Merge #2130

2130: improve compile time a bit r=matklad a=matklad



Co-authored-by: Aleksey Kladov <aleksey.kladov@gmail.com>

crates/ra_hir/src/adt.rs

@@ -3,7 +3,8 @@
 
 use std::sync::Arc;
 
-use hir_def::{name::AsName, type_ref::TypeRef};
+use hir_def::type_ref::TypeRef;
+use hir_expand::name::AsName;
 use ra_arena::{impl_arena_id, Arena, RawId};
 use ra_syntax::ast::{self, NameOwner, StructKind, TypeAscriptionOwner};
 

crates/ra_hir/src/code_model.rs

@@ -6,13 +6,13 @@ pub(crate) mod docs;
 use std::sync::Arc;
 
 use hir_def::{
-    name::{
-        self, AsName, BOOL, CHAR, F32, F64, I128, I16, I32, I64, I8, ISIZE, SELF_TYPE, STR, U128,
-        U16, U32, U64, U8, USIZE,
-    },
     type_ref::{Mutability, TypeRef},
     CrateModuleId, ModuleId,
 };
+use hir_expand::name::{
+    self, AsName, BOOL, CHAR, F32, F64, I128, I16, I32, I64, I8, ISIZE, SELF_TYPE, STR, U128, U16,
+    U32, U64, U8, USIZE,
+};
 use ra_db::{CrateId, Edition};
 use ra_syntax::ast::{self, NameOwner, TypeAscriptionOwner};
 

crates/ra_hir/src/expr/lower.rs

@@ -1,9 +1,9 @@
 //! FIXME: write short doc here
 
-use hir_def::{
+use hir_def::{path::GenericArgs, type_ref::TypeRef};
+use hir_expand::{
+    hygiene::Hygiene,
     name::{self, AsName, Name},
-    path::GenericArgs,
-    type_ref::TypeRef,
 };
 use ra_arena::Arena;
 use ra_syntax::{
@@ -597,7 +597,8 @@ where
     }
 
     fn parse_path(&mut self, path: ast::Path) -> Option<Path> {
-        Path::from_src(Source { ast: path, file_id: self.current_file_id }, self.db)
+        let hygiene = Hygiene::new(self.db, self.current_file_id);
+        Path::from_src(path, &hygiene)
     }
 }
 

crates/ra_hir/src/from_source.rs

@@ -1,6 +1,6 @@
 //! FIXME: write short doc here
 
-use hir_def::name::AsName;
+use hir_expand::name::AsName;
 use ra_syntax::ast::{self, AstNode, NameOwner};
 
 use crate::{

crates/ra_hir/src/generics.rs

@@ -6,10 +6,10 @@
 use std::sync::Arc;
 
 use hir_def::{
-    name::{self, AsName},
     path::Path,
     type_ref::{TypeBound, TypeRef},
 };
+use hir_expand::name::{self, AsName};
 use ra_syntax::ast::{self, DefaultTypeParamOwner, NameOwner, TypeBoundsOwner, TypeParamsOwner};
 
 use crate::{

crates/ra_hir/src/impl_block.rs

@@ -4,6 +4,7 @@ use rustc_hash::FxHashMap;
 use std::sync::Arc;
 
 use hir_def::{attr::Attr, type_ref::TypeRef};
+use hir_expand::hygiene::Hygiene;
 use ra_arena::{impl_arena_id, map::ArenaMap, Arena, RawId};
 use ra_cfg::CfgOptions;
 use ra_syntax::{
@@ -227,10 +228,11 @@ impl ModuleImplBlocks {
         owner: &dyn ast::ModuleItemOwner,
         file_id: HirFileId,
     ) {
+        let hygiene = Hygiene::new(db, file_id);
         for item in owner.items_with_macros() {
             match item {
                 ast::ItemOrMacro::Item(ast::ModuleItem::ImplBlock(impl_block_ast)) => {
-                    let attrs = Attr::from_attrs_owner(file_id, &impl_block_ast, db);
+                    let attrs = Attr::from_attrs_owner(&impl_block_ast, &hygiene);
                     if attrs.map_or(false, |attrs| {
                         attrs.iter().any(|attr| attr.is_cfg_enabled(cfg_options) == Some(false))
                     }) {
@@ -247,7 +249,7 @@ impl ModuleImplBlocks {
                 }
                 ast::ItemOrMacro::Item(_) => (),
                 ast::ItemOrMacro::Macro(macro_call) => {
-                    let attrs = Attr::from_attrs_owner(file_id, &macro_call, db);
+                    let attrs = Attr::from_attrs_owner(&macro_call, &hygiene);
                     if attrs.map_or(false, |attrs| {
                         attrs.iter().any(|attr| attr.is_cfg_enabled(cfg_options) == Some(false))
                     }) {
@@ -256,9 +258,8 @@ impl ModuleImplBlocks {
 
                     //FIXME: we should really cut down on the boilerplate required to process a macro
                     let ast_id = AstId::new(file_id, db.ast_id_map(file_id).ast_id(&macro_call));
-                    if let Some(path) = macro_call
-                        .path()
-                        .and_then(|path| Path::from_src(Source { ast: path, file_id }, db))
+                    if let Some(path) =
+                        macro_call.path().and_then(|path| Path::from_src(path, &hygiene))
                     {
                         if let Some(def) = self.module.resolver(db).resolve_path_as_macro(db, &path)
                         {

crates/ra_hir/src/lib.rs

@@ -60,6 +60,13 @@ use crate::{ids::MacroFileKind, resolve::Resolver};
 
 pub use crate::{
     adt::VariantDef,
+    code_model::{
+        docs::{DocDef, Docs, Documentation},
+        src::{HasBodySource, HasSource, Source},
+        Adt, AssocItem, BuiltinType, Const, ConstData, Container, Crate, CrateDependency,
+        DefWithBody, Enum, EnumVariant, FieldSource, FnData, Function, HasBody, MacroDef, Module,
+        ModuleDef, ModuleSource, Static, Struct, StructField, Trait, TypeAlias, Union,
+    },
     expr::ExprScopes,
     from_source::FromSource,
     generics::{GenericDef, GenericParam, GenericParams, HasGenericParams},
@@ -73,17 +80,8 @@ pub use crate::{
     },
 };
 
-pub use self::code_model::{
-    docs::{DocDef, Docs, Documentation},
-    src::{HasBodySource, HasSource, Source},
-    Adt, AssocItem, BuiltinType, Const, ConstData, Container, Crate, CrateDependency, DefWithBody,
-    Enum, EnumVariant, FieldSource, FnData, Function, HasBody, MacroDef, Module, ModuleDef,
-    ModuleSource, Static, Struct, StructField, Trait, TypeAlias, Union,
-};
-
 pub use hir_def::{
-    either::Either,
-    name::Name,
     path::{Path, PathKind},
     type_ref::Mutability,
 };
+pub use hir_expand::{either::Either, name::Name};

crates/ra_hir/src/nameres/collector.rs

@@ -1,6 +1,7 @@
 //! FIXME: write short doc here
 
-use hir_def::{attr::Attr, name, nameres::raw};
+use hir_def::{attr::Attr, nameres::raw};
+use hir_expand::name;
 use ra_cfg::CfgOptions;
 use ra_db::FileId;
 use ra_syntax::{ast, SmolStr};

crates/ra_hir/src/resolve.rs

@@ -2,10 +2,10 @@
 use std::sync::Arc;
 
 use hir_def::{
-    name::{self, Name},
     path::{Path, PathKind},
     CrateModuleId,
 };
+use hir_expand::name::{self, Name};
 use rustc_hash::FxHashSet;
 
 use crate::{

crates/ra_hir/src/source_binder.rs

@@ -7,7 +7,8 @@
 //! purely for "IDE needs".
 use std::sync::Arc;
 
-use hir_def::{name::AsName, path::known};
+use hir_def::path::known;
+use hir_expand::name::AsName;
 use ra_db::FileId;
 use ra_syntax::{
     ast::{self, AstNode},

crates/ra_hir/src/traits.rs

@@ -2,7 +2,8 @@
 
 use std::sync::Arc;
 
-use hir_def::name::AsName;
+use hir_expand::name::AsName;
+
 use ra_syntax::ast::{self, NameOwner};
 use rustc_hash::FxHashMap;
 

crates/ra_hir/src/ty/autoderef.rs

@@ -5,7 +5,7 @@
 
 use std::iter::successors;
 
-use hir_def::name;
+use hir_expand::name;
 use log::{info, warn};
 
 use super::{traits::Solution, Canonical, Substs, Ty, TypeWalk};

crates/ra_hir/src/ty/infer.rs

@@ -22,10 +22,10 @@ use ena::unify::{InPlaceUnificationTable, NoError, UnifyKey, UnifyValue};
 use rustc_hash::FxHashMap;
 
 use hir_def::{
-    name,
     path::known,
     type_ref::{Mutability, TypeRef},
 };
+use hir_expand::name;
 use ra_arena::map::ArenaMap;
 use ra_prof::profile;
 use test_utils::tested_by;

crates/ra_hir/src/ty/infer/expr.rs

@@ -3,10 +3,8 @@
 use std::iter::{repeat, repeat_with};
 use std::sync::Arc;
 
-use hir_def::{
-    name,
-    path::{GenericArg, GenericArgs},
-};
+use hir_def::path::{GenericArg, GenericArgs};
+use hir_expand::name;
 
 use super::{BindingMode, Expectation, InferenceContext, InferenceDiagnostic, TypeMismatch};
 use crate::{

crates/ra_hir/src/ty/traits/chalk.rs

@@ -9,7 +9,8 @@ use chalk_ir::{
 };
 use chalk_rust_ir::{AssociatedTyDatum, ImplDatum, StructDatum, TraitDatum};
 
-use hir_def::name;
+use hir_expand::name;
+
 use ra_db::salsa::{InternId, InternKey};
 
 use super::{Canonical, ChalkContext, Impl, Obligation};

crates/ra_hir/src/type_alias.rs

@@ -2,10 +2,9 @@
 
 use std::sync::Arc;
 
-use hir_def::{
-    name::{AsName, Name},
-    type_ref::TypeRef,
-};
+use hir_def::type_ref::TypeRef;
+use hir_expand::name::{AsName, Name};
+
 use ra_syntax::ast::NameOwner;
 
 use crate::{

crates/ra_hir_def/src/attr.rs

@@ -2,7 +2,7 @@
 
 use std::sync::Arc;
 
-use hir_expand::db::AstDatabase;
+use hir_expand::hygiene::Hygiene;
 use mbe::ast_to_token_tree;
 use ra_cfg::CfgOptions;
 use ra_syntax::{
@@ -11,7 +11,7 @@ use ra_syntax::{
 };
 use tt::Subtree;
 
-use crate::{path::Path, HirFileId, Source};
+use crate::path::Path;
 
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct Attr {
@@ -26,11 +26,8 @@ pub enum AttrInput {
 }
 
 impl Attr {
-    pub(crate) fn from_src(
-        Source { file_id, ast }: Source<ast::Attr>,
-        db: &impl AstDatabase,
-    ) -> Option<Attr> {
-        let path = Path::from_src(Source { file_id, ast: ast.path()? }, db)?;
+    pub(crate) fn from_src(ast: ast::Attr, hygiene: &Hygiene) -> Option<Attr> {
+        let path = Path::from_src(ast.path()?, hygiene)?;
         let input = match ast.input() {
             None => None,
             Some(ast::AttrInput::Literal(lit)) => {
@@ -46,17 +43,13 @@ impl Attr {
         Some(Attr { path, input })
     }
 
-    pub fn from_attrs_owner(
-        file_id: HirFileId,
-        owner: &dyn AttrsOwner,
-        db: &impl AstDatabase,
-    ) -> Option<Arc<[Attr]>> {
+    pub fn from_attrs_owner(owner: &dyn AttrsOwner, hygiene: &Hygiene) -> Option<Arc<[Attr]>> {
         let mut attrs = owner.attrs().peekable();
         if attrs.peek().is_none() {
             // Avoid heap allocation
             return None;
         }
-        Some(attrs.flat_map(|ast| Attr::from_src(Source { file_id, ast }, db)).collect())
+        Some(attrs.flat_map(|ast| Attr::from_src(ast, hygiene)).collect())
     }
 
     pub fn is_simple_atom(&self, name: &str) -> bool {

crates/ra_hir_def/src/lib.rs

@@ -8,9 +8,7 @@
 //! actually true.
 
 pub mod db;
-pub mod either;
 pub mod attr;
-pub mod name;
 pub mod path;
 pub mod type_ref;
 

crates/ra_hir_def/src/nameres/raw.rs

@@ -2,21 +2,20 @@
 
 use std::{ops::Index, sync::Arc};
 
-use hir_expand::{ast_id_map::AstIdMap, db::AstDatabase};
+use hir_expand::{
+    ast_id_map::AstIdMap,
+    db::AstDatabase,
+    either::Either,
+    hygiene::Hygiene,
+    name::{AsName, Name},
+};
 use ra_arena::{impl_arena_id, map::ArenaMap, Arena, RawId};
 use ra_syntax::{
     ast::{self, AttrsOwner, NameOwner},
     AstNode, AstPtr, SourceFile,
 };
 
-use crate::{
-    attr::Attr,
-    db::DefDatabase2,
-    either::Either,
-    name::{AsName, Name},
-    path::Path,
-    FileAstId, HirFileId, ModuleSource, Source,
-};
+use crate::{attr::Attr, db::DefDatabase2, path::Path, FileAstId, HirFileId, ModuleSource, Source};
 
 /// `RawItems` is a set of top-level items in a file (except for impls).
 ///
@@ -40,10 +39,8 @@ pub struct ImportSourceMap {
 type ImportSourcePtr = Either<AstPtr<ast::UseTree>, AstPtr<ast::ExternCrateItem>>;
 type ImportSource = Either<ast::UseTree, ast::ExternCrateItem>;
 
-impl ImportSourcePtr {
-    fn to_node(self, file: &SourceFile) -> ImportSource {
-        self.map(|ptr| ptr.to_node(file.syntax()), |ptr| ptr.to_node(file.syntax()))
-    }
+fn to_node(ptr: ImportSourcePtr, file: &SourceFile) -> ImportSource {
+    ptr.map(|ptr| ptr.to_node(file.syntax()), |ptr| ptr.to_node(file.syntax()))
 }
 
 impl ImportSourceMap {
@@ -57,7 +54,7 @@ impl ImportSourceMap {
             ModuleSource::Module(m) => m.syntax().ancestors().find_map(SourceFile::cast).unwrap(),
         };
 
-        self.map[import].to_node(&file)
+        to_node(self.map[import], &file)
     }
 }
 
@@ -78,7 +75,7 @@ impl RawItems {
             source_ast_id_map: db.ast_id_map(file_id),
             source_map: ImportSourceMap::default(),
             file_id,
-            db,
+            hygiene: Hygiene::new(db, file_id),
         };
         if let Some(node) = db.parse_or_expand(file_id) {
             if let Some(source_file) = ast::SourceFile::cast(node.clone()) {
@@ -204,15 +201,15 @@ pub struct MacroData {
     pub export: bool,
 }
 
-struct RawItemsCollector<DB> {
+struct RawItemsCollector {
     raw_items: RawItems,
     source_ast_id_map: Arc<AstIdMap>,
     source_map: ImportSourceMap,
     file_id: HirFileId,
-    db: DB,
+    hygiene: Hygiene,
 }
 
-impl<DB: AstDatabase> RawItemsCollector<&DB> {
+impl RawItemsCollector {
     fn process_module(&mut self, current_module: Option<Module>, body: impl ast::ModuleItemOwner) {
         for item_or_macro in body.items_with_macros() {
             match item_or_macro {
@@ -309,9 +306,10 @@ impl<DB: AstDatabase> RawItemsCollector<&DB> {
         let is_prelude = use_item.has_atom_attr("prelude_import");
         let attrs = self.parse_attrs(&use_item);
 
+        let mut buf = Vec::new();
         Path::expand_use_item(
             Source { ast: use_item, file_id: self.file_id },
-            self.db,
+            &self.hygiene,
             |path, use_tree, is_glob, alias| {
                 let import_data = ImportData {
                     path,
@@ -321,14 +319,12 @@ impl<DB: AstDatabase> RawItemsCollector<&DB> {
                     is_extern_crate: false,
                     is_macro_use: false,
                 };
-                self.push_import(
-                    current_module,
-                    attrs.clone(),
-                    import_data,
-                    Either::A(AstPtr::new(use_tree)),
-                );
+                buf.push((import_data, Either::A(AstPtr::new(use_tree))));
             },
-        )
+        );
+        for (import_data, ptr) in buf {
+            self.push_import(current_module, attrs.clone(), import_data, ptr);
+        }
     }
 
     fn add_extern_crate_item(
@@ -361,10 +357,7 @@ impl<DB: AstDatabase> RawItemsCollector<&DB> {
 
     fn add_macro(&mut self, current_module: Option<Module>, m: ast::MacroCall) {
         let attrs = self.parse_attrs(&m);
-        let path = match m
-            .path()
-            .and_then(|path| Path::from_src(Source { ast: path, file_id: self.file_id }, self.db))
-        {
+        let path = match m.path().and_then(|path| Path::from_src(path, &self.hygiene)) {
             Some(it) => it,
             _ => return,
         };
@@ -402,6 +395,6 @@ impl<DB: AstDatabase> RawItemsCollector<&DB> {
     }
 
     fn parse_attrs(&self, item: &impl ast::AttrsOwner) -> Attrs {
-        Attr::from_attrs_owner(self.file_id, item, self.db)
+        Attr::from_attrs_owner(item, &self.hygiene)
     }
 }

crates/ra_hir_def/src/path.rs

@@ -2,18 +2,18 @@
 
 use std::{iter, sync::Arc};
 
-use hir_expand::db::AstDatabase;
+use hir_expand::{
+    either::Either,
+    hygiene::Hygiene,
+    name::{self, AsName, Name},
+};
 use ra_db::CrateId;
 use ra_syntax::{
     ast::{self, NameOwner, TypeAscriptionOwner},
     AstNode,
 };
 
-use crate::{
-    name::{self, AsName, Name},
-    type_ref::TypeRef,
-    Source,
-};
+use crate::{type_ref::TypeRef, Source};
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct Path {
@@ -68,11 +68,11 @@ impl Path {
     /// Calls `cb` with all paths, represented by this use item.
     pub fn expand_use_item(
         item_src: Source<ast::UseItem>,
-        db: &impl AstDatabase,
+        hygiene: &Hygiene,
         mut cb: impl FnMut(Path, &ast::UseTree, bool, Option<Name>),
     ) {
         if let Some(tree) = item_src.ast.use_tree() {
-            expand_use_tree(None, tree, &|| item_src.file_id.macro_crate(db), &mut cb);
+            expand_use_tree(None, tree, hygiene, &mut cb);
         }
     }
 
@@ -89,17 +89,12 @@ impl Path {
     /// Converts an `ast::Path` to `Path`. Works with use trees.
     /// DEPRECATED: It does not handle `$crate` from macro call.
     pub fn from_ast(path: ast::Path) -> Option<Path> {
-        Path::parse(path, &|| None)
+        Path::from_src(path, &Hygiene::new_unhygienic())
     }
 
     /// Converts an `ast::Path` to `Path`. Works with use trees.
     /// It correctly handles `$crate` based path from macro call.
-    pub fn from_src(source: Source<ast::Path>, db: &impl AstDatabase) -> Option<Path> {
-        let file_id = source.file_id;
-        Path::parse(source.ast, &|| file_id.macro_crate(db))
-    }
-
-    fn parse(mut path: ast::Path, macro_crate: &impl Fn() -> Option<CrateId>) -> Option<Path> {
+    pub fn from_src(mut path: ast::Path, hygiene: &Hygiene) -> Option<Path> {
         let mut kind = PathKind::Plain;
         let mut segments = Vec::new();
         loop {
@@ -110,26 +105,28 @@ impl Path {
             }
 
             match segment.kind()? {
-                ast::PathSegmentKind::Name(name) => {
-                    if name.text() == "$crate" {
-                        if let Some(macro_crate) = macro_crate() {
-                            kind = PathKind::DollarCrate(macro_crate);
+                ast::PathSegmentKind::Name(name_ref) => {
+                    // FIXME: this should just return name
+                    match hygiene.name_ref_to_name(name_ref) {
+                        Either::A(name) => {
+                            let args = segment
+                                .type_arg_list()
+                                .and_then(GenericArgs::from_ast)
+                                .or_else(|| {
+                                    GenericArgs::from_fn_like_path_ast(
+                                        segment.param_list(),
+                                        segment.ret_type(),
+                                    )
+                                })
+                                .map(Arc::new);
+                            let segment = PathSegment { name, args_and_bindings: args };
+                            segments.push(segment);
+                        }
+                        Either::B(crate_id) => {
+                            kind = PathKind::DollarCrate(crate_id);
                             break;
                         }
                     }
-
-                    let args = segment
-                        .type_arg_list()
-                        .and_then(GenericArgs::from_ast)
-                        .or_else(|| {
-                            GenericArgs::from_fn_like_path_ast(
-                                segment.param_list(),
-                                segment.ret_type(),
-                            )
-                        })
-                        .map(Arc::new);
-                    let segment = PathSegment { name: name.as_name(), args_and_bindings: args };
-                    segments.push(segment);
                 }
                 ast::PathSegmentKind::Type { type_ref, trait_ref } => {
                     assert!(path.qualifier().is_none()); // this can only occur at the first segment
@@ -143,7 +140,7 @@ impl Path {
                         }
                         // <T as Trait<A>>::Foo desugars to Trait<Self=T, A>::Foo
                         Some(trait_ref) => {
-                            let path = Path::parse(trait_ref.path()?, macro_crate)?;
+                            let path = Path::from_src(trait_ref.path()?, hygiene)?;
                             kind = path.kind;
                             let mut prefix_segments = path.segments;
                             prefix_segments.reverse();
@@ -294,8 +291,8 @@ impl From<Name> for Path {
 fn expand_use_tree(
     prefix: Option<Path>,
     tree: ast::UseTree,
-    macro_crate: &impl Fn() -> Option<CrateId>,
-    cb: &mut impl FnMut(Path, &ast::UseTree, bool, Option<Name>),
+    hygiene: &Hygiene,
+    cb: &mut dyn FnMut(Path, &ast::UseTree, bool, Option<Name>),
 ) {
     if let Some(use_tree_list) = tree.use_tree_list() {
         let prefix = match tree.path() {
@@ -303,13 +300,13 @@ fn expand_use_tree(
             None => prefix,
             // E.g. `use something::{inner}` (prefix is `None`, path is `something`)
             // or `use something::{path::{inner::{innerer}}}` (prefix is `something::path`, path is `inner`)
-            Some(path) => match convert_path(prefix, path, macro_crate) {
+            Some(path) => match convert_path(prefix, path, hygiene) {
                 Some(it) => Some(it),
                 None => return, // FIXME: report errors somewhere
             },
         };
         for child_tree in use_tree_list.use_trees() {
-            expand_use_tree(prefix.clone(), child_tree, macro_crate, cb);
+            expand_use_tree(prefix.clone(), child_tree, hygiene, cb);
         }
     } else {
         let alias = tree.alias().and_then(|a| a.name()).map(|a| a.as_name());
@@ -326,7 +323,7 @@ fn expand_use_tree(
                     }
                 }
             }
-            if let Some(path) = convert_path(prefix, ast_path, macro_crate) {
+            if let Some(path) = convert_path(prefix, ast_path, hygiene) {
                 let is_glob = tree.has_star();
                 cb(path, &tree, is_glob, alias)
             }
@@ -336,37 +333,36 @@ fn expand_use_tree(
     }
 }
 
-fn convert_path(
-    prefix: Option<Path>,
-    path: ast::Path,
-    macro_crate: &impl Fn() -> Option<CrateId>,
-) -> Option<Path> {
+fn convert_path(prefix: Option<Path>, path: ast::Path, hygiene: &Hygiene) -> Option<Path> {
     let prefix = if let Some(qual) = path.qualifier() {
-        Some(convert_path(prefix, qual, macro_crate)?)
+        Some(convert_path(prefix, qual, hygiene)?)
     } else {
         prefix
     };
 
     let segment = path.segment()?;
     let res = match segment.kind()? {
-        ast::PathSegmentKind::Name(name) => {
-            if name.text() == "$crate" {
-                if let Some(krate) = macro_crate() {
+        ast::PathSegmentKind::Name(name_ref) => {
+            match hygiene.name_ref_to_name(name_ref) {
+                Either::A(name) => {
+                    // no type args in use
+                    let mut res = prefix.unwrap_or_else(|| Path {
+                        kind: PathKind::Plain,
+                        segments: Vec::with_capacity(1),
+                    });
+                    res.segments.push(PathSegment {
+                        name,
+                        args_and_bindings: None, // no type args in use
+                    });
+                    res
+                }
+                Either::B(crate_id) => {
                     return Some(Path::from_simple_segments(
-                        PathKind::DollarCrate(krate),
+                        PathKind::DollarCrate(crate_id),
                         iter::empty(),
-                    ));
+                    ))
                 }
             }
-
-            // no type args in use
-            let mut res = prefix
-                .unwrap_or_else(|| Path { kind: PathKind::Plain, segments: Vec::with_capacity(1) });
-            res.segments.push(PathSegment {
-                name: name.as_name(),
-                args_and_bindings: None, // no type args in use
-            });
-            res
         }
         ast::PathSegmentKind::CrateKw => {
             if prefix.is_some() {
@@ -395,8 +391,9 @@ fn convert_path(
 }
 
 pub mod known {
+    use hir_expand::name;
+
     use super::{Path, PathKind};
-    use crate::name;
 
     pub fn std_iter_into_iterator() -> Path {
         Path::from_simple_segments(

crates/ra_hir_expand/src/hygiene.rs

@@ -0,0 +1,46 @@
+//! This modules handles hygiene information.
+//!
+//! Specifically, `ast` + `Hygiene` allows you to create a `Name`. Note that, at
+//! this moment, this is horribly incomplete and handles only `$crate`.
+use ra_db::CrateId;
+use ra_syntax::ast;
+
+use crate::{
+    db::AstDatabase,
+    either::Either,
+    name::{AsName, Name},
+    HirFileId, HirFileIdRepr,
+};
+
+#[derive(Debug)]
+pub struct Hygiene {
+    // This is what `$crate` expands to
+    def_crate: Option<CrateId>,
+}
+
+impl Hygiene {
+    pub fn new(db: &impl AstDatabase, file_id: HirFileId) -> Hygiene {
+        let def_crate = match file_id.0 {
+            HirFileIdRepr::FileId(_) => None,
+            HirFileIdRepr::MacroFile(macro_file) => {
+                let loc = db.lookup_intern_macro(macro_file.macro_call_id);
+                Some(loc.def.krate)
+            }
+        };
+        Hygiene { def_crate }
+    }
+
+    pub fn new_unhygienic() -> Hygiene {
+        Hygiene { def_crate: None }
+    }
+
+    // FIXME: this should just return name
+    pub fn name_ref_to_name(&self, name_ref: ast::NameRef) -> Either<Name, CrateId> {
+        if let Some(def_crate) = self.def_crate {
+            if name_ref.text() == "$crate" {
+                return Either::B(def_crate);
+            }
+        }
+        Either::A(name_ref.as_name())
+    }
+}

crates/ra_hir_expand/src/lib.rs

@@ -6,6 +6,9 @@
 
 pub mod db;
 pub mod ast_id_map;
+pub mod either;
+pub mod name;
+pub mod hygiene;
 
 use std::hash::{Hash, Hasher};
 
@@ -59,17 +62,6 @@ impl HirFileId {
             }
         }
     }
-
-    /// Get the crate which the macro lives in, if it is a macro file.
-    pub fn macro_crate(self, db: &dyn db::AstDatabase) -> Option<CrateId> {
-        match self.0 {
-            HirFileIdRepr::FileId(_) => None,
-            HirFileIdRepr::MacroFile(macro_file) => {
-                let loc = db.lookup_intern_macro(macro_file.macro_call_id);
-                Some(loc.def.krate)
-            }
-        }
-    }
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]