Replace once_cell with std's recently stabilized OnceCell/Lock and LazyCell/Lock

This doesn't get rid of the once_cell dependency, unfortunately, since we have dependencies that use it, but it's a nice to do cleanup. And when our deps will eventually get rid of once_cell we will get rid of it for free.

Author: ChayimFriedman2

Cargo.lock

@@ -23,7 +23,6 @@ fst = { version = "0.4.7", default-features = false }
 indexmap.workspace = true
 itertools.workspace = true
 la-arena.workspace = true
-once_cell = "1.17.0"
 rustc-hash.workspace = true
 tracing.workspace = true
 smallvec.workspace = true

crates/hir-def/Cargo.toml

@@ -12,7 +12,6 @@ use hir_expand::{
 };
 use intern::Interned;
 use la_arena::{Arena, RawIdx};
-use once_cell::unsync::Lazy;
 use stdx::impl_from;
 use syntax::ast::{self, HasGenericParams, HasName, HasTypeBounds};
 use triomphe::Arc;
@@ -394,11 +393,16 @@ impl GenericParams {
 
                     // Don't create an `Expander` if not needed since this
                     // could cause a reparse after the `ItemTree` has been created due to the spanmap.
-                    let mut expander = Lazy::new(|| {
-                        (module.def_map(db), Expander::new(db, loc.id.file_id(), module))
-                    });
+                    let mut expander = None;
                     for param in func_data.params.iter() {
-                        generic_params.fill_implicit_impl_trait_args(db, &mut expander, param);
+                        generic_params.fill_implicit_impl_trait_args(
+                            db,
+                            &mut expander,
+                            &mut || {
+                                (module.def_map(db), Expander::new(db, loc.id.file_id(), module))
+                            },
+                            param,
+                        );
                     }
                     Interned::new(generic_params.finish())
                 }
@@ -597,7 +601,9 @@ impl GenericParamsCollector {
     fn fill_implicit_impl_trait_args(
         &mut self,
         db: &dyn DefDatabase,
-        exp: &mut Lazy<(Arc<DefMap>, Expander), impl FnOnce() -> (Arc<DefMap>, Expander)>,
+        // FIXME: Change this back to `LazyCell` if https://github.com/rust-lang/libs-team/issues/429 is accepted.
+        exp: &mut Option<(Arc<DefMap>, Expander)>,
+        exp_fill: &mut dyn FnMut() -> (Arc<DefMap>, Expander),
         type_ref: &TypeRef,
     ) {
         type_ref.walk(&mut |type_ref| {
@@ -617,7 +623,7 @@ impl GenericParamsCollector {
             }
             if let TypeRef::Macro(mc) = type_ref {
                 let macro_call = mc.to_node(db.upcast());
-                let (def_map, expander) = &mut **exp;
+                let (def_map, expander) = exp.get_or_insert_with(&mut *exp_fill);
 
                 let module = expander.module.local_id;
                 let resolver = |path: &_| {
@@ -637,8 +643,8 @@ impl GenericParamsCollector {
                 {
                     let ctx = expander.ctx(db);
                     let type_ref = TypeRef::from_ast(&ctx, expanded.tree());
-                    self.fill_implicit_impl_trait_args(db, &mut *exp, &type_ref);
-                    exp.1.exit(mark);
+                    self.fill_implicit_impl_trait_args(db, &mut *exp, exp_fill, &type_ref);
+                    exp.get_or_insert_with(&mut *exp_fill).1.exit(mark);
                 }
             }
         });

crates/hir-def/src/generics.rs

@@ -1,12 +1,13 @@
 //! Describes items defined or visible (ie, imported) in a certain scope.
 //! This is shared between modules and blocks.
 
+use std::sync::LazyLock;
+
 use base_db::CrateId;
 use hir_expand::{attrs::AttrId, db::ExpandDatabase, name::Name, AstId, MacroCallId};
 use indexmap::map::Entry;
 use itertools::Itertools;
 use la_arena::Idx;
-use once_cell::sync::Lazy;
 use rustc_hash::{FxHashMap, FxHashSet};
 use smallvec::{smallvec, SmallVec};
 use stdx::format_to;
@@ -129,7 +130,7 @@ struct DeriveMacroInvocation {
     derive_call_ids: SmallVec<[Option<MacroCallId>; 1]>,
 }
 
-pub(crate) static BUILTIN_SCOPE: Lazy<FxIndexMap<Name, PerNs>> = Lazy::new(|| {
+pub(crate) static BUILTIN_SCOPE: LazyLock<FxIndexMap<Name, PerNs>> = LazyLock::new(|| {
     BuiltinType::all_builtin_types()
         .iter()
         .map(|(name, ty)| (name.clone(), PerNs::types((*ty).into(), Visibility::Public, None)))

crates/hir-def/src/item_scope.rs

@@ -40,6 +40,7 @@ use std::{
     fmt::{self, Debug},
     hash::{Hash, Hasher},
     ops::{Index, Range},
+    sync::OnceLock,
 };
 
 use ast::{AstNode, StructKind};
@@ -48,7 +49,6 @@ use either::Either;
 use hir_expand::{attrs::RawAttrs, name::Name, ExpandTo, HirFileId, InFile};
 use intern::{Interned, Symbol};
 use la_arena::{Arena, Idx, RawIdx};
-use once_cell::sync::OnceCell;
 use rustc_hash::FxHashMap;
 use smallvec::SmallVec;
 use span::{AstIdNode, FileAstId, SyntaxContextId};
@@ -101,7 +101,7 @@ pub struct ItemTree {
 impl ItemTree {
     pub(crate) fn file_item_tree_query(db: &dyn DefDatabase, file_id: HirFileId) -> Arc<ItemTree> {
         let _p = tracing::info_span!("file_item_tree_query", ?file_id).entered();
-        static EMPTY: OnceCell<Arc<ItemTree>> = OnceCell::new();
+        static EMPTY: OnceLock<Arc<ItemTree>> = OnceLock::new();
 
         let syntax = db.parse_or_expand(file_id);
 
@@ -152,7 +152,7 @@ impl ItemTree {
 
     pub(crate) fn block_item_tree_query(db: &dyn DefDatabase, block: BlockId) -> Arc<ItemTree> {
         let _p = tracing::info_span!("block_item_tree_query", ?block).entered();
-        static EMPTY: OnceCell<Arc<ItemTree>> = OnceCell::new();
+        static EMPTY: OnceLock<Arc<ItemTree>> = OnceLock::new();
 
         let loc = block.lookup(db);
         let block = loc.ast_id.to_node(db.upcast());
@@ -626,9 +626,9 @@ impl Index<RawVisibilityId> for ItemTree {
     type Output = RawVisibility;
     fn index(&self, index: RawVisibilityId) -> &Self::Output {
         static VIS_PUB: RawVisibility = RawVisibility::Public;
-        static VIS_PRIV_IMPLICIT: OnceCell<RawVisibility> = OnceCell::new();
-        static VIS_PRIV_EXPLICIT: OnceCell<RawVisibility> = OnceCell::new();
-        static VIS_PUB_CRATE: OnceCell<RawVisibility> = OnceCell::new();
+        static VIS_PRIV_IMPLICIT: OnceLock<RawVisibility> = OnceLock::new();
+        static VIS_PRIV_EXPLICIT: OnceLock<RawVisibility> = OnceLock::new();
+        static VIS_PUB_CRATE: OnceLock<RawVisibility> = OnceLock::new();
 
         match index {
             RawVisibilityId::PRIV_IMPLICIT => VIS_PRIV_IMPLICIT.get_or_init(|| {

crates/hir-def/src/item_tree.rs

@@ -29,7 +29,6 @@ chalk-ir.workspace = true
 chalk-recursive.workspace = true
 chalk-derive.workspace = true
 la-arena.workspace = true
-once_cell = "1.17.0"
 triomphe.workspace = true
 nohash-hasher.workspace = true
 typed-arena = "2.0.1"

crates/hir-ty/Cargo.toml

@@ -1,10 +1,10 @@
 //! Interface with `rustc_pattern_analysis`.
 
+use std::cell::LazyCell;
 use std::fmt;
 
 use hir_def::{DefWithBodyId, EnumId, EnumVariantId, HasModule, LocalFieldId, ModuleId, VariantId};
 use intern::sym;
-use once_cell::unsync::Lazy;
 use rustc_pattern_analysis::{
     constructor::{Constructor, ConstructorSet, VariantVisibility},
     usefulness::{compute_match_usefulness, PlaceValidity, UsefulnessReport},
@@ -388,8 +388,9 @@ impl<'db> PatCx for MatchCheckCtx<'db> {
                         let variant = Self::variant_id_for_adt(self.db, ctor, adt).unwrap();
 
                         // Whether we must not match the fields of this variant exhaustively.
-                        let is_non_exhaustive = Lazy::new(|| self.is_foreign_non_exhaustive(adt));
-                        let visibilities = Lazy::new(|| self.db.field_visibilities(variant));
+                        let is_non_exhaustive =
+                            LazyCell::new(|| self.is_foreign_non_exhaustive(adt));
+                        let visibilities = LazyCell::new(|| self.db.field_visibilities(variant));
 
                         self.list_variant_fields(ty, variant)
                             .map(move |(fid, ty)| {

crates/hir-ty/src/diagnostics/match_check/pat_analysis.rs

@@ -22,7 +22,7 @@ mod pat;
 mod path;
 pub(crate) mod unify;
 
-use std::{convert::identity, iter, ops::Index};
+use std::{cell::OnceCell, convert::identity, iter, ops::Index};
 
 use chalk_ir::{
     cast::Cast,
@@ -50,7 +50,6 @@ use hir_expand::name::Name;
 use indexmap::IndexSet;
 use intern::sym;
 use la_arena::{ArenaMap, Entry};
-use once_cell::unsync::OnceCell;
 use rustc_hash::{FxHashMap, FxHashSet};
 use stdx::{always, never};
 use triomphe::Arc;

crates/hir-ty/src/infer.rs

@@ -6,7 +6,7 @@
 //!
 //! This usually involves resolving names, collecting generic arguments etc.
 use std::{
-    cell::{Cell, RefCell, RefMut},
+    cell::{Cell, OnceCell, RefCell, RefMut},
     iter,
     ops::{self, Not as _},
 };
@@ -43,7 +43,6 @@ use hir_def::{
 use hir_expand::{name::Name, ExpandResult};
 use intern::Interned;
 use la_arena::{Arena, ArenaMap};
-use once_cell::unsync::OnceCell;
 use rustc_hash::FxHashSet;
 use rustc_pattern_analysis::Captures;
 use smallvec::SmallVec;

crates/hir-ty/src/lower.rs

@@ -11,6 +11,7 @@ mod simple;
 mod traits;
 
 use std::env;
+use std::sync::LazyLock;
 
 use base_db::SourceDatabaseFileInputExt as _;
 use expect_test::Expect;
@@ -24,7 +25,6 @@ use hir_def::{
     AssocItemId, DefWithBodyId, HasModule, LocalModuleId, Lookup, ModuleDefId,
 };
 use hir_expand::{db::ExpandDatabase, FileRange, InFile};
-use once_cell::race::OnceBool;
 use rustc_hash::FxHashMap;
 use stdx::format_to;
 use syntax::{
@@ -49,8 +49,8 @@ use crate::{
 // `env UPDATE_EXPECT=1 cargo test -p hir_ty` to update the snapshots.
 
 fn setup_tracing() -> Option<tracing::subscriber::DefaultGuard> {
-    static ENABLE: OnceBool = OnceBool::new();
-    if !ENABLE.get_or_init(|| env::var("CHALK_DEBUG").is_ok()) {
+    static ENABLE: LazyLock<bool> = LazyLock::new(|| env::var("CHALK_DEBUG").is_ok());
+    if !*ENABLE {
         return None;
     }