//! This module used to contain a type called `Map`. That type has since been
//! eliminated, and all its methods are now on `TyCtxt`. But the module name
//! stays as `map` because there isn't an obviously better name for it.

use rustc_abi::ExternAbi;
use rustc_ast::visit::{VisitorResult, walk_list};
use rustc_data_structures::fingerprint::Fingerprint;
use rustc_data_structures::fx::FxIndexSet;
use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
use rustc_data_structures::svh::Svh;
use rustc_data_structures::sync::{DynSend, DynSync, par_for_each_in, try_par_for_each_in};
use rustc_hir::def::{DefKind, Res};
use rustc_hir::def_id::{DefId, LOCAL_CRATE, LocalDefId, LocalModDefId};
use rustc_hir::definitions::{DefKey, DefPath, DefPathHash};
use rustc_hir::intravisit::Visitor;
use rustc_hir::*;
use rustc_hir_pretty as pprust_hir;
use rustc_span::def_id::StableCrateId;
use rustc_span::{ErrorGuaranteed, Ident, Span, Symbol, kw, with_metavar_spans};

use crate::hir::{ModuleItems, nested_filter};
use crate::middle::debugger_visualizer::DebuggerVisualizerFile;
use crate::query::LocalCrate;
use crate::ty::TyCtxt;

/// An iterator that walks up the ancestor tree of a given `HirId`.
/// Constructed using `tcx.hir_parent_iter(hir_id)`.
struct ParentHirIterator<'tcx> {
    current_id: HirId,
    tcx: TyCtxt<'tcx>,
    // Cache the current value of `hir_owner_nodes` to avoid repeatedly calling the same query for
    // the same owner, which will uselessly record many times the same query dependency.
    current_owner_nodes: Option<&'tcx OwnerNodes<'tcx>>,
}

impl<'tcx> ParentHirIterator<'tcx> {
    fn new(tcx: TyCtxt<'tcx>, current_id: HirId) -> ParentHirIterator<'tcx> {
        ParentHirIterator { current_id, tcx, current_owner_nodes: None }
    }
}

impl<'tcx> Iterator for ParentHirIterator<'tcx> {
    type Item = HirId;

    fn next(&mut self) -> Option<Self::Item> {
        if self.current_id == CRATE_HIR_ID {
            return None;
        }

        let HirId { owner, local_id } = self.current_id;

        let parent_id = if local_id == ItemLocalId::ZERO {
            // We go from an owner to its parent, so clear the cache.
            self.current_owner_nodes = None;
            self.tcx.hir_owner_parent(owner)
        } else {
            let owner_nodes =
                self.current_owner_nodes.get_or_insert_with(|| self.tcx.hir_owner_nodes(owner));
            let parent_local_id = owner_nodes.nodes[local_id].parent;
            // HIR indexing should have checked that.
            debug_assert_ne!(parent_local_id, local_id);
            HirId { owner, local_id: parent_local_id }
        };

        debug_assert_ne!(parent_id, self.current_id);

        self.current_id = parent_id;
        Some(parent_id)
    }
}

/// An iterator that walks up the ancestor tree of a given `HirId`.
/// Constructed using `tcx.hir_parent_owner_iter(hir_id)`.
pub struct ParentOwnerIterator<'tcx> {
    current_id: HirId,
    tcx: TyCtxt<'tcx>,
}

impl<'tcx> Iterator for ParentOwnerIterator<'tcx> {
    type Item = (OwnerId, OwnerNode<'tcx>);

    fn next(&mut self) -> Option<Self::Item> {
        if self.current_id.local_id.index() != 0 {
            self.current_id.local_id = ItemLocalId::ZERO;
            let node = self.tcx.hir_owner_node(self.current_id.owner);
            return Some((self.current_id.owner, node));
        }
        if self.current_id == CRATE_HIR_ID {
            return None;
        }

        let parent_id = self.tcx.hir_def_key(self.current_id.owner.def_id).parent;
        let parent_id = parent_id.map_or(CRATE_OWNER_ID, |local_def_index| {
            let def_id = LocalDefId { local_def_index };
            self.tcx.local_def_id_to_hir_id(def_id).owner
        });
        self.current_id = HirId::make_owner(parent_id.def_id);

        let node = self.tcx.hir_owner_node(self.current_id.owner);
        Some((self.current_id.owner, node))
    }
}

impl<'tcx> TyCtxt<'tcx> {
    #[inline]
    fn expect_hir_owner_nodes(self, def_id: LocalDefId) -> &'tcx OwnerNodes<'tcx> {
        self.opt_hir_owner_nodes(def_id)
            .unwrap_or_else(|| span_bug!(self.def_span(def_id), "{def_id:?} is not an owner"))
    }

    #[inline]
    pub fn hir_owner_nodes(self, owner_id: OwnerId) -> &'tcx OwnerNodes<'tcx> {
        self.expect_hir_owner_nodes(owner_id.def_id)
    }

    #[inline]
    fn opt_hir_owner_node(self, def_id: LocalDefId) -> Option<OwnerNode<'tcx>> {
        self.opt_hir_owner_nodes(def_id).map(|nodes| nodes.node())
    }

    #[inline]
    pub fn expect_hir_owner_node(self, def_id: LocalDefId) -> OwnerNode<'tcx> {
        self.expect_hir_owner_nodes(def_id).node()
    }

    #[inline]
    pub fn hir_owner_node(self, owner_id: OwnerId) -> OwnerNode<'tcx> {
        self.hir_owner_nodes(owner_id).node()
    }

    /// Retrieves the `hir::Node` corresponding to `id`.
    pub fn hir_node(self, id: HirId) -> Node<'tcx> {
        self.hir_owner_nodes(id.owner).nodes[id.local_id].node
    }

    /// Retrieves the `hir::Node` corresponding to `id`.
    #[inline]
    pub fn hir_node_by_def_id(self, id: LocalDefId) -> Node<'tcx> {
        self.hir_node(self.local_def_id_to_hir_id(id))
    }

    /// Returns `HirId` of the parent HIR node of node with this `hir_id`.
    /// Returns the same `hir_id` if and only if `hir_id == CRATE_HIR_ID`.
    ///
    /// If calling repeatedly and iterating over parents, prefer [`TyCtxt::hir_parent_iter`].
    pub fn parent_hir_id(self, hir_id: HirId) -> HirId {
        let HirId { owner, local_id } = hir_id;
        if local_id == ItemLocalId::ZERO {
            self.hir_owner_parent(owner)
        } else {
            let parent_local_id = self.hir_owner_nodes(owner).nodes[local_id].parent;
            // HIR indexing should have checked that.
            debug_assert_ne!(parent_local_id, local_id);
            HirId { owner, local_id: parent_local_id }
        }
    }

    /// Returns parent HIR node of node with this `hir_id`.
    /// Returns HIR node of the same `hir_id` if and only if `hir_id == CRATE_HIR_ID`.
    pub fn parent_hir_node(self, hir_id: HirId) -> Node<'tcx> {
        self.hir_node(self.parent_hir_id(hir_id))
    }

    #[inline]
    pub fn hir_root_module(self) -> &'tcx Mod<'tcx> {
        match self.hir_owner_node(CRATE_OWNER_ID) {
            OwnerNode::Crate(item) => item,
            _ => bug!(),
        }
    }

    #[inline]
    pub fn hir_free_items(self) -> impl Iterator<Item = ItemId> {
        self.hir_crate_items(()).free_items.iter().copied()
    }

    #[inline]
    pub fn hir_module_free_items(self, module: LocalModDefId) -> impl Iterator<Item = ItemId> {
        self.hir_module_items(module).free_items()
    }

    pub fn hir_def_key(self, def_id: LocalDefId) -> DefKey {
        // Accessing the DefKey is ok, since it is part of DefPathHash.
        self.definitions_untracked().def_key(def_id)
    }

    pub fn hir_def_path(self, def_id: LocalDefId) -> DefPath {
        // Accessing the DefPath is ok, since it is part of DefPathHash.
        self.definitions_untracked().def_path(def_id)
    }

    #[inline]
    pub fn hir_def_path_hash(self, def_id: LocalDefId) -> DefPathHash {
        // Accessing the DefPathHash is ok, it is incr. comp. stable.
        self.definitions_untracked().def_path_hash(def_id)
    }

    pub fn hir_get_if_local(self, id: DefId) -> Option<Node<'tcx>> {
        id.as_local().map(|id| self.hir_node_by_def_id(id))
    }

    pub fn hir_get_generics(self, id: LocalDefId) -> Option<&'tcx Generics<'tcx>> {
        self.opt_hir_owner_node(id)?.generics()
    }

    pub fn hir_item(self, id: ItemId) -> &'tcx Item<'tcx> {
        self.hir_owner_node(id.owner_id).expect_item()
    }

    pub fn hir_trait_item(self, id: TraitItemId) -> &'tcx TraitItem<'tcx> {
        self.hir_owner_node(id.owner_id).expect_trait_item()
    }

    pub fn hir_impl_item(self, id: ImplItemId) -> &'tcx ImplItem<'tcx> {
        self.hir_owner_node(id.owner_id).expect_impl_item()
    }

    pub fn hir_foreign_item(self, id: ForeignItemId) -> &'tcx ForeignItem<'tcx> {
        self.hir_owner_node(id.owner_id).expect_foreign_item()
    }

    pub fn hir_body(self, id: BodyId) -> &'tcx Body<'tcx> {
        self.hir_owner_nodes(id.hir_id.owner).bodies[&id.hir_id.local_id]
    }

    #[track_caller]
    pub fn hir_fn_decl_by_hir_id(self, hir_id: HirId) -> Option<&'tcx FnDecl<'tcx>> {
        self.hir_node(hir_id).fn_decl()
    }

    #[track_caller]
    pub fn hir_fn_sig_by_hir_id(self, hir_id: HirId) -> Option<&'tcx FnSig<'tcx>> {
        self.hir_node(hir_id).fn_sig()
    }

    #[track_caller]
    pub fn hir_enclosing_body_owner(self, hir_id: HirId) -> LocalDefId {
        for (_, node) in self.hir_parent_iter(hir_id) {
            if let Some((def_id, _)) = node.associated_body() {
                return def_id;
            }
        }

        bug!("no `hir_enclosing_body_owner` for hir_id `{}`", hir_id);
    }

    /// Returns the `HirId` that corresponds to the definition of
    /// which this is the body of, i.e., a `fn`, `const` or `static`
    /// item (possibly associated), a closure, or a `hir::AnonConst`.
    pub fn hir_body_owner(self, BodyId { hir_id }: BodyId) -> HirId {
        let parent = self.parent_hir_id(hir_id);
        assert_eq!(self.hir_node(parent).body_id().unwrap().hir_id, hir_id, "{hir_id:?}");
        parent
    }

    pub fn hir_body_owner_def_id(self, BodyId { hir_id }: BodyId) -> LocalDefId {
        self.parent_hir_node(hir_id).associated_body().unwrap().0
    }

    /// Given a `LocalDefId`, returns the `BodyId` associated with it,
    /// if the node is a body owner, otherwise returns `None`.
    pub fn hir_maybe_body_owned_by(self, id: LocalDefId) -> Option<&'tcx Body<'tcx>> {
        Some(self.hir_body(self.hir_node_by_def_id(id).body_id()?))
    }

    /// Given a body owner's id, returns the `BodyId` associated with it.
    #[track_caller]
    pub fn hir_body_owned_by(self, id: LocalDefId) -> &'tcx Body<'tcx> {
        self.hir_maybe_body_owned_by(id).unwrap_or_else(|| {
            let hir_id = self.local_def_id_to_hir_id(id);
            span_bug!(
                self.hir_span(hir_id),
                "body_owned_by: {} has no associated body",
                self.hir_id_to_string(hir_id)
            );
        })
    }

    pub fn hir_body_param_idents(self, id: BodyId) -> impl Iterator<Item = Option<Ident>> {
        self.hir_body(id).params.iter().map(|param| match param.pat.kind {
            PatKind::Binding(_, _, ident, _) => Some(ident),
            PatKind::Wild => Some(Ident::new(kw::Underscore, param.pat.span)),
            _ => None,
        })
    }

    /// Returns the `BodyOwnerKind` of this `LocalDefId`.
    ///
    /// Panics if `LocalDefId` does not have an associated body.
    pub fn hir_body_owner_kind(self, def_id: impl Into<DefId>) -> BodyOwnerKind {
        let def_id = def_id.into();
        match self.def_kind(def_id) {
            DefKind::Const { .. } | DefKind::AssocConst { .. } | DefKind::AnonConst => {
                BodyOwnerKind::Const { inline: false }
            }
            DefKind::InlineConst => BodyOwnerKind::Const { inline: true },
            DefKind::Ctor(..) | DefKind::Fn | DefKind::AssocFn => BodyOwnerKind::Fn,
            DefKind::Closure | DefKind::SyntheticCoroutineBody => BodyOwnerKind::Closure,
            DefKind::Static { safety: _, mutability, nested: false } => {
                BodyOwnerKind::Static(mutability)
            }
            DefKind::GlobalAsm => BodyOwnerKind::GlobalAsm,
            dk => bug!("{:?} is not a body node: {:?}", def_id, dk),
        }
    }

    /// Returns the `ConstContext` of the body associated with this `LocalDefId`.
    ///
    /// Panics if `LocalDefId` does not have an associated body.
    ///
    /// This should only be used for determining the context of a body, a return
    /// value of `Some` does not always suggest that the owner of the body is `const`,
    /// just that it has to be checked as if it were.
    pub fn hir_body_const_context(self, local_def_id: LocalDefId) -> Option<ConstContext> {
        let def_id = local_def_id.into();
        let ccx = match self.hir_body_owner_kind(def_id) {
            BodyOwnerKind::Const { inline } => ConstContext::Const { inline },
            BodyOwnerKind::Static(mutability) => ConstContext::Static(mutability),

            BodyOwnerKind::Fn if self.is_constructor(def_id) => return None,
            // Const closures use their parent's const context
            BodyOwnerKind::Closure if self.is_const_fn(def_id) => {
                return self.hir_body_const_context(self.local_parent(local_def_id));
            }
            BodyOwnerKind::Fn if self.is_const_fn(def_id) => ConstContext::ConstFn,
            BodyOwnerKind::Fn | BodyOwnerKind::Closure | BodyOwnerKind::GlobalAsm => return None,
        };

        Some(ccx)
    }

    /// Returns an iterator of the `DefId`s for all body-owners in this
    /// crate.
    #[inline]
    pub fn hir_body_owners(self) -> impl Iterator<Item = LocalDefId> {
        self.hir_crate_items(()).body_owners.iter().copied()
    }

    #[inline]
    pub fn par_hir_body_owners(self, f: impl Fn(LocalDefId) + DynSend + DynSync) {
        par_for_each_in(&self.hir_crate_items(()).body_owners[..], |&&def_id| f(def_id));
    }

    pub fn hir_ty_param_owner(self, def_id: LocalDefId) -> LocalDefId {
        let def_kind = self.def_kind(def_id);
        match def_kind {
            DefKind::Trait | DefKind::TraitAlias => def_id,
            DefKind::LifetimeParam | DefKind::TyParam | DefKind::ConstParam => {
                self.local_parent(def_id)
            }
            _ => bug!("ty_param_owner: {:?} is a {:?} not a type parameter", def_id, def_kind),
        }
    }

    pub fn hir_ty_param_name(self, def_id: LocalDefId) -> Symbol {
        let def_kind = self.def_kind(def_id);
        match def_kind {
            DefKind::Trait | DefKind::TraitAlias => kw::SelfUpper,
            DefKind::LifetimeParam | DefKind::TyParam | DefKind::ConstParam => {
                self.item_name(def_id.to_def_id())
            }
            _ => bug!("ty_param_name: {:?} is a {:?} not a type parameter", def_id, def_kind),
        }
    }

    /// Gets the attributes on the crate. This is preferable to
    /// invoking `krate.attrs` because it registers a tighter
    /// dep-graph access.
    pub fn hir_krate_attrs(self) -> &'tcx [Attribute] {
        self.hir_attrs(CRATE_HIR_ID)
    }

    pub fn hir_rustc_coherence_is_core(self) -> bool {
        find_attr!(self.hir_krate_attrs(), RustcCoherenceIsCore(..))
    }

    pub fn hir_get_module(self, module: LocalModDefId) -> (&'tcx Mod<'tcx>, Span, HirId) {
        let hir_id = HirId::make_owner(module.to_local_def_id());
        match self.hir_owner_node(hir_id.owner) {
            OwnerNode::Item(&Item { span, kind: ItemKind::Mod(_, m), .. }) => (m, span, hir_id),
            OwnerNode::Crate(item) => (item, item.spans.inner_span, hir_id),
            node => panic!("not a module: {node:?}"),
        }
    }

    /// Walks the contents of the local crate. See also `visit_all_item_likes_in_crate`.
    pub fn hir_walk_toplevel_module<V>(self, visitor: &mut V) -> V::Result
    where
        V: Visitor<'tcx>,
    {
        let (top_mod, span, hir_id) = self.hir_get_module(LocalModDefId::CRATE_DEF_ID);
        visitor.visit_mod(top_mod, span, hir_id)
    }

    /// Walks the attributes in a crate.
    pub fn hir_walk_attributes<V>(self, visitor: &mut V) -> V::Result
    where
        V: Visitor<'tcx>,
    {
        let krate = self.hir_crate_items(());
        for owner in krate.owners() {
            let attrs = self.hir_attr_map(owner);
            for attrs in attrs.map.values() {
                walk_list!(visitor, visit_attribute, *attrs);
            }
        }
        V::Result::output()
    }

    /// Visits all item-likes in the crate in some deterministic (but unspecified) order. If you
    /// need to process every item-like, and don't care about visiting nested items in a particular
    /// order then this method is the best choice. If you do care about this nesting, you should
    /// use the `tcx.hir_walk_toplevel_module`.
    ///
    /// Note that this function will access HIR for all the item-likes in the crate. If you only
    /// need to access some of them, it is usually better to manually loop on the iterators
    /// provided by `tcx.hir_crate_items(())`.
    ///
    /// Please see the notes in `intravisit.rs` for more information.
    pub fn hir_visit_all_item_likes_in_crate<V>(self, visitor: &mut V) -> V::Result
    where
        V: Visitor<'tcx>,
    {
        let krate = self.hir_crate_items(());
        walk_list!(visitor, visit_item, krate.free_items().map(|id| self.hir_item(id)));
        walk_list!(
            visitor,
            visit_trait_item,
            krate.trait_items().map(|id| self.hir_trait_item(id))
        );
        walk_list!(visitor, visit_impl_item, krate.impl_items().map(|id| self.hir_impl_item(id)));
        walk_list!(
            visitor,
            visit_foreign_item,
            krate.foreign_items().map(|id| self.hir_foreign_item(id))
        );
        V::Result::output()
    }

    /// This method is the equivalent of `visit_all_item_likes_in_crate` but restricted to
    /// item-likes in a single module.
    pub fn hir_visit_item_likes_in_module<V>(
        self,
        module: LocalModDefId,
        visitor: &mut V,
    ) -> V::Result
    where
        V: Visitor<'tcx>,
    {
        let module = self.hir_module_items(module);
        walk_list!(visitor, visit_item, module.free_items().map(|id| self.hir_item(id)));
        walk_list!(
            visitor,
            visit_trait_item,
            module.trait_items().map(|id| self.hir_trait_item(id))
        );
        walk_list!(visitor, visit_impl_item, module.impl_items().map(|id| self.hir_impl_item(id)));
        walk_list!(
            visitor,
            visit_foreign_item,
            module.foreign_items().map(|id| self.hir_foreign_item(id))
        );
        V::Result::output()
    }

    pub fn hir_for_each_module(self, mut f: impl FnMut(LocalModDefId)) {
        let crate_items = self.hir_crate_items(());
        for module in crate_items.submodules.iter() {
            f(LocalModDefId::new_unchecked(module.def_id))
        }
    }

    #[inline]
    pub fn par_hir_for_each_module(self, f: impl Fn(LocalModDefId) + DynSend + DynSync) {
        let crate_items = self.hir_crate_items(());
        par_for_each_in(&crate_items.submodules[..], |module| {
            f(LocalModDefId::new_unchecked(module.def_id))
        })
    }

    #[inline]
    pub fn try_par_hir_for_each_module(
        self,
        f: impl Fn(LocalModDefId) -> Result<(), ErrorGuaranteed> + DynSend + DynSync,
    ) -> Result<(), ErrorGuaranteed> {
        let crate_items = self.hir_crate_items(());
        try_par_for_each_in(&crate_items.submodules[..], |module| {
            f(LocalModDefId::new_unchecked(module.def_id))
        })
    }

    /// Returns an iterator for the nodes in the ancestor tree of the `current_id`
    /// until the crate root is reached. Prefer this over your own loop using `parent_id`.
    #[inline]
    pub fn hir_parent_id_iter(self, current_id: HirId) -> impl Iterator<Item = HirId> {
        ParentHirIterator::new(self, current_id)
    }

    /// Returns an iterator for the nodes in the ancestor tree of the `current_id`
    /// until the crate root is reached. Prefer this over your own loop using `parent_id`.
    #[inline]
    pub fn hir_parent_iter(self, current_id: HirId) -> impl Iterator<Item = (HirId, Node<'tcx>)> {
        self.hir_parent_id_iter(current_id).map(move |id| (id, self.hir_node(id)))
    }

    /// Returns an iterator for the nodes in the ancestor tree of the `current_id`
    /// until the crate root is reached. Prefer this over your own loop using `parent_id`.
    #[inline]
    pub fn hir_parent_owner_iter(self, current_id: HirId) -> ParentOwnerIterator<'tcx> {
        ParentOwnerIterator { current_id, tcx: self }
    }

    /// Checks if the node is left-hand side of an assignment.
    pub fn hir_is_lhs(self, id: HirId) -> bool {
        match self.parent_hir_node(id) {
            Node::Expr(expr) => match expr.kind {
                ExprKind::Assign(lhs, _rhs, _span) => lhs.hir_id == id,
                _ => false,
            },
            _ => false,
        }
    }

    /// Whether the expression pointed at by `hir_id` belongs to a `const` evaluation context.
    /// Used exclusively for diagnostics, to avoid suggestion function calls.
    pub fn hir_is_inside_const_context(self, hir_id: HirId) -> bool {
        self.hir_body_const_context(self.hir_enclosing_body_owner(hir_id)).is_some()
    }

    /// Retrieves the `HirId` for `id`'s enclosing function *if* the `id` block or return is
    /// in the "tail" position of the function, in other words if it's likely to correspond
    /// to the return type of the function.
    ///
    /// ```
    /// fn foo(x: usize) -> bool {
    ///     if x == 1 {
    ///         // If `get_fn_id_for_return_block` gets passed the `id` corresponding to this, it
    ///         // will return `foo`'s `HirId`.
    ///         true
    ///     } else {
    ///         false
    ///     }
    /// }
    /// ```
    ///
    /// ```compile_fail,E0308
    /// fn foo(x: usize) -> bool {
    ///     loop {
    ///         // If `get_fn_id_for_return_block` gets passed the `id` corresponding to this, it
    ///         // will return `None`.
    ///         true
    ///     }
    ///     false
    /// }
    /// ```
    pub fn hir_get_fn_id_for_return_block(self, id: HirId) -> Option<HirId> {
        let enclosing_body_owner = self.local_def_id_to_hir_id(self.hir_enclosing_body_owner(id));

        // Return `None` if the `id` expression is not the returned value of the enclosing body
        let mut iter = [id].into_iter().chain(self.hir_parent_id_iter(id)).peekable();
        while let Some(cur_id) = iter.next() {
            if enclosing_body_owner == cur_id {
                break;
            }

            // A return statement is always the value returned from the enclosing body regardless of
            // what the parent expressions are.
            if let Node::Expr(Expr { kind: ExprKind::Ret(_), .. }) = self.hir_node(cur_id) {
                break;
            }

            // If the current expression's value doesnt get used as the parent expressions value
            // then return `None`
            if let Some(&parent_id) = iter.peek() {
                match self.hir_node(parent_id) {
                    // The current node is not the tail expression of the block expression parent
                    // expr.
                    Node::Block(Block { expr: Some(e), .. }) if cur_id != e.hir_id => return None,
                    Node::Block(Block { expr: Some(e), .. })
                        if matches!(e.kind, ExprKind::If(_, _, None)) =>
                    {
                        return None;
                    }

                    // The current expression's value does not pass up through these parent
                    // expressions.
                    Node::Block(Block { expr: None, .. })
                    | Node::Expr(Expr { kind: ExprKind::Loop(..), .. })
                    | Node::LetStmt(..) => return None,

                    _ => {}
                }
            }
        }

        Some(enclosing_body_owner)
    }

    /// Retrieves the `OwnerId` for `id`'s parent item, or `id` itself if no
    /// parent item is in this map. The "parent item" is the closest parent node
    /// in the HIR which is recorded by the map and is an item, either an item
    /// in a module, trait, or impl.
    pub fn hir_get_parent_item(self, hir_id: HirId) -> OwnerId {
        if hir_id.local_id != ItemLocalId::ZERO {
            // If this is a child of a HIR owner, return the owner.
            hir_id.owner
        } else if let Some((def_id, _node)) = self.hir_parent_owner_iter(hir_id).next() {
            def_id
        } else {
            CRATE_OWNER_ID
        }
    }

    /// When on an if expression, a match arm tail expression or a match arm, give back
    /// the enclosing `if` or `match` expression.
    ///
    /// Used by error reporting when there's a type error in an if or match arm caused by the
    /// expression needing to be unit.
    pub fn hir_get_if_cause(self, hir_id: HirId) -> Option<&'tcx Expr<'tcx>> {
        for (_, node) in self.hir_parent_iter(hir_id) {
            match node {
                Node::Item(_)
                | Node::ForeignItem(_)
                | Node::TraitItem(_)
                | Node::ImplItem(_)
                | Node::Stmt(Stmt { kind: StmtKind::Let(_), .. }) => break,
                Node::Expr(expr @ Expr { kind: ExprKind::If(..) | ExprKind::Match(..), .. }) => {
                    return Some(expr);
                }
                _ => {}
            }
        }
        None
    }

    /// Returns the nearest enclosing scope. A scope is roughly an item or block.
    pub fn hir_get_enclosing_scope(self, hir_id: HirId) -> Option<HirId> {
        for (hir_id, node) in self.hir_parent_iter(hir_id) {
            if let Node::Item(Item {
                kind:
                    ItemKind::Fn { .. }
                    | ItemKind::Const(..)
                    | ItemKind::Static(..)
                    | ItemKind::Mod(..)
                    | ItemKind::Enum(..)
                    | ItemKind::Struct(..)
                    | ItemKind::Union(..)
                    | ItemKind::Trait(..)
                    | ItemKind::Impl { .. },
                ..
            })
            | Node::ForeignItem(ForeignItem { kind: ForeignItemKind::Fn(..), .. })
            | Node::TraitItem(TraitItem { kind: TraitItemKind::Fn(..), .. })
            | Node::ImplItem(ImplItem { kind: ImplItemKind::Fn(..), .. })
            | Node::Block(_) = node
            {
                return Some(hir_id);
            }
        }
        None
    }

    /// Returns the defining scope for an opaque type definition.
    pub fn hir_get_defining_scope(self, id: HirId) -> HirId {
        let mut scope = id;
        loop {
            scope = self.hir_get_enclosing_scope(scope).unwrap_or(CRATE_HIR_ID);
            if scope == CRATE_HIR_ID || !matches!(self.hir_node(scope), Node::Block(_)) {
                return scope;
            }
        }
    }

    /// Get a representation of this `id` for debugging purposes.
    /// NOTE: Do NOT use this in diagnostics!
    pub fn hir_id_to_string(self, id: HirId) -> String {
        let path_str = |def_id: LocalDefId| self.def_path_str(def_id);

        let span_str =
            || self.sess.source_map().span_to_snippet(self.hir_span(id)).unwrap_or_default();
        let node_str = |prefix| format!("{id} ({prefix} `{}`)", span_str());

        match self.hir_node(id) {
            Node::Item(item) => {
                let item_str = match item.kind {
                    ItemKind::ExternCrate(..) => "extern crate",
                    ItemKind::Use(..) => "use",
                    ItemKind::Static(..) => "static",
                    ItemKind::Const(..) => "const",
                    ItemKind::Fn { .. } => "fn",
                    ItemKind::Macro(..) => "macro",
                    ItemKind::Mod(..) => "mod",
                    ItemKind::ForeignMod { .. } => "foreign mod",
                    ItemKind::GlobalAsm { .. } => "global asm",
                    ItemKind::TyAlias(..) => "ty",
                    ItemKind::Enum(..) => "enum",
                    ItemKind::Struct(..) => "struct",
                    ItemKind::Union(..) => "union",
                    ItemKind::Trait(..) => "trait",
                    ItemKind::TraitAlias(..) => "trait alias",
                    ItemKind::Impl { .. } => "impl",
                };
                format!("{id} ({item_str} {})", path_str(item.owner_id.def_id))
            }
            Node::ForeignItem(item) => {
                format!("{id} (foreign item {})", path_str(item.owner_id.def_id))
            }
            Node::ImplItem(ii) => {
                let kind = match ii.kind {
                    ImplItemKind::Const(..) => "associated constant",
                    ImplItemKind::Fn(fn_sig, _) => match fn_sig.decl.implicit_self {
                        ImplicitSelfKind::None => "associated function",
                        _ => "method",
                    },
                    ImplItemKind::Type(_) => "associated type",
                };
                format!("{id} ({kind} `{}` in {})", ii.ident, path_str(ii.owner_id.def_id))
            }
            Node::TraitItem(ti) => {
                let kind = match ti.kind {
                    TraitItemKind::Const(..) => "associated constant",
                    TraitItemKind::Fn(fn_sig, _) => match fn_sig.decl.implicit_self {
                        ImplicitSelfKind::None => "associated function",
                        _ => "trait method",
                    },
                    TraitItemKind::Type(..) => "associated type",
                };

                format!("{id} ({kind} `{}` in {})", ti.ident, path_str(ti.owner_id.def_id))
            }
            Node::Variant(variant) => {
                format!("{id} (variant `{}` in {})", variant.ident, path_str(variant.def_id))
            }
            Node::Field(field) => {
                format!("{id} (field `{}` in {})", field.ident, path_str(field.def_id))
            }
            Node::AnonConst(_) => node_str("const"),
            Node::ConstBlock(_) => node_str("const"),
            Node::ConstArg(_) => node_str("const"),
            Node::Expr(_) => node_str("expr"),
            Node::ExprField(_) => node_str("expr field"),
            Node::ConstArgExprField(_) => node_str("const arg expr field"),
            Node::Stmt(_) => node_str("stmt"),
            Node::PathSegment(_) => node_str("path segment"),
            Node::Ty(_) => node_str("type"),
            Node::AssocItemConstraint(_) => node_str("assoc item constraint"),
            Node::TraitRef(_) => node_str("trait ref"),
            Node::OpaqueTy(_) => node_str("opaque type"),
            Node::Pat(_) => node_str("pat"),
            Node::TyPat(_) => node_str("pat ty"),
            Node::PatField(_) => node_str("pattern field"),
            Node::PatExpr(_) => node_str("pattern literal"),
            Node::Param(_) => node_str("param"),
            Node::Arm(_) => node_str("arm"),
            Node::Block(_) => node_str("block"),
            Node::Infer(_) => node_str("infer"),
            Node::LetStmt(_) => node_str("local"),
            Node::Ctor(ctor) => format!(
                "{id} (ctor {})",
                ctor.ctor_def_id().map_or("<missing path>".into(), |def_id| path_str(def_id)),
            ),
            Node::Lifetime(_) => node_str("lifetime"),
            Node::GenericParam(param) => {
                format!("{id} (generic_param {})", path_str(param.def_id))
            }
            Node::Crate(..) => String::from("(root_crate)"),
            Node::WherePredicate(_) => node_str("where predicate"),
            Node::Synthetic => unreachable!(),
            Node::Err(_) => node_str("error"),
            Node::PreciseCapturingNonLifetimeArg(_param) => node_str("parameter"),
        }
    }

    pub fn hir_get_foreign_abi(self, hir_id: HirId) -> ExternAbi {
        let parent = self.hir_get_parent_item(hir_id);
        if let OwnerNode::Item(Item { kind: ItemKind::ForeignMod { abi, .. }, .. }) =
            self.hir_owner_node(parent)
        {
            return *abi;
        }
        bug!(
            "expected foreign mod or inlined parent, found {}",
            self.hir_id_to_string(HirId::make_owner(parent.def_id))
        )
    }

    pub fn hir_expect_item(self, id: LocalDefId) -> &'tcx Item<'tcx> {
        match self.expect_hir_owner_node(id) {
            OwnerNode::Item(item) => item,
            _ => bug!("expected item, found {}", self.hir_id_to_string(HirId::make_owner(id))),
        }
    }

    pub fn hir_expect_impl_item(self, id: LocalDefId) -> &'tcx ImplItem<'tcx> {
        match self.expect_hir_owner_node(id) {
            OwnerNode::ImplItem(item) => item,
            _ => bug!("expected impl item, found {}", self.hir_id_to_string(HirId::make_owner(id))),
        }
    }

    pub fn hir_expect_trait_item(self, id: LocalDefId) -> &'tcx TraitItem<'tcx> {
        match self.expect_hir_owner_node(id) {
            OwnerNode::TraitItem(item) => item,
            _ => {
                bug!("expected trait item, found {}", self.hir_id_to_string(HirId::make_owner(id)))
            }
        }
    }

    pub fn hir_get_fn_output(self, def_id: LocalDefId) -> Option<&'tcx FnRetTy<'tcx>> {
        Some(&self.opt_hir_owner_node(def_id)?.fn_decl()?.output)
    }

    #[track_caller]
    pub fn hir_expect_opaque_ty(self, id: LocalDefId) -> &'tcx OpaqueTy<'tcx> {
        match self.hir_node_by_def_id(id) {
            Node::OpaqueTy(opaq) => opaq,
            _ => {
                bug!(
                    "expected opaque type definition, found {}",
                    self.hir_id_to_string(self.local_def_id_to_hir_id(id))
                )
            }
        }
    }

    pub fn hir_expect_expr(self, id: HirId) -> &'tcx Expr<'tcx> {
        match self.hir_node(id) {
            Node::Expr(expr) => expr,
            _ => bug!("expected expr, found {}", self.hir_id_to_string(id)),
        }
    }

    pub fn hir_opt_delegation_sig_id(self, def_id: LocalDefId) -> Option<DefId> {
        self.opt_hir_owner_node(def_id)?.fn_decl()?.opt_delegation_sig_id()
    }

    #[inline]
    fn hir_opt_ident(self, id: HirId) -> Option<Ident> {
        match self.hir_node(id) {
            Node::Pat(&Pat { kind: PatKind::Binding(_, _, ident, _), .. }) => Some(ident),
            // A `Ctor` doesn't have an identifier itself, but its parent
            // struct/variant does. Compare with `hir::Map::span`.
            Node::Ctor(..) => match self.parent_hir_node(id) {
                Node::Item(item) => Some(item.kind.ident().unwrap()),
                Node::Variant(variant) => Some(variant.ident),
                _ => unreachable!(),
            },
            node => node.ident(),
        }
    }

    #[inline]
    pub(super) fn hir_opt_ident_span(self, id: HirId) -> Option<Span> {
        self.hir_opt_ident(id).map(|ident| ident.span)
    }

    #[inline]
    pub fn hir_ident(self, id: HirId) -> Ident {
        self.hir_opt_ident(id).unwrap()
    }

    #[inline]
    pub fn hir_opt_name(self, id: HirId) -> Option<Symbol> {
        self.hir_opt_ident(id).map(|ident| ident.name)
    }

    pub fn hir_name(self, id: HirId) -> Symbol {
        self.hir_opt_name(id).unwrap_or_else(|| bug!("no name for {}", self.hir_id_to_string(id)))
    }

    /// Given a node ID, gets a list of attributes associated with the AST
    /// corresponding to the node-ID.
    pub fn hir_attrs(self, id: HirId) -> &'tcx [Attribute] {
        self.hir_attr_map(id.owner).get(id.local_id)
    }

    /// Gets the span of the definition of the specified HIR node.
    /// This is used by `tcx.def_span`.
    pub fn hir_span(self, hir_id: HirId) -> Span {
        fn until_within(outer: Span, end: Span) -> Span {
            if let Some(end) = end.find_ancestor_inside(outer) {
                outer.with_hi(end.hi())
            } else {
                outer
            }
        }

        fn named_span(item_span: Span, ident: Ident, generics: Option<&Generics<'_>>) -> Span {
            let mut span = until_within(item_span, ident.span);
            if let Some(g) = generics
                && !g.span.is_dummy()
                && let Some(g_span) = g.span.find_ancestor_inside(item_span)
            {
                span = span.to(g_span);
            }
            span
        }

        let span = match self.hir_node(hir_id) {
            // Function-like.
            Node::Item(Item { kind: ItemKind::Fn { sig, .. }, span: outer_span, .. })
            | Node::TraitItem(TraitItem {
                kind: TraitItemKind::Fn(sig, ..),
                span: outer_span,
                ..
            })
            | Node::ImplItem(ImplItem {
                kind: ImplItemKind::Fn(sig, ..), span: outer_span, ..
            })
            | Node::ForeignItem(ForeignItem {
                kind: ForeignItemKind::Fn(sig, ..),
                span: outer_span,
                ..
            }) => {
                // Ensure that the returned span has the item's SyntaxContext, and not the
                // SyntaxContext of the visibility.
                sig.span.find_ancestor_in_same_ctxt(*outer_span).unwrap_or(*outer_span)
            }
            // Impls, including their where clauses.
            Node::Item(Item {
                kind: ItemKind::Impl(Impl { generics, .. }),
                span: outer_span,
                ..
            }) => until_within(*outer_span, generics.where_clause_span),
            // Constants and Statics.
            Node::Item(Item {
                kind: ItemKind::Const(_, _, ty, _) | ItemKind::Static(_, _, ty, _),
                span: outer_span,
                ..
            })
            | Node::TraitItem(TraitItem {
                kind: TraitItemKind::Const(ty, ..),
                span: outer_span,
                ..
            })
            | Node::ImplItem(ImplItem {
                kind: ImplItemKind::Const(ty, ..),
                span: outer_span,
                ..
            })
            | Node::ForeignItem(ForeignItem {
                kind: ForeignItemKind::Static(ty, ..),
                span: outer_span,
                ..
            }) => until_within(*outer_span, ty.span),
            // With generics and bounds.
            Node::Item(Item {
                kind: ItemKind::Trait(_, _, _, _, generics, bounds, _),
                span: outer_span,
                ..
            })
            | Node::TraitItem(TraitItem {
                kind: TraitItemKind::Type(bounds, _),
                generics,
                span: outer_span,
                ..
            }) => {
                let end = if let Some(b) = bounds.last() { b.span() } else { generics.span };
                until_within(*outer_span, end)
            }
            // Other cases.
            Node::Item(item) => match &item.kind {
                ItemKind::Use(path, _) => {
                    // Ensure that the returned span has the item's SyntaxContext, and not the
                    // SyntaxContext of the path.
                    path.span.find_ancestor_in_same_ctxt(item.span).unwrap_or(item.span)
                }
                _ => {
                    if let Some(ident) = item.kind.ident() {
                        named_span(item.span, ident, item.kind.generics())
                    } else {
                        item.span
                    }
                }
            },
            Node::Variant(variant) => named_span(variant.span, variant.ident, None),
            Node::ImplItem(item) => named_span(item.span, item.ident, Some(item.generics)),
            Node::ForeignItem(item) => named_span(item.span, item.ident, None),
            Node::Ctor(_) => return self.hir_span(self.parent_hir_id(hir_id)),
            Node::Expr(Expr {
                kind: ExprKind::Closure(Closure { fn_decl_span, .. }),
                span,
                ..
            }) => {
                // Ensure that the returned span has the item's SyntaxContext.
                fn_decl_span.find_ancestor_inside(*span).unwrap_or(*span)
            }
            _ => self.hir_span_with_body(hir_id),
        };
        debug_assert_eq!(span.ctxt(), self.hir_span_with_body(hir_id).ctxt());
        span
    }

    /// Like `hir_span()`, but includes the body of items
    /// (instead of just the item header)
    pub fn hir_span_with_body(self, hir_id: HirId) -> Span {
        match self.hir_node(hir_id) {
            Node::Param(param) => param.span,
            Node::Item(item) => item.span,
            Node::ForeignItem(foreign_item) => foreign_item.span,
            Node::TraitItem(trait_item) => trait_item.span,
            Node::ImplItem(impl_item) => impl_item.span,
            Node::Variant(variant) => variant.span,
            Node::Field(field) => field.span,
            Node::AnonConst(constant) => constant.span,
            Node::ConstBlock(constant) => self.hir_body(constant.body).value.span,
            Node::ConstArg(const_arg) => const_arg.span,
            Node::Expr(expr) => expr.span,
            Node::ExprField(field) => field.span,
            Node::ConstArgExprField(field) => field.span,
            Node::Stmt(stmt) => stmt.span,
            Node::PathSegment(seg) => {
                let ident_span = seg.ident.span;
                ident_span
                    .with_hi(seg.args.map_or_else(|| ident_span.hi(), |args| args.span_ext.hi()))
            }
            Node::Ty(ty) => ty.span,
            Node::AssocItemConstraint(constraint) => constraint.span,
            Node::TraitRef(tr) => tr.path.span,
            Node::OpaqueTy(op) => op.span,
            Node::Pat(pat) => pat.span,
            Node::TyPat(pat) => pat.span,
            Node::PatField(field) => field.span,
            Node::PatExpr(lit) => lit.span,
            Node::Arm(arm) => arm.span,
            Node::Block(block) => block.span,
            Node::Ctor(..) => self.hir_span_with_body(self.parent_hir_id(hir_id)),
            Node::Lifetime(lifetime) => lifetime.ident.span,
            Node::GenericParam(param) => param.span,
            Node::Infer(i) => i.span,
            Node::LetStmt(local) => local.span,
            Node::Crate(item) => item.spans.inner_span,
            Node::WherePredicate(pred) => pred.span,
            Node::PreciseCapturingNonLifetimeArg(param) => param.ident.span,
            Node::Synthetic => unreachable!(),
            Node::Err(span) => span,
        }
    }

    pub fn hir_span_if_local(self, id: DefId) -> Option<Span> {
        id.is_local().then(|| self.def_span(id))
    }

    pub fn hir_res_span(self, res: Res) -> Option<Span> {
        match res {
            Res::Err => None,
            Res::Local(id) => Some(self.hir_span(id)),
            res => self.hir_span_if_local(res.opt_def_id()?),
        }
    }

    /// Returns the HirId of `N` in `struct Foo<const N: usize = { ... }>` when
    /// called with the HirId for the `{ ... }` anon const
    pub fn hir_opt_const_param_default_param_def_id(self, anon_const: HirId) -> Option<LocalDefId> {
        let const_arg = self.parent_hir_id(anon_const);
        match self.parent_hir_node(const_arg) {
            Node::GenericParam(GenericParam {
                def_id: param_id,
                kind: GenericParamKind::Const { .. },
                ..
            }) => Some(*param_id),
            _ => None,
        }
    }

    pub fn hir_maybe_get_struct_pattern_shorthand_field(self, expr: &Expr<'_>) -> Option<Symbol> {
        let local = match expr {
            Expr {
                kind:
                    ExprKind::Path(QPath::Resolved(
                        None,
                        Path {
                            res: def::Res::Local(_), segments: [PathSegment { ident, .. }], ..
                        },
                    )),
                ..
            } => Some(ident),
            _ => None,
        }?;

        match self.parent_hir_node(expr.hir_id) {
            Node::ExprField(field) => {
                if field.ident.name == local.name && field.is_shorthand {
                    return Some(local.name);
                }
            }
            _ => {}
        }

        None
    }
}

impl<'tcx> intravisit::HirTyCtxt<'tcx> for TyCtxt<'tcx> {
    fn hir_node(&self, hir_id: HirId) -> Node<'tcx> {
        (*self).hir_node(hir_id)
    }

    fn hir_body(&self, id: BodyId) -> &'tcx Body<'tcx> {
        (*self).hir_body(id)
    }

    fn hir_item(&self, id: ItemId) -> &'tcx Item<'tcx> {
        (*self).hir_item(id)
    }

    fn hir_trait_item(&self, id: TraitItemId) -> &'tcx TraitItem<'tcx> {
        (*self).hir_trait_item(id)
    }

    fn hir_impl_item(&self, id: ImplItemId) -> &'tcx ImplItem<'tcx> {
        (*self).hir_impl_item(id)
    }

    fn hir_foreign_item(&self, id: ForeignItemId) -> &'tcx ForeignItem<'tcx> {
        (*self).hir_foreign_item(id)
    }
}

impl<'tcx> pprust_hir::PpAnn for TyCtxt<'tcx> {
    fn nested(&self, state: &mut pprust_hir::State<'_>, nested: pprust_hir::Nested) {
        pprust_hir::PpAnn::nested(&(self as &dyn intravisit::HirTyCtxt<'_>), state, nested)
    }
}

pub(super) fn crate_hash(tcx: TyCtxt<'_>, _: LocalCrate) -> Svh {
    let krate = tcx.hir_crate(());
    let hir_body_hash = krate.opt_hir_hash.expect("HIR hash missing while computing crate hash");

    let upstream_crates = upstream_crates(tcx);

    let resolutions = tcx.resolutions(());

    // We hash the final, remapped names of all local source files so we
    // don't have to include the path prefix remapping commandline args.
    // If we included the full mapping in the SVH, we could only have
    // reproducible builds by compiling from the same directory. So we just
    // hash the result of the mapping instead of the mapping itself.
    let mut source_file_names: Vec<_> = tcx
        .sess
        .source_map()
        .files()
        .iter()
        .filter(|source_file| source_file.cnum == LOCAL_CRATE)
        .map(|source_file| source_file.stable_id)
        .collect();

    source_file_names.sort_unstable();

    // We have to take care of debugger visualizers explicitly. The HIR (and
    // thus `hir_body_hash`) contains the #[debugger_visualizer] attributes but
    // these attributes only store the file path to the visualizer file, not
    // their content. Yet that content is exported into crate metadata, so any
    // changes to it need to be reflected in the crate hash.
    let debugger_visualizers: Vec<_> = tcx
        .debugger_visualizers(LOCAL_CRATE)
        .iter()
        // We ignore the path to the visualizer file since it's not going to be
        // encoded in crate metadata and we already hash the full contents of
        // the file.
        .map(DebuggerVisualizerFile::path_erased)
        .collect();

    let crate_hash: Fingerprint = tcx.with_stable_hashing_context(|mut hcx| {
        let mut stable_hasher = StableHasher::new();
        hir_body_hash.hash_stable(&mut hcx, &mut stable_hasher);
        upstream_crates.hash_stable(&mut hcx, &mut stable_hasher);
        source_file_names.hash_stable(&mut hcx, &mut stable_hasher);
        debugger_visualizers.hash_stable(&mut hcx, &mut stable_hasher);
        if tcx.sess.opts.incremental.is_some() {
            let definitions = tcx.untracked().definitions.freeze();
            let mut owner_spans: Vec<_> = tcx
                .hir_crate_items(())
                .definitions()
                .map(|def_id| {
                    let def_path_hash = definitions.def_path_hash(def_id);
                    let span = tcx.source_span(def_id);
                    debug_assert_eq!(span.parent(), None);
                    (def_path_hash, span)
                })
                .collect();
            owner_spans.sort_unstable_by_key(|bn| bn.0);
            owner_spans.hash_stable(&mut hcx, &mut stable_hasher);
        }
        tcx.sess.opts.dep_tracking_hash(true).hash_stable(&mut hcx, &mut stable_hasher);
        tcx.stable_crate_id(LOCAL_CRATE).hash_stable(&mut hcx, &mut stable_hasher);
        // Hash visibility information since it does not appear in HIR.
        // FIXME: Figure out how to remove `visibilities_for_hashing` by hashing visibilities on
        // the fly in the resolver, storing only their accumulated hash in `ResolverGlobalCtxt`,
        // and combining it with other hashes here.
        resolutions.visibilities_for_hashing.hash_stable(&mut hcx, &mut stable_hasher);
        with_metavar_spans(|mspans| {
            mspans.freeze_and_get_read_spans().hash_stable(&mut hcx, &mut stable_hasher);
        });
        stable_hasher.finish()
    });

    Svh::new(crate_hash)
}

fn upstream_crates(tcx: TyCtxt<'_>) -> Vec<(StableCrateId, Svh)> {
    let mut upstream_crates: Vec<_> = tcx
        .crates(())
        .iter()
        .map(|&cnum| {
            let stable_crate_id = tcx.stable_crate_id(cnum);
            let hash = tcx.crate_hash(cnum);
            (stable_crate_id, hash)
        })
        .collect();
    upstream_crates.sort_unstable_by_key(|&(stable_crate_id, _)| stable_crate_id);
    upstream_crates
}

pub(super) fn hir_module_items(tcx: TyCtxt<'_>, module_id: LocalModDefId) -> ModuleItems {
    let mut collector = ItemCollector::new(tcx, false);

    let (hir_mod, span, hir_id) = tcx.hir_get_module(module_id);
    collector.visit_mod(hir_mod, span, hir_id);

    let ItemCollector {
        submodules,
        items,
        trait_items,
        impl_items,
        foreign_items,
        body_owners,
        opaques,
        nested_bodies,
        eiis,
        ..
    } = collector;
    ModuleItems {
        add_root: false,
        submodules: submodules.into_boxed_slice(),
        free_items: items.into_boxed_slice(),
        trait_items: trait_items.into_boxed_slice(),
        impl_items: impl_items.into_boxed_slice(),
        foreign_items: foreign_items.into_boxed_slice(),
        body_owners: body_owners.into_boxed_slice(),
        opaques: opaques.into_boxed_slice(),
        nested_bodies: nested_bodies.into_boxed_slice(),
        delayed_lint_items: Box::new([]),
        eiis: eiis.into_boxed_slice(),
    }
}

pub(crate) fn hir_crate_items(tcx: TyCtxt<'_>, _: ()) -> ModuleItems {
    let mut collector = ItemCollector::new(tcx, true);

    // A "crate collector" and "module collector" start at a
    // module item (the former starts at the crate root) but only
    // the former needs to collect it. ItemCollector does not do this for us.
    collector.submodules.push(CRATE_OWNER_ID);
    tcx.hir_walk_toplevel_module(&mut collector);

    let ItemCollector {
        submodules,
        items,
        trait_items,
        impl_items,
        foreign_items,
        body_owners,
        opaques,
        nested_bodies,
        mut delayed_lint_items,
        eiis,
        ..
    } = collector;

    // The crate could have delayed lints too, but would not be picked up by the visitor.
    // The `delayed_lint_items` list is smart - it only contains items which we know from
    // earlier passes is guaranteed to contain lints. It's a little harder to determine that
    // for sure here, so we simply always add the crate to the list. If it has no lints,
    // we'll discover that later. The cost of this should be low, there's only one crate
    // after all compared to the many items we have we wouldn't want to iterate over later.
    delayed_lint_items.push(CRATE_OWNER_ID);

    ModuleItems {
        add_root: true,
        submodules: submodules.into_boxed_slice(),
        free_items: items.into_boxed_slice(),
        trait_items: trait_items.into_boxed_slice(),
        impl_items: impl_items.into_boxed_slice(),
        foreign_items: foreign_items.into_boxed_slice(),
        body_owners: body_owners.into_boxed_slice(),
        opaques: opaques.into_boxed_slice(),
        nested_bodies: nested_bodies.into_boxed_slice(),
        delayed_lint_items: delayed_lint_items.into_boxed_slice(),
        eiis: eiis.into_boxed_slice(),
    }
}

struct ItemCollector<'tcx> {
    // When true, it collects all items in the create,
    // otherwise it collects items in some module.
    crate_collector: bool,
    tcx: TyCtxt<'tcx>,
    submodules: Vec<OwnerId>,
    items: Vec<ItemId>,
    trait_items: Vec<TraitItemId>,
    impl_items: Vec<ImplItemId>,
    foreign_items: Vec<ForeignItemId>,
    body_owners: Vec<LocalDefId>,
    opaques: Vec<LocalDefId>,
    nested_bodies: Vec<LocalDefId>,
    delayed_lint_items: Vec<OwnerId>,
    eiis: Vec<LocalDefId>,
    delayed_ids: Option<&'tcx FxIndexSet<LocalDefId>>,
}

impl<'tcx> ItemCollector<'tcx> {
    fn new(tcx: TyCtxt<'tcx>, crate_collector: bool) -> ItemCollector<'tcx> {
        let mut collector = ItemCollector {
            crate_collector,
            tcx,
            submodules: Vec::default(),
            items: Vec::default(),
            trait_items: Vec::default(),
            impl_items: Vec::default(),
            foreign_items: Vec::default(),
            body_owners: Vec::default(),
            opaques: Vec::default(),
            nested_bodies: Vec::default(),
            delayed_lint_items: Vec::default(),
            eiis: Vec::default(),
            delayed_ids: None,
        };

        if crate_collector {
            let krate = tcx.hir_crate(());
            collector.delayed_ids = Some(&krate.delayed_ids);

            let delayed_kinds =
                krate.delayed_ids.iter().copied().map(|id| (id, krate.owners[id].expect_delayed()));

            // FIXME(fn_delegation): need to add delayed lints, eiis
            for (def_id, kind) in delayed_kinds {
                let owner_id = OwnerId { def_id };

                match kind {
                    DelayedOwnerKind::Item => collector.items.push(ItemId { owner_id }),
                    DelayedOwnerKind::ImplItem => {
                        collector.impl_items.push(ImplItemId { owner_id })
                    }
                    DelayedOwnerKind::TraitItem => {
                        collector.trait_items.push(TraitItemId { owner_id })
                    }
                };

                collector.body_owners.push(def_id);
            }
        }

        collector
    }
}

impl<'hir> Visitor<'hir> for ItemCollector<'hir> {
    type NestedFilter = nested_filter::All;

    #[inline]
    fn visit_if_delayed(&self, def_id: LocalDefId) -> bool {
        !self.crate_collector || self.delayed_ids.is_none_or(|ids| !ids.contains(&def_id))
    }

    fn maybe_tcx(&mut self) -> Self::MaybeTyCtxt {
        self.tcx
    }

    fn visit_item(&mut self, item: &'hir Item<'hir>) {
        if Node::Item(item).associated_body().is_some() {
            self.body_owners.push(item.owner_id.def_id);
        }

        self.items.push(item.item_id());
        if self.crate_collector && item.has_delayed_lints {
            self.delayed_lint_items.push(item.item_id().owner_id);
        }

        if let ItemKind::Static(..) | ItemKind::Fn { .. } | ItemKind::Macro(..) = &item.kind
            && item.eii
        {
            self.eiis.push(item.owner_id.def_id)
        }

        // Items that are modules are handled here instead of in visit_mod.
        if let ItemKind::Mod(_, module) = &item.kind {
            self.submodules.push(item.owner_id);
            // A module collector does not recurse inside nested modules.
            if self.crate_collector {
                intravisit::walk_mod(self, module);
            }
        } else {
            intravisit::walk_item(self, item)
        }
    }

    fn visit_foreign_item(&mut self, item: &'hir ForeignItem<'hir>) {
        self.foreign_items.push(item.foreign_item_id());
        if self.crate_collector && item.has_delayed_lints {
            self.delayed_lint_items.push(item.foreign_item_id().owner_id);
        }
        intravisit::walk_foreign_item(self, item)
    }

    fn visit_anon_const(&mut self, c: &'hir AnonConst) {
        self.body_owners.push(c.def_id);
        intravisit::walk_anon_const(self, c)
    }

    fn visit_inline_const(&mut self, c: &'hir ConstBlock) {
        self.body_owners.push(c.def_id);
        self.nested_bodies.push(c.def_id);
        intravisit::walk_inline_const(self, c)
    }

    fn visit_opaque_ty(&mut self, o: &'hir OpaqueTy<'hir>) {
        self.opaques.push(o.def_id);
        intravisit::walk_opaque_ty(self, o)
    }

    fn visit_expr(&mut self, ex: &'hir Expr<'hir>) {
        if let ExprKind::Closure(closure) = ex.kind {
            self.body_owners.push(closure.def_id);
            self.nested_bodies.push(closure.def_id);
        }
        intravisit::walk_expr(self, ex)
    }

    fn visit_trait_item(&mut self, item: &'hir TraitItem<'hir>) {
        if Node::TraitItem(item).associated_body().is_some() {
            self.body_owners.push(item.owner_id.def_id);
        }

        self.trait_items.push(item.trait_item_id());
        if self.crate_collector && item.has_delayed_lints {
            self.delayed_lint_items.push(item.trait_item_id().owner_id);
        }

        intravisit::walk_trait_item(self, item)
    }

    fn visit_impl_item(&mut self, item: &'hir ImplItem<'hir>) {
        if Node::ImplItem(item).associated_body().is_some() {
            self.body_owners.push(item.owner_id.def_id);
        }

        self.impl_items.push(item.impl_item_id());
        if self.crate_collector && item.has_delayed_lints {
            self.delayed_lint_items.push(item.impl_item_id().owner_id);
        }

        intravisit::walk_impl_item(self, item)
    }
}
