Split out hir-def attribute handling parts into hir-expand

36 files changed, 435 insertions, 382 deletions

diff --git a/Cargo.lock b/Cargo.lock
index d27ae416f04..5f426d88562 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -519,6 +519,7 @@ dependencies = [
  "hkalbasi-rustc-ap-rustc_abi",
  "hkalbasi-rustc-ap-rustc_index",
  "indexmap",
+ "intern",
  "itertools",
  "la-arena",
  "limit",
@@ -544,6 +545,7 @@ dependencies = [
  "either",
  "expect-test",
  "hashbrown",
+ "intern",
  "itertools",
  "la-arena",
  "limit",
@@ -574,6 +576,7 @@ dependencies = [
  "hir-def",
  "hir-expand",
  "hkalbasi-rustc-ap-rustc_index",
+ "intern",
  "itertools",
  "la-arena",
  "limit",
@@ -804,6 +807,16 @@ dependencies = [
 ]
 
 [[package]]
+name = "intern"
+version = "0.0.0"
+dependencies = [
+ "dashmap",
+ "hashbrown",
+ "once_cell",
+ "rustc-hash",
+]
+
+[[package]]
 name = "itertools"
 version = "0.10.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
diff --git a/crates/hir-def/Cargo.toml b/crates/hir-def/Cargo.toml
index 698be76656c..a1078427707 100644
--- a/crates/hir-def/Cargo.toml
+++ b/crates/hir-def/Cargo.toml
@@ -29,6 +29,7 @@ smallvec = "1.10.0"
 tracing = "0.1.35"
 
 stdx = { path = "../stdx", version = "0.0.0" }
+intern = { path = "../intern", version = "0.0.0" }
 base-db = { path = "../base-db", version = "0.0.0" }
 syntax = { path = "../syntax", version = "0.0.0" }
 profile = { path = "../profile", version = "0.0.0" }
diff --git a/crates/hir-def/src/adt.rs b/crates/hir-def/src/adt.rs
index db3b4194881..cd35ba00f6f 100644
--- a/crates/hir-def/src/adt.rs
+++ b/crates/hir-def/src/adt.rs
@@ -8,6 +8,7 @@ use hir_expand::{
     name::{AsName, Name},
     HirFileId, InFile,
 };
+use intern::Interned;
 use la_arena::{Arena, ArenaMap};
 use rustc_abi::{Integer, IntegerType};
 use syntax::ast::{self, HasName, HasVisibility};
@@ -17,7 +18,6 @@ use crate::{
     body::{CfgExpander, LowerCtx},
     builtin_type::{BuiltinInt, BuiltinUint},
     db::DefDatabase,
-    intern::Interned,
     item_tree::{AttrOwner, Field, FieldAstId, Fields, ItemTree, ModItem, RawVisibilityId},
     layout::{Align, ReprFlags, ReprOptions},
     nameres::diagnostics::DefDiagnostic,
diff --git a/crates/hir-def/src/attr.rs b/crates/hir-def/src/attr.rs
index ab5d180e1bb..eb88a74e448 100644
--- a/crates/hir-def/src/attr.rs
+++ b/crates/hir-def/src/attr.rs
@@ -1,27 +1,27 @@
 //! A higher level attributes based on TokenTree, with also some shortcuts.
 
-use std::{fmt, hash::Hash, ops, sync::Arc};
+use std::{hash::Hash, ops, sync::Arc};
 
 use base_db::CrateId;
 use cfg::{CfgExpr, CfgOptions};
 use either::Either;
-use hir_expand::{hygiene::Hygiene, name::AsName, HirFileId, InFile};
+use hir_expand::{
+    attrs::{collect_attrs, Attr, AttrId, RawAttrs},
+    HirFileId, InFile,
+};
 use itertools::Itertools;
 use la_arena::{ArenaMap, Idx, RawIdx};
-use mbe::{syntax_node_to_token_tree, DelimiterKind, Punct};
-use smallvec::{smallvec, SmallVec};
+use mbe::DelimiterKind;
 use syntax::{
-    ast::{self, AstNode, HasAttrs, IsString},
-    match_ast, AstPtr, AstToken, SmolStr, SyntaxNode, TextRange, TextSize,
+    ast::{self, HasAttrs, IsString},
+    AstPtr, AstToken, SmolStr, TextRange, TextSize,
 };
 use tt::Subtree;
 
 use crate::{
     db::DefDatabase,
-    intern::Interned,
     item_tree::{AttrOwner, Fields, ItemTreeId, ItemTreeNode},
     nameres::{ModuleOrigin, ModuleSource},
-    path::{ModPath, PathKind},
     src::{HasChildSource, HasSource},
     AdtId, AttrDefId, EnumId, GenericParamId, LocalEnumVariantId, LocalFieldId, Lookup, MacroId,
     VariantId,
@@ -47,12 +47,6 @@ impl From<Documentation> for String {
     }
 }
 
-/// Syntactical attributes, without filtering of `cfg_attr`s.
-#[derive(Default, Debug, Clone, PartialEq, Eq)]
-pub(crate) struct RawAttrs {
-    entries: Option<Arc<[Attr]>>,
-}
-
 #[derive(Default, Debug, Clone, PartialEq, Eq)]
 pub struct Attrs(RawAttrs);
 
@@ -62,30 +56,21 @@ pub struct AttrsWithOwner {
     owner: AttrDefId,
 }
 
-impl ops::Deref for RawAttrs {
-    type Target = [Attr];
-
-    fn deref(&self) -> &[Attr] {
-        match &self.entries {
-            Some(it) => &*it,
-            None => &[],
-        }
-    }
-}
 impl Attrs {
     pub fn get(&self, id: AttrId) -> Option<&Attr> {
         (**self).iter().find(|attr| attr.id == id)
     }
+
+    pub(crate) fn filter(db: &dyn DefDatabase, krate: CrateId, raw_attrs: RawAttrs) -> Attrs {
+        Attrs(raw_attrs.filter(db.upcast(), krate))
+    }
 }
 
 impl ops::Deref for Attrs {
     type Target = [Attr];
 
     fn deref(&self) -> &[Attr] {
-        match &self.0.entries {
-            Some(it) => &*it,
-            None => &[],
-        }
+        &self.0
     }
 }
 
@@ -97,114 +82,6 @@ impl ops::Deref for AttrsWithOwner {
     }
 }
 
-impl RawAttrs {
-    pub(crate) const EMPTY: Self = Self { entries: None };
-
-    pub(crate) fn new(db: &dyn DefDatabase, owner: &dyn ast::HasAttrs, hygiene: &Hygiene) -> Self {
-        let entries = collect_attrs(owner)
-            .filter_map(|(id, attr)| match attr {
-                Either::Left(attr) => {
-                    attr.meta().and_then(|meta| Attr::from_src(db, meta, hygiene, id))
-                }
-                Either::Right(comment) => comment.doc_comment().map(|doc| Attr {
-                    id,
-                    input: Some(Interned::new(AttrInput::Literal(SmolStr::new(doc)))),
-                    path: Interned::new(ModPath::from(hir_expand::name!(doc))),
-                }),
-            })
-            .collect::<Arc<_>>();
-
-        Self { entries: if entries.is_empty() { None } else { Some(entries) } }
-    }
-
-    fn from_attrs_owner(db: &dyn DefDatabase, owner: InFile<&dyn ast::HasAttrs>) -> Self {
-        let hygiene = Hygiene::new(db.upcast(), owner.file_id);
-        Self::new(db, owner.value, &hygiene)
-    }
-
-    pub(crate) fn merge(&self, other: Self) -> Self {
-        // FIXME: This needs to fixup `AttrId`s
-        match (&self.entries, other.entries) {
-            (None, None) => Self::EMPTY,
-            (None, entries @ Some(_)) => Self { entries },
-            (Some(entries), None) => Self { entries: Some(entries.clone()) },
-            (Some(a), Some(b)) => {
-                let last_ast_index = a.last().map_or(0, |it| it.id.ast_index + 1);
-                Self {
-                    entries: Some(
-                        a.iter()
-                            .cloned()
-                            .chain(b.iter().map(|it| {
-                                let mut it = it.clone();
-                                it.id.ast_index += last_ast_index;
-                                it
-                            }))
-                            .collect(),
-                    ),
-                }
-            }
-        }
-    }
-
-    /// Processes `cfg_attr`s, returning the resulting semantic `Attrs`.
-    pub(crate) fn filter(self, db: &dyn DefDatabase, krate: CrateId) -> Attrs {
-        let has_cfg_attrs = self.iter().any(|attr| {
-            attr.path.as_ident().map_or(false, |name| *name == hir_expand::name![cfg_attr])
-        });
-        if !has_cfg_attrs {
-            return Attrs(self);
-        }
-
-        let crate_graph = db.crate_graph();
-        let new_attrs = self
-            .iter()
-            .flat_map(|attr| -> SmallVec<[_; 1]> {
-                let is_cfg_attr =
-                    attr.path.as_ident().map_or(false, |name| *name == hir_expand::name![cfg_attr]);
-                if !is_cfg_attr {
-                    return smallvec![attr.clone()];
-                }
-
-                let subtree = match attr.token_tree_value() {
-                    Some(it) => it,
-                    _ => return smallvec![attr.clone()],
-                };
-
-                // Input subtree is: `(cfg, $(attr),+)`
-                // Split it up into a `cfg` subtree and the `attr` subtrees.
-                // FIXME: There should be a common API for this.
-                let mut parts = subtree.token_trees.split(|tt| {
-                    matches!(tt, tt::TokenTree::Leaf(tt::Leaf::Punct(Punct { char: ',', .. })))
-                });
-                let cfg = match parts.next() {
-                    Some(it) => it,
-                    None => return smallvec![],
-                };
-                let cfg = Subtree { delimiter: subtree.delimiter, token_trees: cfg.to_vec() };
-                let cfg = CfgExpr::parse(&cfg);
-                let index = attr.id;
-                let attrs = parts.filter(|a| !a.is_empty()).filter_map(|attr| {
-                    let tree = Subtree { delimiter: None, token_trees: attr.to_vec() };
-                    // FIXME hygiene
-                    let hygiene = Hygiene::new_unhygienic();
-                    Attr::from_tt(db, &tree, &hygiene, index)
-                });
-
-                let cfg_options = &crate_graph[krate].cfg_options;
-                if cfg_options.check(&cfg) == Some(false) {
-                    smallvec![]
-                } else {
-                    cov_mark::hit!(cfg_attr_active);
-
-                    attrs.collect()
-                }
-            })
-            .collect();
-
-        Attrs(RawAttrs { entries: Some(new_attrs) })
-    }
-}
-
 impl Attrs {
     pub const EMPTY: Self = Self(RawAttrs::EMPTY);
 
@@ -403,7 +280,7 @@ impl AttrsWithOwner {
                         .raw_attrs(AttrOwner::ModItem(definition_tree_id.value.into()))
                         .clone(),
                     ModuleOrigin::BlockExpr { block } => RawAttrs::from_attrs_owner(
-                        db,
+                        db.upcast(),
                         InFile::new(block.file_id, block.to_node(db.upcast()))
                             .as_ref()
                             .map(|it| it as &dyn ast::HasAttrs),
@@ -439,7 +316,7 @@ impl AttrsWithOwner {
                 GenericParamId::ConstParamId(it) => {
                     let src = it.parent().child_source(db);
                     RawAttrs::from_attrs_owner(
-                        db,
+                        db.upcast(),
                         src.with_value(src.value[it.local_id()].as_ref().either(
                             |it| match it {
                                 ast::TypeOrConstParam::Type(it) => it as _,
@@ -452,7 +329,7 @@ impl AttrsWithOwner {
                 GenericParamId::TypeParamId(it) => {
                     let src = it.parent().child_source(db);
                     RawAttrs::from_attrs_owner(
-                        db,
+                        db.upcast(),
                         src.with_value(src.value[it.local_id()].as_ref().either(
                             |it| match it {
                                 ast::TypeOrConstParam::Type(it) => it as _,
@@ -464,14 +341,14 @@ impl AttrsWithOwner {
                 }
                 GenericParamId::LifetimeParamId(it) => {
                     let src = it.parent.child_source(db);
-                    RawAttrs::from_attrs_owner(db, src.with_value(&src.value[it.local_id]))
+                    RawAttrs::from_attrs_owner(db.upcast(), src.with_value(&src.value[it.local_id]))
                 }
             },
             AttrDefId::ExternBlockId(it) => attrs_from_item_tree(it.lookup(db).id, db),
         };
 
-        let attrs = raw_attrs.filter(db, def.krate(db));
-        Self { attrs, owner: def }
+        let attrs = raw_attrs.filter(db.upcast(), def.krate(db));
+        Self { attrs: Attrs(attrs), owner: def }
     }
 
     pub fn source_map(&self, db: &dyn DefDatabase) -> AttrSourceMap {
@@ -627,40 +504,6 @@ fn doc_indent(attrs: &Attrs) -> usize {
         .unwrap_or(0)
 }
 
-fn inner_attributes(
-    syntax: &SyntaxNode,
-) -> Option<impl Iterator<Item = Either<ast::Attr, ast::Comment>>> {
-    let node = match_ast! {
-        match syntax {
-            ast::SourceFile(_) => syntax.clone(),
-            ast::ExternBlock(it) => it.extern_item_list()?.syntax().clone(),
-            ast::Fn(it) => it.body()?.stmt_list()?.syntax().clone(),
-            ast::Impl(it) => it.assoc_item_list()?.syntax().clone(),
-            ast::Module(it) => it.item_list()?.syntax().clone(),
-            ast::BlockExpr(it) => {
-                use syntax::SyntaxKind::{BLOCK_EXPR , EXPR_STMT};
-                // Block expressions accept outer and inner attributes, but only when they are the outer
-                // expression of an expression statement or the final expression of another block expression.
-                let may_carry_attributes = matches!(
-                    it.syntax().parent().map(|it| it.kind()),
-                     Some(BLOCK_EXPR | EXPR_STMT)
-                );
-                if !may_carry_attributes {
-                    return None
-                }
-                syntax.clone()
-            },
-            _ => return None,
-        }
-    };
-
-    let attrs = ast::AttrDocCommentIter::from_syntax_node(&node).filter(|el| match el {
-        Either::Left(attr) => attr.kind().is_inner(),
-        Either::Right(comment) => comment.is_inner(),
-    });
-    Some(attrs)
-}
-
 #[derive(Debug)]
 pub struct AttrSourceMap {
     source: Vec<Either<ast::Attr, ast::Comment>>,
@@ -779,128 +622,6 @@ fn get_doc_string_in_attr(it: &ast::Attr) -> Option<ast::String> {
     }
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub struct AttrId {
-    pub(crate) ast_index: u32,
-}
-
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub struct Attr {
-    pub(crate) id: AttrId,
-    pub(crate) path: Interned<ModPath>,
-    pub(crate) input: Option<Interned<AttrInput>>,
-}
-
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub enum AttrInput {
-    /// `#[attr = "string"]`
-    Literal(SmolStr),
-    /// `#[attr(subtree)]`
-    TokenTree(tt::Subtree, mbe::TokenMap),
-}
-
-impl fmt::Display for AttrInput {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self {
-            AttrInput::Literal(lit) => write!(f, " = \"{}\"", lit.escape_debug()),
-            AttrInput::TokenTree(subtree, _) => subtree.fmt(f),
-        }
-    }
-}
-
-impl Attr {
-    fn from_src(
-        db: &dyn DefDatabase,
-        ast: ast::Meta,
-        hygiene: &Hygiene,
-        id: AttrId,
-    ) -> Option<Attr> {
-        let path = Interned::new(ModPath::from_src(db.upcast(), ast.path()?, hygiene)?);
-        let input = if let Some(ast::Expr::Literal(lit)) = ast.expr() {
-            let value = match lit.kind() {
-                ast::LiteralKind::String(string) => string.value()?.into(),
-                _ => lit.syntax().first_token()?.text().trim_matches('"').into(),
-            };
-            Some(Interned::new(AttrInput::Literal(value)))
-        } else if let Some(tt) = ast.token_tree() {
-            let (tree, map) = syntax_node_to_token_tree(tt.syntax());
-            Some(Interned::new(AttrInput::TokenTree(tree, map)))
-        } else {
-            None
-        };
-        Some(Attr { id, path, input })
-    }
-
-    fn from_tt(
-        db: &dyn DefDatabase,
-        tt: &tt::Subtree,
-        hygiene: &Hygiene,
-        id: AttrId,
-    ) -> Option<Attr> {
-        let (parse, _) = mbe::token_tree_to_syntax_node(tt, mbe::TopEntryPoint::MetaItem);
-        let ast = ast::Meta::cast(parse.syntax_node())?;
-
-        Self::from_src(db, ast, hygiene, id)
-    }
-
-    pub fn path(&self) -> &ModPath {
-        &self.path
-    }
-}
-
-impl Attr {
-    /// #[path = "string"]
-    pub fn string_value(&self) -> Option<&SmolStr> {
-        match self.input.as_deref()? {
-            AttrInput::Literal(it) => Some(it),
-            _ => None,
-        }
-    }
-
-    /// #[path(ident)]
-    pub fn single_ident_value(&self) -> Option<&tt::Ident> {
-        match self.input.as_deref()? {
-            AttrInput::TokenTree(subtree, _) => match &*subtree.token_trees {
-                [tt::TokenTree::Leaf(tt::Leaf::Ident(ident))] => Some(ident),
-                _ => None,
-            },
-            _ => None,
-        }
-    }
-
-    /// #[path TokenTree]
-    pub fn token_tree_value(&self) -> Option<&Subtree> {
-        match self.input.as_deref()? {
-            AttrInput::TokenTree(subtree, _) => Some(subtree),
-            _ => None,
-        }
-    }
-
-    /// Parses this attribute as a token tree consisting of comma separated paths.
-    pub fn parse_path_comma_token_tree(&self) -> Option<impl Iterator<Item = ModPath> + '_> {
-        let args = self.token_tree_value()?;
-
-        if args.delimiter_kind() != Some(DelimiterKind::Parenthesis) {
-            return None;
-        }
-        let paths = args
-            .token_trees
-            .split(|tt| matches!(tt, tt::TokenTree::Leaf(tt::Leaf::Punct(Punct { char: ',', .. }))))
-            .filter_map(|tts| {
-                if tts.is_empty() {
-                    return None;
-                }
-                let segments = tts.iter().filter_map(|tt| match tt {
-                    tt::TokenTree::Leaf(tt::Leaf::Ident(id)) => Some(id.as_name()),
-                    _ => None,
-                });
-                Some(ModPath::from_segments(PathKind::Plain, segments))
-            });
-
-        Some(paths)
-    }
-}
-
 #[derive(Debug, Clone, Copy)]
 pub struct AttrQuery<'attr> {
     attrs: &'attr Attrs,
@@ -953,21 +674,6 @@ fn attrs_from_item_tree<N: ItemTreeNode>(id: ItemTreeId<N>, db: &dyn DefDatabase
     tree.raw_attrs(mod_item.into()).clone()
 }
 
-fn collect_attrs(
-    owner: &dyn ast::HasAttrs,
-) -> impl Iterator<Item = (AttrId, Either<ast::Attr, ast::Comment>)> {
-    let inner_attrs = inner_attributes(owner.syntax()).into_iter().flatten();
-    let outer_attrs =
-        ast::AttrDocCommentIter::from_syntax_node(owner.syntax()).filter(|el| match el {
-            Either::Left(attr) => attr.kind().is_outer(),
-            Either::Right(comment) => comment.is_outer(),
-        });
-    outer_attrs
-        .chain(inner_attrs)
-        .enumerate()
-        .map(|(id, attr)| (AttrId { ast_index: id as u32 }, attr))
-}
-
 pub(crate) fn variants_attrs_source_map(
     db: &dyn DefDatabase,
     def: EnumId,
diff --git a/crates/hir-def/src/body.rs b/crates/hir-def/src/body.rs
index 78fbaa9d7d3..9713256813e 100644
--- a/crates/hir-def/src/body.rs
+++ b/crates/hir-def/src/body.rs
@@ -12,7 +12,9 @@ use base_db::CrateId;
 use cfg::{CfgExpr, CfgOptions};
 use drop_bomb::DropBomb;
 use either::Either;
-use hir_expand::{hygiene::Hygiene, ExpandError, ExpandResult, HirFileId, InFile, MacroCallId};
+use hir_expand::{
+    attrs::RawAttrs, hygiene::Hygiene, ExpandError, ExpandResult, HirFileId, InFile, MacroCallId,
+};
 use la_arena::{Arena, ArenaMap};
 use limit::Limit;
 use profile::Count;
@@ -20,7 +22,7 @@ use rustc_hash::FxHashMap;
 use syntax::{ast, AstPtr, SyntaxNodePtr};
 
 use crate::{
-    attr::{Attrs, RawAttrs},
+    attr::Attrs,
     db::DefDatabase,
     expr::{dummy_expr_id, Expr, ExprId, Label, LabelId, Pat, PatId},
     item_scope::BuiltinShadowMode,
@@ -64,7 +66,7 @@ impl CfgExpander {
     }
 
     pub(crate) fn parse_attrs(&self, db: &dyn DefDatabase, owner: &dyn ast::HasAttrs) -> Attrs {
-        RawAttrs::new(db, owner, &self.hygiene).filter(db, self.krate)
+        Attrs::filter(db, self.krate, RawAttrs::new(db.upcast(), owner, &self.hygiene))
     }
 
     pub(crate) fn is_cfg_enabled(&self, db: &dyn DefDatabase, owner: &dyn ast::HasAttrs) -> bool {
diff --git a/crates/hir-def/src/body/lower.rs b/crates/hir-def/src/body/lower.rs
index e8da24e3add..4c29e16b2b8 100644
--- a/crates/hir-def/src/body/lower.rs
+++ b/crates/hir-def/src/body/lower.rs
@@ -10,6 +10,7 @@ use hir_expand::{
     name::{name, AsName, Name},
     AstId, ExpandError, HirFileId, InFile,
 };
+use intern::Interned;
 use la_arena::Arena;
 use once_cell::unsync::OnceCell;
 use profile::Count;
@@ -33,7 +34,6 @@ use crate::{
         Label, LabelId, Literal, MatchArm, Movability, Pat, PatId, RecordFieldPat, RecordLitField,
         Statement,
     },
-    intern::Interned,
     item_scope::BuiltinShadowMode,
     path::{GenericArgs, Path},
     type_ref::{Mutability, Rawness, TypeRef},
diff --git a/crates/hir-def/src/data.rs b/crates/hir-def/src/data.rs
index e6b05f27a54..f461e85b018 100644
--- a/crates/hir-def/src/data.rs
+++ b/crates/hir-def/src/data.rs
@@ -3,6 +3,7 @@
 use std::sync::Arc;
 
 use hir_expand::{name::Name, AstId, ExpandResult, HirFileId, InFile, MacroCallId, MacroDefKind};
+use intern::Interned;
 use smallvec::SmallVec;
 use syntax::ast;
 
@@ -10,7 +11,6 @@ use crate::{
     attr::Attrs,
     body::{Expander, Mark},
     db::DefDatabase,
-    intern::Interned,
     item_tree::{self, AssocItem, FnFlags, ItemTree, ItemTreeId, ModItem, Param, TreeId},
     nameres::{
         attr_resolution::ResolvedAttr,
diff --git a/crates/hir-def/src/db.rs b/crates/hir-def/src/db.rs
index 431c8255497..65cdd1b69b1 100644
--- a/crates/hir-def/src/db.rs
+++ b/crates/hir-def/src/db.rs
@@ -4,6 +4,7 @@ use std::sync::Arc;
 use base_db::{salsa, CrateId, SourceDatabase, Upcast};
 use either::Either;
 use hir_expand::{db::AstDatabase, HirFileId};
+use intern::Interned;
 use la_arena::ArenaMap;
 use syntax::{ast, AstPtr, SmolStr};
 
@@ -17,7 +18,6 @@ use crate::{
     },
     generics::GenericParams,
     import_map::ImportMap,
-    intern::Interned,
     item_tree::{AttrOwner, ItemTree},
     lang_item::{LangItemTarget, LangItems},
     nameres::{diagnostics::DefDiagnostic, DefMap},
diff --git a/crates/hir-def/src/expr.rs b/crates/hir-def/src/expr.rs
index 7b656942119..48028b7c6a8 100644
--- a/crates/hir-def/src/expr.rs
+++ b/crates/hir-def/src/expr.rs
@@ -15,11 +15,11 @@
 use std::fmt;
 
 use hir_expand::name::Name;
+use intern::Interned;
 use la_arena::{Idx, RawIdx};
 
 use crate::{
     builtin_type::{BuiltinFloat, BuiltinInt, BuiltinUint},
-    intern::Interned,
     path::{GenericArgs, Path},
     type_ref::{Mutability, Rawness, TypeRef},
     BlockId,
diff --git a/crates/hir-def/src/generics.rs b/crates/hir-def/src/generics.rs
index f74559f5d66..b2ab0c30e03 100644
--- a/crates/hir-def/src/generics.rs
+++ b/crates/hir-def/src/generics.rs
@@ -9,6 +9,7 @@ use hir_expand::{
     name::{AsName, Name},
     ExpandResult, HirFileId, InFile,
 };
+use intern::Interned;
 use la_arena::{Arena, ArenaMap, Idx};
 use once_cell::unsync::Lazy;
 use std::ops::DerefMut;
@@ -20,7 +21,6 @@ use crate::{
     child_by_source::ChildBySource,
     db::DefDatabase,
     dyn_map::DynMap,
-    intern::Interned,
     keys,
     src::{HasChildSource, HasSource},
     type_ref::{LifetimeRef, TypeBound, TypeRef},
diff --git a/crates/hir-def/src/item_scope.rs b/crates/hir-def/src/item_scope.rs
index c7b213b7e98..53a4173ff42 100644
--- a/crates/hir-def/src/item_scope.rs
+++ b/crates/hir-def/src/item_scope.rs
@@ -4,7 +4,7 @@
 use std::collections::hash_map::Entry;
 
 use base_db::CrateId;
-use hir_expand::{name::Name, AstId, MacroCallId};
+use hir_expand::{attrs::AttrId, name::Name, AstId, MacroCallId};
 use itertools::Itertools;
 use once_cell::sync::Lazy;
 use profile::Count;
@@ -14,8 +14,8 @@ use stdx::format_to;
 use syntax::ast;
 
 use crate::{
-    attr::AttrId, db::DefDatabase, per_ns::PerNs, visibility::Visibility, AdtId, BuiltinType,
-    ConstId, HasModule, ImplId, LocalModuleId, MacroId, ModuleDefId, ModuleId, TraitId,
+    db::DefDatabase, per_ns::PerNs, visibility::Visibility, AdtId, BuiltinType, ConstId, HasModule,
+    ImplId, LocalModuleId, MacroId, ModuleDefId, ModuleId, TraitId,
 };
 
 #[derive(Copy, Clone, Debug)]
diff --git a/crates/hir-def/src/item_tree.rs b/crates/hir-def/src/item_tree.rs
index 80297f8adf1..3e1f7d44460 100644
--- a/crates/hir-def/src/item_tree.rs
+++ b/crates/hir-def/src/item_tree.rs
@@ -48,10 +48,12 @@ use base_db::CrateId;
 use either::Either;
 use hir_expand::{
     ast_id_map::FileAstId,
+    attrs::RawAttrs,
     hygiene::Hygiene,
     name::{name, AsName, Name},
     ExpandTo, HirFileId, InFile,
 };
+use intern::Interned;
 use la_arena::{Arena, Idx, IdxRange, RawIdx};
 use profile::Count;
 use rustc_hash::FxHashMap;
@@ -60,10 +62,9 @@ use stdx::never;
 use syntax::{ast, match_ast, SyntaxKind};
 
 use crate::{
-    attr::{Attrs, RawAttrs},
+    attr::Attrs,
     db::DefDatabase,
     generics::GenericParams,
-    intern::Interned,
     path::{path, AssociatedTypeBinding, GenericArgs, ImportAlias, ModPath, Path, PathKind},
     type_ref::{Mutability, TraitRef, TypeBound, TypeRef},
     visibility::RawVisibility,
@@ -120,7 +121,7 @@ impl ItemTree {
         let mut item_tree = match_ast! {
             match syntax {
                 ast::SourceFile(file) => {
-                    top_attrs = Some(RawAttrs::new(db, &file, ctx.hygiene()));
+                    top_attrs = Some(RawAttrs::new(db.upcast(), &file, ctx.hygiene()));
                     ctx.lower_module_items(&file)
                 },
                 ast::MacroItems(items) => {
@@ -152,7 +153,11 @@ impl ItemTree {
 
     /// Returns the inner attributes of the source file.
     pub fn top_level_attrs(&self, db: &dyn DefDatabase, krate: CrateId) -> Attrs {
-        self.attrs.get(&AttrOwner::TopLevel).unwrap_or(&RawAttrs::EMPTY).clone().filter(db, krate)
+        Attrs::filter(
+            db,
+            krate,
+            self.attrs.get(&AttrOwner::TopLevel).unwrap_or(&RawAttrs::EMPTY).clone(),
+        )
     }
 
     pub(crate) fn raw_attrs(&self, of: AttrOwner) -> &RawAttrs {
@@ -160,7 +165,7 @@ impl ItemTree {
     }
 
     pub(crate) fn attrs(&self, db: &dyn DefDatabase, krate: CrateId, of: AttrOwner) -> Attrs {
-        self.raw_attrs(of).clone().filter(db, krate)
+        Attrs::filter(db, krate, self.raw_attrs(of).clone())
     }
 
     pub fn pretty_print(&self) -> String {
diff --git a/crates/hir-def/src/item_tree/lower.rs b/crates/hir-def/src/item_tree/lower.rs
index b25274bccc9..27705cbbbdc 100644
--- a/crates/hir-def/src/item_tree/lower.rs
+++ b/crates/hir-def/src/item_tree/lower.rs
@@ -99,7 +99,7 @@ impl<'a> Ctx<'a> {
     }
 
     fn lower_mod_item(&mut self, item: &ast::Item) -> Option<ModItem> {
-        let attrs = RawAttrs::new(self.db, item, self.hygiene());
+        let attrs = RawAttrs::new(self.db.upcast(), item, self.hygiene());
         let item: ModItem = match item {
             ast::Item::Struct(ast) => self.lower_struct(ast)?.into(),
             ast::Item::Union(ast) => self.lower_union(ast)?.into(),
@@ -173,7 +173,7 @@ impl<'a> Ctx<'a> {
         for field in fields.fields() {
             if let Some(data) = self.lower_record_field(&field) {
                 let idx = self.data().fields.alloc(data);
-                self.add_attrs(idx.into(), RawAttrs::new(self.db, &field, self.hygiene()));
+                self.add_attrs(idx.into(), RawAttrs::new(self.db.upcast(), &field, self.hygiene()));
             }
         }
         let end = self.next_field_idx();
@@ -194,7 +194,7 @@ impl<'a> Ctx<'a> {
         for (i, field) in fields.fields().enumerate() {
             let data = self.lower_tuple_field(i, &field);
             let idx = self.data().fields.alloc(data);
-            self.add_attrs(idx.into(), RawAttrs::new(self.db, &field, self.hygiene()));
+            self.add_attrs(idx.into(), RawAttrs::new(self.db.upcast(), &field, self.hygiene()));
         }
         let end = self.next_field_idx();
         IdxRange::new(start..end)
@@ -239,7 +239,10 @@ impl<'a> Ctx<'a> {
         for variant in variants.variants() {
             if let Some(data) = self.lower_variant(&variant) {
                 let idx = self.data().variants.alloc(data);
-                self.add_attrs(idx.into(), RawAttrs::new(self.db, &variant, self.hygiene()));
+                self.add_attrs(
+                    idx.into(),
+                    RawAttrs::new(self.db.upcast(), &variant, self.hygiene()),
+                );
             }
         }
         let end = self.next_variant_idx();
@@ -283,7 +286,10 @@ impl<'a> Ctx<'a> {
                 };
                 let ty = Interned::new(self_type);
                 let idx = self.data().params.alloc(Param::Normal(None, ty));
-                self.add_attrs(idx.into(), RawAttrs::new(self.db, &self_param, self.hygiene()));
+                self.add_attrs(
+                    idx.into(),
+                    RawAttrs::new(self.db.upcast(), &self_param, self.hygiene()),
+                );
                 has_self_param = true;
             }
             for param in param_list.params() {
@@ -307,7 +313,7 @@ impl<'a> Ctx<'a> {
                         self.data().params.alloc(Param::Normal(name, ty))
                     }
                 };
-                self.add_attrs(idx.into(), RawAttrs::new(self.db, &param, self.hygiene()));
+                self.add_attrs(idx.into(), RawAttrs::new(self.db.upcast(), &param, self.hygiene()));
             }
         }
         let end_param = self.next_param_idx();
@@ -442,7 +448,7 @@ impl<'a> Ctx<'a> {
         let items = trait_def.assoc_item_list().map(|list| {
             list.assoc_items()
                 .filter_map(|item| {
-                    let attrs = RawAttrs::new(self.db, &item, self.hygiene());
+                    let attrs = RawAttrs::new(self.db.upcast(), &item, self.hygiene());
                     self.lower_assoc_item(&item).map(|item| {
                         self.add_attrs(ModItem::from(item).into(), attrs);
                         item
@@ -471,7 +477,7 @@ impl<'a> Ctx<'a> {
             .flat_map(|it| it.assoc_items())
             .filter_map(|item| {
                 let assoc = self.lower_assoc_item(&item)?;
-                let attrs = RawAttrs::new(self.db, &item, self.hygiene());
+                let attrs = RawAttrs::new(self.db.upcast(), &item, self.hygiene());
                 self.add_attrs(ModItem::from(assoc).into(), attrs);
                 Some(assoc)
             })
@@ -541,7 +547,7 @@ impl<'a> Ctx<'a> {
                     // (in other words, the knowledge that they're in an extern block must not be used).
                     // This is because an extern block can contain macros whose ItemTree's top-level items
                     // should be considered to be in an extern block too.
-                    let attrs = RawAttrs::new(self.db, &item, self.hygiene());
+                    let attrs = RawAttrs::new(self.db.upcast(), &item, self.hygiene());
                     let id: ModItem = match item {
                         ast::ExternItem::Fn(ast) => self.lower_function(&ast)?.into(),
                         ast::ExternItem::Static(ast) => self.lower_static(&ast)?.into(),
diff --git a/crates/hir-def/src/item_tree/pretty.rs b/crates/hir-def/src/item_tree/pretty.rs
index 48c40df22ff..8f230b87d01 100644
--- a/crates/hir-def/src/item_tree/pretty.rs
+++ b/crates/hir-def/src/item_tree/pretty.rs
@@ -3,7 +3,6 @@
 use std::fmt::{self, Write};
 
 use crate::{
-    attr::RawAttrs,
     generics::{TypeOrConstParamData, WherePredicate, WherePredicateTypeTarget},
     pretty::{print_path, print_type_bounds, print_type_ref},
     visibility::RawVisibility,
diff --git a/crates/hir-def/src/keys.rs b/crates/hir-def/src/keys.rs
index c5cb9a2af53..72beec8186c 100644
--- a/crates/hir-def/src/keys.rs
+++ b/crates/hir-def/src/keys.rs
@@ -2,12 +2,11 @@
 
 use std::marker::PhantomData;
 
-use hir_expand::MacroCallId;
+use hir_expand::{attrs::AttrId, MacroCallId};
 use rustc_hash::FxHashMap;
 use syntax::{ast, AstNode, AstPtr};
 
 use crate::{
-    attr::AttrId,
     dyn_map::{DynMap, Policy},
     ConstId, EnumId, EnumVariantId, FieldId, FunctionId, ImplId, LifetimeParamId, Macro2Id,
     MacroRulesId, ProcMacroId, StaticId, StructId, TraitId, TypeAliasId, TypeOrConstParamId,
diff --git a/crates/hir-def/src/lib.rs b/crates/hir-def/src/lib.rs
index 8267ef09cb0..cc0ea14d015 100644
--- a/crates/hir-def/src/lib.rs
+++ b/crates/hir-def/src/lib.rs
@@ -28,7 +28,6 @@ pub mod dyn_map;
 pub mod keys;
 
 pub mod item_tree;
-pub mod intern;
 
 pub mod adt;
 pub mod data;
@@ -61,10 +60,10 @@ use std::{
     sync::Arc,
 };
 
-use attr::Attr;
 use base_db::{impl_intern_key, salsa, CrateId, ProcMacroKind};
 use hir_expand::{
     ast_id_map::FileAstId,
+    attrs::{Attr, AttrId, AttrInput},
     builtin_attr_macro::BuiltinAttrExpander,
     builtin_derive_macro::BuiltinDeriveExpander,
     builtin_fn_macro::{BuiltinFnLikeExpander, EagerExpander},
@@ -82,7 +81,6 @@ use syntax::ast;
 
 use crate::{
     adt::VariantData,
-    attr::AttrId,
     builtin_type::BuiltinType,
     item_tree::{
         Const, Enum, Function, Impl, ItemTreeId, ItemTreeNode, MacroDef, MacroRules, ModItem,
@@ -971,7 +969,7 @@ fn attr_macro_as_call_id(
     is_derive: bool,
 ) -> MacroCallId {
     let mut arg = match macro_attr.input.as_deref() {
-        Some(attr::AttrInput::TokenTree(tt, map)) => (tt.clone(), map.clone()),
+        Some(AttrInput::TokenTree(tt, map)) => (tt.clone(), map.clone()),
         _ => Default::default(),
     };
 
@@ -990,3 +988,10 @@ fn attr_macro_as_call_id(
     );
     res
 }
+intern::impl_internable!(
+    crate::type_ref::TypeRef,
+    crate::type_ref::TraitRef,
+    crate::type_ref::TypeBound,
+    crate::path::GenericArgs,
+    generics::GenericParams,
+);
diff --git a/crates/hir-def/src/nameres/attr_resolution.rs b/crates/hir-def/src/nameres/attr_resolution.rs
index 3650204ee9d..79cabeb0fb7 100644
--- a/crates/hir-def/src/nameres/attr_resolution.rs
+++ b/crates/hir-def/src/nameres/attr_resolution.rs
@@ -1,10 +1,9 @@
 //! Post-nameres attribute resolution.
 
-use hir_expand::MacroCallId;
+use hir_expand::{attrs::Attr, MacroCallId};
 use syntax::{ast, SmolStr};
 
 use crate::{
-    attr::Attr,
     attr_macro_as_call_id, builtin_attr,
     db::DefDatabase,
     item_scope::BuiltinShadowMode,
diff --git a/crates/hir-def/src/nameres/collector.rs b/crates/hir-def/src/nameres/collector.rs
index 160203b7783..ad31e9aac2b 100644
--- a/crates/hir-def/src/nameres/collector.rs
+++ b/crates/hir-def/src/nameres/collector.rs
@@ -10,6 +10,7 @@ use cfg::{CfgExpr, CfgOptions};
 use either::Either;
 use hir_expand::{
     ast_id_map::FileAstId,
+    attrs::{Attr, AttrId},
     builtin_attr_macro::find_builtin_attr,
     builtin_derive_macro::find_builtin_derive,
     builtin_fn_macro::find_builtin_macro,
@@ -26,7 +27,7 @@ use stdx::always;
 use syntax::{ast, SmolStr};
 
 use crate::{
-    attr::{Attr, AttrId, Attrs},
+    attr::Attrs,
     attr_macro_as_call_id,
     db::DefDatabase,
     derive_macro_as_call_id,
diff --git a/crates/hir-def/src/nameres/diagnostics.rs b/crates/hir-def/src/nameres/diagnostics.rs
index 06614229198..74b25f4cc98 100644
--- a/crates/hir-def/src/nameres/diagnostics.rs
+++ b/crates/hir-def/src/nameres/diagnostics.rs
@@ -2,12 +2,11 @@
 
 use base_db::CrateId;
 use cfg::{CfgExpr, CfgOptions};
-use hir_expand::MacroCallKind;
+use hir_expand::{attrs::AttrId, MacroCallKind};
 use la_arena::Idx;
 use syntax::ast::{self, AnyHasAttrs};
 
 use crate::{
-    attr::AttrId,
     item_tree::{self, ItemTreeId},
     nameres::LocalModuleId,
     path::ModPath,
diff --git a/crates/hir-def/src/path.rs b/crates/hir-def/src/path.rs
index 592223f7d85..25a23fcd61a 100644
--- a/crates/hir-def/src/path.rs
+++ b/crates/hir-def/src/path.rs
@@ -8,10 +8,10 @@ use std::{
 
 use crate::{
     body::LowerCtx,
-    intern::Interned,
     type_ref::{ConstScalarOrPath, LifetimeRef},
 };
 use hir_expand::name::Name;
+use intern::Interned;
 use syntax::ast;
 
 use crate::type_ref::{TypeBound, TypeRef};
diff --git a/crates/hir-def/src/path/lower.rs b/crates/hir-def/src/path/lower.rs
index cfa3a6baaf8..d570191595b 100644
--- a/crates/hir-def/src/path/lower.rs
+++ b/crates/hir-def/src/path/lower.rs
@@ -1,9 +1,10 @@
 //! Transforms syntax into `Path` objects, ideally with accounting for hygiene
 
-use crate::{intern::Interned, type_ref::ConstScalarOrPath};
+use crate::type_ref::ConstScalarOrPath;
 
 use either::Either;
 use hir_expand::name::{name, AsName};
+use intern::Interned;
 use syntax::ast::{self, AstNode, HasTypeBounds};
 
 use super::AssociatedTypeBinding;
diff --git a/crates/hir-def/src/pretty.rs b/crates/hir-def/src/pretty.rs
index befd0c5ffa0..1c0bd204d30 100644
--- a/crates/hir-def/src/pretty.rs
+++ b/crates/hir-def/src/pretty.rs
@@ -3,10 +3,10 @@
 use std::fmt::{self, Write};
 
 use hir_expand::mod_path::PathKind;
+use intern::Interned;
 use itertools::Itertools;
 
 use crate::{
-    intern::Interned,
     path::{GenericArg, GenericArgs, Path},
     type_ref::{Mutability, TraitBoundModifier, TypeBound, TypeRef},
 };
diff --git a/crates/hir-def/src/resolver.rs b/crates/hir-def/src/resolver.rs
index 1ef7f9577fe..86958e3daea 100644
--- a/crates/hir-def/src/resolver.rs
+++ b/crates/hir-def/src/resolver.rs
@@ -4,6 +4,7 @@ use std::{hash::BuildHasherDefault, sync::Arc};
 use base_db::CrateId;
 use hir_expand::name::{name, Name};
 use indexmap::IndexMap;
+use intern::Interned;
 use rustc_hash::FxHashSet;
 use smallvec::{smallvec, SmallVec};
 
@@ -13,7 +14,6 @@ use crate::{
     db::DefDatabase,
     expr::{ExprId, LabelId, PatId},
     generics::{GenericParams, TypeOrConstParamData},
-    intern::Interned,
     item_scope::{BuiltinShadowMode, BUILTIN_SCOPE},
     nameres::DefMap,
     path::{ModPath, PathKind},
diff --git a/crates/hir-def/src/type_ref.rs b/crates/hir-def/src/type_ref.rs
index f8bb78ddcfe..0149fdaa43c 100644
--- a/crates/hir-def/src/type_ref.rs
+++ b/crates/hir-def/src/type_ref.rs
@@ -7,13 +7,13 @@ use hir_expand::{
     name::{AsName, Name},
     AstId,
 };
+use intern::Interned;
 use syntax::ast::{self, HasName};
 
 use crate::{
     body::LowerCtx,
     builtin_type::{BuiltinInt, BuiltinType, BuiltinUint},
     expr::Literal,
-    intern::Interned,
     path::Path,
 };
 
diff --git a/crates/hir-expand/Cargo.toml b/crates/hir-expand/Cargo.toml
index 77eb1fd4504..a73e690a7e0 100644
--- a/crates/hir-expand/Cargo.toml
+++ b/crates/hir-expand/Cargo.toml
@@ -22,6 +22,7 @@ hashbrown = { version = "0.12.1", features = [
 smallvec = { version = "1.10.0", features = ["const_new"] }
 
 stdx = { path = "../stdx", version = "0.0.0" }
+intern = { path = "../intern", version = "0.0.0" }
 base-db = { path = "../base-db", version = "0.0.0" }
 cfg = { path = "../cfg", version = "0.0.0" }
 syntax = { path = "../syntax", version = "0.0.0" }
diff --git a/crates/hir-expand/src/attrs.rs b/crates/hir-expand/src/attrs.rs
new file mode 100644
index 00000000000..6967d153271
--- /dev/null
+++ b/crates/hir-expand/src/attrs.rs
@@ -0,0 +1,313 @@
+use std::{fmt, ops, sync::Arc};
+
+use base_db::CrateId;
+use cfg::CfgExpr;
+use either::Either;
+use intern::Interned;
+use mbe::{syntax_node_to_token_tree, DelimiterKind, Punct};
+use smallvec::{smallvec, SmallVec};
+use syntax::{ast, match_ast, AstNode, SmolStr, SyntaxNode};
+use tt::Subtree;
+
+use crate::{
+    db::AstDatabase,
+    hygiene::Hygiene,
+    mod_path::{ModPath, PathKind},
+    name::AsName,
+    InFile,
+};
+
+/// Syntactical attributes, without filtering of `cfg_attr`s.
+#[derive(Default, Debug, Clone, PartialEq, Eq)]
+pub struct RawAttrs {
+    entries: Option<Arc<[Attr]>>,
+}
+
+impl ops::Deref for RawAttrs {
+    type Target = [Attr];
+
+    fn deref(&self) -> &[Attr] {
+        match &self.entries {
+            Some(it) => &*it,
+            None => &[],
+        }
+    }
+}
+
+impl RawAttrs {
+    pub const EMPTY: Self = Self { entries: None };
+
+    pub fn new(db: &dyn AstDatabase, owner: &dyn ast::HasAttrs, hygiene: &Hygiene) -> Self {
+        let entries = collect_attrs(owner)
+            .filter_map(|(id, attr)| match attr {
+                Either::Left(attr) => {
+                    attr.meta().and_then(|meta| Attr::from_src(db, meta, hygiene, id))
+                }
+                Either::Right(comment) => comment.doc_comment().map(|doc| Attr {
+                    id,
+                    input: Some(Interned::new(AttrInput::Literal(SmolStr::new(doc)))),
+                    path: Interned::new(ModPath::from(crate::name!(doc))),
+                }),
+            })
+            .collect::<Arc<_>>();
+
+        Self { entries: if entries.is_empty() { None } else { Some(entries) } }
+    }
+
+    pub fn from_attrs_owner(db: &dyn AstDatabase, owner: InFile<&dyn ast::HasAttrs>) -> Self {
+        let hygiene = Hygiene::new(db, owner.file_id);
+        Self::new(db, owner.value, &hygiene)
+    }
+
+    pub fn merge(&self, other: Self) -> Self {
+        match (&self.entries, other.entries) {
+            (None, None) => Self::EMPTY,
+            (None, entries @ Some(_)) => Self { entries },
+            (Some(entries), None) => Self { entries: Some(entries.clone()) },
+            (Some(a), Some(b)) => {
+                let last_ast_index = a.last().map_or(0, |it| it.id.ast_index + 1);
+                Self {
+                    entries: Some(
+                        a.iter()
+                            .cloned()
+                            .chain(b.iter().map(|it| {
+                                let mut it = it.clone();
+                                it.id.ast_index += last_ast_index;
+                                it
+                            }))
+                            .collect(),
+                    ),
+                }
+            }
+        }
+    }
+
+    /// Processes `cfg_attr`s, returning the resulting semantic `Attrs`.
+    pub fn filter(self, db: &dyn AstDatabase, krate: CrateId) -> RawAttrs {
+        let has_cfg_attrs = self
+            .iter()
+            .any(|attr| attr.path.as_ident().map_or(false, |name| *name == crate::name![cfg_attr]));
+        if !has_cfg_attrs {
+            return self;
+        }
+
+        let crate_graph = db.crate_graph();
+        let new_attrs = self
+            .iter()
+            .flat_map(|attr| -> SmallVec<[_; 1]> {
+                let is_cfg_attr =
+                    attr.path.as_ident().map_or(false, |name| *name == crate::name![cfg_attr]);
+                if !is_cfg_attr {
+                    return smallvec![attr.clone()];
+                }
+
+                let subtree = match attr.token_tree_value() {
+                    Some(it) => it,
+                    _ => return smallvec![attr.clone()],
+                };
+
+                // Input subtree is: `(cfg, $(attr),+)`
+                // Split it up into a `cfg` subtree and the `attr` subtrees.
+                // FIXME: There should be a common API for this.
+                let mut parts = subtree.token_trees.split(|tt| {
+                    matches!(tt, tt::TokenTree::Leaf(tt::Leaf::Punct(Punct { char: ',', .. })))
+                });
+                let cfg = match parts.next() {
+                    Some(it) => it,
+                    None => return smallvec![],
+                };
+                let cfg = Subtree { delimiter: subtree.delimiter, token_trees: cfg.to_vec() };
+                let cfg = CfgExpr::parse(&cfg);
+                let index = attr.id;
+                let attrs = parts.filter(|a| !a.is_empty()).filter_map(|attr| {
+                    let tree = Subtree { delimiter: None, token_trees: attr.to_vec() };
+                    // FIXME hygiene
+                    let hygiene = Hygiene::new_unhygienic();
+                    Attr::from_tt(db, &tree, &hygiene, index)
+                });
+
+                let cfg_options = &crate_graph[krate].cfg_options;
+                if cfg_options.check(&cfg) == Some(false) {
+                    smallvec![]
+                } else {
+                    cov_mark::hit!(cfg_attr_active);
+
+                    attrs.collect()
+                }
+            })
+            .collect();
+
+        RawAttrs { entries: Some(new_attrs) }
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct AttrId {
+    pub ast_index: u32,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Attr {
+    pub id: AttrId,
+    pub path: Interned<ModPath>,
+    pub input: Option<Interned<AttrInput>>,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub enum AttrInput {
+    /// `#[attr = "string"]`
+    Literal(SmolStr),
+    /// `#[attr(subtree)]`
+    TokenTree(tt::Subtree, mbe::TokenMap),
+}
+
+impl fmt::Display for AttrInput {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            AttrInput::Literal(lit) => write!(f, " = \"{}\"", lit.escape_debug()),
+            AttrInput::TokenTree(subtree, _) => subtree.fmt(f),
+        }
+    }
+}
+
+impl Attr {
+    fn from_src(
+        db: &dyn AstDatabase,
+        ast: ast::Meta,
+        hygiene: &Hygiene,
+        id: AttrId,
+    ) -> Option<Attr> {
+        let path = Interned::new(ModPath::from_src(db, ast.path()?, hygiene)?);
+        let input = if let Some(ast::Expr::Literal(lit)) = ast.expr() {
+            let value = match lit.kind() {
+                ast::LiteralKind::String(string) => string.value()?.into(),
+                _ => lit.syntax().first_token()?.text().trim_matches('"').into(),
+            };
+            Some(Interned::new(AttrInput::Literal(value)))
+        } else if let Some(tt) = ast.token_tree() {
+            let (tree, map) = syntax_node_to_token_tree(tt.syntax());
+            Some(Interned::new(AttrInput::TokenTree(tree, map)))
+        } else {
+            None
+        };
+        Some(Attr { id, path, input })
+    }
+
+    fn from_tt(
+        db: &dyn AstDatabase,
+        tt: &tt::Subtree,
+        hygiene: &Hygiene,
+        id: AttrId,
+    ) -> Option<Attr> {
+        let (parse, _) = mbe::token_tree_to_syntax_node(tt, mbe::TopEntryPoint::MetaItem);
+        let ast = ast::Meta::cast(parse.syntax_node())?;
+
+        Self::from_src(db, ast, hygiene, id)
+    }
+
+    pub fn path(&self) -> &ModPath {
+        &self.path
+    }
+}
+
+impl Attr {
+    /// #[path = "string"]
+    pub fn string_value(&self) -> Option<&SmolStr> {
+        match self.input.as_deref()? {
+            AttrInput::Literal(it) => Some(it),
+            _ => None,
+        }
+    }
+
+    /// #[path(ident)]
+    pub fn single_ident_value(&self) -> Option<&tt::Ident> {
+        match self.input.as_deref()? {
+            AttrInput::TokenTree(subtree, _) => match &*subtree.token_trees {
+                [tt::TokenTree::Leaf(tt::Leaf::Ident(ident))] => Some(ident),
+                _ => None,
+            },
+            _ => None,
+        }
+    }
+
+    /// #[path TokenTree]
+    pub fn token_tree_value(&self) -> Option<&Subtree> {
+        match self.input.as_deref()? {
+            AttrInput::TokenTree(subtree, _) => Some(subtree),
+            _ => None,
+        }
+    }
+
+    /// Parses this attribute as a token tree consisting of comma separated paths.
+    pub fn parse_path_comma_token_tree(&self) -> Option<impl Iterator<Item = ModPath> + '_> {
+        let args = self.token_tree_value()?;
+
+        if args.delimiter_kind() != Some(DelimiterKind::Parenthesis) {
+            return None;
+        }
+        let paths = args
+            .token_trees
+            .split(|tt| matches!(tt, tt::TokenTree::Leaf(tt::Leaf::Punct(Punct { char: ',', .. }))))
+            .filter_map(|tts| {
+                if tts.is_empty() {
+                    return None;
+                }
+                let segments = tts.iter().filter_map(|tt| match tt {
+                    tt::TokenTree::Leaf(tt::Leaf::Ident(id)) => Some(id.as_name()),
+                    _ => None,
+                });
+                Some(ModPath::from_segments(PathKind::Plain, segments))
+            });
+
+        Some(paths)
+    }
+}
+
+pub fn collect_attrs(
+    owner: &dyn ast::HasAttrs,
+) -> impl Iterator<Item = (AttrId, Either<ast::Attr, ast::Comment>)> {
+    let inner_attrs = inner_attributes(owner.syntax()).into_iter().flatten();
+    let outer_attrs =
+        ast::AttrDocCommentIter::from_syntax_node(owner.syntax()).filter(|el| match el {
+            Either::Left(attr) => attr.kind().is_outer(),
+            Either::Right(comment) => comment.is_outer(),
+        });
+    outer_attrs
+        .chain(inner_attrs)
+        .enumerate()
+        .map(|(id, attr)| (AttrId { ast_index: id as u32 }, attr))
+}
+
+fn inner_attributes(
+    syntax: &SyntaxNode,
+) -> Option<impl Iterator<Item = Either<ast::Attr, ast::Comment>>> {
+    let node = match_ast! {
+        match syntax {
+            ast::SourceFile(_) => syntax.clone(),
+            ast::ExternBlock(it) => it.extern_item_list()?.syntax().clone(),
+            ast::Fn(it) => it.body()?.stmt_list()?.syntax().clone(),
+            ast::Impl(it) => it.assoc_item_list()?.syntax().clone(),
+            ast::Module(it) => it.item_list()?.syntax().clone(),
+            ast::BlockExpr(it) => {
+                use syntax::SyntaxKind::{BLOCK_EXPR , EXPR_STMT};
+                // Block expressions accept outer and inner attributes, but only when they are the outer
+                // expression of an expression statement or the final expression of another block expression.
+                let may_carry_attributes = matches!(
+                    it.syntax().parent().map(|it| it.kind()),
+                     Some(BLOCK_EXPR | EXPR_STMT)
+                );
+                if !may_carry_attributes {
+                    return None
+                }
+                syntax.clone()
+            },
+            _ => return None,
+        }
+    };
+
+    let attrs = ast::AttrDocCommentIter::from_syntax_node(&node).filter(|el| match el {
+        Either::Left(attr) => attr.kind().is_inner(),
+        Either::Right(comment) => comment.is_inner(),
+    });
+    Some(attrs)
+}
diff --git a/crates/hir-expand/src/lib.rs b/crates/hir-expand/src/lib.rs
index bc5f9f3b8af..9d61588a8b5 100644
--- a/crates/hir-expand/src/lib.rs
+++ b/crates/hir-expand/src/lib.rs
@@ -17,6 +17,7 @@ pub mod proc_macro;
 pub mod quote;
 pub mod eager;
 pub mod mod_path;
+pub mod attrs;
 mod fixup;
 
 pub use mbe::{Origin, ValueResult};
@@ -1031,3 +1032,5 @@ impl ExpandTo {
 pub struct UnresolvedMacro {
     pub path: ModPath,
 }
+
+intern::impl_internable!(ModPath, attrs::AttrInput);
diff --git a/crates/hir-ty/Cargo.toml b/crates/hir-ty/Cargo.toml
index ae837ac6dce..75b33da1f23 100644
--- a/crates/hir-ty/Cargo.toml
+++ b/crates/hir-ty/Cargo.toml
@@ -29,6 +29,7 @@ typed-arena = "2.0.1"
 rustc_index = { version = "0.0.20221221", package = "hkalbasi-rustc-ap-rustc_index", default-features = false }
 
 stdx = { path = "../stdx", version = "0.0.0" }
+intern = { path = "../intern", version = "0.0.0" }
 hir-def = { path = "../hir-def", version = "0.0.0" }
 hir-expand = { path = "../hir-expand", version = "0.0.0" }
 base-db = { path = "../base-db", version = "0.0.0" }
diff --git a/crates/hir-ty/src/display.rs b/crates/hir-ty/src/display.rs
index 66e813eed8b..f9642aa7475 100644
--- a/crates/hir-ty/src/display.rs
+++ b/crates/hir-ty/src/display.rs
@@ -11,7 +11,6 @@ use hir_def::{
     db::DefDatabase,
     find_path,
     generics::{TypeOrConstParamData, TypeParamProvenance},
-    intern::{Internable, Interned},
     item_scope::ItemInNs,
     path::{Path, PathKind},
     type_ref::{ConstScalar, TraitBoundModifier, TypeBound, TypeRef},
@@ -19,6 +18,7 @@ use hir_def::{
     HasModule, ItemContainerId, Lookup, ModuleDefId, ModuleId, TraitId,
 };
 use hir_expand::{hygiene::Hygiene, name::Name};
+use intern::{Internable, Interned};
 use itertools::Itertools;
 use smallvec::SmallVec;
 use syntax::SmolStr;
diff --git a/crates/hir-ty/src/interner.rs b/crates/hir-ty/src/interner.rs
index 441503a300e..7bf73560cbe 100644
--- a/crates/hir-ty/src/interner.rs
+++ b/crates/hir-ty/src/interner.rs
@@ -4,11 +4,8 @@
 use crate::{chalk_db, tls, GenericArg};
 use base_db::salsa::InternId;
 use chalk_ir::{Goal, GoalData};
-use hir_def::{
-    intern::{impl_internable, InternStorage, Internable, Interned},
-    type_ref::ConstScalar,
-    TypeAliasId,
-};
+use hir_def::{type_ref::ConstScalar, TypeAliasId};
+use intern::{impl_internable, Interned};
 use smallvec::SmallVec;
 use std::{fmt, sync::Arc};
 
diff --git a/crates/hir-ty/src/lower.rs b/crates/hir-ty/src/lower.rs
index 592410008a6..4b1f40f91d6 100644
--- a/crates/hir-ty/src/lower.rs
+++ b/crates/hir-ty/src/lower.rs
@@ -23,7 +23,6 @@ use hir_def::{
     generics::{
         TypeOrConstParamData, TypeParamProvenance, WherePredicate, WherePredicateTypeTarget,
     },
-    intern::Interned,
     lang_item::lang_attr,
     path::{GenericArg, ModPath, Path, PathKind, PathSegment, PathSegments},
     resolver::{HasResolver, Resolver, TypeNs},
@@ -35,6 +34,7 @@ use hir_def::{
     TypeAliasId, TypeOrConstParamId, TypeParamId, UnionId, VariantId,
 };
 use hir_expand::{name::Name, ExpandResult};
+use intern::Interned;
 use itertools::Either;
 use la_arena::ArenaMap;
 use rustc_hash::FxHashSet;
diff --git a/crates/hir-ty/src/utils.rs b/crates/hir-ty/src/utils.rs
index 9893566bd54..4f516e18be6 100644
--- a/crates/hir-ty/src/utils.rs
+++ b/crates/hir-ty/src/utils.rs
@@ -11,13 +11,13 @@ use hir_def::{
         GenericParams, TypeOrConstParamData, TypeParamProvenance, WherePredicate,
         WherePredicateTypeTarget,
     },
-    intern::Interned,
     resolver::{HasResolver, TypeNs},
     type_ref::{TraitBoundModifier, TypeRef},
     ConstParamId, FunctionId, GenericDefId, ItemContainerId, Lookup, TraitId, TypeAliasId,
     TypeOrConstParamId, TypeParamId,
 };
 use hir_expand::name::Name;
+use intern::Interned;
 use itertools::Either;
 use rustc_hash::FxHashSet;
 use smallvec::{smallvec, SmallVec};
diff --git a/crates/hir/src/lib.rs b/crates/hir/src/lib.rs
index 08fd4453dfc..ad44e240423 100644
--- a/crates/hir/src/lib.rs
+++ b/crates/hir/src/lib.rs
@@ -107,7 +107,7 @@ pub use {
     cfg::{CfgAtom, CfgExpr, CfgOptions},
     hir_def::{
         adt::StructKind,
-        attr::{Attr, Attrs, AttrsWithOwner, Documentation},
+        attr::{Attrs, AttrsWithOwner, Documentation},
         builtin_attr::AttributeTemplate,
         find_path::PrefixKind,
         import_map,
@@ -122,6 +122,7 @@ pub use {
         ModuleDefId,
     },
     hir_expand::{
+        attrs::Attr,
         name::{known, Name},
         ExpandResult, HirFileId, InFile, MacroFile, Origin,
     },
diff --git a/crates/hir/src/semantics/source_to_def.rs b/crates/hir/src/semantics/source_to_def.rs
index fa45e3c12eb..2b5bfda1d43 100644
--- a/crates/hir/src/semantics/source_to_def.rs
+++ b/crates/hir/src/semantics/source_to_def.rs
@@ -87,7 +87,6 @@
 
 use base_db::FileId;
 use hir_def::{
-    attr::AttrId,
     child_by_source::ChildBySource,
     dyn_map::DynMap,
     expr::{LabelId, PatId},
@@ -96,7 +95,7 @@ use hir_def::{
     GenericDefId, GenericParamId, ImplId, LifetimeParamId, MacroId, ModuleId, StaticId, StructId,
     TraitId, TypeAliasId, TypeParamId, UnionId, VariantId,
 };
-use hir_expand::{name::AsName, HirFileId, MacroCallId};
+use hir_expand::{attrs::AttrId, name::AsName, HirFileId, MacroCallId};
 use rustc_hash::FxHashMap;
 use smallvec::SmallVec;
 use stdx::impl_from;
diff --git a/crates/intern/Cargo.toml b/crates/intern/Cargo.toml
new file mode 100644
index 00000000000..dd5110255c5
--- /dev/null
+++ b/crates/intern/Cargo.toml
@@ -0,0 +1,13 @@
+[package]
+name = "intern"
+version = "0.0.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+# We need to freeze the version of the crate, as the raw-api feature is considered unstable
+dashmap = { version = "=5.4.0", features = ["raw-api"] }
+hashbrown = { version = "0.12.1", default-features = false }
+once_cell = "1.15.0"
+rustc-hash = "1.1.0"
diff --git a/crates/hir-def/src/intern.rs b/crates/intern/src/lib.rs
index f08521a3403..fb2903696b3 100644
--- a/crates/hir-def/src/intern.rs
+++ b/crates/intern/src/lib.rs
@@ -14,8 +14,6 @@ use hashbrown::HashMap;
 use once_cell::sync::OnceCell;
 use rustc_hash::FxHasher;
 
-use crate::generics::GenericParams;
-
 type InternMap<T> = DashMap<Arc<T>, (), BuildHasherDefault<FxHasher>>;
 type Guard<T> = dashmap::RwLockWriteGuard<
     'static,
@@ -204,9 +202,9 @@ pub trait Internable: Hash + Eq + 'static {
 #[doc(hidden)]
 macro_rules! _impl_internable {
     ( $($t:path),+ $(,)? ) => { $(
-        impl Internable for $t {
-            fn storage() -> &'static InternStorage<Self> {
-                static STORAGE: InternStorage<$t> = InternStorage::new();
+        impl $crate::Internable for $t {
+            fn storage() -> &'static $crate::InternStorage<Self> {
+                static STORAGE: $crate::InternStorage<$t> = $crate::InternStorage::new();
                 &STORAGE
             }
         }
@@ -215,13 +213,4 @@ macro_rules! _impl_internable {
 
 pub use crate::_impl_internable as impl_internable;
 
-impl_internable!(
-    crate::type_ref::TypeRef,
-    crate::type_ref::TraitRef,
-    crate::type_ref::TypeBound,
-    crate::path::ModPath,
-    crate::path::GenericArgs,
-    crate::attr::AttrInput,
-    GenericParams,
-    str,
-);
+impl_internable!(str,);