Turn transitive dependencies into a query

crates/base-db/src/input.rs

@@ -460,6 +460,32 @@ pub struct Crate {
     pub env: Env,
 }
 
+#[salsa::tracked]
+impl Crate {
+    /// Returns an iterator over all transitive dependencies of the given crate,
+    /// including the crate itself.
+    ///
+    /// **Warning**: do not use this query in `hir-*` crates! It kills incrementality across crate metadata modifications.
+    #[salsa::tracked(returns(deref))]
+    pub fn transitive_deps(self, db: &dyn salsa::Database) -> Box<[Crate]> {
+        // There is a bit of duplication here and in `CrateGraphBuilder` in the same method, but it's not terrible
+        // and removing that is a bit difficult.
+        let mut worklist = vec![self];
+        let mut deps_seen = FxHashSet::default();
+        let mut deps = Vec::new();
+
+        while let Some(krate) = worklist.pop() {
+            if !deps_seen.insert(krate) {
+                continue;
+            }
+            deps.push(krate);
+
+            worklist.extend(krate.data(db).dependencies.iter().map(|dep| dep.crate_id));
+        }
+        deps.into_boxed_slice()
+    }
+}
+
 /// The mapping from [`UniqueCrateData`] to their [`Crate`] input.
 #[derive(Debug, Default)]
 pub struct CratesMap(DashMap<UniqueCrateData, Crate, BuildHasherDefault<FxHasher>>);

crates/base-db/src/lib.rs

@@ -257,13 +257,6 @@ pub trait RootQueryDb: SourceDatabase + salsa::Database {
     #[salsa::input]
     fn all_crates(&self) -> Arc<Box<[Crate]>>;
 
-    /// Returns an iterator over all transitive dependencies of the given crate,
-    /// including the crate itself.
-    ///
-    /// **Warning**: do not use this query in `hir-*` crates! It kills incrementality across crate metadata modifications.
-    #[salsa::transparent]
-    fn transitive_deps(&self, crate_id: Crate) -> FxHashSet<Crate>;
-
     /// Returns all transitive reverse dependencies of the given crate,
     /// including the crate itself.
     ///
@@ -273,23 +266,6 @@ pub trait RootQueryDb: SourceDatabase + salsa::Database {
     fn transitive_rev_deps(&self, of: Crate) -> FxHashSet<Crate>;
 }
 
-fn transitive_deps(db: &dyn SourceDatabase, crate_id: Crate) -> FxHashSet<Crate> {
-    // There is a bit of duplication here and in `CrateGraphBuilder` in the same method, but it's not terrible
-    // and removing that is a bit difficult.
-    let mut worklist = vec![crate_id];
-    let mut deps = FxHashSet::default();
-
-    while let Some(krate) = worklist.pop() {
-        if !deps.insert(krate) {
-            continue;
-        }
-
-        worklist.extend(krate.data(db).dependencies.iter().map(|dep| dep.crate_id));
-    }
-
-    deps
-}
-
 #[salsa_macros::db]
 pub trait SourceDatabase: salsa::Database {
     /// Text of the file.

crates/hir-def/src/db.rs

@@ -273,10 +273,9 @@ pub trait DefDatabase: InternDatabase + ExpandDatabase + SourceDatabase {
 
     // endregion:visibilities
 
-    #[salsa::invoke(crate::lang_item::notable_traits_in_deps)]
-    fn notable_traits_in_deps(&self, krate: Crate) -> Arc<[Arc<[TraitId]>]>;
     #[salsa::invoke(crate::lang_item::crate_notable_traits)]
-    fn crate_notable_traits(&self, krate: Crate) -> Option<Arc<[TraitId]>>;
+    #[salsa::transparent]
+    fn crate_notable_traits(&self, krate: Crate) -> Option<&[TraitId]>;
 
     #[salsa::invoke(crate_supports_no_std)]
     fn crate_supports_no_std(&self, crate_id: Crate) -> bool;

crates/hir-def/src/lang_item.rs

@@ -5,7 +5,6 @@
 use hir_expand::name::Name;
 use intern::{Symbol, sym};
 use rustc_hash::FxHashMap;
-use triomphe::Arc;
 
 use crate::{
     AdtId, AssocItemId, AttrDefId, Crate, EnumId, EnumVariantId, FunctionId, ImplId, ModuleDefId,
@@ -223,16 +222,8 @@ pub(crate) fn lang_attr(db: &dyn DefDatabase, item: AttrDefId) -> Option<LangIte
     db.attrs(item).lang_item()
 }
 
-pub(crate) fn notable_traits_in_deps(db: &dyn DefDatabase, krate: Crate) -> Arc<[Arc<[TraitId]>]> {
-    let _p = tracing::info_span!("notable_traits_in_deps", ?krate).entered();
-    Arc::from_iter(
-        db.transitive_deps(krate).into_iter().filter_map(|krate| db.crate_notable_traits(krate)),
-    )
-}
-
-pub(crate) fn crate_notable_traits(db: &dyn DefDatabase, krate: Crate) -> Option<Arc<[TraitId]>> {
-    let _p = tracing::info_span!("crate_notable_traits", ?krate).entered();
-
+#[salsa::tracked(returns(as_deref))]
+pub(crate) fn crate_notable_traits(db: &dyn DefDatabase, krate: Crate) -> Option<Box<[TraitId]>> {
     let mut traits = Vec::new();
 
     let crate_def_map = crate_def_map(db, krate);

crates/hir-ty/src/drop.rs

@@ -28,10 +28,10 @@ fn has_destructor(db: &dyn HirDatabase, adt: AdtId) -> bool {
     };
     let impls = match module.containing_block() {
         Some(block) => match TraitImpls::for_block(db, block) {
-            Some(it) => it,
+            Some(it) => &**it,
             None => return false,
         },
-        None => &**TraitImpls::for_crate(db, module.krate()),
+        None => TraitImpls::for_crate(db, module.krate()),
     };
     !impls.for_trait_and_self_ty(drop_trait, &SimplifiedType::Adt(adt.into())).is_empty()
 }

crates/hir-ty/src/method_resolution.rs

@@ -687,7 +687,7 @@ impl TraitImpls {
 
     #[salsa::tracked(returns(ref))]
     pub fn for_crate_and_deps(db: &dyn HirDatabase, krate: Crate) -> Box<[Arc<Self>]> {
-        db.transitive_deps(krate).iter().map(|&dep| Self::for_crate(db, dep).clone()).collect()
+        krate.transitive_deps(db).iter().map(|&dep| Self::for_crate(db, dep).clone()).collect()
     }
 }
 

crates/hir-ty/src/tests/incremental.rs

@@ -613,6 +613,7 @@ fn main() {
                 "impl_signature_with_source_map_shim",
                 "callable_item_signature_shim",
                 "TraitImpls::for_crate_and_deps_",
+                "Crate::transitive_deps_",
                 "TraitImpls::for_crate_",
                 "impl_trait_with_diagnostics_shim",
                 "impl_self_ty_with_diagnostics_shim",

crates/hir/src/lib.rs

@@ -250,6 +250,14 @@ impl Crate {
         db.transitive_rev_deps(self.id).into_iter().map(|id| Crate { id })
     }
 
+    pub fn notable_traits_in_deps(self, db: &dyn HirDatabase) -> impl Iterator<Item = &TraitId> {
+        self.id
+            .transitive_deps(db)
+            .into_iter()
+            .filter_map(|&krate| db.crate_notable_traits(krate))
+            .flatten()
+    }
+
     pub fn root_module(self) -> Module {
         Module { id: CrateRootModuleId::from(self.id).into() }
     }

crates/ide/src/hover.rs

@@ -8,7 +8,6 @@ use std::{iter, ops::Not};
 use either::Either;
 use hir::{
     DisplayTarget, GenericDef, GenericSubstitution, HasCrate, HasSource, LangItem, Semantics,
-    db::DefDatabase,
 };
 use ide_db::{
     FileRange, FxIndexSet, MiniCore, Ranker, RootDatabase,
@@ -522,9 +521,8 @@ fn notable_traits<'db>(
         return Vec::new();
     }
 
-    db.notable_traits_in_deps(ty.krate(db).into())
-        .iter()
-        .flat_map(|it| &**it)
+    ty.krate(db)
+        .notable_traits_in_deps(db)
         .filter_map(move |&trait_| {
             let trait_ = trait_.into();
             ty.impls_trait(db, trait_, &[]).then(|| {