10 files changed, 1634 insertions, 0 deletions

diff --git a/crates/ra_hir_def/Cargo.toml b/crates/ra_hir_def/Cargo.toml
new file mode 100644
index 000000000..746c907e8
--- /dev/null
+++ b/crates/ra_hir_def/Cargo.toml
@@ -0,0 +1,21 @@
+[package]
+edition = "2018"
+name = "ra_hir_def"
+version = "0.1.0"
+authors = ["rust-analyzer developers"]
+
+[dependencies]
+log = "0.4.5"
+once_cell = "1.0.1"
+relative-path = "1.0.0"
+rustc-hash = "1.0"
+
+ra_arena = { path = "../ra_arena" }
+ra_db = { path = "../ra_db" }
+ra_syntax = { path = "../ra_syntax" }
+ra_prof = { path = "../ra_prof" }
+hir_expand = { path = "../ra_hir_expand", package = "ra_hir_expand" }
+test_utils = { path = "../test_utils" }
+mbe = { path = "../ra_mbe", package = "ra_mbe" }
+ra_cfg = { path = "../ra_cfg" }
+tt = { path = "../ra_tt", package = "ra_tt" }
diff --git a/crates/ra_hir_def/src/attr.rs b/crates/ra_hir_def/src/attr.rs
new file mode 100644
index 000000000..0e961ca12
--- /dev/null
+++ b/crates/ra_hir_def/src/attr.rs
@@ -0,0 +1,84 @@
+//! A higher level attributes based on TokenTree, with also some shortcuts.
+
+use std::sync::Arc;
+
+use hir_expand::hygiene::Hygiene;
+use mbe::ast_to_token_tree;
+use ra_cfg::CfgOptions;
+use ra_syntax::{
+    ast::{self, AstNode, AttrsOwner},
+    SmolStr,
+};
+use tt::Subtree;
+
+use crate::path::Path;
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Attr {
+    pub(crate) path: Path,
+    pub(crate) input: Option<AttrInput>,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum AttrInput {
+    Literal(SmolStr),
+    TokenTree(Subtree),
+}
+
+impl Attr {
+    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)) => {
+                // FIXME: escape? raw string?
+                let value = lit.syntax().first_token()?.text().trim_matches('"').into();
+                Some(AttrInput::Literal(value))
+            }
+            Some(ast::AttrInput::TokenTree(tt)) => {
+                Some(AttrInput::TokenTree(ast_to_token_tree(&tt)?.0))
+            }
+        };
+
+        Some(Attr { path, input })
+    }
+
+    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(ast, hygiene)).collect())
+    }
+
+    pub fn is_simple_atom(&self, name: &str) -> bool {
+        // FIXME: Avoid cloning
+        self.path.as_ident().map_or(false, |s| s.to_string() == name)
+    }
+
+    // FIXME: handle cfg_attr :-)
+    pub fn as_cfg(&self) -> Option<&Subtree> {
+        if !self.is_simple_atom("cfg") {
+            return None;
+        }
+        match &self.input {
+            Some(AttrInput::TokenTree(subtree)) => Some(subtree),
+            _ => None,
+        }
+    }
+
+    pub fn as_path(&self) -> Option<&SmolStr> {
+        if !self.is_simple_atom("path") {
+            return None;
+        }
+        match &self.input {
+            Some(AttrInput::Literal(it)) => Some(it),
+            _ => None,
+        }
+    }
+
+    pub fn is_cfg_enabled(&self, cfg_options: &CfgOptions) -> Option<bool> {
+        cfg_options.is_cfg_enabled(self.as_cfg()?)
+    }
+}
diff --git a/crates/ra_hir_def/src/builtin_type.rs b/crates/ra_hir_def/src/builtin_type.rs
new file mode 100644
index 000000000..12929caa9
--- /dev/null
+++ b/crates/ra_hir_def/src/builtin_type.rs
@@ -0,0 +1,63 @@
+//! This module defines built-in types.
+//!
+//! A peculiarity of built-in types is that they are always available and are
+//! not associated with any particular crate.
+
+use hir_expand::name::{self, Name};
+
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+pub enum Signedness {
+    Signed,
+    Unsigned,
+}
+
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+pub enum IntBitness {
+    Xsize,
+    X8,
+    X16,
+    X32,
+    X64,
+    X128,
+}
+
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+pub enum FloatBitness {
+    X32,
+    X64,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum BuiltinType {
+    Char,
+    Bool,
+    Str,
+    Int { signedness: Signedness, bitness: IntBitness },
+    Float { bitness: FloatBitness },
+}
+
+impl BuiltinType {
+    #[rustfmt::skip]
+    pub const ALL: &'static [(Name, BuiltinType)] = &[
+        (name::CHAR, BuiltinType::Char),
+        (name::BOOL, BuiltinType::Bool),
+        (name::STR,  BuiltinType::Str ),
+
+        (name::ISIZE, BuiltinType::Int { signedness: Signedness::Signed,   bitness: IntBitness::Xsize }),
+        (name::I8,    BuiltinType::Int { signedness: Signedness::Signed,   bitness: IntBitness::X8    }),
+        (name::I16,   BuiltinType::Int { signedness: Signedness::Signed,   bitness: IntBitness::X16   }),
+        (name::I32,   BuiltinType::Int { signedness: Signedness::Signed,   bitness: IntBitness::X32   }),
+        (name::I64,   BuiltinType::Int { signedness: Signedness::Signed,   bitness: IntBitness::X64   }),
+        (name::I128,  BuiltinType::Int { signedness: Signedness::Signed,   bitness: IntBitness::X128  }),
+
+        (name::USIZE, BuiltinType::Int { signedness: Signedness::Unsigned, bitness: IntBitness::Xsize }),
+        (name::U8,    BuiltinType::Int { signedness: Signedness::Unsigned, bitness: IntBitness::X8    }),
+        (name::U16,   BuiltinType::Int { signedness: Signedness::Unsigned, bitness: IntBitness::X16   }),
+        (name::U32,   BuiltinType::Int { signedness: Signedness::Unsigned, bitness: IntBitness::X32   }),
+        (name::U64,   BuiltinType::Int { signedness: Signedness::Unsigned, bitness: IntBitness::X64   }),
+        (name::U128,  BuiltinType::Int { signedness: Signedness::Unsigned, bitness: IntBitness::X128  }),
+
+        (name::F32, BuiltinType::Float { bitness: FloatBitness::X32 }),
+        (name::F64, BuiltinType::Float { bitness: FloatBitness::X64 }),
+    ];
+}
diff --git a/crates/ra_hir_def/src/db.rs b/crates/ra_hir_def/src/db.rs
new file mode 100644
index 000000000..b271636b0
--- /dev/null
+++ b/crates/ra_hir_def/src/db.rs
@@ -0,0 +1,40 @@
+//! Defines database & queries for name resolution.
+use std::sync::Arc;
+
+use hir_expand::{db::AstDatabase, HirFileId};
+use ra_db::{salsa, SourceDatabase};
+use ra_syntax::ast;
+
+use crate::nameres::raw::{ImportSourceMap, RawItems};
+
+#[salsa::query_group(InternDatabaseStorage)]
+pub trait InternDatabase: SourceDatabase {
+    #[salsa::interned]
+    fn intern_function(&self, loc: crate::ItemLoc<ast::FnDef>) -> crate::FunctionId;
+    #[salsa::interned]
+    fn intern_struct(&self, loc: crate::ItemLoc<ast::StructDef>) -> crate::StructId;
+    #[salsa::interned]
+    fn intern_union(&self, loc: crate::ItemLoc<ast::StructDef>) -> crate::UnionId;
+    #[salsa::interned]
+    fn intern_enum(&self, loc: crate::ItemLoc<ast::EnumDef>) -> crate::EnumId;
+    #[salsa::interned]
+    fn intern_const(&self, loc: crate::ItemLoc<ast::ConstDef>) -> crate::ConstId;
+    #[salsa::interned]
+    fn intern_static(&self, loc: crate::ItemLoc<ast::StaticDef>) -> crate::StaticId;
+    #[salsa::interned]
+    fn intern_trait(&self, loc: crate::ItemLoc<ast::TraitDef>) -> crate::TraitId;
+    #[salsa::interned]
+    fn intern_type_alias(&self, loc: crate::ItemLoc<ast::TypeAliasDef>) -> crate::TypeAliasId;
+}
+
+#[salsa::query_group(DefDatabase2Storage)]
+pub trait DefDatabase2: InternDatabase + AstDatabase {
+    #[salsa::invoke(RawItems::raw_items_with_source_map_query)]
+    fn raw_items_with_source_map(
+        &self,
+        file_id: HirFileId,
+    ) -> (Arc<RawItems>, Arc<ImportSourceMap>);
+
+    #[salsa::invoke(RawItems::raw_items_query)]
+    fn raw_items(&self, file_id: HirFileId) -> Arc<RawItems>;
+}
diff --git a/crates/ra_hir_def/src/lib.rs b/crates/ra_hir_def/src/lib.rs
new file mode 100644
index 000000000..93ad40005
--- /dev/null
+++ b/crates/ra_hir_def/src/lib.rs
@@ -0,0 +1,362 @@
+//! `hir_def` crate contains everything between macro expansion and type
+//! inference.
+//!
+//! It defines various items (structs, enums, traits) which comprises Rust code,
+//! as well as an algorithm for resolving paths to such entities.
+//!
+//! Note that `hir_def` is a work in progress, so not all of the above is
+//! actually true.
+
+pub mod db;
+pub mod attr;
+pub mod path;
+pub mod type_ref;
+pub mod builtin_type;
+
+// FIXME: this should be private
+pub mod nameres;
+
+use std::hash::{Hash, Hasher};
+
+use hir_expand::{ast_id_map::FileAstId, db::AstDatabase, AstId, HirFileId};
+use ra_arena::{impl_arena_id, RawId};
+use ra_db::{salsa, CrateId, FileId};
+use ra_syntax::{ast, AstNode, SyntaxNode};
+
+use crate::{builtin_type::BuiltinType, db::InternDatabase};
+
+#[derive(Debug, PartialEq, Eq, Clone, Copy)]
+pub struct Source<T> {
+    pub file_id: HirFileId,
+    pub ast: T,
+}
+
+pub enum ModuleSource {
+    SourceFile(ast::SourceFile),
+    Module(ast::Module),
+}
+
+impl ModuleSource {
+    pub fn new(
+        db: &impl db::DefDatabase2,
+        file_id: Option<FileId>,
+        decl_id: Option<AstId<ast::Module>>,
+    ) -> ModuleSource {
+        match (file_id, decl_id) {
+            (Some(file_id), _) => {
+                let source_file = db.parse(file_id).tree();
+                ModuleSource::SourceFile(source_file)
+            }
+            (None, Some(item_id)) => {
+                let module = item_id.to_node(db);
+                assert!(module.item_list().is_some(), "expected inline module");
+                ModuleSource::Module(module)
+            }
+            (None, None) => panic!(),
+        }
+    }
+
+    // FIXME: this methods do not belong here
+    pub fn from_position(
+        db: &impl db::DefDatabase2,
+        position: ra_db::FilePosition,
+    ) -> ModuleSource {
+        let parse = db.parse(position.file_id);
+        match &ra_syntax::algo::find_node_at_offset::<ast::Module>(
+            parse.tree().syntax(),
+            position.offset,
+        ) {
+            Some(m) if !m.has_semi() => ModuleSource::Module(m.clone()),
+            _ => {
+                let source_file = parse.tree();
+                ModuleSource::SourceFile(source_file)
+            }
+        }
+    }
+
+    pub fn from_child_node(
+        db: &impl db::DefDatabase2,
+        file_id: FileId,
+        child: &SyntaxNode,
+    ) -> ModuleSource {
+        if let Some(m) = child.ancestors().filter_map(ast::Module::cast).find(|it| !it.has_semi()) {
+            ModuleSource::Module(m)
+        } else {
+            let source_file = db.parse(file_id).tree();
+            ModuleSource::SourceFile(source_file)
+        }
+    }
+
+    pub fn from_file_id(db: &impl db::DefDatabase2, file_id: FileId) -> ModuleSource {
+        let source_file = db.parse(file_id).tree();
+        ModuleSource::SourceFile(source_file)
+    }
+}
+
+impl<T> Source<T> {
+    pub fn map<F: FnOnce(T) -> U, U>(self, f: F) -> Source<U> {
+        Source { file_id: self.file_id, ast: f(self.ast) }
+    }
+    pub fn file_syntax(&self, db: &impl AstDatabase) -> SyntaxNode {
+        db.parse_or_expand(self.file_id).expect("source created from invalid file")
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct ModuleId {
+    pub krate: CrateId,
+    pub module_id: CrateModuleId,
+}
+
+/// An ID of a module, **local** to a specific crate
+// FIXME: rename to `LocalModuleId`.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct CrateModuleId(RawId);
+impl_arena_id!(CrateModuleId);
+
+macro_rules! impl_intern_key {
+    ($name:ident) => {
+        impl salsa::InternKey for $name {
+            fn from_intern_id(v: salsa::InternId) -> Self {
+                $name(v)
+            }
+            fn as_intern_id(&self) -> salsa::InternId {
+                self.0
+            }
+        }
+    };
+}
+
+#[derive(Debug)]
+pub struct ItemLoc<N: AstNode> {
+    pub(crate) module: ModuleId,
+    ast_id: AstId<N>,
+}
+
+impl<N: AstNode> PartialEq for ItemLoc<N> {
+    fn eq(&self, other: &Self) -> bool {
+        self.module == other.module && self.ast_id == other.ast_id
+    }
+}
+impl<N: AstNode> Eq for ItemLoc<N> {}
+impl<N: AstNode> Hash for ItemLoc<N> {
+    fn hash<H: Hasher>(&self, hasher: &mut H) {
+        self.module.hash(hasher);
+        self.ast_id.hash(hasher);
+    }
+}
+
+impl<N: AstNode> Clone for ItemLoc<N> {
+    fn clone(&self) -> ItemLoc<N> {
+        ItemLoc { module: self.module, ast_id: self.ast_id }
+    }
+}
+
+#[derive(Clone, Copy)]
+pub struct LocationCtx<DB> {
+    db: DB,
+    module: ModuleId,
+    file_id: HirFileId,
+}
+
+impl<'a, DB> LocationCtx<&'a DB> {
+    pub fn new(db: &'a DB, module: ModuleId, file_id: HirFileId) -> LocationCtx<&'a DB> {
+        LocationCtx { db, module, file_id }
+    }
+}
+
+impl<'a, DB: AstDatabase + InternDatabase> LocationCtx<&'a DB> {
+    pub fn to_def<N, DEF>(self, ast: &N) -> DEF
+    where
+        N: AstNode,
+        DEF: AstItemDef<N>,
+    {
+        DEF::from_ast(self, ast)
+    }
+}
+
+pub trait AstItemDef<N: AstNode>: salsa::InternKey + Clone {
+    fn intern(db: &impl InternDatabase, loc: ItemLoc<N>) -> Self;
+    fn lookup_intern(self, db: &impl InternDatabase) -> ItemLoc<N>;
+
+    fn from_ast(ctx: LocationCtx<&(impl AstDatabase + InternDatabase)>, ast: &N) -> Self {
+        let items = ctx.db.ast_id_map(ctx.file_id);
+        let item_id = items.ast_id(ast);
+        Self::from_ast_id(ctx, item_id)
+    }
+    fn from_ast_id(ctx: LocationCtx<&impl InternDatabase>, ast_id: FileAstId<N>) -> Self {
+        let loc = ItemLoc { module: ctx.module, ast_id: AstId::new(ctx.file_id, ast_id) };
+        Self::intern(ctx.db, loc)
+    }
+    fn source(self, db: &(impl AstDatabase + InternDatabase)) -> Source<N> {
+        let loc = self.lookup_intern(db);
+        let ast = loc.ast_id.to_node(db);
+        Source { file_id: loc.ast_id.file_id(), ast }
+    }
+    fn module(self, db: &impl InternDatabase) -> ModuleId {
+        let loc = self.lookup_intern(db);
+        loc.module
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct FunctionId(salsa::InternId);
+impl_intern_key!(FunctionId);
+
+impl AstItemDef<ast::FnDef> for FunctionId {
+    fn intern(db: &impl InternDatabase, loc: ItemLoc<ast::FnDef>) -> Self {
+        db.intern_function(loc)
+    }
+    fn lookup_intern(self, db: &impl InternDatabase) -> ItemLoc<ast::FnDef> {
+        db.lookup_intern_function(self)
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct StructId(salsa::InternId);
+impl_intern_key!(StructId);
+impl AstItemDef<ast::StructDef> for StructId {
+    fn intern(db: &impl InternDatabase, loc: ItemLoc<ast::StructDef>) -> Self {
+        db.intern_struct(loc)
+    }
+    fn lookup_intern(self, db: &impl InternDatabase) -> ItemLoc<ast::StructDef> {
+        db.lookup_intern_struct(self)
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct UnionId(salsa::InternId);
+impl_intern_key!(UnionId);
+impl AstItemDef<ast::StructDef> for UnionId {
+    fn intern(db: &impl InternDatabase, loc: ItemLoc<ast::StructDef>) -> Self {
+        db.intern_union(loc)
+    }
+    fn lookup_intern(self, db: &impl InternDatabase) -> ItemLoc<ast::StructDef> {
+        db.lookup_intern_union(self)
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct EnumId(salsa::InternId);
+impl_intern_key!(EnumId);
+impl AstItemDef<ast::EnumDef> for EnumId {
+    fn intern(db: &impl InternDatabase, loc: ItemLoc<ast::EnumDef>) -> Self {
+        db.intern_enum(loc)
+    }
+    fn lookup_intern(self, db: &impl InternDatabase) -> ItemLoc<ast::EnumDef> {
+        db.lookup_intern_enum(self)
+    }
+}
+
+// FIXME: rename to `VariantId`, only enums can ave variants
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct EnumVariantId {
+    parent: EnumId,
+    local_id: LocalEnumVariantId,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct LocalEnumVariantId(RawId);
+impl_arena_id!(LocalEnumVariantId);
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct ConstId(salsa::InternId);
+impl_intern_key!(ConstId);
+impl AstItemDef<ast::ConstDef> for ConstId {
+    fn intern(db: &impl InternDatabase, loc: ItemLoc<ast::ConstDef>) -> Self {
+        db.intern_const(loc)
+    }
+    fn lookup_intern(self, db: &impl InternDatabase) -> ItemLoc<ast::ConstDef> {
+        db.lookup_intern_const(self)
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct StaticId(salsa::InternId);
+impl_intern_key!(StaticId);
+impl AstItemDef<ast::StaticDef> for StaticId {
+    fn intern(db: &impl InternDatabase, loc: ItemLoc<ast::StaticDef>) -> Self {
+        db.intern_static(loc)
+    }
+    fn lookup_intern(self, db: &impl InternDatabase) -> ItemLoc<ast::StaticDef> {
+        db.lookup_intern_static(self)
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct TraitId(salsa::InternId);
+impl_intern_key!(TraitId);
+impl AstItemDef<ast::TraitDef> for TraitId {
+    fn intern(db: &impl InternDatabase, loc: ItemLoc<ast::TraitDef>) -> Self {
+        db.intern_trait(loc)
+    }
+    fn lookup_intern(self, db: &impl InternDatabase) -> ItemLoc<ast::TraitDef> {
+        db.lookup_intern_trait(self)
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct TypeAliasId(salsa::InternId);
+impl_intern_key!(TypeAliasId);
+impl AstItemDef<ast::TypeAliasDef> for TypeAliasId {
+    fn intern(db: &impl InternDatabase, loc: ItemLoc<ast::TypeAliasDef>) -> Self {
+        db.intern_type_alias(loc)
+    }
+    fn lookup_intern(self, db: &impl InternDatabase) -> ItemLoc<ast::TypeAliasDef> {
+        db.lookup_intern_type_alias(self)
+    }
+}
+
+macro_rules! impl_froms {
+    ($e:ident: $($v:ident $(($($sv:ident),*))?),*) => {
+        $(
+            impl From<$v> for $e {
+                fn from(it: $v) -> $e {
+                    $e::$v(it)
+                }
+            }
+            $($(
+                impl From<$sv> for $e {
+                    fn from(it: $sv) -> $e {
+                        $e::$v($v::$sv(it))
+                    }
+                }
+            )*)?
+        )*
+    }
+}
+
+/// A Data Type
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum AdtId {
+    StructId(StructId),
+    UnionId(UnionId),
+    EnumId(EnumId),
+}
+impl_froms!(AdtId: StructId, UnionId, EnumId);
+
+/// The defs which can be visible in the module.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum ModuleDefId {
+    ModuleId(ModuleId),
+    FunctionId(FunctionId),
+    AdtId(AdtId),
+    // Can't be directly declared, but can be imported.
+    EnumVariantId(EnumVariantId),
+    ConstId(ConstId),
+    StaticId(StaticId),
+    TraitId(TraitId),
+    TypeAliasId(TypeAliasId),
+    BuiltinType(BuiltinType),
+}
+impl_froms!(
+    ModuleDefId: ModuleId,
+    FunctionId,
+    AdtId(StructId, EnumId, UnionId),
+    EnumVariantId,
+    ConstId,
+    StaticId,
+    TraitId,
+    TypeAliasId,
+    BuiltinType
+);
diff --git a/crates/ra_hir_def/src/nameres.rs b/crates/ra_hir_def/src/nameres.rs
new file mode 100644
index 000000000..11ba8a777
--- /dev/null
+++ b/crates/ra_hir_def/src/nameres.rs
@@ -0,0 +1,5 @@
+//! FIXME: write short doc here
+
+// FIXME: review privacy of submodules
+pub mod raw;
+pub mod mod_resolution;
diff --git a/crates/ra_hir_def/src/nameres/mod_resolution.rs b/crates/ra_hir_def/src/nameres/mod_resolution.rs
new file mode 100644
index 000000000..7d7e2779a
--- /dev/null
+++ b/crates/ra_hir_def/src/nameres/mod_resolution.rs
@@ -0,0 +1,77 @@
+//! This module resolves `mod foo;` declaration to file.
+use hir_expand::name::Name;
+use ra_db::FileId;
+use ra_syntax::SmolStr;
+use relative_path::RelativePathBuf;
+
+use crate::{db::DefDatabase2, HirFileId};
+
+#[derive(Clone, Debug)]
+pub struct ModDir {
+    /// `.` for `mod.rs`, `lib.rs`
+    /// `./foo` for `foo.rs`
+    /// `./foo/bar` for `mod bar { mod x; }` nested in `foo.rs`
+    path: RelativePathBuf,
+    /// inside `./foo.rs`, mods with `#[path]` should *not* be relative to `./foo/`
+    root_non_dir_owner: bool,
+}
+
+impl ModDir {
+    pub fn root() -> ModDir {
+        ModDir { path: RelativePathBuf::default(), root_non_dir_owner: false }
+    }
+
+    pub fn descend_into_definition(&self, name: &Name, attr_path: Option<&SmolStr>) -> ModDir {
+        let mut path = self.path.clone();
+        match attr_to_path(attr_path) {
+            None => path.push(&name.to_string()),
+            Some(attr_path) => {
+                if self.root_non_dir_owner {
+                    assert!(path.pop());
+                }
+                path.push(attr_path);
+            }
+        }
+        ModDir { path, root_non_dir_owner: false }
+    }
+
+    pub fn resolve_declaration(
+        &self,
+        db: &impl DefDatabase2,
+        file_id: HirFileId,
+        name: &Name,
+        attr_path: Option<&SmolStr>,
+    ) -> Result<(FileId, ModDir), RelativePathBuf> {
+        let file_id = file_id.original_file(db);
+
+        let mut candidate_files = Vec::new();
+        match attr_to_path(attr_path) {
+            Some(attr_path) => {
+                let base =
+                    if self.root_non_dir_owner { self.path.parent().unwrap() } else { &self.path };
+                candidate_files.push(base.join(attr_path))
+            }
+            None => {
+                candidate_files.push(self.path.join(&format!("{}.rs", name)));
+                candidate_files.push(self.path.join(&format!("{}/mod.rs", name)));
+            }
+        };
+
+        for candidate in candidate_files.iter() {
+            if let Some(file_id) = db.resolve_relative_path(file_id, candidate) {
+                let mut root_non_dir_owner = false;
+                let mut mod_path = RelativePathBuf::new();
+                if !(candidate.ends_with("mod.rs") || attr_path.is_some()) {
+                    root_non_dir_owner = true;
+                    mod_path.push(&name.to_string());
+                }
+                return Ok((file_id, ModDir { path: mod_path, root_non_dir_owner }));
+            }
+        }
+        Err(candidate_files.remove(0))
+    }
+}
+
+fn attr_to_path(attr: Option<&SmolStr>) -> Option<RelativePathBuf> {
+    attr.and_then(|it| RelativePathBuf::from_path(&it.replace("\\", "/")).ok())
+}
diff --git a/crates/ra_hir_def/src/nameres/raw.rs b/crates/ra_hir_def/src/nameres/raw.rs
new file mode 100644
index 000000000..86c05d602
--- /dev/null
+++ b/crates/ra_hir_def/src/nameres/raw.rs
@@ -0,0 +1,400 @@
+//! FIXME: write short doc here
+
+use std::{ops::Index, sync::Arc};
+
+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, path::Path, FileAstId, HirFileId, ModuleSource, Source};
+
+/// `RawItems` is a set of top-level items in a file (except for impls).
+///
+/// It is the input to name resolution algorithm. `RawItems` are not invalidated
+/// on most edits.
+#[derive(Debug, Default, PartialEq, Eq)]
+pub struct RawItems {
+    modules: Arena<Module, ModuleData>,
+    imports: Arena<ImportId, ImportData>,
+    defs: Arena<Def, DefData>,
+    macros: Arena<Macro, MacroData>,
+    /// items for top-level module
+    items: Vec<RawItem>,
+}
+
+#[derive(Debug, Default, PartialEq, Eq)]
+pub struct ImportSourceMap {
+    map: ArenaMap<ImportId, ImportSourcePtr>,
+}
+
+type ImportSourcePtr = Either<AstPtr<ast::UseTree>, AstPtr<ast::ExternCrateItem>>;
+type ImportSource = Either<ast::UseTree, ast::ExternCrateItem>;
+
+fn to_node(ptr: ImportSourcePtr, file: &SourceFile) -> ImportSource {
+    ptr.map(|ptr| ptr.to_node(file.syntax()), |ptr| ptr.to_node(file.syntax()))
+}
+
+impl ImportSourceMap {
+    fn insert(&mut self, import: ImportId, ptr: ImportSourcePtr) {
+        self.map.insert(import, ptr)
+    }
+
+    pub fn get(&self, source: &ModuleSource, import: ImportId) -> ImportSource {
+        let file = match source {
+            ModuleSource::SourceFile(file) => file.clone(),
+            ModuleSource::Module(m) => m.syntax().ancestors().find_map(SourceFile::cast).unwrap(),
+        };
+
+        to_node(self.map[import], &file)
+    }
+}
+
+impl RawItems {
+    pub(crate) fn raw_items_query(
+        db: &(impl DefDatabase2 + AstDatabase),
+        file_id: HirFileId,
+    ) -> Arc<RawItems> {
+        db.raw_items_with_source_map(file_id).0
+    }
+
+    pub(crate) fn raw_items_with_source_map_query(
+        db: &(impl DefDatabase2 + AstDatabase),
+        file_id: HirFileId,
+    ) -> (Arc<RawItems>, Arc<ImportSourceMap>) {
+        let mut collector = RawItemsCollector {
+            raw_items: RawItems::default(),
+            source_ast_id_map: db.ast_id_map(file_id),
+            source_map: ImportSourceMap::default(),
+            file_id,
+            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()) {
+                collector.process_module(None, source_file);
+            } else if let Some(item_list) = ast::MacroItems::cast(node) {
+                collector.process_module(None, item_list);
+            }
+        }
+        (Arc::new(collector.raw_items), Arc::new(collector.source_map))
+    }
+
+    pub fn items(&self) -> &[RawItem] {
+        &self.items
+    }
+}
+
+impl Index<Module> for RawItems {
+    type Output = ModuleData;
+    fn index(&self, idx: Module) -> &ModuleData {
+        &self.modules[idx]
+    }
+}
+
+impl Index<ImportId> for RawItems {
+    type Output = ImportData;
+    fn index(&self, idx: ImportId) -> &ImportData {
+        &self.imports[idx]
+    }
+}
+
+impl Index<Def> for RawItems {
+    type Output = DefData;
+    fn index(&self, idx: Def) -> &DefData {
+        &self.defs[idx]
+    }
+}
+
+impl Index<Macro> for RawItems {
+    type Output = MacroData;
+    fn index(&self, idx: Macro) -> &MacroData {
+        &self.macros[idx]
+    }
+}
+
+// Avoid heap allocation on items without attributes.
+type Attrs = Option<Arc<[Attr]>>;
+
+#[derive(Debug, PartialEq, Eq, Clone)]
+pub struct RawItem {
+    attrs: Attrs,
+    pub kind: RawItemKind,
+}
+
+impl RawItem {
+    pub fn attrs(&self) -> &[Attr] {
+        self.attrs.as_ref().map_or(&[], |it| &*it)
+    }
+}
+
+#[derive(Debug, PartialEq, Eq, Clone, Copy)]
+pub enum RawItemKind {
+    Module(Module),
+    Import(ImportId),
+    Def(Def),
+    Macro(Macro),
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Module(RawId);
+impl_arena_id!(Module);
+
+#[derive(Debug, PartialEq, Eq)]
+pub enum ModuleData {
+    Declaration { name: Name, ast_id: FileAstId<ast::Module> },
+    Definition { name: Name, ast_id: FileAstId<ast::Module>, items: Vec<RawItem> },
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct ImportId(RawId);
+impl_arena_id!(ImportId);
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ImportData {
+    pub path: Path,
+    pub alias: Option<Name>,
+    pub is_glob: bool,
+    pub is_prelude: bool,
+    pub is_extern_crate: bool,
+    pub is_macro_use: bool,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Def(RawId);
+impl_arena_id!(Def);
+
+#[derive(Debug, PartialEq, Eq)]
+pub struct DefData {
+    pub name: Name,
+    pub kind: DefKind,
+}
+
+#[derive(Debug, PartialEq, Eq, Clone, Copy)]
+pub enum DefKind {
+    Function(FileAstId<ast::FnDef>),
+    Struct(FileAstId<ast::StructDef>),
+    Union(FileAstId<ast::StructDef>),
+    Enum(FileAstId<ast::EnumDef>),
+    Const(FileAstId<ast::ConstDef>),
+    Static(FileAstId<ast::StaticDef>),
+    Trait(FileAstId<ast::TraitDef>),
+    TypeAlias(FileAstId<ast::TypeAliasDef>),
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Macro(RawId);
+impl_arena_id!(Macro);
+
+#[derive(Debug, PartialEq, Eq)]
+pub struct MacroData {
+    pub ast_id: FileAstId<ast::MacroCall>,
+    pub path: Path,
+    pub name: Option<Name>,
+    pub export: bool,
+}
+
+struct RawItemsCollector {
+    raw_items: RawItems,
+    source_ast_id_map: Arc<AstIdMap>,
+    source_map: ImportSourceMap,
+    file_id: HirFileId,
+    hygiene: Hygiene,
+}
+
+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 {
+                ast::ItemOrMacro::Macro(m) => self.add_macro(current_module, m),
+                ast::ItemOrMacro::Item(item) => self.add_item(current_module, item),
+            }
+        }
+    }
+
+    fn add_item(&mut self, current_module: Option<Module>, item: ast::ModuleItem) {
+        let attrs = self.parse_attrs(&item);
+        let (kind, name) = match item {
+            ast::ModuleItem::Module(module) => {
+                self.add_module(current_module, module);
+                return;
+            }
+            ast::ModuleItem::UseItem(use_item) => {
+                self.add_use_item(current_module, use_item);
+                return;
+            }
+            ast::ModuleItem::ExternCrateItem(extern_crate) => {
+                self.add_extern_crate_item(current_module, extern_crate);
+                return;
+            }
+            ast::ModuleItem::ImplBlock(_) => {
+                // impls don't participate in name resolution
+                return;
+            }
+            ast::ModuleItem::StructDef(it) => {
+                let id = self.source_ast_id_map.ast_id(&it);
+                let name = it.name();
+                if it.is_union() {
+                    (DefKind::Union(id), name)
+                } else {
+                    (DefKind::Struct(id), name)
+                }
+            }
+            ast::ModuleItem::EnumDef(it) => {
+                (DefKind::Enum(self.source_ast_id_map.ast_id(&it)), it.name())
+            }
+            ast::ModuleItem::FnDef(it) => {
+                (DefKind::Function(self.source_ast_id_map.ast_id(&it)), it.name())
+            }
+            ast::ModuleItem::TraitDef(it) => {
+                (DefKind::Trait(self.source_ast_id_map.ast_id(&it)), it.name())
+            }
+            ast::ModuleItem::TypeAliasDef(it) => {
+                (DefKind::TypeAlias(self.source_ast_id_map.ast_id(&it)), it.name())
+            }
+            ast::ModuleItem::ConstDef(it) => {
+                (DefKind::Const(self.source_ast_id_map.ast_id(&it)), it.name())
+            }
+            ast::ModuleItem::StaticDef(it) => {
+                (DefKind::Static(self.source_ast_id_map.ast_id(&it)), it.name())
+            }
+        };
+        if let Some(name) = name {
+            let name = name.as_name();
+            let def = self.raw_items.defs.alloc(DefData { name, kind });
+            self.push_item(current_module, attrs, RawItemKind::Def(def));
+        }
+    }
+
+    fn add_module(&mut self, current_module: Option<Module>, module: ast::Module) {
+        let name = match module.name() {
+            Some(it) => it.as_name(),
+            None => return,
+        };
+        let attrs = self.parse_attrs(&module);
+
+        let ast_id = self.source_ast_id_map.ast_id(&module);
+        if module.has_semi() {
+            let item = self.raw_items.modules.alloc(ModuleData::Declaration { name, ast_id });
+            self.push_item(current_module, attrs, RawItemKind::Module(item));
+            return;
+        }
+
+        if let Some(item_list) = module.item_list() {
+            let item = self.raw_items.modules.alloc(ModuleData::Definition {
+                name,
+                ast_id,
+                items: Vec::new(),
+            });
+            self.process_module(Some(item), item_list);
+            self.push_item(current_module, attrs, RawItemKind::Module(item));
+            return;
+        }
+        // FIXME: restore this mark once we complete hir splitting
+        // tested_by!(name_res_works_for_broken_modules);
+    }
+
+    fn add_use_item(&mut self, current_module: Option<Module>, use_item: ast::UseItem) {
+        // FIXME: cfg_attr
+        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.hygiene,
+            |path, use_tree, is_glob, alias| {
+                let import_data = ImportData {
+                    path,
+                    alias,
+                    is_glob,
+                    is_prelude,
+                    is_extern_crate: false,
+                    is_macro_use: false,
+                };
+                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(
+        &mut self,
+        current_module: Option<Module>,
+        extern_crate: ast::ExternCrateItem,
+    ) {
+        if let Some(name_ref) = extern_crate.name_ref() {
+            let path = Path::from_name_ref(&name_ref);
+            let alias = extern_crate.alias().and_then(|a| a.name()).map(|it| it.as_name());
+            let attrs = self.parse_attrs(&extern_crate);
+            // FIXME: cfg_attr
+            let is_macro_use = extern_crate.has_atom_attr("macro_use");
+            let import_data = ImportData {
+                path,
+                alias,
+                is_glob: false,
+                is_prelude: false,
+                is_extern_crate: true,
+                is_macro_use,
+            };
+            self.push_import(
+                current_module,
+                attrs,
+                import_data,
+                Either::B(AstPtr::new(&extern_crate)),
+            );
+        }
+    }
+
+    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(path, &self.hygiene)) {
+            Some(it) => it,
+            _ => return,
+        };
+
+        let name = m.name().map(|it| it.as_name());
+        let ast_id = self.source_ast_id_map.ast_id(&m);
+        // FIXME: cfg_attr
+        let export = m.attrs().filter_map(|x| x.simple_name()).any(|name| name == "macro_export");
+
+        let m = self.raw_items.macros.alloc(MacroData { ast_id, path, name, export });
+        self.push_item(current_module, attrs, RawItemKind::Macro(m));
+    }
+
+    fn push_import(
+        &mut self,
+        current_module: Option<Module>,
+        attrs: Attrs,
+        data: ImportData,
+        source: ImportSourcePtr,
+    ) {
+        let import = self.raw_items.imports.alloc(data);
+        self.source_map.insert(import, source);
+        self.push_item(current_module, attrs, RawItemKind::Import(import))
+    }
+
+    fn push_item(&mut self, current_module: Option<Module>, attrs: Attrs, kind: RawItemKind) {
+        match current_module {
+            Some(module) => match &mut self.raw_items.modules[module] {
+                ModuleData::Definition { items, .. } => items,
+                ModuleData::Declaration { .. } => unreachable!(),
+            },
+            None => &mut self.raw_items.items,
+        }
+        .push(RawItem { attrs, kind })
+    }
+
+    fn parse_attrs(&self, item: &impl ast::AttrsOwner) -> Attrs {
+        Attr::from_attrs_owner(item, &self.hygiene)
+    }
+}
diff --git a/crates/ra_hir_def/src/path.rs b/crates/ra_hir_def/src/path.rs
new file mode 100644
index 000000000..04039376f
--- /dev/null
+++ b/crates/ra_hir_def/src/path.rs
@@ -0,0 +1,420 @@
+//! FIXME: write short doc here
+
+use std::{iter, sync::Arc};
+
+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::{type_ref::TypeRef, Source};
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct Path {
+    pub kind: PathKind,
+    pub segments: Vec<PathSegment>,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct PathSegment {
+    pub name: Name,
+    pub args_and_bindings: Option<Arc<GenericArgs>>,
+}
+
+/// Generic arguments to a path segment (e.g. the `i32` in `Option<i32>`). This
+/// can (in the future) also include bindings of associated types, like in
+/// `Iterator<Item = Foo>`.
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct GenericArgs {
+    pub args: Vec<GenericArg>,
+    /// This specifies whether the args contain a Self type as the first
+    /// element. This is the case for path segments like `<T as Trait>`, where
+    /// `T` is actually a type parameter for the path `Trait` specifying the
+    /// Self type. Otherwise, when we have a path `Trait<X, Y>`, the Self type
+    /// is left out.
+    pub has_self_type: bool,
+    /// Associated type bindings like in `Iterator<Item = T>`.
+    pub bindings: Vec<(Name, TypeRef)>,
+}
+
+/// A single generic argument.
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub enum GenericArg {
+    Type(TypeRef),
+    // or lifetime...
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub enum PathKind {
+    Plain,
+    Self_,
+    Super,
+    Crate,
+    // Absolute path
+    Abs,
+    // Type based path like `<T>::foo`
+    Type(Box<TypeRef>),
+    // `$crate` from macro expansion
+    DollarCrate(CrateId),
+}
+
+impl Path {
+    /// Calls `cb` with all paths, represented by this use item.
+    pub fn expand_use_item(
+        item_src: Source<ast::UseItem>,
+        hygiene: &Hygiene,
+        mut cb: impl FnMut(Path, &ast::UseTree, bool, Option<Name>),
+    ) {
+        if let Some(tree) = item_src.ast.use_tree() {
+            expand_use_tree(None, tree, hygiene, &mut cb);
+        }
+    }
+
+    pub fn from_simple_segments(kind: PathKind, segments: impl IntoIterator<Item = Name>) -> Path {
+        Path {
+            kind,
+            segments: segments
+                .into_iter()
+                .map(|name| PathSegment { name, args_and_bindings: None })
+                .collect(),
+        }
+    }
+
+    /// Converts an `ast::Path` to `Path`. Works with use trees.
+    /// DEPRECATED: It does not handle `$crate` from macro call.
+    pub fn from_ast(path: ast::Path) -> Option<Path> {
+        Path::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(mut path: ast::Path, hygiene: &Hygiene) -> Option<Path> {
+        let mut kind = PathKind::Plain;
+        let mut segments = Vec::new();
+        loop {
+            let segment = path.segment()?;
+
+            if segment.has_colon_colon() {
+                kind = PathKind::Abs;
+            }
+
+            match segment.kind()? {
+                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;
+                        }
+                    }
+                }
+                ast::PathSegmentKind::Type { type_ref, trait_ref } => {
+                    assert!(path.qualifier().is_none()); // this can only occur at the first segment
+
+                    let self_type = TypeRef::from_ast(type_ref?);
+
+                    match trait_ref {
+                        // <T>::foo
+                        None => {
+                            kind = PathKind::Type(Box::new(self_type));
+                        }
+                        // <T as Trait<A>>::Foo desugars to Trait<Self=T, A>::Foo
+                        Some(trait_ref) => {
+                            let path = Path::from_src(trait_ref.path()?, hygiene)?;
+                            kind = path.kind;
+                            let mut prefix_segments = path.segments;
+                            prefix_segments.reverse();
+                            segments.extend(prefix_segments);
+                            // Insert the type reference (T in the above example) as Self parameter for the trait
+                            let mut last_segment = segments.last_mut()?;
+                            if last_segment.args_and_bindings.is_none() {
+                                last_segment.args_and_bindings =
+                                    Some(Arc::new(GenericArgs::empty()));
+                            };
+                            let args = last_segment.args_and_bindings.as_mut().unwrap();
+                            let mut args_inner = Arc::make_mut(args);
+                            args_inner.has_self_type = true;
+                            args_inner.args.insert(0, GenericArg::Type(self_type));
+                        }
+                    }
+                }
+                ast::PathSegmentKind::CrateKw => {
+                    kind = PathKind::Crate;
+                    break;
+                }
+                ast::PathSegmentKind::SelfKw => {
+                    kind = PathKind::Self_;
+                    break;
+                }
+                ast::PathSegmentKind::SuperKw => {
+                    kind = PathKind::Super;
+                    break;
+                }
+            }
+            path = match qualifier(&path) {
+                Some(it) => it,
+                None => break,
+            };
+        }
+        segments.reverse();
+        return Some(Path { kind, segments });
+
+        fn qualifier(path: &ast::Path) -> Option<ast::Path> {
+            if let Some(q) = path.qualifier() {
+                return Some(q);
+            }
+            // FIXME: this bottom up traversal is not too precise.
+            // Should we handle do a top-down analysis, recording results?
+            let use_tree_list = path.syntax().ancestors().find_map(ast::UseTreeList::cast)?;
+            let use_tree = use_tree_list.parent_use_tree();
+            use_tree.path()
+        }
+    }
+
+    /// Converts an `ast::NameRef` into a single-identifier `Path`.
+    pub fn from_name_ref(name_ref: &ast::NameRef) -> Path {
+        name_ref.as_name().into()
+    }
+
+    /// `true` is this path is a single identifier, like `foo`
+    pub fn is_ident(&self) -> bool {
+        self.kind == PathKind::Plain && self.segments.len() == 1
+    }
+
+    /// `true` if this path is just a standalone `self`
+    pub fn is_self(&self) -> bool {
+        self.kind == PathKind::Self_ && self.segments.is_empty()
+    }
+
+    /// If this path is a single identifier, like `foo`, return its name.
+    pub fn as_ident(&self) -> Option<&Name> {
+        if self.kind != PathKind::Plain || self.segments.len() > 1 {
+            return None;
+        }
+        self.segments.first().map(|s| &s.name)
+    }
+
+    pub fn expand_macro_expr(&self) -> Option<Name> {
+        self.as_ident().and_then(|name| Some(name.clone()))
+    }
+
+    pub fn is_type_relative(&self) -> bool {
+        match self.kind {
+            PathKind::Type(_) => true,
+            _ => false,
+        }
+    }
+}
+
+impl GenericArgs {
+    pub fn from_ast(node: ast::TypeArgList) -> Option<GenericArgs> {
+        let mut args = Vec::new();
+        for type_arg in node.type_args() {
+            let type_ref = TypeRef::from_ast_opt(type_arg.type_ref());
+            args.push(GenericArg::Type(type_ref));
+        }
+        // lifetimes ignored for now
+        let mut bindings = Vec::new();
+        for assoc_type_arg in node.assoc_type_args() {
+            if let Some(name_ref) = assoc_type_arg.name_ref() {
+                let name = name_ref.as_name();
+                let type_ref = TypeRef::from_ast_opt(assoc_type_arg.type_ref());
+                bindings.push((name, type_ref));
+            }
+        }
+        if args.is_empty() && bindings.is_empty() {
+            None
+        } else {
+            Some(GenericArgs { args, has_self_type: false, bindings })
+        }
+    }
+
+    /// Collect `GenericArgs` from the parts of a fn-like path, i.e. `Fn(X, Y)
+    /// -> Z` (which desugars to `Fn<(X, Y), Output=Z>`).
+    pub(crate) fn from_fn_like_path_ast(
+        params: Option<ast::ParamList>,
+        ret_type: Option<ast::RetType>,
+    ) -> Option<GenericArgs> {
+        let mut args = Vec::new();
+        let mut bindings = Vec::new();
+        if let Some(params) = params {
+            let mut param_types = Vec::new();
+            for param in params.params() {
+                let type_ref = TypeRef::from_ast_opt(param.ascribed_type());
+                param_types.push(type_ref);
+            }
+            let arg = GenericArg::Type(TypeRef::Tuple(param_types));
+            args.push(arg);
+        }
+        if let Some(ret_type) = ret_type {
+            let type_ref = TypeRef::from_ast_opt(ret_type.type_ref());
+            bindings.push((name::OUTPUT_TYPE, type_ref))
+        }
+        if args.is_empty() && bindings.is_empty() {
+            None
+        } else {
+            Some(GenericArgs { args, has_self_type: false, bindings })
+        }
+    }
+
+    pub(crate) fn empty() -> GenericArgs {
+        GenericArgs { args: Vec::new(), has_self_type: false, bindings: Vec::new() }
+    }
+}
+
+impl From<Name> for Path {
+    fn from(name: Name) -> Path {
+        Path::from_simple_segments(PathKind::Plain, iter::once(name))
+    }
+}
+
+fn expand_use_tree(
+    prefix: Option<Path>,
+    tree: ast::UseTree,
+    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() {
+            // E.g. use something::{{{inner}}};
+            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, 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, hygiene, cb);
+        }
+    } else {
+        let alias = tree.alias().and_then(|a| a.name()).map(|a| a.as_name());
+        if let Some(ast_path) = tree.path() {
+            // Handle self in a path.
+            // E.g. `use something::{self, <...>}`
+            if ast_path.qualifier().is_none() {
+                if let Some(segment) = ast_path.segment() {
+                    if segment.kind() == Some(ast::PathSegmentKind::SelfKw) {
+                        if let Some(prefix) = prefix {
+                            cb(prefix, &tree, false, alias);
+                            return;
+                        }
+                    }
+                }
+            }
+            if let Some(path) = convert_path(prefix, ast_path, hygiene) {
+                let is_glob = tree.has_star();
+                cb(path, &tree, is_glob, alias)
+            }
+            // FIXME: report errors somewhere
+            // We get here if we do
+        }
+    }
+}
+
+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, hygiene)?)
+    } else {
+        prefix
+    };
+
+    let segment = path.segment()?;
+    let res = match segment.kind()? {
+        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(crate_id),
+                        iter::empty(),
+                    ))
+                }
+            }
+        }
+        ast::PathSegmentKind::CrateKw => {
+            if prefix.is_some() {
+                return None;
+            }
+            Path::from_simple_segments(PathKind::Crate, iter::empty())
+        }
+        ast::PathSegmentKind::SelfKw => {
+            if prefix.is_some() {
+                return None;
+            }
+            Path::from_simple_segments(PathKind::Self_, iter::empty())
+        }
+        ast::PathSegmentKind::SuperKw => {
+            if prefix.is_some() {
+                return None;
+            }
+            Path::from_simple_segments(PathKind::Super, iter::empty())
+        }
+        ast::PathSegmentKind::Type { .. } => {
+            // not allowed in imports
+            return None;
+        }
+    };
+    Some(res)
+}
+
+pub mod known {
+    use hir_expand::name;
+
+    use super::{Path, PathKind};
+
+    pub fn std_iter_into_iterator() -> Path {
+        Path::from_simple_segments(
+            PathKind::Abs,
+            vec![name::STD, name::ITER, name::INTO_ITERATOR_TYPE],
+        )
+    }
+
+    pub fn std_ops_try() -> Path {
+        Path::from_simple_segments(PathKind::Abs, vec![name::STD, name::OPS, name::TRY_TYPE])
+    }
+
+    pub fn std_result_result() -> Path {
+        Path::from_simple_segments(PathKind::Abs, vec![name::STD, name::RESULT, name::RESULT_TYPE])
+    }
+
+    pub fn std_future_future() -> Path {
+        Path::from_simple_segments(PathKind::Abs, vec![name::STD, name::FUTURE, name::FUTURE_TYPE])
+    }
+
+    pub fn std_boxed_box() -> Path {
+        Path::from_simple_segments(PathKind::Abs, vec![name::STD, name::BOXED, name::BOX_TYPE])
+    }
+}
diff --git a/crates/ra_hir_def/src/type_ref.rs b/crates/ra_hir_def/src/type_ref.rs
new file mode 100644
index 000000000..8af061116
--- /dev/null
+++ b/crates/ra_hir_def/src/type_ref.rs
@@ -0,0 +1,162 @@
+//! HIR for references to types. Paths in these are not yet resolved. They can
+//! be directly created from an ast::TypeRef, without further queries.
+
+use ra_syntax::ast::{self, TypeAscriptionOwner, TypeBoundsOwner};
+
+use crate::path::Path;
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+pub enum Mutability {
+    Shared,
+    Mut,
+}
+
+impl Mutability {
+    pub fn from_mutable(mutable: bool) -> Mutability {
+        if mutable {
+            Mutability::Mut
+        } else {
+            Mutability::Shared
+        }
+    }
+
+    pub fn as_keyword_for_ref(self) -> &'static str {
+        match self {
+            Mutability::Shared => "",
+            Mutability::Mut => "mut ",
+        }
+    }
+
+    pub fn as_keyword_for_ptr(self) -> &'static str {
+        match self {
+            Mutability::Shared => "const ",
+            Mutability::Mut => "mut ",
+        }
+    }
+}
+
+/// Compare ty::Ty
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+pub enum TypeRef {
+    Never,
+    Placeholder,
+    Tuple(Vec<TypeRef>),
+    Path(Path),
+    RawPtr(Box<TypeRef>, Mutability),
+    Reference(Box<TypeRef>, Mutability),
+    Array(Box<TypeRef> /*, Expr*/),
+    Slice(Box<TypeRef>),
+    /// A fn pointer. Last element of the vector is the return type.
+    Fn(Vec<TypeRef>),
+    // For
+    ImplTrait(Vec<TypeBound>),
+    DynTrait(Vec<TypeBound>),
+    Error,
+}
+
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+pub enum TypeBound {
+    Path(Path),
+    // also for<> bounds
+    // also Lifetimes
+    Error,
+}
+
+impl TypeRef {
+    /// Converts an `ast::TypeRef` to a `hir::TypeRef`.
+    pub fn from_ast(node: ast::TypeRef) -> Self {
+        match node {
+            ast::TypeRef::ParenType(inner) => TypeRef::from_ast_opt(inner.type_ref()),
+            ast::TypeRef::TupleType(inner) => {
+                TypeRef::Tuple(inner.fields().map(TypeRef::from_ast).collect())
+            }
+            ast::TypeRef::NeverType(..) => TypeRef::Never,
+            ast::TypeRef::PathType(inner) => {
+                // FIXME: Use `Path::from_src`
+                inner.path().and_then(Path::from_ast).map(TypeRef::Path).unwrap_or(TypeRef::Error)
+            }
+            ast::TypeRef::PointerType(inner) => {
+                let inner_ty = TypeRef::from_ast_opt(inner.type_ref());
+                let mutability = Mutability::from_mutable(inner.is_mut());
+                TypeRef::RawPtr(Box::new(inner_ty), mutability)
+            }
+            ast::TypeRef::ArrayType(inner) => {
+                TypeRef::Array(Box::new(TypeRef::from_ast_opt(inner.type_ref())))
+            }
+            ast::TypeRef::SliceType(inner) => {
+                TypeRef::Slice(Box::new(TypeRef::from_ast_opt(inner.type_ref())))
+            }
+            ast::TypeRef::ReferenceType(inner) => {
+                let inner_ty = TypeRef::from_ast_opt(inner.type_ref());
+                let mutability = Mutability::from_mutable(inner.is_mut());
+                TypeRef::Reference(Box::new(inner_ty), mutability)
+            }
+            ast::TypeRef::PlaceholderType(_inner) => TypeRef::Placeholder,
+            ast::TypeRef::FnPointerType(inner) => {
+                let ret_ty = TypeRef::from_ast_opt(inner.ret_type().and_then(|rt| rt.type_ref()));
+                let mut params = if let Some(pl) = inner.param_list() {
+                    pl.params().map(|p| p.ascribed_type()).map(TypeRef::from_ast_opt).collect()
+                } else {
+                    Vec::new()
+                };
+                params.push(ret_ty);
+                TypeRef::Fn(params)
+            }
+            // for types are close enough for our purposes to the inner type for now...
+            ast::TypeRef::ForType(inner) => TypeRef::from_ast_opt(inner.type_ref()),
+            ast::TypeRef::ImplTraitType(inner) => {
+                TypeRef::ImplTrait(type_bounds_from_ast(inner.type_bound_list()))
+            }
+            ast::TypeRef::DynTraitType(inner) => {
+                TypeRef::DynTrait(type_bounds_from_ast(inner.type_bound_list()))
+            }
+        }
+    }
+
+    pub fn from_ast_opt(node: Option<ast::TypeRef>) -> Self {
+        if let Some(node) = node {
+            TypeRef::from_ast(node)
+        } else {
+            TypeRef::Error
+        }
+    }
+
+    pub fn unit() -> TypeRef {
+        TypeRef::Tuple(Vec::new())
+    }
+}
+
+pub(crate) fn type_bounds_from_ast(type_bounds_opt: Option<ast::TypeBoundList>) -> Vec<TypeBound> {
+    if let Some(type_bounds) = type_bounds_opt {
+        type_bounds.bounds().map(TypeBound::from_ast).collect()
+    } else {
+        vec![]
+    }
+}
+
+impl TypeBound {
+    pub fn from_ast(node: ast::TypeBound) -> Self {
+        match node.kind() {
+            ast::TypeBoundKind::PathType(path_type) => {
+                let path = match path_type.path() {
+                    Some(p) => p,
+                    None => return TypeBound::Error,
+                };
+                // FIXME: Use `Path::from_src`
+                let path = match Path::from_ast(path) {
+                    Some(p) => p,
+                    None => return TypeBound::Error,
+                };
+                TypeBound::Path(path)
+            }
+            ast::TypeBoundKind::ForType(_) | ast::TypeBoundKind::Lifetime(_) => TypeBound::Error,
+        }
+    }
+
+    pub fn as_path(&self) -> Option<&Path> {
+        match self {
+            TypeBound::Path(p) => Some(p),
+            _ => None,
+        }
+    }
+}