diff --git a/compiler/rustc_codegen_ssa/src/back/symbol_export.rs b/compiler/rustc_codegen_ssa/src/back/symbol_export.rs
index 765bd877db169..7b7c676c26cd1 100644
--- a/compiler/rustc_codegen_ssa/src/back/symbol_export.rs
+++ b/compiler/rustc_codegen_ssa/src/back/symbol_export.rs
@@ -1,12 +1,10 @@
 use std::collections::hash_map::Entry::*;
 
 use rustc_ast::expand::allocator::ALLOCATOR_METHODS;
-use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir as hir;
-use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, LocalDefId, CRATE_DEF_INDEX, LOCAL_CRATE};
+use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, LocalDefId, LOCAL_CRATE};
 use rustc_hir::Node;
-use rustc_index::vec::IndexVec;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::middle::exported_symbols::{
     metadata_symbol_name, ExportedSymbol, SymbolExportLevel,
@@ -277,17 +275,6 @@ fn upstream_monomorphizations_provider(
 
     let mut instances: DefIdMap<FxHashMap<_, _>> = Default::default();
 
-    let cnum_stable_ids: IndexVec<CrateNum, Fingerprint> = {
-        let mut cnum_stable_ids = IndexVec::from_elem_n(Fingerprint::ZERO, cnums.len() + 1);
-
-        for &cnum in cnums.iter() {
-            cnum_stable_ids[cnum] =
-                tcx.def_path_hash(DefId { krate: cnum, index: CRATE_DEF_INDEX }).0;
-        }
-
-        cnum_stable_ids
-    };
-
     let drop_in_place_fn_def_id = tcx.lang_items().drop_in_place_fn();
 
     for &cnum in cnums.iter() {
@@ -316,7 +303,7 @@ fn upstream_monomorphizations_provider(
                     // If there are multiple monomorphizations available,
                     // we select one deterministically.
                     let other_cnum = *e.get();
-                    if cnum_stable_ids[other_cnum] > cnum_stable_ids[cnum] {
+                    if tcx.stable_crate_id(other_cnum) > tcx.stable_crate_id(cnum) {
                         e.insert(cnum);
                     }
                 }
diff --git a/compiler/rustc_hir/src/def.rs b/compiler/rustc_hir/src/def.rs
index 53d60d280c001..324e110005717 100644
--- a/compiler/rustc_hir/src/def.rs
+++ b/compiler/rustc_hir/src/def.rs
@@ -1,4 +1,4 @@
-use crate::def_id::{DefId, CRATE_DEF_INDEX, LOCAL_CRATE};
+use crate::def_id::DefId;
 use crate::hir;
 
 use rustc_ast as ast;
@@ -124,9 +124,7 @@ impl DefKind {
     pub fn descr(self, def_id: DefId) -> &'static str {
         match self {
             DefKind::Fn => "function",
-            DefKind::Mod if def_id.index == CRATE_DEF_INDEX && def_id.krate != LOCAL_CRATE => {
-                "crate"
-            }
+            DefKind::Mod if def_id.is_crate_root() && !def_id.is_local() => "crate",
             DefKind::Mod => "module",
             DefKind::Static(..) => "static",
             DefKind::Enum => "enum",
diff --git a/compiler/rustc_hir/src/definitions.rs b/compiler/rustc_hir/src/definitions.rs
index 4908992085a6e..bce9ba12ac0c4 100644
--- a/compiler/rustc_hir/src/definitions.rs
+++ b/compiler/rustc_hir/src/definitions.rs
@@ -353,11 +353,6 @@ impl Definitions {
         }
     }
 
-    /// Retrieves the root definition.
-    pub fn get_root_def(&self) -> LocalDefId {
-        LocalDefId { local_def_index: CRATE_DEF_INDEX }
-    }
-
     /// Adds a definition with a parent definition.
     pub fn create_def(
         &mut self,
diff --git a/compiler/rustc_hir/src/hir_id.rs b/compiler/rustc_hir/src/hir_id.rs
index 3b5e4dcf5e011..e0ff28dff15cd 100644
--- a/compiler/rustc_hir/src/hir_id.rs
+++ b/compiler/rustc_hir/src/hir_id.rs
@@ -1,4 +1,4 @@
-use crate::def_id::{LocalDefId, CRATE_DEF_INDEX};
+use crate::def_id::{LocalDefId, CRATE_DEF_ID};
 use std::fmt;
 
 /// Uniquely identifies a node in the HIR of the current crate. It is
@@ -84,8 +84,5 @@ impl ItemLocalId {
     pub const INVALID: ItemLocalId = ItemLocalId::MAX;
 }
 
-/// The `HirId` corresponding to `CRATE_NODE_ID` and `CRATE_DEF_INDEX`.
-pub const CRATE_HIR_ID: HirId = HirId {
-    owner: LocalDefId { local_def_index: CRATE_DEF_INDEX },
-    local_id: ItemLocalId::from_u32(0),
-};
+/// The `HirId` corresponding to `CRATE_NODE_ID` and `CRATE_DEF_ID`.
+pub const CRATE_HIR_ID: HirId = HirId { owner: CRATE_DEF_ID, local_id: ItemLocalId::from_u32(0) };
diff --git a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
index 63bf929fb8639..9c88171d17566 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
@@ -5,7 +5,7 @@ use crate::native_libs;
 
 use rustc_ast as ast;
 use rustc_hir::def::{CtorKind, DefKind, Res};
-use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, CRATE_DEF_INDEX, LOCAL_CRATE};
+use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, LOCAL_CRATE};
 use rustc_hir::definitions::{DefKey, DefPath, DefPathHash};
 use rustc_middle::metadata::ModChild;
 use rustc_middle::middle::exported_symbols::ExportedSymbol;
@@ -324,7 +324,7 @@ pub(in crate::rmeta) fn provide(providers: &mut Providers) {
                     continue;
                 }
 
-                bfs_queue.push_back(DefId { krate: cnum, index: CRATE_DEF_INDEX });
+                bfs_queue.push_back(cnum.as_def_id());
             }
 
             let mut add_child = |bfs_queue: &mut VecDeque<_>, child: &ModChild, parent: DefId| {
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index e967750aebb52..50010fb83cf3b 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -1633,7 +1633,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             let hir = tcx.hir();
 
             let proc_macro_decls_static = tcx.proc_macro_decls_static(()).unwrap().local_def_index;
-            let stability = tcx.lookup_stability(DefId::local(CRATE_DEF_INDEX));
+            let stability = tcx.lookup_stability(CRATE_DEF_ID);
             let macros =
                 self.lazy(tcx.resolutions(()).proc_macros.iter().map(|p| p.local_def_index));
             let spans = self.tcx.sess.parse_sess.proc_macro_quoted_spans();
diff --git a/compiler/rustc_middle/src/dep_graph/dep_node.rs b/compiler/rustc_middle/src/dep_graph/dep_node.rs
index d20be0a34d2d5..8402ca3028cce 100644
--- a/compiler/rustc_middle/src/dep_graph/dep_node.rs
+++ b/compiler/rustc_middle/src/dep_graph/dep_node.rs
@@ -60,7 +60,7 @@ use crate::mir::mono::MonoItem;
 use crate::ty::TyCtxt;
 
 use rustc_data_structures::fingerprint::Fingerprint;
-use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, CRATE_DEF_INDEX};
+use rustc_hir::def_id::{CrateNum, DefId, LocalDefId};
 use rustc_hir::definitions::DefPathHash;
 use rustc_hir::HirId;
 use rustc_query_system::dep_graph::FingerprintStyle;
@@ -366,7 +366,7 @@ impl<'tcx> DepNodeParams<TyCtxt<'tcx>> for CrateNum {
 
     #[inline(always)]
     fn to_fingerprint(&self, tcx: TyCtxt<'tcx>) -> Fingerprint {
-        let def_id = DefId { krate: *self, index: CRATE_DEF_INDEX };
+        let def_id = self.as_def_id();
         def_id.to_fingerprint(tcx)
     }
 
diff --git a/compiler/rustc_middle/src/middle/stability.rs b/compiler/rustc_middle/src/middle/stability.rs
index fd6e241346db8..758658c3d8c94 100644
--- a/compiler/rustc_middle/src/middle/stability.rs
+++ b/compiler/rustc_middle/src/middle/stability.rs
@@ -11,7 +11,7 @@ use rustc_errors::{Applicability, Diagnostic};
 use rustc_feature::GateIssue;
 use rustc_hir as hir;
 use rustc_hir::def::DefKind;
-use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_INDEX};
+use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::{self, HirId};
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_session::lint::builtin::{DEPRECATED, DEPRECATED_IN_FUTURE, SOFT_UNSTABLE};
@@ -370,8 +370,7 @@ impl<'tcx> TyCtxt<'tcx> {
             };
         }
 
-        let is_staged_api =
-            self.lookup_stability(DefId { index: CRATE_DEF_INDEX, ..def_id }).is_some();
+        let is_staged_api = self.lookup_stability(def_id.krate.as_def_id()).is_some();
         if !is_staged_api {
             return EvalResult::Allow;
         }
diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs
index 49769b7ae3d89..4f4b6cf704fa9 100644
--- a/compiler/rustc_middle/src/mir/mod.rs
+++ b/compiler/rustc_middle/src/mir/mod.rs
@@ -15,7 +15,7 @@ use crate::ty::{AdtDef, InstanceDef, Region, ScalarInt, UserTypeAnnotationIndex}
 
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir::def::{CtorKind, Namespace};
-use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_INDEX};
+use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID};
 use rustc_hir::{self, GeneratorKind};
 use rustc_hir::{self as hir, HirId};
 use rustc_session::Session;
@@ -385,7 +385,7 @@ impl<'tcx> Body<'tcx> {
     pub fn new_cfg_only(basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>) -> Self {
         let mut body = Body {
             phase: MirPhase::Built,
-            source: MirSource::item(DefId::local(CRATE_DEF_INDEX)),
+            source: MirSource::item(CRATE_DEF_ID.to_def_id()),
             basic_blocks,
             source_scopes: IndexVec::new(),
             generator: None,
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index c2accea11ba2a..2901772bc74ec 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -36,7 +36,7 @@ use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::tagged_ptr::CopyTaggedPtr;
 use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, CtorOf, DefKind, Res};
-use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, LocalDefIdMap, CRATE_DEF_INDEX};
+use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, LocalDefIdMap, CRATE_DEF_ID};
 use rustc_hir::Node;
 use rustc_macros::HashStable;
 use rustc_query_system::ich::StableHashingContext;
@@ -319,7 +319,7 @@ impl Visibility {
     pub fn from_hir(visibility: &hir::Visibility<'_>, id: hir::HirId, tcx: TyCtxt<'_>) -> Self {
         match visibility.node {
             hir::VisibilityKind::Public => Visibility::Public,
-            hir::VisibilityKind::Crate(_) => Visibility::Restricted(DefId::local(CRATE_DEF_INDEX)),
+            hir::VisibilityKind::Crate(_) => Visibility::Restricted(CRATE_DEF_ID.to_def_id()),
             hir::VisibilityKind::Restricted { ref path, .. } => match path.res {
                 // If there is no resolution, `resolve` will have already reported an error, so
                 // assume that the visibility is public to avoid reporting more privacy errors.
@@ -1992,8 +1992,8 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     fn opt_item_name(self, def_id: DefId) -> Option<Symbol> {
-        if def_id.index == CRATE_DEF_INDEX {
-            Some(self.crate_name(def_id.krate))
+        if let Some(cnum) = def_id.as_crate_root() {
+            Some(self.crate_name(cnum))
         } else {
             let def_key = self.def_key(def_id);
             match def_key.disambiguated_data.data {
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index 4379adb604e1f..d2c5bd1898614 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -6,7 +6,7 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sso::SsoHashSet;
 use rustc_hir as hir;
 use rustc_hir::def::{self, CtorKind, DefKind, Namespace};
-use rustc_hir::def_id::{DefId, DefIdSet, CRATE_DEF_INDEX, LOCAL_CRATE};
+use rustc_hir::def_id::{DefId, DefIdSet, CRATE_DEF_ID, LOCAL_CRATE};
 use rustc_hir::definitions::{DefPathData, DefPathDataName, DisambiguatedDefPathData};
 use rustc_hir::ItemKind;
 use rustc_session::config::TrimmedDefPaths;
@@ -336,9 +336,7 @@ pub trait PrettyPrinter<'tcx>:
 
         // If `def_id` is a direct or injected extern crate, return the
         // path to the crate followed by the path to the item within the crate.
-        if def_id.index == CRATE_DEF_INDEX {
-            let cnum = def_id.krate;
-
+        if let Some(cnum) = def_id.as_crate_root() {
             if cnum == LOCAL_CRATE {
                 return Ok((self.path_crate(cnum)?, true));
             }
@@ -2228,11 +2226,11 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
                     ty::BrNamed(_, _) => br.kind,
                     ty::BrAnon(i) => {
                         let name = region_map[&(i + 1)];
-                        ty::BrNamed(DefId::local(CRATE_DEF_INDEX), name)
+                        ty::BrNamed(CRATE_DEF_ID.to_def_id(), name)
                     }
                     ty::BrEnv => {
                         let name = region_map[&0];
-                        ty::BrNamed(DefId::local(CRATE_DEF_INDEX), name)
+                        ty::BrNamed(CRATE_DEF_ID.to_def_id(), name)
                     }
                 };
                 self.tcx.mk_region(ty::ReLateBound(
@@ -2258,7 +2256,7 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
                             }
                         };
                         do_continue(&mut self, name);
-                        ty::BrNamed(DefId::local(CRATE_DEF_INDEX), name)
+                        ty::BrNamed(CRATE_DEF_ID.to_def_id(), name)
                     }
                 };
                 tcx.mk_region(ty::ReLateBound(ty::INNERMOST, ty::BoundRegion { var: br.var, kind }))
@@ -2693,7 +2691,7 @@ fn for_each_def(tcx: TyCtxt<'_>, mut collect_fn: impl for<'b> FnMut(&'b Ident, N
     let mut seen_defs: DefIdSet = Default::default();
 
     for &cnum in tcx.crates(()).iter() {
-        let def_id = DefId { krate: cnum, index: CRATE_DEF_INDEX };
+        let def_id = cnum.as_def_id();
 
         // Ignore crates that are not direct dependencies.
         match tcx.extern_crate(def_id) {
diff --git a/compiler/rustc_middle/src/ty/structural_impls.rs b/compiler/rustc_middle/src/ty/structural_impls.rs
index 5c7910db362d2..4ef6ff1835ffd 100644
--- a/compiler/rustc_middle/src/ty/structural_impls.rs
+++ b/compiler/rustc_middle/src/ty/structural_impls.rs
@@ -10,7 +10,6 @@ use crate::ty::{self, InferConst, Lift, Term, Ty, TyCtxt};
 use rustc_data_structures::functor::IdFunctor;
 use rustc_hir as hir;
 use rustc_hir::def::Namespace;
-use rustc_hir::def_id::CRATE_DEF_INDEX;
 use rustc_index::vec::{Idx, IndexVec};
 
 use std::fmt;
@@ -71,7 +70,7 @@ impl fmt::Debug for ty::BoundRegionKind {
         match *self {
             ty::BrAnon(n) => write!(f, "BrAnon({:?})", n),
             ty::BrNamed(did, name) => {
-                if did.index == CRATE_DEF_INDEX {
+                if did.is_crate_root() {
                     write!(f, "BrNamed({})", name)
                 } else {
                     write!(f, "BrNamed({:?}, {})", did, name)
diff --git a/compiler/rustc_monomorphize/src/partitioning/default.rs b/compiler/rustc_monomorphize/src/partitioning/default.rs
index c4ffb19f87a91..1677419887988 100644
--- a/compiler/rustc_monomorphize/src/partitioning/default.rs
+++ b/compiler/rustc_monomorphize/src/partitioning/default.rs
@@ -2,7 +2,7 @@ use std::collections::hash_map::Entry;
 
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_hir::def::DefKind;
-use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX, LOCAL_CRATE};
+use rustc_hir::def_id::{DefId, LOCAL_CRATE};
 use rustc_hir::definitions::DefPathDataName;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::middle::exported_symbols::SymbolExportLevel;
@@ -335,10 +335,10 @@ fn compute_codegen_unit_name(
     let mut cgu_def_id = None;
     // Walk backwards from the item we want to find the module for.
     loop {
-        if current_def_id.index == CRATE_DEF_INDEX {
+        if current_def_id.is_crate_root() {
             if cgu_def_id.is_none() {
                 // If we have not found a module yet, take the crate root.
-                cgu_def_id = Some(DefId { krate: def_id.krate, index: CRATE_DEF_INDEX });
+                cgu_def_id = Some(def_id.krate.as_def_id());
             }
             break;
         } else if tcx.def_kind(current_def_id) == DefKind::Mod {
diff --git a/compiler/rustc_passes/src/entry.rs b/compiler/rustc_passes/src/entry.rs
index 5a1373ad1a218..db083d0453bc0 100644
--- a/compiler/rustc_passes/src/entry.rs
+++ b/compiler/rustc_passes/src/entry.rs
@@ -1,21 +1,18 @@
 use rustc_ast::entry::EntryPointType;
 use rustc_errors::struct_span_err;
-use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID, CRATE_DEF_INDEX, LOCAL_CRATE};
+use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID, LOCAL_CRATE};
 use rustc_hir::itemlikevisit::ItemLikeVisitor;
 use rustc_hir::{ForeignItem, ImplItem, Item, ItemKind, Node, TraitItem, CRATE_HIR_ID};
-use rustc_middle::hir::map::Map;
 use rustc_middle::ty::query::Providers;
-use rustc_middle::ty::TyCtxt;
+use rustc_middle::ty::{DefIdTree, TyCtxt};
 use rustc_session::config::{CrateType, EntryFnType};
 use rustc_session::parse::feature_err;
 use rustc_session::Session;
 use rustc_span::symbol::sym;
 use rustc_span::{Span, DUMMY_SP};
 
-struct EntryContext<'a, 'tcx> {
-    session: &'a Session,
-
-    map: Map<'tcx>,
+struct EntryContext<'tcx> {
+    tcx: TyCtxt<'tcx>,
 
     /// The function that has attribute named `main`.
     attr_main_fn: Option<(LocalDefId, Span)>,
@@ -28,10 +25,9 @@ struct EntryContext<'a, 'tcx> {
     non_main_fns: Vec<Span>,
 }
 
-impl<'a, 'tcx> ItemLikeVisitor<'tcx> for EntryContext<'a, 'tcx> {
+impl<'tcx> ItemLikeVisitor<'tcx> for EntryContext<'tcx> {
     fn visit_item(&mut self, item: &'tcx Item<'tcx>) {
-        let def_key = self.map.def_key(item.def_id);
-        let at_root = def_key.parent == Some(CRATE_DEF_INDEX);
+        let at_root = self.tcx.local_parent(item.def_id) == Some(CRATE_DEF_ID);
         find_item(item, self, at_root);
     }
 
@@ -60,13 +56,8 @@ fn entry_fn(tcx: TyCtxt<'_>, (): ()) -> Option<(DefId, EntryFnType)> {
         return None;
     }
 
-    let mut ctxt = EntryContext {
-        session: tcx.sess,
-        map: tcx.hir(),
-        attr_main_fn: None,
-        start_fn: None,
-        non_main_fns: Vec::new(),
-    };
+    let mut ctxt =
+        EntryContext { tcx, attr_main_fn: None, start_fn: None, non_main_fns: Vec::new() };
 
     tcx.hir().visit_all_item_likes(&mut ctxt);
 
@@ -75,11 +66,11 @@ fn entry_fn(tcx: TyCtxt<'_>, (): ()) -> Option<(DefId, EntryFnType)> {
 
 // Beware, this is duplicated in `librustc_builtin_macros/test_harness.rs`
 // (with `ast::Item`), so make sure to keep them in sync.
-fn entry_point_type(ctxt: &EntryContext<'_, '_>, item: &Item<'_>, at_root: bool) -> EntryPointType {
-    let attrs = ctxt.map.attrs(item.hir_id());
-    if ctxt.session.contains_name(attrs, sym::start) {
+fn entry_point_type(ctxt: &EntryContext<'_>, item: &Item<'_>, at_root: bool) -> EntryPointType {
+    let attrs = ctxt.tcx.hir().attrs(item.hir_id());
+    if ctxt.tcx.sess.contains_name(attrs, sym::start) {
         EntryPointType::Start
-    } else if ctxt.session.contains_name(attrs, sym::rustc_main) {
+    } else if ctxt.tcx.sess.contains_name(attrs, sym::rustc_main) {
         EntryPointType::MainAttr
     } else if item.ident.name == sym::main {
         if at_root {
@@ -98,16 +89,16 @@ fn throw_attr_err(sess: &Session, span: Span, attr: &str) {
         .emit();
 }
 
-fn find_item(item: &Item<'_>, ctxt: &mut EntryContext<'_, '_>, at_root: bool) {
+fn find_item(item: &Item<'_>, ctxt: &mut EntryContext<'_>, at_root: bool) {
     match entry_point_type(ctxt, item, at_root) {
         EntryPointType::None => (),
         _ if !matches!(item.kind, ItemKind::Fn(..)) => {
-            let attrs = ctxt.map.attrs(item.hir_id());
-            if let Some(attr) = ctxt.session.find_by_name(attrs, sym::start) {
-                throw_attr_err(&ctxt.session, attr.span, "start");
+            let attrs = ctxt.tcx.hir().attrs(item.hir_id());
+            if let Some(attr) = ctxt.tcx.sess.find_by_name(attrs, sym::start) {
+                throw_attr_err(&ctxt.tcx.sess, attr.span, "start");
             }
-            if let Some(attr) = ctxt.session.find_by_name(attrs, sym::rustc_main) {
-                throw_attr_err(&ctxt.session, attr.span, "rustc_main");
+            if let Some(attr) = ctxt.tcx.sess.find_by_name(attrs, sym::rustc_main) {
+                throw_attr_err(&ctxt.tcx.sess, attr.span, "rustc_main");
             }
         }
         EntryPointType::MainNamed => (),
@@ -119,7 +110,7 @@ fn find_item(item: &Item<'_>, ctxt: &mut EntryContext<'_, '_>, at_root: bool) {
                 ctxt.attr_main_fn = Some((item.def_id, item.span));
             } else {
                 struct_span_err!(
-                    ctxt.session,
+                    ctxt.tcx.sess,
                     item.span,
                     E0137,
                     "multiple functions with a `#[main]` attribute"
@@ -133,7 +124,7 @@ fn find_item(item: &Item<'_>, ctxt: &mut EntryContext<'_, '_>, at_root: bool) {
             if ctxt.start_fn.is_none() {
                 ctxt.start_fn = Some((item.def_id, item.span));
             } else {
-                struct_span_err!(ctxt.session, item.span, E0138, "multiple `start` functions")
+                struct_span_err!(ctxt.tcx.sess, item.span, E0138, "multiple `start` functions")
                     .span_label(ctxt.start_fn.unwrap().1, "previous `#[start]` function here")
                     .span_label(item.span, "multiple `start` functions")
                     .emit();
@@ -142,7 +133,7 @@ fn find_item(item: &Item<'_>, ctxt: &mut EntryContext<'_, '_>, at_root: bool) {
     }
 }
 
-fn configure_main(tcx: TyCtxt<'_>, visitor: &EntryContext<'_, '_>) -> Option<(DefId, EntryFnType)> {
+fn configure_main(tcx: TyCtxt<'_>, visitor: &EntryContext<'_>) -> Option<(DefId, EntryFnType)> {
     if let Some((def_id, _)) = visitor.start_fn {
         Some((def_id.to_def_id(), EntryFnType::Start))
     } else if let Some((def_id, _)) = visitor.attr_main_fn {
@@ -177,7 +168,7 @@ fn configure_main(tcx: TyCtxt<'_>, visitor: &EntryContext<'_, '_>) -> Option<(De
     }
 }
 
-fn no_main_err(tcx: TyCtxt<'_>, visitor: &EntryContext<'_, '_>) {
+fn no_main_err(tcx: TyCtxt<'_>, visitor: &EntryContext<'_>) {
     let sp = tcx.def_span(CRATE_DEF_ID);
     if *tcx.sess.parse_sess.reached_eof.borrow() {
         // There's an unclosed brace that made the parser reach `Eof`, we shouldn't complain about
diff --git a/compiler/rustc_passes/src/hir_id_validator.rs b/compiler/rustc_passes/src/hir_id_validator.rs
index 56755d68686e3..379a6827c8aac 100644
--- a/compiler/rustc_passes/src/hir_id_validator.rs
+++ b/compiler/rustc_passes/src/hir_id_validator.rs
@@ -1,7 +1,7 @@
 use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::sync::Lock;
 use rustc_hir as hir;
-use rustc_hir::def_id::{LocalDefId, CRATE_DEF_INDEX};
+use rustc_hir::def_id::{LocalDefId, CRATE_DEF_ID};
 use rustc_hir::intravisit;
 use rustc_hir::itemlikevisit::ItemLikeVisitor;
 use rustc_hir::{HirId, ItemLocalId};
@@ -89,7 +89,7 @@ impl<'a, 'hir> HirIdValidator<'a, 'hir> {
         self.owner = Some(owner);
         walk(self);
 
-        if owner.local_def_index == CRATE_DEF_INDEX {
+        if owner == CRATE_DEF_ID {
             return;
         }
 
diff --git a/compiler/rustc_passes/src/stability.rs b/compiler/rustc_passes/src/stability.rs
index 01ba9e35c24dc..35a858cb86c3f 100644
--- a/compiler/rustc_passes/src/stability.rs
+++ b/compiler/rustc_passes/src/stability.rs
@@ -6,7 +6,7 @@ use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
 use rustc_errors::struct_span_err;
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
-use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID, CRATE_DEF_INDEX};
+use rustc_hir::def_id::{LocalDefId, CRATE_DEF_ID};
 use rustc_hir::hir_id::CRATE_HIR_ID;
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_hir::{FieldDef, Generics, HirId, Item, TraitRef, Ty, TyKind, Variant};
@@ -703,7 +703,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'tcx> {
                 let Some(cnum) = self.tcx.extern_mod_stmt_cnum(item.def_id) else {
                     return;
                 };
-                let def_id = DefId { krate: cnum, index: CRATE_DEF_INDEX };
+                let def_id = cnum.as_def_id();
                 self.tcx.check_stability(def_id, Some(item.hir_id()), item.span, None);
             }
 
diff --git a/compiler/rustc_query_impl/src/profiling_support.rs b/compiler/rustc_query_impl/src/profiling_support.rs
index acccf43f06285..b20aa7b53468a 100644
--- a/compiler/rustc_query_impl/src/profiling_support.rs
+++ b/compiler/rustc_query_impl/src/profiling_support.rs
@@ -1,7 +1,7 @@
 use measureme::{StringComponent, StringId};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::profiling::SelfProfiler;
-use rustc_hir::def_id::{CrateNum, DefId, DefIndex, LocalDefId, CRATE_DEF_INDEX, LOCAL_CRATE};
+use rustc_hir::def_id::{CrateNum, DefId, DefIndex, LocalDefId, LOCAL_CRATE};
 use rustc_hir::definitions::DefPathData;
 use rustc_middle::ty::{TyCtxt, WithOptConstParam};
 use rustc_query_system::query::QueryCache;
@@ -143,7 +143,7 @@ impl SpecIntoSelfProfilingString for CrateNum {
         &self,
         builder: &mut QueryKeyStringBuilder<'_, '_, '_>,
     ) -> StringId {
-        builder.def_id_to_string_id(DefId { krate: *self, index: CRATE_DEF_INDEX })
+        builder.def_id_to_string_id(self.as_def_id())
     }
 }
 
diff --git a/compiler/rustc_resolve/src/build_reduced_graph.rs b/compiler/rustc_resolve/src/build_reduced_graph.rs
index 54e8c03156d55..77995b60a557e 100644
--- a/compiler/rustc_resolve/src/build_reduced_graph.rs
+++ b/compiler/rustc_resolve/src/build_reduced_graph.rs
@@ -23,7 +23,7 @@ use rustc_errors::{struct_span_err, Applicability};
 use rustc_expand::base::SyntaxExtension;
 use rustc_expand::expand::AstFragment;
 use rustc_hir::def::{self, *};
-use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_INDEX};
+use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID};
 use rustc_metadata::creader::LoadedMacro;
 use rustc_middle::bug;
 use rustc_middle::metadata::ModChild;
@@ -140,8 +140,8 @@ impl<'a> Resolver<'a> {
                     let parent = def_key.parent.map(|index| {
                         self.get_nearest_non_block_module(DefId { index, krate: def_id.krate })
                     });
-                    let name = if def_id.index == CRATE_DEF_INDEX {
-                        self.cstore().crate_name(def_id.krate)
+                    let name = if let Some(cnum) = def_id.as_crate_root() {
+                        self.cstore().crate_name(cnum)
                     } else {
                         def_key.disambiguated_data.data.get_opt_name().expect("module without name")
                     };
@@ -250,7 +250,7 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
         match vis.kind {
             ast::VisibilityKind::Public => Ok(ty::Visibility::Public),
             ast::VisibilityKind::Crate(..) => {
-                Ok(ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX)))
+                Ok(ty::Visibility::Restricted(CRATE_DEF_ID.to_def_id()))
             }
             ast::VisibilityKind::Inherited => {
                 Ok(match self.parent_scope.module.kind {
@@ -759,7 +759,7 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
                     let mut ctor_vis = if vis == ty::Visibility::Public
                         && self.r.session.contains_name(&item.attrs, sym::non_exhaustive)
                     {
-                        ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX))
+                        ty::Visibility::Restricted(CRATE_DEF_ID.to_def_id())
                     } else {
                         vis
                     };
@@ -1108,7 +1108,7 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
                 root_span: span,
                 span,
                 module_path: Vec::new(),
-                vis: Cell::new(ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX))),
+                vis: Cell::new(ty::Visibility::Restricted(CRATE_DEF_ID.to_def_id())),
                 used: Cell::new(false),
             })
         };
@@ -1244,7 +1244,7 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
             let vis = if is_macro_export {
                 ty::Visibility::Public
             } else {
-                ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX))
+                ty::Visibility::Restricted(CRATE_DEF_ID.to_def_id())
             };
             let binding = (res, vis, span, expansion).to_name_binding(self.r.arenas);
             self.r.set_binding_parent_module(binding, parent_scope.module);
@@ -1490,7 +1490,7 @@ impl<'a, 'b> Visitor<'b> for BuildReducedGraphVisitor<'a, 'b> {
         let ctor_vis = if vis == ty::Visibility::Public
             && self.r.session.contains_name(&variant.attrs, sym::non_exhaustive)
         {
-            ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX))
+            ty::Visibility::Restricted(CRATE_DEF_ID.to_def_id())
         } else {
             vis
         };
diff --git a/compiler/rustc_resolve/src/diagnostics.rs b/compiler/rustc_resolve/src/diagnostics.rs
index f3b8c1e266c58..899980a4c0887 100644
--- a/compiler/rustc_resolve/src/diagnostics.rs
+++ b/compiler/rustc_resolve/src/diagnostics.rs
@@ -10,7 +10,7 @@ use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed
 use rustc_feature::BUILTIN_ATTRIBUTES;
 use rustc_hir::def::Namespace::{self, *};
 use rustc_hir::def::{self, CtorKind, CtorOf, DefKind, NonMacroAttrKind, PerNS};
-use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX, LOCAL_CRATE};
+use rustc_hir::def_id::{DefId, CRATE_DEF_ID, LOCAL_CRATE};
 use rustc_hir::PrimTy;
 use rustc_middle::bug;
 use rustc_middle::ty::DefIdTree;
@@ -1167,7 +1167,7 @@ impl<'a> Resolver<'a> {
                 }
                 Scope::ExternPrelude => {
                     suggestions.extend(this.extern_prelude.iter().filter_map(|(ident, _)| {
-                        let res = Res::Def(DefKind::Mod, DefId::local(CRATE_DEF_INDEX));
+                        let res = Res::Def(DefKind::Mod, CRATE_DEF_ID.to_def_id());
                         filter_fn(res).then_some(TypoSuggestion::typo_from_res(ident.name, res))
                     }));
                 }
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index 763f31622bc1f..1a98dd38fc97e 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -19,7 +19,7 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_errors::DiagnosticId;
 use rustc_hir::def::Namespace::{self, *};
 use rustc_hir::def::{self, CtorKind, DefKind, PartialRes, PerNS};
-use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX};
+use rustc_hir::def_id::{DefId, CRATE_DEF_ID};
 use rustc_hir::{PrimTy, TraitCandidate};
 use rustc_middle::{bug, span_bug};
 use rustc_session::lint;
@@ -2210,7 +2210,7 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
                 // trait to resolve.  In that case, we leave the `B`
                 // segment to be resolved by type-check.
                 return Ok(Some(PartialRes::with_unresolved_segments(
-                    Res::Def(DefKind::Mod, DefId::local(CRATE_DEF_INDEX)),
+                    Res::Def(DefKind::Mod, CRATE_DEF_ID.to_def_id()),
                     path.len(),
                 )));
             }
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index 0926f24ae70ef..17a9ef4b4db83 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -19,7 +19,7 @@ use rustc_errors::{
 use rustc_hir as hir;
 use rustc_hir::def::Namespace::{self, *};
 use rustc_hir::def::{self, CtorKind, CtorOf, DefKind};
-use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX, LOCAL_CRATE};
+use rustc_hir::def_id::{DefId, CRATE_DEF_ID, LOCAL_CRATE};
 use rustc_hir::PrimTy;
 use rustc_session::parse::feature_err;
 use rustc_span::edition::Edition;
@@ -351,7 +351,7 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
                 }
             })
             .collect::<Vec<_>>();
-        let crate_def_id = DefId::local(CRATE_DEF_INDEX);
+        let crate_def_id = CRATE_DEF_ID.to_def_id();
         if candidates.is_empty() && is_expected(Res::Def(DefKind::Enum, crate_def_id)) {
             let mut enum_candidates: Vec<_> = self
                 .r
@@ -1331,10 +1331,8 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
                             names.extend(extern_prelude.iter().flat_map(|(ident, _)| {
                                 self.r.crate_loader.maybe_process_path_extern(ident.name).and_then(
                                     |crate_id| {
-                                        let crate_mod = Res::Def(
-                                            DefKind::Mod,
-                                            DefId { krate: crate_id, index: CRATE_DEF_INDEX },
-                                        );
+                                        let crate_mod =
+                                            Res::Def(DefKind::Mod, crate_id.as_def_id());
 
                                         if filter_fn(crate_mod) {
                                             Some(TypoSuggestion::typo_from_res(
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index 0335c40d70d8c..5389cb19b58e4 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -37,7 +37,7 @@ use rustc_expand::base::{DeriveResolutions, SyntaxExtension, SyntaxExtensionKind
 use rustc_hir::def::Namespace::*;
 use rustc_hir::def::{self, CtorOf, DefKind, PartialRes};
 use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, DefPathHash, LocalDefId};
-use rustc_hir::def_id::{CRATE_DEF_ID, CRATE_DEF_INDEX, LOCAL_CRATE};
+use rustc_hir::def_id::{CRATE_DEF_ID, LOCAL_CRATE};
 use rustc_hir::definitions::{DefKey, DefPathData, Definitions};
 use rustc_hir::TraitCandidate;
 use rustc_index::vec::IndexVec;
@@ -755,7 +755,7 @@ impl<'a> NameBinding<'a> {
             NameBindingKind::Module(&ModuleData {
                 kind: ModuleKind::Def(DefKind::Mod, def_id, _),
                 ..
-            }) => def_id.index == CRATE_DEF_INDEX,
+            }) => def_id.is_crate_root(),
             _ => false,
         }
     }
@@ -1207,18 +1207,17 @@ impl<'a> Resolver<'a> {
         );
 
         let definitions = Definitions::new(session.local_stable_crate_id(), krate.spans.inner_span);
-        let root = definitions.get_root_def();
 
         let mut visibilities = FxHashMap::default();
         visibilities.insert(CRATE_DEF_ID, ty::Visibility::Public);
 
         let mut def_id_to_node_id = IndexVec::default();
-        assert_eq!(def_id_to_node_id.push(CRATE_NODE_ID), root);
+        assert_eq!(def_id_to_node_id.push(CRATE_NODE_ID), CRATE_DEF_ID);
         let mut node_id_to_def_id = FxHashMap::default();
-        node_id_to_def_id.insert(CRATE_NODE_ID, root);
+        node_id_to_def_id.insert(CRATE_NODE_ID, CRATE_DEF_ID);
 
         let mut invocation_parents = FxHashMap::default();
-        invocation_parents.insert(LocalExpnId::ROOT, (root, ImplTraitContext::Existential));
+        invocation_parents.insert(LocalExpnId::ROOT, (CRATE_DEF_ID, ImplTraitContext::Existential));
 
         let mut extern_prelude: FxHashMap<Ident, ExternPreludeEntry<'_>> = session
             .opts
diff --git a/compiler/rustc_span/src/def_id.rs b/compiler/rustc_span/src/def_id.rs
index 6d1b36796d869..d5f806308cf41 100644
--- a/compiler/rustc_span/src/def_id.rs
+++ b/compiler/rustc_span/src/def_id.rs
@@ -283,8 +283,19 @@ impl DefId {
         self.as_local().unwrap_or_else(|| panic!("DefId::expect_local: `{:?}` isn't local", self))
     }
 
+    #[inline]
+    pub fn is_crate_root(self) -> bool {
+        self.index == CRATE_DEF_INDEX
+    }
+
+    #[inline]
+    pub fn as_crate_root(self) -> Option<CrateNum> {
+        if self.is_crate_root() { Some(self.krate) } else { None }
+    }
+
+    #[inline]
     pub fn is_top_level_module(self) -> bool {
-        self.is_local() && self.index == CRATE_DEF_INDEX
+        self.is_local() && self.is_crate_root()
     }
 }
 
@@ -357,7 +368,7 @@ impl LocalDefId {
 
     #[inline]
     pub fn is_top_level_module(self) -> bool {
-        self.local_def_index == CRATE_DEF_INDEX
+        self == CRATE_DEF_ID
     }
 }
 
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index 21016afbf5f99..a070cef227252 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -15,7 +15,7 @@ use rustc_attr as attr;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, DefKind, Res};
-use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX, LOCAL_CRATE};
+use rustc_hir::def_id::{DefId, LOCAL_CRATE};
 use rustc_infer::infer::region_constraints::{Constraint, RegionConstraintData};
 use rustc_middle::middle::resolve_lifetime as rl;
 use rustc_middle::ty::fold::TypeFolder;
@@ -1975,7 +1975,7 @@ fn clean_extern_crate(
     // this is the ID of the `extern crate` statement
     let cnum = cx.tcx.extern_mod_stmt_cnum(krate.def_id).unwrap_or(LOCAL_CRATE);
     // this is the ID of the crate itself
-    let crate_def_id = DefId { krate: cnum, index: CRATE_DEF_INDEX };
+    let crate_def_id = cnum.as_def_id();
     let attrs = cx.tcx.hir().attrs(krate.hir_id());
     let ty_vis = cx.tcx.visibility(krate.def_id);
     let please_inline = ty_vis.is_public()
@@ -2094,7 +2094,7 @@ fn clean_use_statement(
     } else {
         if inline_attr.is_none() {
             if let Res::Def(DefKind::Mod, did) = path.res {
-                if !did.is_local() && did.index == CRATE_DEF_INDEX {
+                if !did.is_local() && did.is_crate_root() {
                     // if we're `pub use`ing an extern crate root, don't inline it unless we
                     // were specifically asked for it
                     denied = true;
diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index 4b473df155f58..e30bc6e0a97ee 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -20,7 +20,7 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::thin_vec::ThinVec;
 use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, DefKind, Res};
-use rustc_hir::def_id::{CrateNum, DefId, DefIndex, CRATE_DEF_INDEX, LOCAL_CRATE};
+use rustc_hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
 use rustc_hir::lang_items::LangItem;
 use rustc_hir::{BodyId, Mutability};
 use rustc_index::vec::IndexVec;
@@ -104,14 +104,6 @@ impl ItemId {
             ItemId::Primitive(_, krate) => krate,
         }
     }
-
-    #[inline]
-    crate fn index(self) -> Option<DefIndex> {
-        match self {
-            ItemId::DefId(id) => Some(id.index),
-            _ => None,
-        }
-    }
 }
 
 impl From<DefId> for ItemId {
@@ -160,7 +152,7 @@ impl ExternalCrate {
 
     #[inline]
     crate fn def_id(&self) -> DefId {
-        DefId { krate: self.crate_num, index: CRATE_DEF_INDEX }
+        self.crate_num.as_def_id()
     }
 
     crate fn src(&self, tcx: TyCtxt<'_>) -> FileName {
@@ -217,7 +209,7 @@ impl ExternalCrate {
 
         // Failing that, see if there's an attribute specifying where to find this
         // external crate
-        let did = DefId { krate: self.crate_num, index: CRATE_DEF_INDEX };
+        let did = self.crate_num.as_def_id();
         tcx.get_attrs(did)
             .lists(sym::doc)
             .filter(|a| a.has_name(sym::html_root_url))
@@ -559,7 +551,7 @@ impl Item {
     }
 
     crate fn is_crate(&self) -> bool {
-        self.is_mod() && self.item_id.as_def_id().map_or(false, |did| did.index == CRATE_DEF_INDEX)
+        self.is_mod() && self.item_id.as_def_id().map_or(false, |did| did.is_crate_root())
     }
     crate fn is_mod(&self) -> bool {
         self.type_() == ItemType::Module
diff --git a/src/librustdoc/formats/cache.rs b/src/librustdoc/formats/cache.rs
index e138e434c4e04..efd1a78a9d9a5 100644
--- a/src/librustdoc/formats/cache.rs
+++ b/src/librustdoc/formats/cache.rs
@@ -1,7 +1,7 @@
 use std::mem;
 
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_hir::def_id::{CrateNum, DefId, CRATE_DEF_INDEX};
+use rustc_hir::def_id::{CrateNum, DefId};
 use rustc_middle::middle::privacy::AccessLevels;
 use rustc_middle::ty::TyCtxt;
 use rustc_span::{sym, Symbol};
@@ -293,7 +293,7 @@ impl<'a, 'tcx> DocFolder for CacheBuilder<'a, 'tcx> {
                     // A crate has a module at its root, containing all items,
                     // which should not be indexed. The crate-item itself is
                     // inserted later on when serializing the search-index.
-                    if item.item_id.index().map_or(false, |idx| idx != CRATE_DEF_INDEX) {
+                    if item.item_id.as_def_id().map_or(false, |idx| !idx.is_crate_root()) {
                         let desc = item.doc_value().map_or_else(String::new, |x| {
                             short_markdown_summary(x.as_str(), &item.link_names(self.cache))
                         });
diff --git a/src/librustdoc/html/format.rs b/src/librustdoc/html/format.rs
index 55b0028180f66..6954e2363f5f0 100644
--- a/src/librustdoc/html/format.rs
+++ b/src/librustdoc/html/format.rs
@@ -18,7 +18,6 @@ use rustc_hir::def_id::DefId;
 use rustc_middle::ty;
 use rustc_middle::ty::DefIdTree;
 use rustc_middle::ty::TyCtxt;
-use rustc_span::def_id::CRATE_DEF_INDEX;
 use rustc_span::{sym, Symbol};
 use rustc_target::spec::abi::Abi;
 
@@ -1312,7 +1311,7 @@ impl clean::Visibility {
                 //                 visibility, so it shouldn't matter.
                 let parent_module = find_nearest_parent_module(cx.tcx(), item_did.expect_def_id());
 
-                if vis_did.index == CRATE_DEF_INDEX {
+                if vis_did.is_crate_root() {
                     "pub(crate) ".to_owned()
                 } else if parent_module == Some(vis_did) {
                     // `pub(in foo)` where `foo` is the parent module
@@ -1360,7 +1359,7 @@ impl clean::Visibility {
                 //                 visibility, so it shouldn't matter.
                 let parent_module = find_nearest_parent_module(tcx, item_did);
 
-                if vis_did.index == CRATE_DEF_INDEX {
+                if vis_did.is_crate_root() {
                     "pub(crate) ".to_owned()
                 } else if parent_module == Some(vis_did) {
                     // `pub(in foo)` where `foo` is the parent module
diff --git a/src/librustdoc/json/conversions.rs b/src/librustdoc/json/conversions.rs
index 0b5fb48059579..56b02cd848041 100644
--- a/src/librustdoc/json/conversions.rs
+++ b/src/librustdoc/json/conversions.rs
@@ -10,7 +10,6 @@ use std::fmt;
 use rustc_ast::ast;
 use rustc_hir::{def::CtorKind, def_id::DefId};
 use rustc_middle::ty::{self, TyCtxt};
-use rustc_span::def_id::CRATE_DEF_INDEX;
 use rustc_span::Pos;
 use rustc_target::spec::abi::Abi as RustcAbi;
 
@@ -83,7 +82,7 @@ impl JsonRenderer<'_> {
         match v {
             Public => Visibility::Public,
             Inherited => Visibility::Default,
-            Restricted(did) if did.index == CRATE_DEF_INDEX => Visibility::Crate,
+            Restricted(did) if did.is_crate_root() => Visibility::Crate,
             Restricted(did) => Visibility::Restricted {
                 parent: from_item_id(did.into()),
                 path: self.tcx.def_path(did).to_string_no_crate_verbose(),
diff --git a/src/librustdoc/visit_lib.rs b/src/librustdoc/visit_lib.rs
index 5bcec779bc0e7..9723cdbe3345f 100644
--- a/src/librustdoc/visit_lib.rs
+++ b/src/librustdoc/visit_lib.rs
@@ -1,6 +1,6 @@
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir::def::{DefKind, Res};
-use rustc_hir::def_id::{CrateNum, DefId, CRATE_DEF_INDEX};
+use rustc_hir::def_id::{CrateNum, DefId};
 use rustc_middle::middle::privacy::{AccessLevel, AccessLevels};
 use rustc_middle::ty::TyCtxt;
 
@@ -29,7 +29,7 @@ impl<'a, 'tcx> LibEmbargoVisitor<'a, 'tcx> {
     }
 
     crate fn visit_lib(&mut self, cnum: CrateNum) {
-        let did = DefId { krate: cnum, index: CRATE_DEF_INDEX };
+        let did = cnum.as_def_id();
         self.update(did, Some(AccessLevel::Public));
         self.visit_mod(did);
     }
diff --git a/src/tools/clippy/clippy_lints/src/missing_doc.rs b/src/tools/clippy/clippy_lints/src/missing_doc.rs
index fc0483a929a7a..5816a95dcebff 100644
--- a/src/tools/clippy/clippy_lints/src/missing_doc.rs
+++ b/src/tools/clippy/clippy_lints/src/missing_doc.rs
@@ -10,7 +10,7 @@ use clippy_utils::diagnostics::span_lint;
 use rustc_ast::ast;
 use rustc_hir as hir;
 use rustc_lint::{LateContext, LateLintPass, LintContext};
-use rustc_middle::ty;
+use rustc_middle::ty::{self, DefIdTree};
 use rustc_session::{declare_tool_lint, impl_lint_pass};
 use rustc_span::def_id::CRATE_DEF_ID;
 use rustc_span::source_map::Span;
@@ -114,8 +114,8 @@ impl<'tcx> LateLintPass<'tcx> for MissingDoc {
             hir::ItemKind::Fn(..) => {
                 // ignore main()
                 if it.ident.name == sym::main {
-                    let def_key = cx.tcx.hir().def_key(it.def_id);
-                    if def_key.parent == Some(hir::def_id::CRATE_DEF_INDEX) {
+                    let at_root = cx.tcx.local_parent(it.def_id) == Some(CRATE_DEF_ID);
+                    if at_root {
                         return;
                     }
                 }