items(&self) -> impl Iterator<Item = ImplItemId> {
        self.impl_items.iter().copied()
    }

    pub fn foreign_items(&self) -> impl Iterator<Item = ForeignItemId> {
        self.foreign_items.iter().copied()
    }

    pub fn owners(&self) -> impl Iterator<Item = OwnerId> {
        self.add_root
            .then_some(CRATE_OWNER_ID)
            .into_iter()
            .chain(self.free_items.iter().map(|id| id.owner_id))
            .chain(self.trait_items.iter().map(|id| id.owner_id))
            .chain(self.impl_items.iter().map(|id| id.owner_id))
            .chain(self.foreign_items.iter().map(|id| id.owner_id))
    }

    pub fn opaques(&self) -> impl Iterator<Item = LocalDefId> {
        self.opaques.iter().copied()
    }

    /// Closures and inline consts
    pub fn nested_bodies(&self) -> impl Iterator<Item = LocalDefId> {
        self.nested_bodies.iter().copied()
    }

    pub fn definitions(&self) -> impl Iterator<Item = LocalDefId> {
        self.owners().map(|id| id.def_id)
    }

    /// Closures and inline consts
    pub fn par_nested_bodies(
        &self,
        f: impl Fn(LocalDefId) -> Result<(), ErrorGuaranteed> + DynSend + DynSync,
    ) -> Result<(), ErrorGuaranteed> {
        try_par_for_each_in(&self.nested_bodies[..], |&&id| f(id))
    }

    pub fn par_items(
        &self,
        f: impl Fn(ItemId) -> Result<(), ErrorGuaranteed> + DynSend + DynSync,
    ) -> Result<(), ErrorGuaranteed> {
        try_par_for_each_in(&self.free_items[..], |&&id| f(id))
    }

    pub fn par_trait_items(
        &self,
        f: impl Fn(TraitItemId) -> Result<(), ErrorGuaranteed> + DynSend + DynSync,
    ) -> Result<(), ErrorGuaranteed> {
        try_par_for_each_in(&self.trait_items[..], |&&id| f(id))
    }

    pub fn par_impl_items(
        &self,
        f: impl Fn(ImplItemId) -> Result<(), ErrorGuaranteed> + DynSend + DynSync,
    ) -> Result<(), ErrorGuaranteed> {
        try_par_for_each_in(&self.impl_items[..], |&&id| f(id))
    }

    pub fn par_foreign_items(
        &self,
        f: impl Fn(ForeignItemId) -> Result<(), ErrorGuaranteed> + DynSend + DynSync,
    ) -> Result<(), ErrorGuaranteed> {
        try_par_for_each_in(&self.foreign_items[..], |&&id| f(id))
    }

    pub fn par_opaques(
        &self,
        f: impl Fn(LocalDefId) -> Result<(), ErrorGuaranteed> + DynSend + DynSync,
    ) -> Result<(), ErrorGuaranteed> {
        try_par_for_each_in(&self.opaques[..], |&&id| f(id))
    }
}

impl<'tcx> TyCtxt<'tcx> {
    pub fn force_delayed_owners_lowering(self) {
        let krate = self.hir_crate(());
        self.ensure_done().hir_crate_items(());

        for &id in &krate.delayed_ids {
            self.ensure_done().lower_delayed_owner(id);
        }

        let (_, krate) = krate.delayed_resolver.steal();
        let prof = self.sess.prof.clone();

        // Drop AST to free memory. It can be expensive so try to drop it on a separate thread.
        spawn(move || {
            let _timer = prof.verbose_generic_activity("drop_ast");
            drop(krate);
        });
    }

    pub fn parent_module(self, id: HirId) -> LocalModDefId {
        if !id.is_owner() && self.def_kind(id.owner) == DefKind::Mod {
            LocalModDefId::new_unchecked(id.owner.def_id)
        } else {
            self.parent_module_from_def_id(id.owner.def_id)
        }
    }

    pub fn parent_module_from_def_id(self, mut id: LocalDefId) -> LocalModDefId {
        while let Some(parent) = self.opt_local_parent(id) {
            id = parent;
            if self.def_kind(id) == DefKind::Mod {
                break;
            }
        }
        LocalModDefId::new_unchecked(id)
    }

    /// Returns `true` if this is a foreign item (i.e., linked via `extern { ... }`).
    pub fn is_foreign_item(self, def_id: impl Into<DefId>) -> bool {
        self.opt_parent(def_id.into())
            .is_some_and(|parent| matches!(self.def_kind(parent), DefKind::ForeignMod))
    }

    pub fn hash_owner_nodes(
        self,
        node: OwnerNode<'_>,
        bodies: &SortedMap<ItemLocalId, &Body<'_>>,
        attrs: &SortedMap<ItemLocalId, &[Attribute]>,
        delayed_lints: &[DelayedLint],
        define_opaque: Option<&[(Span, LocalDefId)]>,
    ) -> Hashes {
        if !self.needs_crate_hash() {
            return Hashes {
                opt_hash_including_bodies: None,
                attrs_hash: None,
                delayed_lints_hash: None,
            };
        }

        self.with_stable_hashing_context(|mut hcx| {
            let mut stable_hasher = StableHasher::new();
            node.hash_stable(&mut hcx, &mut stable_hasher);
            // Bodies are stored out of line, so we need to pull them explicitly in the hash.
            bodies.hash_stable(&mut hcx, &mut stable_hasher);
            let h1 = stable_hasher.finish();

            let mut stable_hasher = StableHasher::new();
            attrs.hash_stable(&mut hcx, &mut stable_hasher);

            // Hash the defined opaque types, which are not present in the attrs.
            define_opaque.hash_stable(&mut hcx, &mut stable_hasher);

            let h2 = stable_hasher.finish();

            // hash lints emitted during ast lowering
            let mut stable_hasher = StableHasher::new();
            delayed_lints.hash_stable(&mut hcx, &mut stable_hasher);
            let h3 = stable_hasher.finish();

            Hashes {
                opt_hash_including_bodies: Some(h1),
                attrs_hash: Some(h2),
                delayed_lints_hash: Some(h3),
            }
        })
    }

    pub fn qpath_is_lang_item(self, qpath: QPath<'_>, lang_item: LangItem) -> bool {
        self.qpath_lang_item(qpath) == Some(lang_item)
    }

    /// This does not use typeck results since this is intended to be used with generated code.
    pub fn qpath_lang_item(self, qpath: QPath<'_>) -> Option<LangItem> {
        if let QPath::Resolved(_, path) = qpath
            && let Res::Def(_, def_id) = path.res
        {
            return self.lang_items().from_def_id(def_id);
        }
        None
    }

    /// Whether this expression constitutes a read of value of the type that
    /// it evaluates to.
    ///
    /// This is used to determine if we should consider the block to diverge
    /// if the expression evaluates to `!`, and if we should insert a `NeverToAny`
    /// coercion for values of type `!`.
    ///
    /// This function generally returns `false` if the expression is a place
    /// expression and the *parent* expression is the scrutinee of a match or
    /// the pointee of an `&` addr-of expression, since both of those parent
    /// expressions take a *place* and not a value.
    pub fn expr_guaranteed_to_constitute_read_for_never(self, expr: &Expr<'_>) -> bool {
        // We only care about place exprs. Anything else returns an immediate
        // which would constitute a read. We don't care about distinguishing
        // "syntactic" place exprs since if the base of a field projection is
        // not a place then it would've been UB to read from it anyways since
        // that constitutes a read.
        if !expr.is_syntactic_place_expr() {
            return true;
        }

        let parent_node = self.parent_hir_node(expr.hir_id);
        match parent_node {
            Node::Expr(parent_expr) => {
                match parent_expr.kind {
                    // Addr-of, field projections, and LHS of assignment don't constitute reads.
                    // Assignment does call `drop_in_place`, though, but its safety
                    // requirements are not the same.
                    ExprKind::AddrOf(..) | ExprKind::Field(..) => false,

                    // Place-preserving expressions only constitute reads if their
                    // parent expression constitutes a read.
                    ExprKind::Type(..) | ExprKind::UnsafeBinderCast(..) => {
                        self.expr_guaranteed_to_constitute_read_for_never(parent_expr)
                    }

                    ExprKind::Assign(lhs, _, _) => {
                        // Only the LHS does not constitute a read
                        expr.hir_id != lhs.hir_id
                    }

                    // See note on `PatKind::Or` in `Pat::is_guaranteed_to_constitute_read_for_never`
                    // for why this is `all`.
                    ExprKind::Match(scrutinee, arms, _) => {
                        assert_eq!(scrutinee.hir_id, expr.hir_id);
                        arms.iter().all(|arm| arm.pat.is_guaranteed_to_constitute_read_for_never())
                    }
                    ExprKind::Let(LetExpr { init, pat, .. }) => {
                        assert_eq!(init.hir_id, expr.hir_id);
                        pat.is_guaranteed_to_constitute_read_for_never()
                    }

                    // Any expression child of these expressions constitute reads.
                    ExprKind::Array(_)
                    | ExprKind::Call(_, _)
                    | ExprKind::Use(_, _)
                    | ExprKind::MethodCall(_, _, _, _)
                    | ExprKind::Tup(_)
                    | ExprKind::Binary(_, _, _)
                    | ExprKind::Unary(_, _)
                    | ExprKind::Cast(_, _)
                    | ExprKind::DropTemps(_)
                    | ExprKind::If(_, _, _)
                    | ExprKind::Closure(_)
                    | ExprKind::Block(_, _)
                    | ExprKind::AssignOp(_, _, _)
                    | ExprKind::Index(_, _, _)
                    | ExprKind::Break(_, _)
                    | ExprKind::Ret(_)
                    | ExprKind::Become(_)
                    | ExprKind::InlineAsm(_)
                    | ExprKind::Struct(_, _, _)
                    | ExprKind::Repeat(_, _)
                    | ExprKind::Yield(_, _) => true,

                    // These expressions have no (direct) sub-exprs.
                    ExprKind::ConstBlock(_)
                    | ExprKind::Loop(_, _, _, _)
                    | ExprKind::Lit(_)
                    | ExprKind::Path(_)
                    | ExprKind::Continue(_)
                    | ExprKind::OffsetOf(_, _)
                    | ExprKind::Err(_) => unreachable!("no sub-expr expected for {:?}", expr.kind),
                }
            }

            // If we have a subpattern that performs a read, we want to consider this
            // to diverge for compatibility to support something like `let x: () = *never_ptr;`.
            Node::LetStmt(LetStmt { init: Some(target), pat, .. }) => {
                assert_eq!(target.hir_id, expr.hir_id);
                pat.is_guaranteed_to_constitute_read_for_never()
            }

            // These nodes (if they have a sub-expr) do constitute a read.
            Node::Block(_)
            | Node::Arm(_)
            | Node::ExprField(_)
            | Node::AnonConst(_)
            | Node::ConstBlock(_)
            | Node::ConstArg(_)
            | Node::Stmt(_)
            | Node::Item(Item { kind: ItemKind::Const(..) | ItemKind::Static(..), .. })
            | Node::TraitItem(TraitItem { kind: TraitItemKind::Const(..), .. })
            | Node::ImplItem(ImplItem { kind: ImplItemKind::Const(..), .. }) => true,

            Node::TyPat(_) | Node::Pat(_) => {
                self.dcx().span_delayed_bug(expr.span, "place expr not allowed in pattern");
                true
            }

            // These nodes do not have direct sub-exprs.
            Node::Param(_)
            | Node::Item(_)
            | Node::ForeignItem(_)
            | Node::TraitItem(_)
            | Node::ImplItem(_)
            | Node::Variant(_)
            | Node::Field(_)
            | Node::PathSegment(_)
            | Node::Ty(_)
            | Node::AssocItemConstraint(_)
            | Node::TraitRef(_)
            | Node::PatField(_)
            | Node::PatExpr(_)
            | Node::LetStmt(_)
            | Node::Synthetic
            | Node::Err(_)
            | Node::Ctor(_)
            | Node::Lifetime(_)
            | Node::GenericParam(_)
            | Node::Crate(_)
            | Node::Infer(_)
            | Node::WherePredicate(_)
            | Node::PreciseCapturingNonLifetimeArg(_)
            | Node::ConstArgExprField(_)
            | Node::OpaqueTy(_) => {
                unreachable!("no sub-expr expected for {parent_node:?}")
            }
        }
    }

    #[inline]
    fn hir_owner_parent_impl(self, owner_id: OwnerId) -> HirId {
        self.opt_local_parent(owner_id.def_id).map_or(CRATE_HIR_ID, |parent_def_id| {
            let parent_owner_id = self.local_def_id_to_hir_id(parent_def_id).owner;
            HirId {
                owner: parent_owner_id,
                local_id: self
                    .hir_crate(())
                    .owner(self, parent_owner_id.def_id)
                    .unwrap()
                    .parenting
                    .get(&owner_id.def_id)
                    .copied()
                    .unwrap_or(ItemLocalId::ZERO),
            }
        })
    }

    /// Optimization of `hir_owner_parent` query as an inlined function
    /// in case of non-incremental build. The query itself renamed to `hir_owner_parent_q`.
    #[inline]
    pub fn hir_owner_parent(self, owner_id: OwnerId) -> HirId {
        if self.dep_graph.is_fully_enabled() {
            self.hir_owner_parent_q(owner_id)
        } else {
            self.hir_owner_parent_impl(owner_id)
        }
    }
}

/// Hashes computed by [`TyCtxt::hash_owner_nodes`] if necessary.
#[derive(Clone, Copy, Debug)]
pub struct Hashes {
    pub opt_hash_including_bodies: Option<Fingerprint>,
    pub attrs_hash: Option<Fingerprint>,
    pub delayed_lints_hash: Option<Fingerprint>,
}

pub fn provide(providers: &mut Providers) {
    providers.hir_crate_items = map::hir_crate_items;
    providers.crate_hash = map::crate_hash;
    providers.hir_module_items = map::hir_module_items;
    providers.local_def_id_to_hir_id = |tcx, def_id| match tcx.hir_crate(()).owner(tcx, def_id) {
        MaybeOwner::Owner(_) => HirId::make_owner(def_id),
        MaybeOwner::NonOwner(hir_id) => hir_id,
        MaybeOwner::Phantom => bug!("no HirId for {:?}", def_id),
        MaybeOwner::Delayed(_) => bug!("delayed owner should be lowered {:?}", def_id),
    };
    providers.opt_hir_owner_nodes =
        |tcx, id| tcx.hir_crate(()).owner(tcx, id).as_owner().map(|i| &i.nodes);
    providers.hir_owner_parent_q = |tcx, owner_id| tcx.hir_owner_parent_impl(owner_id);
    providers.hir_attr_map = |tcx, id| {
        tcx.hir_crate(()).owner(tcx, id.def_id).as_owner().map_or(AttributeMap::EMPTY, |o| &o.attrs)
    };
    providers.opt_ast_lowering_delayed_lints =
        |tcx, id| tcx.hir_crate(()).owner(tcx, id.def_id).as_owner().map(|o| &o.delayed_lints);
    providers.def_span = |tcx, def_id| tcx.hir_span(tcx.local_def_id_to_hir_id(def_id));
    providers.def_ident_span = |tcx, def_id| {
        let hir_id = tcx.local_def_id_to_hir_id(def_id);
        tcx.hir_opt_ident_span(hir_id)
    };
    providers.ty_span = |tcx, def_id| {
        let node = tcx.hir_node_by_def_id(def_id);
        match node.ty() {
            Some(ty) => ty.span,
            None => bug!("{def_id:?} doesn't have a type: {node:#?}"),
        }
    };
    providers.fn_arg_idents = |tcx, def_id| {
        let node = tcx.hir_node_by_def_id(def_id);
        if let Some(body_id) = node.body_id() {
            tcx.arena.alloc_from_iter(tcx.hir_body_param_idents(body_id))
        } else if let Node::TraitItem(&TraitItem {
            kind: TraitItemKind::Fn(_, TraitFn::Required(idents)),
            ..
        })
        | Node::ForeignItem(&ForeignItem {
            kind: ForeignItemKind::Fn(_, idents, _),
            ..
        }) = node
        {
            idents
        } else {
            span_bug!(
                tcx.hir_span(tcx.local_def_id_to_hir_id(def_id)),
                "fn_arg_idents: unexpected item {:?}",
                def_id
            );
        }
    };
    providers.all_local_trait_impls = |tcx, ()| &tcx.resolutions(()).trait_impls;
    providers.local_trait_impls =
        |tcx, trait_id| tcx.resolutions(()).trait_impls.get(&trait_id).map_or(&[], |xs| &xs[..]);
    providers.expn_that_defined =
        |tcx, id| tcx.resolutions(()).expn_that_defined.get(&id).copied().unwrap_or(ExpnId::root());
    providers.in_scope_traits_map = |tcx, id| {
        tcx.hir_crate(()).owner(tcx, id.def_id).as_owner().map(|owner_info| &owner_info.trait_map)
    };
}