Rewrite attribute handling

Basically, we switch to expanding cfg_attr in AST form, filter irrelevant attributes from the item tree, and move hir-def attributes (non-item-tree) to be flag-based.

The main motivation is memory usage, although this also simplifies the code, and fixes some bugs around handling of `cfg_attr`s.

crates/base-db/src/editioned_file_id.rs

@@ -0,0 +1,291 @@
+//! Defines [`EditionedFileId`], an interned wrapper around [`span::EditionedFileId`] that
+//! is interned (so queries can take it) and remembers its crate.
+
+use core::fmt;
+use std::hash::{Hash, Hasher};
+
+use span::Edition;
+use vfs::FileId;
+
+use crate::{Crate, RootQueryDb};
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
+pub struct EditionedFileId(
+    salsa::Id,
+    std::marker::PhantomData<&'static salsa::plumbing::interned::Value<EditionedFileId>>,
+);
+
+const _: () = {
+    use salsa::plumbing as zalsa_;
+    use zalsa_::interned as zalsa_struct_;
+    type Configuration_ = EditionedFileId;
+
+    #[derive(Debug, Clone, PartialEq, Eq)]
+    pub struct EditionedFileIdData {
+        editioned_file_id: span::EditionedFileId,
+        krate: Crate,
+    }
+
+    /// We like to include the origin crate in an `EditionedFileId` (for use in the item tree),
+    /// but this poses us a problem.
+    ///
+    /// Spans contain `EditionedFileId`s, and we don't want to make them store the crate too
+    /// because that will increase their size, which will increase memory usage significantly.
+    /// Furthermore, things using spans do not generally need the crate: they are using the
+    /// file id for queries like `ast_id_map` or `parse`, which do not care about the crate.
+    ///
+    /// To solve this, we hash **only the `span::EditionedFileId`**, but on still compare
+    /// the crate in equality check. This preserves the invariant of `Hash` and `Eq` -
+    /// although same hashes can be used for different items, same file ids used for multiple
+    /// crates is a rare thing, and different items always have different hashes. Then,
+    /// when we only have a `span::EditionedFileId`, we use the `intern()` method to
+    /// reuse existing file ids, and create new one only if needed. See [`from_span_guess_origin`].
+    ///
+    /// See this for more info: https://rust-lang.zulipchat.com/#narrow/channel/185405-t-compiler.2Frust-analyzer/topic/Letting.20EditionedFileId.20know.20its.20crate/near/530189401
+    ///
+    /// [`from_span_guess_origin`]: EditionedFileId::from_span_guess_origin
+    #[derive(Hash, PartialEq, Eq)]
+    struct WithoutCrate {
+        editioned_file_id: span::EditionedFileId,
+    }
+
+    impl Hash for EditionedFileIdData {
+        #[inline]
+        fn hash<H: Hasher>(&self, state: &mut H) {
+            let EditionedFileIdData { editioned_file_id, krate: _ } = *self;
+            editioned_file_id.hash(state);
+        }
+    }
+
+    impl zalsa_struct_::HashEqLike<WithoutCrate> for EditionedFileIdData {
+        #[inline]
+        fn hash<H: Hasher>(&self, state: &mut H) {
+            Hash::hash(self, state);
+        }
+
+        #[inline]
+        fn eq(&self, data: &WithoutCrate) -> bool {
+            let EditionedFileIdData { editioned_file_id, krate: _ } = *self;
+            editioned_file_id == data.editioned_file_id
+        }
+    }
+
+    impl zalsa_::HasJar for EditionedFileId {
+        type Jar = zalsa_struct_::JarImpl<EditionedFileId>;
+        const KIND: zalsa_::JarKind = zalsa_::JarKind::Struct;
+    }
+
+    zalsa_::register_jar! {
+        zalsa_::ErasedJar::erase::<EditionedFileId>()
+    }
+
+    impl zalsa_struct_::Configuration for EditionedFileId {
+        const LOCATION: salsa::plumbing::Location =
+            salsa::plumbing::Location { file: file!(), line: line!() };
+        const DEBUG_NAME: &'static str = "EditionedFileId";
+        const REVISIONS: std::num::NonZeroUsize = std::num::NonZeroUsize::MAX;
+        const PERSIST: bool = false;
+
+        type Fields<'a> = EditionedFileIdData;
+        type Struct<'db> = EditionedFileId;
+
+        fn serialize<S>(_: &Self::Fields<'_>, _: S) -> Result<S::Ok, S::Error>
+        where
+            S: zalsa_::serde::Serializer,
+        {
+            unimplemented!("attempted to serialize value that set `PERSIST` to false")
+        }
+
+        fn deserialize<'de, D>(_: D) -> Result<Self::Fields<'static>, D::Error>
+        where
+            D: zalsa_::serde::Deserializer<'de>,
+        {
+            unimplemented!("attempted to deserialize value that cannot set `PERSIST` to false");
+        }
+    }
+
+    impl Configuration_ {
+        pub fn ingredient(zalsa: &zalsa_::Zalsa) -> &zalsa_struct_::IngredientImpl<Self> {
+            static CACHE: zalsa_::IngredientCache<zalsa_struct_::IngredientImpl<EditionedFileId>> =
+                zalsa_::IngredientCache::new();
+
+            // SAFETY: `lookup_jar_by_type` returns a valid ingredient index, and the only
+            // ingredient created by our jar is the struct ingredient.
+            unsafe {
+                CACHE.get_or_create(zalsa, || {
+                    zalsa.lookup_jar_by_type::<zalsa_struct_::JarImpl<EditionedFileId>>()
+                })
+            }
+        }
+    }
+
+    impl zalsa_::AsId for EditionedFileId {
+        fn as_id(&self) -> salsa::Id {
+            self.0.as_id()
+        }
+    }
+    impl zalsa_::FromId for EditionedFileId {
+        fn from_id(id: salsa::Id) -> Self {
+            Self(<salsa::Id>::from_id(id), std::marker::PhantomData)
+        }
+    }
+
+    unsafe impl Send for EditionedFileId {}
+    unsafe impl Sync for EditionedFileId {}
+
+    impl std::fmt::Debug for EditionedFileId {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            Self::default_debug_fmt(*self, f)
+        }
+    }
+
+    impl zalsa_::SalsaStructInDb for EditionedFileId {
+        type MemoIngredientMap = salsa::plumbing::MemoIngredientSingletonIndex;
+
+        fn lookup_ingredient_index(aux: &zalsa_::Zalsa) -> salsa::plumbing::IngredientIndices {
+            aux.lookup_jar_by_type::<zalsa_struct_::JarImpl<EditionedFileId>>().into()
+        }
+
+        fn entries(zalsa: &zalsa_::Zalsa) -> impl Iterator<Item = zalsa_::DatabaseKeyIndex> + '_ {
+            let _ingredient_index =
+                zalsa.lookup_jar_by_type::<zalsa_struct_::JarImpl<EditionedFileId>>();
+            <EditionedFileId>::ingredient(zalsa).entries(zalsa).map(|entry| entry.key())
+        }
+
+        #[inline]
+        fn cast(id: salsa::Id, type_id: std::any::TypeId) -> Option<Self> {
+            if type_id == std::any::TypeId::of::<EditionedFileId>() {
+                Some(<Self as salsa::plumbing::FromId>::from_id(id))
+            } else {
+                None
+            }
+        }
+
+        #[inline]
+        unsafe fn memo_table(
+            zalsa: &zalsa_::Zalsa,
+            id: zalsa_::Id,
+            current_revision: zalsa_::Revision,
+        ) -> zalsa_::MemoTableWithTypes<'_> {
+            // SAFETY: Guaranteed by caller.
+            unsafe {
+                zalsa.table().memos::<zalsa_struct_::Value<EditionedFileId>>(id, current_revision)
+            }
+        }
+    }
+
+    unsafe impl zalsa_::Update for EditionedFileId {
+        unsafe fn maybe_update(old_pointer: *mut Self, new_value: Self) -> bool {
+            if unsafe { *old_pointer } != new_value {
+                unsafe { *old_pointer = new_value };
+                true
+            } else {
+                false
+            }
+        }
+    }
+
+    impl EditionedFileId {
+        pub fn from_span(
+            db: &(impl salsa::Database + ?Sized),
+            editioned_file_id: span::EditionedFileId,
+            krate: Crate,
+        ) -> Self {
+            let (zalsa, zalsa_local) = db.zalsas();
+            Configuration_::ingredient(zalsa).intern(
+                zalsa,
+                zalsa_local,
+                EditionedFileIdData { editioned_file_id, krate },
+                |_, data| data,
+            )
+        }
+
+        /// Guesses the crate for the file.
+        ///
+        /// Only use this if you cannot precisely determine the origin. This can happen in one of two cases:
+        ///
+        ///  1. The file is not in the module tree.
+        ///  2. You are latency sensitive and cannot afford calling the def map to precisely compute the origin
+        ///     (e.g. on enter feature, folding, etc.).
+        pub fn from_span_guess_origin(
+            db: &dyn RootQueryDb,
+            editioned_file_id: span::EditionedFileId,
+        ) -> Self {
+            let (zalsa, zalsa_local) = db.zalsas();
+            Configuration_::ingredient(zalsa).intern(
+                zalsa,
+                zalsa_local,
+                WithoutCrate { editioned_file_id },
+                |_, _| {
+                    // FileId not in the database.
+                    let krate = db
+                        .relevant_crates(editioned_file_id.file_id())
+                        .first()
+                        .copied()
+                        .unwrap_or_else(|| db.all_crates()[0]);
+                    EditionedFileIdData { editioned_file_id, krate }
+                },
+            )
+        }
+
+        pub fn editioned_file_id(self, db: &dyn salsa::Database) -> span::EditionedFileId {
+            let zalsa = db.zalsa();
+            let fields = Configuration_::ingredient(zalsa).fields(zalsa, self);
+            fields.editioned_file_id
+        }
+
+        pub fn krate(self, db: &dyn salsa::Database) -> Crate {
+            let zalsa = db.zalsa();
+            let fields = Configuration_::ingredient(zalsa).fields(zalsa, self);
+            fields.krate
+        }
+
+        /// Default debug formatting for this struct (may be useful if you define your own `Debug` impl)
+        pub fn default_debug_fmt(this: Self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            zalsa_::with_attached_database(|db| {
+                let zalsa = db.zalsa();
+                let fields = Configuration_::ingredient(zalsa).fields(zalsa, this);
+                fmt::Debug::fmt(fields, f)
+            })
+            .unwrap_or_else(|| {
+                f.debug_tuple("EditionedFileId").field(&zalsa_::AsId::as_id(&this)).finish()
+            })
+        }
+    }
+};
+
+impl EditionedFileId {
+    #[inline]
+    pub fn new(db: &dyn salsa::Database, file_id: FileId, edition: Edition, krate: Crate) -> Self {
+        EditionedFileId::from_span(db, span::EditionedFileId::new(file_id, edition), krate)
+    }
+
+    /// Attaches the current edition and guesses the crate for the file.
+    ///
+    /// Only use this if you cannot precisely determine the origin. This can happen in one of two cases:
+    ///
+    ///  1. The file is not in the module tree.
+    ///  2. You are latency sensitive and cannot afford calling the def map to precisely compute the origin
+    ///     (e.g. on enter feature, folding, etc.).
+    #[inline]
+    pub fn current_edition_guess_origin(db: &dyn RootQueryDb, file_id: FileId) -> Self {
+        Self::from_span_guess_origin(db, span::EditionedFileId::current_edition(file_id))
+    }
+
+    #[inline]
+    pub fn file_id(self, db: &dyn salsa::Database) -> vfs::FileId {
+        let id = self.editioned_file_id(db);
+        id.file_id()
+    }
+
+    #[inline]
+    pub fn unpack(self, db: &dyn salsa::Database) -> (vfs::FileId, span::Edition) {
+        let id = self.editioned_file_id(db);
+        (id.file_id(), id.edition())
+    }
+
+    #[inline]
+    pub fn edition(self, db: &dyn salsa::Database) -> Edition {
+        self.editioned_file_id(db).edition()
+    }
+}

crates/base-db/src/input.rs

@@ -829,9 +829,10 @@ pub(crate) fn transitive_rev_deps(db: &dyn RootQueryDb, of: Crate) -> FxHashSet<
     rev_deps
 }
 
-impl BuiltCrateData {
-    pub fn root_file_id(&self, db: &dyn salsa::Database) -> EditionedFileId {
-        EditionedFileId::new(db, self.root_file_id, self.edition)
+impl Crate {
+    pub fn root_file_id(self, db: &dyn salsa::Database) -> EditionedFileId {
+        let data = self.data(db);
+        EditionedFileId::new(db, data.root_file_id, data.edition, self)
     }
 }
 

crates/base-db/src/lib.rs

@@ -5,6 +5,7 @@ pub use salsa_macros;
 
 // FIXME: Rename this crate, base db is non descriptive
 mod change;
+mod editioned_file_id;
 mod input;
 pub mod target;
 
@@ -17,6 +18,7 @@ use std::{
 
 pub use crate::{
     change::FileChange,
+    editioned_file_id::EditionedFileId,
     input::{
         BuiltCrateData, BuiltDependency, Crate, CrateBuilder, CrateBuilderId, CrateDataBuilder,
         CrateDisplayName, CrateGraphBuilder, CrateName, CrateOrigin, CratesIdMap, CratesMap,
@@ -29,7 +31,6 @@ pub use query_group::{self};
 use rustc_hash::{FxHashSet, FxHasher};
 use salsa::{Durability, Setter};
 pub use semver::{BuildMetadata, Prerelease, Version, VersionReq};
-use span::Edition;
 use syntax::{Parse, SyntaxError, ast};
 use triomphe::Arc;
 pub use vfs::{AnchoredPath, AnchoredPathBuf, FileId, VfsPath, file_set::FileSet};
@@ -175,42 +176,6 @@ impl Files {
     }
 }
 
-#[salsa_macros::interned(no_lifetime, debug, constructor=from_span, revisions = usize::MAX)]
-#[derive(PartialOrd, Ord)]
-pub struct EditionedFileId {
-    pub editioned_file_id: span::EditionedFileId,
-}
-
-impl EditionedFileId {
-    // Salsa already uses the name `new`...
-    #[inline]
-    pub fn new(db: &dyn salsa::Database, file_id: FileId, edition: Edition) -> Self {
-        EditionedFileId::from_span(db, span::EditionedFileId::new(file_id, edition))
-    }
-
-    #[inline]
-    pub fn current_edition(db: &dyn salsa::Database, file_id: FileId) -> Self {
-        EditionedFileId::new(db, file_id, Edition::CURRENT)
-    }
-
-    #[inline]
-    pub fn file_id(self, db: &dyn salsa::Database) -> vfs::FileId {
-        let id = self.editioned_file_id(db);
-        id.file_id()
-    }
-
-    #[inline]
-    pub fn unpack(self, db: &dyn salsa::Database) -> (vfs::FileId, span::Edition) {
-        let id = self.editioned_file_id(db);
-        (id.file_id(), id.edition())
-    }
-
-    #[inline]
-    pub fn edition(self, db: &dyn SourceDatabase) -> Edition {
-        self.editioned_file_id(db).edition()
-    }
-}
-
 #[salsa_macros::input(debug)]
 pub struct FileText {
     #[returns(ref)]