Rename ra_hir -> hir

10 files changed, 3853 insertions, 0 deletions

diff --git a/crates/hir/Cargo.toml b/crates/hir/Cargo.toml
new file mode 100644
index 000000000..dbb2986b6
--- /dev/null
+++ b/crates/hir/Cargo.toml
@@ -0,0 +1,24 @@
+[package]
+name = "hir"
+version = "0.0.0"
+license = "MIT OR Apache-2.0"
+authors = ["rust-analyzer developers"]
+edition = "2018"
+
+[lib]
+doctest = false
+
+[dependencies]
+log = "0.4.8"
+rustc-hash = "1.1.0"
+either = "1.5.3"
+arrayvec = "0.5.1"
+itertools = "0.9.0"
+
+stdx = { path = "../stdx" }
+syntax = { path = "../syntax" }
+base_db = { path = "../base_db" }
+profile = { path = "../profile" }
+hir_expand = { path = "../hir_expand" }
+hir_def = { path = "../hir_def" }
+hir_ty = { path = "../hir_ty" }
diff --git a/crates/hir/src/code_model.rs b/crates/hir/src/code_model.rs
new file mode 100644
index 000000000..8ffb9e99b
--- /dev/null
+++ b/crates/hir/src/code_model.rs
@@ -0,0 +1,1712 @@
+//! FIXME: write short doc here
+use std::{iter, sync::Arc};
+
+use arrayvec::ArrayVec;
+use base_db::{CrateId, Edition, FileId};
+use either::Either;
+use hir_def::{
+    adt::ReprKind,
+    adt::StructKind,
+    adt::VariantData,
+    builtin_type::BuiltinType,
+    docs::Documentation,
+    expr::{BindingAnnotation, Pat, PatId},
+    import_map,
+    per_ns::PerNs,
+    resolver::{HasResolver, Resolver},
+    src::HasSource as _,
+    type_ref::{Mutability, TypeRef},
+    AdtId, AssocContainerId, ConstId, DefWithBodyId, EnumId, FunctionId, GenericDefId, HasModule,
+    ImplId, LocalEnumVariantId, LocalFieldId, LocalModuleId, Lookup, ModuleId, StaticId, StructId,
+    TraitId, TypeAliasId, TypeParamId, UnionId,
+};
+use hir_expand::{
+    diagnostics::DiagnosticSink,
+    name::{name, AsName},
+    MacroDefId, MacroDefKind,
+};
+use hir_ty::{
+    autoderef,
+    display::{HirDisplayError, HirFormatter},
+    method_resolution, ApplicationTy, CallableDefId, Canonical, FnSig, GenericPredicate,
+    InEnvironment, Substs, TraitEnvironment, Ty, TyDefId, TypeCtor,
+};
+use rustc_hash::FxHashSet;
+use stdx::impl_from;
+use syntax::{
+    ast::{self, AttrsOwner, NameOwner},
+    AstNode,
+};
+
+use crate::{
+    db::{DefDatabase, HirDatabase},
+    has_source::HasSource,
+    HirDisplay, InFile, Name,
+};
+
+/// hir::Crate describes a single crate. It's the main interface with which
+/// a crate's dependencies interact. Mostly, it should be just a proxy for the
+/// root module.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Crate {
+    pub(crate) id: CrateId,
+}
+
+#[derive(Debug)]
+pub struct CrateDependency {
+    pub krate: Crate,
+    pub name: Name,
+}
+
+impl Crate {
+    pub fn dependencies(self, db: &dyn HirDatabase) -> Vec<CrateDependency> {
+        db.crate_graph()[self.id]
+            .dependencies
+            .iter()
+            .map(|dep| {
+                let krate = Crate { id: dep.crate_id };
+                let name = dep.as_name();
+                CrateDependency { krate, name }
+            })
+            .collect()
+    }
+
+    // FIXME: add `transitive_reverse_dependencies`.
+    pub fn reverse_dependencies(self, db: &dyn HirDatabase) -> Vec<Crate> {
+        let crate_graph = db.crate_graph();
+        crate_graph
+            .iter()
+            .filter(|&krate| {
+                crate_graph[krate].dependencies.iter().any(|it| it.crate_id == self.id)
+            })
+            .map(|id| Crate { id })
+            .collect()
+    }
+
+    pub fn root_module(self, db: &dyn HirDatabase) -> Module {
+        let module_id = db.crate_def_map(self.id).root;
+        Module::new(self, module_id)
+    }
+
+    pub fn root_file(self, db: &dyn HirDatabase) -> FileId {
+        db.crate_graph()[self.id].root_file_id
+    }
+
+    pub fn edition(self, db: &dyn HirDatabase) -> Edition {
+        db.crate_graph()[self.id].edition
+    }
+
+    pub fn display_name(self, db: &dyn HirDatabase) -> Option<String> {
+        db.crate_graph()[self.id].display_name.clone()
+    }
+
+    pub fn query_external_importables(
+        self,
+        db: &dyn DefDatabase,
+        query: &str,
+    ) -> impl Iterator<Item = Either<ModuleDef, MacroDef>> {
+        import_map::search_dependencies(
+            db,
+            self.into(),
+            import_map::Query::new(query).anchor_end().case_sensitive().limit(40),
+        )
+        .into_iter()
+        .map(|item| match item {
+            ItemInNs::Types(mod_id) | ItemInNs::Values(mod_id) => Either::Left(mod_id.into()),
+            ItemInNs::Macros(mac_id) => Either::Right(mac_id.into()),
+        })
+    }
+
+    pub fn all(db: &dyn HirDatabase) -> Vec<Crate> {
+        db.crate_graph().iter().map(|id| Crate { id }).collect()
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Module {
+    pub(crate) id: ModuleId,
+}
+
+/// The defs which can be visible in the module.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum ModuleDef {
+    Module(Module),
+    Function(Function),
+    Adt(Adt),
+    // Can't be directly declared, but can be imported.
+    EnumVariant(EnumVariant),
+    Const(Const),
+    Static(Static),
+    Trait(Trait),
+    TypeAlias(TypeAlias),
+    BuiltinType(BuiltinType),
+}
+impl_from!(
+    Module,
+    Function,
+    Adt(Struct, Enum, Union),
+    EnumVariant,
+    Const,
+    Static,
+    Trait,
+    TypeAlias,
+    BuiltinType
+    for ModuleDef
+);
+
+impl ModuleDef {
+    pub fn module(self, db: &dyn HirDatabase) -> Option<Module> {
+        match self {
+            ModuleDef::Module(it) => it.parent(db),
+            ModuleDef::Function(it) => Some(it.module(db)),
+            ModuleDef::Adt(it) => Some(it.module(db)),
+            ModuleDef::EnumVariant(it) => Some(it.module(db)),
+            ModuleDef::Const(it) => Some(it.module(db)),
+            ModuleDef::Static(it) => Some(it.module(db)),
+            ModuleDef::Trait(it) => Some(it.module(db)),
+            ModuleDef::TypeAlias(it) => Some(it.module(db)),
+            ModuleDef::BuiltinType(_) => None,
+        }
+    }
+
+    pub fn definition_visibility(&self, db: &dyn HirDatabase) -> Option<Visibility> {
+        let module = match self {
+            ModuleDef::Module(it) => it.parent(db)?,
+            ModuleDef::Function(it) => return Some(it.visibility(db)),
+            ModuleDef::Adt(it) => it.module(db),
+            ModuleDef::EnumVariant(it) => {
+                let parent = it.parent_enum(db);
+                let module = it.module(db);
+                return module.visibility_of(db, &ModuleDef::Adt(Adt::Enum(parent)));
+            }
+            ModuleDef::Const(it) => return Some(it.visibility(db)),
+            ModuleDef::Static(it) => it.module(db),
+            ModuleDef::Trait(it) => it.module(db),
+            ModuleDef::TypeAlias(it) => return Some(it.visibility(db)),
+            ModuleDef::BuiltinType(_) => return None,
+        };
+
+        module.visibility_of(db, self)
+    }
+
+    pub fn name(self, db: &dyn HirDatabase) -> Option<Name> {
+        match self {
+            ModuleDef::Adt(it) => Some(it.name(db)),
+            ModuleDef::Trait(it) => Some(it.name(db)),
+            ModuleDef::Function(it) => Some(it.name(db)),
+            ModuleDef::EnumVariant(it) => Some(it.name(db)),
+            ModuleDef::TypeAlias(it) => Some(it.name(db)),
+
+            ModuleDef::Module(it) => it.name(db),
+            ModuleDef::Const(it) => it.name(db),
+            ModuleDef::Static(it) => it.name(db),
+
+            ModuleDef::BuiltinType(it) => Some(it.as_name()),
+        }
+    }
+}
+
+pub use hir_def::{
+    attr::Attrs, item_scope::ItemInNs, item_tree::ItemTreeNode, visibility::Visibility,
+    AssocItemId, AssocItemLoc,
+};
+
+impl Module {
+    pub(crate) fn new(krate: Crate, crate_module_id: LocalModuleId) -> Module {
+        Module { id: ModuleId { krate: krate.id, local_id: crate_module_id } }
+    }
+
+    /// Name of this module.
+    pub fn name(self, db: &dyn HirDatabase) -> Option<Name> {
+        let def_map = db.crate_def_map(self.id.krate);
+        let parent = def_map[self.id.local_id].parent?;
+        def_map[parent].children.iter().find_map(|(name, module_id)| {
+            if *module_id == self.id.local_id {
+                Some(name.clone())
+            } else {
+                None
+            }
+        })
+    }
+
+    /// Returns the crate this module is part of.
+    pub fn krate(self) -> Crate {
+        Crate { id: self.id.krate }
+    }
+
+    /// Topmost parent of this module. Every module has a `crate_root`, but some
+    /// might be missing `krate`. This can happen if a module's file is not included
+    /// in the module tree of any target in `Cargo.toml`.
+    pub fn crate_root(self, db: &dyn HirDatabase) -> Module {
+        let def_map = db.crate_def_map(self.id.krate);
+        self.with_module_id(def_map.root)
+    }
+
+    /// Iterates over all child modules.
+    pub fn children(self, db: &dyn HirDatabase) -> impl Iterator<Item = Module> {
+        let def_map = db.crate_def_map(self.id.krate);
+        let children = def_map[self.id.local_id]
+            .children
+            .iter()
+            .map(|(_, module_id)| self.with_module_id(*module_id))
+            .collect::<Vec<_>>();
+        children.into_iter()
+    }
+
+    /// Finds a parent module.
+    pub fn parent(self, db: &dyn HirDatabase) -> Option<Module> {
+        let def_map = db.crate_def_map(self.id.krate);
+        let parent_id = def_map[self.id.local_id].parent?;
+        Some(self.with_module_id(parent_id))
+    }
+
+    pub fn path_to_root(self, db: &dyn HirDatabase) -> Vec<Module> {
+        let mut res = vec![self];
+        let mut curr = self;
+        while let Some(next) = curr.parent(db) {
+            res.push(next);
+            curr = next
+        }
+        res
+    }
+
+    /// Returns a `ModuleScope`: a set of items, visible in this module.
+    pub fn scope(
+        self,
+        db: &dyn HirDatabase,
+        visible_from: Option<Module>,
+    ) -> Vec<(Name, ScopeDef)> {
+        db.crate_def_map(self.id.krate)[self.id.local_id]
+            .scope
+            .entries()
+            .filter_map(|(name, def)| {
+                if let Some(m) = visible_from {
+                    let filtered =
+                        def.filter_visibility(|vis| vis.is_visible_from(db.upcast(), m.id));
+                    if filtered.is_none() && !def.is_none() {
+                        None
+                    } else {
+                        Some((name, filtered))
+                    }
+                } else {
+                    Some((name, def))
+                }
+            })
+            .flat_map(|(name, def)| {
+                ScopeDef::all_items(def).into_iter().map(move |item| (name.clone(), item))
+            })
+            .collect()
+    }
+
+    pub fn visibility_of(self, db: &dyn HirDatabase, def: &ModuleDef) -> Option<Visibility> {
+        db.crate_def_map(self.id.krate)[self.id.local_id].scope.visibility_of(def.clone().into())
+    }
+
+    pub fn diagnostics(self, db: &dyn HirDatabase, sink: &mut DiagnosticSink) {
+        let _p = profile::span("Module::diagnostics");
+        let crate_def_map = db.crate_def_map(self.id.krate);
+        crate_def_map.add_diagnostics(db.upcast(), self.id.local_id, sink);
+        for decl in self.declarations(db) {
+            match decl {
+                crate::ModuleDef::Function(f) => f.diagnostics(db, sink),
+                crate::ModuleDef::Module(m) => {
+                    // Only add diagnostics from inline modules
+                    if crate_def_map[m.id.local_id].origin.is_inline() {
+                        m.diagnostics(db, sink)
+                    }
+                }
+                _ => (),
+            }
+        }
+
+        for impl_def in self.impl_defs(db) {
+            for item in impl_def.items(db) {
+                if let AssocItem::Function(f) = item {
+                    f.diagnostics(db, sink);
+                }
+            }
+        }
+    }
+
+    pub fn declarations(self, db: &dyn HirDatabase) -> Vec<ModuleDef> {
+        let def_map = db.crate_def_map(self.id.krate);
+        def_map[self.id.local_id].scope.declarations().map(ModuleDef::from).collect()
+    }
+
+    pub fn impl_defs(self, db: &dyn HirDatabase) -> Vec<ImplDef> {
+        let def_map = db.crate_def_map(self.id.krate);
+        def_map[self.id.local_id].scope.impls().map(ImplDef::from).collect()
+    }
+
+    pub(crate) fn with_module_id(self, module_id: LocalModuleId) -> Module {
+        Module::new(self.krate(), module_id)
+    }
+
+    /// Finds a path that can be used to refer to the given item from within
+    /// this module, if possible.
+    pub fn find_use_path(
+        self,
+        db: &dyn DefDatabase,
+        item: impl Into<ItemInNs>,
+    ) -> Option<hir_def::path::ModPath> {
+        hir_def::find_path::find_path(db, item.into(), self.into())
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Field {
+    pub(crate) parent: VariantDef,
+    pub(crate) id: LocalFieldId,
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub enum FieldSource {
+    Named(ast::RecordField),
+    Pos(ast::TupleField),
+}
+
+impl Field {
+    pub fn name(&self, db: &dyn HirDatabase) -> Name {
+        self.parent.variant_data(db).fields()[self.id].name.clone()
+    }
+
+    /// Returns the type as in the signature of the struct (i.e., with
+    /// placeholder types for type parameters). This is good for showing
+    /// signature help, but not so good to actually get the type of the field
+    /// when you actually have a variable of the struct.
+    pub fn signature_ty(&self, db: &dyn HirDatabase) -> Type {
+        let var_id = self.parent.into();
+        let generic_def_id: GenericDefId = match self.parent {
+            VariantDef::Struct(it) => it.id.into(),
+            VariantDef::Union(it) => it.id.into(),
+            VariantDef::EnumVariant(it) => it.parent.id.into(),
+        };
+        let substs = Substs::type_params(db, generic_def_id);
+        let ty = db.field_types(var_id)[self.id].clone().subst(&substs);
+        Type::new(db, self.parent.module(db).id.krate, var_id, ty)
+    }
+
+    pub fn parent_def(&self, _db: &dyn HirDatabase) -> VariantDef {
+        self.parent
+    }
+}
+
+impl HasVisibility for Field {
+    fn visibility(&self, db: &dyn HirDatabase) -> Visibility {
+        let variant_data = self.parent.variant_data(db);
+        let visibility = &variant_data.fields()[self.id].visibility;
+        let parent_id: hir_def::VariantId = self.parent.into();
+        visibility.resolve(db.upcast(), &parent_id.resolver(db.upcast()))
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Struct {
+    pub(crate) id: StructId,
+}
+
+impl Struct {
+    pub fn module(self, db: &dyn HirDatabase) -> Module {
+        Module { id: self.id.lookup(db.upcast()).container.module(db.upcast()) }
+    }
+
+    pub fn krate(self, db: &dyn HirDatabase) -> Option<Crate> {
+        Some(self.module(db).krate())
+    }
+
+    pub fn name(self, db: &dyn HirDatabase) -> Name {
+        db.struct_data(self.id).name.clone()
+    }
+
+    pub fn fields(self, db: &dyn HirDatabase) -> Vec<Field> {
+        db.struct_data(self.id)
+            .variant_data
+            .fields()
+            .iter()
+            .map(|(id, _)| Field { parent: self.into(), id })
+            .collect()
+    }
+
+    pub fn ty(self, db: &dyn HirDatabase) -> Type {
+        Type::from_def(db, self.id.lookup(db.upcast()).container.module(db.upcast()).krate, self.id)
+    }
+
+    pub fn repr(self, db: &dyn HirDatabase) -> Option<ReprKind> {
+        db.struct_data(self.id).repr.clone()
+    }
+
+    fn variant_data(self, db: &dyn HirDatabase) -> Arc<VariantData> {
+        db.struct_data(self.id).variant_data.clone()
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Union {
+    pub(crate) id: UnionId,
+}
+
+impl Union {
+    pub fn name(self, db: &dyn HirDatabase) -> Name {
+        db.union_data(self.id).name.clone()
+    }
+
+    pub fn module(self, db: &dyn HirDatabase) -> Module {
+        Module { id: self.id.lookup(db.upcast()).container.module(db.upcast()) }
+    }
+
+    pub fn ty(self, db: &dyn HirDatabase) -> Type {
+        Type::from_def(db, self.id.lookup(db.upcast()).container.module(db.upcast()).krate, self.id)
+    }
+
+    pub fn fields(self, db: &dyn HirDatabase) -> Vec<Field> {
+        db.union_data(self.id)
+            .variant_data
+            .fields()
+            .iter()
+            .map(|(id, _)| Field { parent: self.into(), id })
+            .collect()
+    }
+
+    fn variant_data(self, db: &dyn HirDatabase) -> Arc<VariantData> {
+        db.union_data(self.id).variant_data.clone()
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Enum {
+    pub(crate) id: EnumId,
+}
+
+impl Enum {
+    pub fn module(self, db: &dyn HirDatabase) -> Module {
+        Module { id: self.id.lookup(db.upcast()).container.module(db.upcast()) }
+    }
+
+    pub fn krate(self, db: &dyn HirDatabase) -> Option<Crate> {
+        Some(self.module(db).krate())
+    }
+
+    pub fn name(self, db: &dyn HirDatabase) -> Name {
+        db.enum_data(self.id).name.clone()
+    }
+
+    pub fn variants(self, db: &dyn HirDatabase) -> Vec<EnumVariant> {
+        db.enum_data(self.id)
+            .variants
+            .iter()
+            .map(|(id, _)| EnumVariant { parent: self, id })
+            .collect()
+    }
+
+    pub fn ty(self, db: &dyn HirDatabase) -> Type {
+        Type::from_def(db, self.id.lookup(db.upcast()).container.module(db.upcast()).krate, self.id)
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct EnumVariant {
+    pub(crate) parent: Enum,
+    pub(crate) id: LocalEnumVariantId,
+}
+
+impl EnumVariant {
+    pub fn module(self, db: &dyn HirDatabase) -> Module {
+        self.parent.module(db)
+    }
+    pub fn parent_enum(self, _db: &dyn HirDatabase) -> Enum {
+        self.parent
+    }
+
+    pub fn name(self, db: &dyn HirDatabase) -> Name {
+        db.enum_data(self.parent.id).variants[self.id].name.clone()
+    }
+
+    pub fn fields(self, db: &dyn HirDatabase) -> Vec<Field> {
+        self.variant_data(db)
+            .fields()
+            .iter()
+            .map(|(id, _)| Field { parent: self.into(), id })
+            .collect()
+    }
+
+    pub fn kind(self, db: &dyn HirDatabase) -> StructKind {
+        self.variant_data(db).kind()
+    }
+
+    pub(crate) fn variant_data(self, db: &dyn HirDatabase) -> Arc<VariantData> {
+        db.enum_data(self.parent.id).variants[self.id].variant_data.clone()
+    }
+}
+
+/// A Data Type
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum Adt {
+    Struct(Struct),
+    Union(Union),
+    Enum(Enum),
+}
+impl_from!(Struct, Union, Enum for Adt);
+
+impl Adt {
+    pub fn has_non_default_type_params(self, db: &dyn HirDatabase) -> bool {
+        let subst = db.generic_defaults(self.into());
+        subst.iter().any(|ty| &ty.value == &Ty::Unknown)
+    }
+
+    /// Turns this ADT into a type. Any type parameters of the ADT will be
+    /// turned into unknown types, which is good for e.g. finding the most
+    /// general set of completions, but will not look very nice when printed.
+    pub fn ty(self, db: &dyn HirDatabase) -> Type {
+        let id = AdtId::from(self);
+        Type::from_def(db, id.module(db.upcast()).krate, id)
+    }
+
+    pub fn module(self, db: &dyn HirDatabase) -> Module {
+        match self {
+            Adt::Struct(s) => s.module(db),
+            Adt::Union(s) => s.module(db),
+            Adt::Enum(e) => e.module(db),
+        }
+    }
+
+    pub fn krate(self, db: &dyn HirDatabase) -> Option<Crate> {
+        Some(self.module(db).krate())
+    }
+
+    pub fn name(self, db: &dyn HirDatabase) -> Name {
+        match self {
+            Adt::Struct(s) => s.name(db),
+            Adt::Union(u) => u.name(db),
+            Adt::Enum(e) => e.name(db),
+        }
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum VariantDef {
+    Struct(Struct),
+    Union(Union),
+    EnumVariant(EnumVariant),
+}
+impl_from!(Struct, Union, EnumVariant for VariantDef);
+
+impl VariantDef {
+    pub fn fields(self, db: &dyn HirDatabase) -> Vec<Field> {
+        match self {
+            VariantDef::Struct(it) => it.fields(db),
+            VariantDef::Union(it) => it.fields(db),
+            VariantDef::EnumVariant(it) => it.fields(db),
+        }
+    }
+
+    pub fn module(self, db: &dyn HirDatabase) -> Module {
+        match self {
+            VariantDef::Struct(it) => it.module(db),
+            VariantDef::Union(it) => it.module(db),
+            VariantDef::EnumVariant(it) => it.module(db),
+        }
+    }
+
+    pub fn name(&self, db: &dyn HirDatabase) -> Name {
+        match self {
+            VariantDef::Struct(s) => s.name(db),
+            VariantDef::Union(u) => u.name(db),
+            VariantDef::EnumVariant(e) => e.name(db),
+        }
+    }
+
+    pub(crate) fn variant_data(self, db: &dyn HirDatabase) -> Arc<VariantData> {
+        match self {
+            VariantDef::Struct(it) => it.variant_data(db),
+            VariantDef::Union(it) => it.variant_data(db),
+            VariantDef::EnumVariant(it) => it.variant_data(db),
+        }
+    }
+}
+
+/// The defs which have a body.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum DefWithBody {
+    Function(Function),
+    Static(Static),
+    Const(Const),
+}
+impl_from!(Function, Const, Static for DefWithBody);
+
+impl DefWithBody {
+    pub fn module(self, db: &dyn HirDatabase) -> Module {
+        match self {
+            DefWithBody::Const(c) => c.module(db),
+            DefWithBody::Function(f) => f.module(db),
+            DefWithBody::Static(s) => s.module(db),
+        }
+    }
+
+    pub fn name(self, db: &dyn HirDatabase) -> Option<Name> {
+        match self {
+            DefWithBody::Function(f) => Some(f.name(db)),
+            DefWithBody::Static(s) => s.name(db),
+            DefWithBody::Const(c) => c.name(db),
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Function {
+    pub(crate) id: FunctionId,
+}
+
+impl Function {
+    pub fn module(self, db: &dyn HirDatabase) -> Module {
+        self.id.lookup(db.upcast()).module(db.upcast()).into()
+    }
+
+    pub fn krate(self, db: &dyn HirDatabase) -> Option<Crate> {
+        Some(self.module(db).krate())
+    }
+
+    pub fn name(self, db: &dyn HirDatabase) -> Name {
+        db.function_data(self.id).name.clone()
+    }
+
+    pub fn has_self_param(self, db: &dyn HirDatabase) -> bool {
+        db.function_data(self.id).has_self_param
+    }
+
+    pub fn params(self, db: &dyn HirDatabase) -> Vec<TypeRef> {
+        db.function_data(self.id).params.clone()
+    }
+
+    pub fn is_unsafe(self, db: &dyn HirDatabase) -> bool {
+        db.function_data(self.id).is_unsafe
+    }
+
+    pub fn diagnostics(self, db: &dyn HirDatabase, sink: &mut DiagnosticSink) {
+        hir_ty::diagnostics::validate_body(db, self.id.into(), sink)
+    }
+}
+
+impl HasVisibility for Function {
+    fn visibility(&self, db: &dyn HirDatabase) -> Visibility {
+        let function_data = db.function_data(self.id);
+        let visibility = &function_data.visibility;
+        visibility.resolve(db.upcast(), &self.id.resolver(db.upcast()))
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Const {
+    pub(crate) id: ConstId,
+}
+
+impl Const {
+    pub fn module(self, db: &dyn HirDatabase) -> Module {
+        Module { id: self.id.lookup(db.upcast()).module(db.upcast()) }
+    }
+
+    pub fn krate(self, db: &dyn HirDatabase) -> Option<Crate> {
+        Some(self.module(db).krate())
+    }
+
+    pub fn name(self, db: &dyn HirDatabase) -> Option<Name> {
+        db.const_data(self.id).name.clone()
+    }
+}
+
+impl HasVisibility for Const {
+    fn visibility(&self, db: &dyn HirDatabase) -> Visibility {
+        let function_data = db.const_data(self.id);
+        let visibility = &function_data.visibility;
+        visibility.resolve(db.upcast(), &self.id.resolver(db.upcast()))
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Static {
+    pub(crate) id: StaticId,
+}
+
+impl Static {
+    pub fn module(self, db: &dyn HirDatabase) -> Module {
+        Module { id: self.id.lookup(db.upcast()).module(db.upcast()) }
+    }
+
+    pub fn krate(self, db: &dyn HirDatabase) -> Option<Crate> {
+        Some(self.module(db).krate())
+    }
+
+    pub fn name(self, db: &dyn HirDatabase) -> Option<Name> {
+        db.static_data(self.id).name.clone()
+    }
+
+    pub fn is_mut(self, db: &dyn HirDatabase) -> bool {
+        db.static_data(self.id).mutable
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Trait {
+    pub(crate) id: TraitId,
+}
+
+impl Trait {
+    pub fn module(self, db: &dyn HirDatabase) -> Module {
+        Module { id: self.id.lookup(db.upcast()).container.module(db.upcast()) }
+    }
+
+    pub fn name(self, db: &dyn HirDatabase) -> Name {
+        db.trait_data(self.id).name.clone()
+    }
+
+    pub fn items(self, db: &dyn HirDatabase) -> Vec<AssocItem> {
+        db.trait_data(self.id).items.iter().map(|(_name, it)| (*it).into()).collect()
+    }
+
+    pub fn is_auto(self, db: &dyn HirDatabase) -> bool {
+        db.trait_data(self.id).auto
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct TypeAlias {
+    pub(crate) id: TypeAliasId,
+}
+
+impl TypeAlias {
+    pub fn has_non_default_type_params(self, db: &dyn HirDatabase) -> bool {
+        let subst = db.generic_defaults(self.id.into());
+        subst.iter().any(|ty| &ty.value == &Ty::Unknown)
+    }
+
+    pub fn module(self, db: &dyn HirDatabase) -> Module {
+        Module { id: self.id.lookup(db.upcast()).module(db.upcast()) }
+    }
+
+    pub fn krate(self, db: &dyn HirDatabase) -> Option<Crate> {
+        Some(self.module(db).krate())
+    }
+
+    pub fn type_ref(self, db: &dyn HirDatabase) -> Option<TypeRef> {
+        db.type_alias_data(self.id).type_ref.clone()
+    }
+
+    pub fn ty(self, db: &dyn HirDatabase) -> Type {
+        Type::from_def(db, self.id.lookup(db.upcast()).module(db.upcast()).krate, self.id)
+    }
+
+    pub fn name(self, db: &dyn HirDatabase) -> Name {
+        db.type_alias_data(self.id).name.clone()
+    }
+}
+
+impl HasVisibility for TypeAlias {
+    fn visibility(&self, db: &dyn HirDatabase) -> Visibility {
+        let function_data = db.type_alias_data(self.id);
+        let visibility = &function_data.visibility;
+        visibility.resolve(db.upcast(), &self.id.resolver(db.upcast()))
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct MacroDef {
+    pub(crate) id: MacroDefId,
+}
+
+impl MacroDef {
+    /// FIXME: right now, this just returns the root module of the crate that
+    /// defines this macro. The reasons for this is that macros are expanded
+    /// early, in `hir_expand`, where modules simply do not exist yet.
+    pub fn module(self, db: &dyn HirDatabase) -> Option<Module> {
+        let krate = self.id.krate?;
+        let module_id = db.crate_def_map(krate).root;
+        Some(Module::new(Crate { id: krate }, module_id))
+    }
+
+    /// XXX: this parses the file
+    pub fn name(self, db: &dyn HirDatabase) -> Option<Name> {
+        self.source(db).value.name().map(|it| it.as_name())
+    }
+
+    /// Indicate it is a proc-macro
+    pub fn is_proc_macro(&self) -> bool {
+        matches!(self.id.kind, MacroDefKind::CustomDerive(_))
+    }
+
+    /// Indicate it is a derive macro
+    pub fn is_derive_macro(&self) -> bool {
+        matches!(self.id.kind, MacroDefKind::CustomDerive(_) | MacroDefKind::BuiltInDerive(_))
+    }
+}
+
+/// Invariant: `inner.as_assoc_item(db).is_some()`
+/// We do not actively enforce this invariant.
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub enum AssocItem {
+    Function(Function),
+    Const(Const),
+    TypeAlias(TypeAlias),
+}
+pub enum AssocItemContainer {
+    Trait(Trait),
+    ImplDef(ImplDef),
+}
+pub trait AsAssocItem {
+    fn as_assoc_item(self, db: &dyn HirDatabase) -> Option<AssocItem>;
+}
+
+impl AsAssocItem for Function {
+    fn as_assoc_item(self, db: &dyn HirDatabase) -> Option<AssocItem> {
+        as_assoc_item(db, AssocItem::Function, self.id)
+    }
+}
+impl AsAssocItem for Const {
+    fn as_assoc_item(self, db: &dyn HirDatabase) -> Option<AssocItem> {
+        as_assoc_item(db, AssocItem::Const, self.id)
+    }
+}
+impl AsAssocItem for TypeAlias {
+    fn as_assoc_item(self, db: &dyn HirDatabase) -> Option<AssocItem> {
+        as_assoc_item(db, AssocItem::TypeAlias, self.id)
+    }
+}
+fn as_assoc_item<ID, DEF, CTOR, AST>(db: &dyn HirDatabase, ctor: CTOR, id: ID) -> Option<AssocItem>
+where
+    ID: Lookup<Data = AssocItemLoc<AST>>,
+    DEF: From<ID>,
+    CTOR: FnOnce(DEF) -> AssocItem,
+    AST: ItemTreeNode,
+{
+    match id.lookup(db.upcast()).container {
+        AssocContainerId::TraitId(_) | AssocContainerId::ImplId(_) => Some(ctor(DEF::from(id))),
+        AssocContainerId::ContainerId(_) => None,
+    }
+}
+
+impl AssocItem {
+    pub fn module(self, db: &dyn HirDatabase) -> Module {
+        match self {
+            AssocItem::Function(f) => f.module(db),
+            AssocItem::Const(c) => c.module(db),
+            AssocItem::TypeAlias(t) => t.module(db),
+        }
+    }
+    pub fn container(self, db: &dyn HirDatabase) -> AssocItemContainer {
+        let container = match self {
+            AssocItem::Function(it) => it.id.lookup(db.upcast()).container,
+            AssocItem::Const(it) => it.id.lookup(db.upcast()).container,
+            AssocItem::TypeAlias(it) => it.id.lookup(db.upcast()).container,
+        };
+        match container {
+            AssocContainerId::TraitId(id) => AssocItemContainer::Trait(id.into()),
+            AssocContainerId::ImplId(id) => AssocItemContainer::ImplDef(id.into()),
+            AssocContainerId::ContainerId(_) => panic!("invalid AssocItem"),
+        }
+    }
+}
+
+impl HasVisibility for AssocItem {
+    fn visibility(&self, db: &dyn HirDatabase) -> Visibility {
+        match self {
+            AssocItem::Function(f) => f.visibility(db),
+            AssocItem::Const(c) => c.visibility(db),
+            AssocItem::TypeAlias(t) => t.visibility(db),
+        }
+    }
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
+pub enum GenericDef {
+    Function(Function),
+    Adt(Adt),
+    Trait(Trait),
+    TypeAlias(TypeAlias),
+    ImplDef(ImplDef),
+    // enum variants cannot have generics themselves, but their parent enums
+    // can, and this makes some code easier to write
+    EnumVariant(EnumVariant),
+    // consts can have type parameters from their parents (i.e. associated consts of traits)
+    Const(Const),
+}
+impl_from!(
+    Function,
+    Adt(Struct, Enum, Union),
+    Trait,
+    TypeAlias,
+    ImplDef,
+    EnumVariant,
+    Const
+    for GenericDef
+);
+
+impl GenericDef {
+    pub fn params(self, db: &dyn HirDatabase) -> Vec<TypeParam> {
+        let generics: Arc<hir_def::generics::GenericParams> = db.generic_params(self.into());
+        generics
+            .types
+            .iter()
+            .map(|(local_id, _)| TypeParam { id: TypeParamId { parent: self.into(), local_id } })
+            .collect()
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub struct Local {
+    pub(crate) parent: DefWithBodyId,
+    pub(crate) pat_id: PatId,
+}
+
+impl Local {
+    pub fn is_param(self, db: &dyn HirDatabase) -> bool {
+        let src = self.source(db);
+        match src.value {
+            Either::Left(bind_pat) => {
+                bind_pat.syntax().ancestors().any(|it| ast::Param::can_cast(it.kind()))
+            }
+            Either::Right(_self_param) => true,
+        }
+    }
+
+    // FIXME: why is this an option? It shouldn't be?
+    pub fn name(self, db: &dyn HirDatabase) -> Option<Name> {
+        let body = db.body(self.parent.into());
+        match &body[self.pat_id] {
+            Pat::Bind { name, .. } => Some(name.clone()),
+            _ => None,
+        }
+    }
+
+    pub fn is_self(self, db: &dyn HirDatabase) -> bool {
+        self.name(db) == Some(name![self])
+    }
+
+    pub fn is_mut(self, db: &dyn HirDatabase) -> bool {
+        let body = db.body(self.parent.into());
+        match &body[self.pat_id] {
+            Pat::Bind { mode, .. } => match mode {
+                BindingAnnotation::Mutable | BindingAnnotation::RefMut => true,
+                _ => false,
+            },
+            _ => false,
+        }
+    }
+
+    pub fn parent(self, _db: &dyn HirDatabase) -> DefWithBody {
+        self.parent.into()
+    }
+
+    pub fn module(self, db: &dyn HirDatabase) -> Module {
+        self.parent(db).module(db)
+    }
+
+    pub fn ty(self, db: &dyn HirDatabase) -> Type {
+        let def = DefWithBodyId::from(self.parent);
+        let infer = db.infer(def);
+        let ty = infer[self.pat_id].clone();
+        let krate = def.module(db.upcast()).krate;
+        Type::new(db, krate, def, ty)
+    }
+
+    pub fn source(self, db: &dyn HirDatabase) -> InFile<Either<ast::IdentPat, ast::SelfParam>> {
+        let (_body, source_map) = db.body_with_source_map(self.parent.into());
+        let src = source_map.pat_syntax(self.pat_id).unwrap(); // Hmm...
+        let root = src.file_syntax(db.upcast());
+        src.map(|ast| {
+            ast.map_left(|it| it.cast().unwrap().to_node(&root)).map_right(|it| it.to_node(&root))
+        })
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub struct TypeParam {
+    pub(crate) id: TypeParamId,
+}
+
+impl TypeParam {
+    pub fn name(self, db: &dyn HirDatabase) -> Name {
+        let params = db.generic_params(self.id.parent);
+        params.types[self.id.local_id].name.clone().unwrap_or_else(Name::missing)
+    }
+
+    pub fn module(self, db: &dyn HirDatabase) -> Module {
+        self.id.parent.module(db.upcast()).into()
+    }
+
+    pub fn ty(self, db: &dyn HirDatabase) -> Type {
+        let resolver = self.id.parent.resolver(db.upcast());
+        let environment = TraitEnvironment::lower(db, &resolver);
+        let ty = Ty::Placeholder(self.id);
+        Type {
+            krate: self.id.parent.module(db.upcast()).krate,
+            ty: InEnvironment { value: ty, environment },
+        }
+    }
+
+    pub fn default(self, db: &dyn HirDatabase) -> Option<Type> {
+        let params = db.generic_defaults(self.id.parent);
+        let local_idx = hir_ty::param_idx(db, self.id)?;
+        let resolver = self.id.parent.resolver(db.upcast());
+        let environment = TraitEnvironment::lower(db, &resolver);
+        let ty = params.get(local_idx)?.clone();
+        let subst = Substs::type_params(db, self.id.parent);
+        let ty = ty.subst(&subst.prefix(local_idx));
+        Some(Type {
+            krate: self.id.parent.module(db.upcast()).krate,
+            ty: InEnvironment { value: ty, environment },
+        })
+    }
+}
+
+// FIXME: rename from `ImplDef` to `Impl`
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct ImplDef {
+    pub(crate) id: ImplId,
+}
+
+impl ImplDef {
+    pub fn all_in_crate(db: &dyn HirDatabase, krate: Crate) -> Vec<ImplDef> {
+        let inherent = db.inherent_impls_in_crate(krate.id);
+        let trait_ = db.trait_impls_in_crate(krate.id);
+
+        inherent.all_impls().chain(trait_.all_impls()).map(Self::from).collect()
+    }
+    pub fn for_trait(db: &dyn HirDatabase, krate: Crate, trait_: Trait) -> Vec<ImplDef> {
+        let impls = db.trait_impls_in_crate(krate.id);
+        impls.for_trait(trait_.id).map(Self::from).collect()
+    }
+
+    pub fn target_trait(self, db: &dyn HirDatabase) -> Option<TypeRef> {
+        db.impl_data(self.id).target_trait.clone()
+    }
+
+    pub fn target_type(self, db: &dyn HirDatabase) -> TypeRef {
+        db.impl_data(self.id).target_type.clone()
+    }
+
+    pub fn target_ty(self, db: &dyn HirDatabase) -> Type {
+        let impl_data = db.impl_data(self.id);
+        let resolver = self.id.resolver(db.upcast());
+        let ctx = hir_ty::TyLoweringContext::new(db, &resolver);
+        let environment = TraitEnvironment::lower(db, &resolver);
+        let ty = Ty::from_hir(&ctx, &impl_data.target_type);
+        Type {
+            krate: self.id.lookup(db.upcast()).container.module(db.upcast()).krate,
+            ty: InEnvironment { value: ty, environment },
+        }
+    }
+
+    pub fn items(self, db: &dyn HirDatabase) -> Vec<AssocItem> {
+        db.impl_data(self.id).items.iter().map(|it| (*it).into()).collect()
+    }
+
+    pub fn is_negative(self, db: &dyn HirDatabase) -> bool {
+        db.impl_data(self.id).is_negative
+    }
+
+    pub fn module(self, db: &dyn HirDatabase) -> Module {
+        self.id.lookup(db.upcast()).container.module(db.upcast()).into()
+    }
+
+    pub fn krate(self, db: &dyn HirDatabase) -> Crate {
+        Crate { id: self.module(db).id.krate }
+    }
+
+    pub fn is_builtin_derive(self, db: &dyn HirDatabase) -> Option<InFile<ast::Attr>> {
+        let src = self.source(db);
+        let item = src.file_id.is_builtin_derive(db.upcast())?;
+        let hygenic = hir_expand::hygiene::Hygiene::new(db.upcast(), item.file_id);
+
+        let attr = item
+            .value
+            .attrs()
+            .filter_map(|it| {
+                let path = hir_def::path::ModPath::from_src(it.path()?, &hygenic)?;
+                if path.as_ident()?.to_string() == "derive" {
+                    Some(it)
+                } else {
+                    None
+                }
+            })
+            .last()?;
+
+        Some(item.with_value(attr))
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub struct Type {
+    krate: CrateId,
+    ty: InEnvironment<Ty>,
+}
+
+impl Type {
+    pub(crate) fn new_with_resolver(
+        db: &dyn HirDatabase,
+        resolver: &Resolver,
+        ty: Ty,
+    ) -> Option<Type> {
+        let krate = resolver.krate()?;
+        Some(Type::new_with_resolver_inner(db, krate, resolver, ty))
+    }
+    pub(crate) fn new_with_resolver_inner(
+        db: &dyn HirDatabase,
+        krate: CrateId,
+        resolver: &Resolver,
+        ty: Ty,
+    ) -> Type {
+        let environment = TraitEnvironment::lower(db, &resolver);
+        Type { krate, ty: InEnvironment { value: ty, environment } }
+    }
+
+    fn new(db: &dyn HirDatabase, krate: CrateId, lexical_env: impl HasResolver, ty: Ty) -> Type {
+        let resolver = lexical_env.resolver(db.upcast());
+        let environment = TraitEnvironment::lower(db, &resolver);
+        Type { krate, ty: InEnvironment { value: ty, environment } }
+    }
+
+    fn from_def(
+        db: &dyn HirDatabase,
+        krate: CrateId,
+        def: impl HasResolver + Into<TyDefId> + Into<GenericDefId>,
+    ) -> Type {
+        let substs = Substs::build_for_def(db, def).fill_with_unknown().build();
+        let ty = db.ty(def.into()).subst(&substs);
+        Type::new(db, krate, def, ty)
+    }
+
+    pub fn is_unit(&self) -> bool {
+        matches!(
+            self.ty.value,
+            Ty::Apply(ApplicationTy { ctor: TypeCtor::Tuple { cardinality: 0 }, .. })
+        )
+    }
+    pub fn is_bool(&self) -> bool {
+        matches!(self.ty.value, Ty::Apply(ApplicationTy { ctor: TypeCtor::Bool, .. }))
+    }
+
+    pub fn is_mutable_reference(&self) -> bool {
+        matches!(
+            self.ty.value,
+            Ty::Apply(ApplicationTy { ctor: TypeCtor::Ref(Mutability::Mut), .. })
+        )
+    }
+
+    pub fn is_unknown(&self) -> bool {
+        matches!(self.ty.value, Ty::Unknown)
+    }
+
+    /// Checks that particular type `ty` implements `std::future::Future`.
+    /// This function is used in `.await` syntax completion.
+    pub fn impls_future(&self, db: &dyn HirDatabase) -> bool {
+        let krate = self.krate;
+
+        let std_future_trait =
+            db.lang_item(krate, "future_trait".into()).and_then(|it| it.as_trait());
+        let std_future_trait = match std_future_trait {
+            Some(it) => it,
+            None => return false,
+        };
+
+        let canonical_ty = Canonical { value: self.ty.value.clone(), kinds: Arc::new([]) };
+        method_resolution::implements_trait(
+            &canonical_ty,
+            db,
+            self.ty.environment.clone(),
+            krate,
+            std_future_trait,
+        )
+    }
+
+    pub fn impls_trait(&self, db: &dyn HirDatabase, trait_: Trait, args: &[Type]) -> bool {
+        let trait_ref = hir_ty::TraitRef {
+            trait_: trait_.id,
+            substs: Substs::build_for_def(db, trait_.id)
+                .push(self.ty.value.clone())
+                .fill(args.iter().map(|t| t.ty.value.clone()))
+                .build(),
+        };
+
+        let goal = Canonical {
+            value: hir_ty::InEnvironment::new(
+                self.ty.environment.clone(),
+                hir_ty::Obligation::Trait(trait_ref),
+            ),
+            kinds: Arc::new([]),
+        };
+
+        db.trait_solve(self.krate, goal).is_some()
+    }
+
+    pub fn as_callable(&self, db: &dyn HirDatabase) -> Option<Callable> {
+        let def = match self.ty.value {
+            Ty::Apply(ApplicationTy { ctor: TypeCtor::FnDef(def), parameters: _ }) => Some(def),
+            _ => None,
+        };
+
+        let sig = self.ty.value.callable_sig(db)?;
+        Some(Callable { ty: self.clone(), sig, def, is_bound_method: false })
+    }
+
+    pub fn is_closure(&self) -> bool {
+        matches!(&self.ty.value, Ty::Apply(ApplicationTy { ctor: TypeCtor::Closure { .. }, .. }))
+    }
+
+    pub fn is_fn(&self) -> bool {
+        matches!(&self.ty.value,
+            Ty::Apply(ApplicationTy { ctor: TypeCtor::FnDef(..), .. }) |
+            Ty::Apply(ApplicationTy { ctor: TypeCtor::FnPtr { .. }, .. })
+        )
+    }
+
+    pub fn is_packed(&self, db: &dyn HirDatabase) -> bool {
+        let adt_id = match self.ty.value {
+            Ty::Apply(ApplicationTy { ctor: TypeCtor::Adt(adt_id), .. }) => adt_id,
+            _ => return false,
+        };
+
+        let adt = adt_id.into();
+        match adt {
+            Adt::Struct(s) => matches!(s.repr(db), Some(ReprKind::Packed)),
+            _ => false,
+        }
+    }
+
+    pub fn is_raw_ptr(&self) -> bool {
+        matches!(&self.ty.value, Ty::Apply(ApplicationTy { ctor: TypeCtor::RawPtr(..), .. }))
+    }
+
+    pub fn contains_unknown(&self) -> bool {
+        return go(&self.ty.value);
+
+        fn go(ty: &Ty) -> bool {
+            match ty {
+                Ty::Unknown => true,
+                Ty::Apply(a_ty) => a_ty.parameters.iter().any(go),
+                _ => false,
+            }
+        }
+    }
+
+    pub fn fields(&self, db: &dyn HirDatabase) -> Vec<(Field, Type)> {
+        if let Ty::Apply(a_ty) = &self.ty.value {
+            let variant_id = match a_ty.ctor {
+                TypeCtor::Adt(AdtId::StructId(s)) => s.into(),
+                TypeCtor::Adt(AdtId::UnionId(u)) => u.into(),
+                _ => return Vec::new(),
+            };
+
+            return db
+                .field_types(variant_id)
+                .iter()
+                .map(|(local_id, ty)| {
+                    let def = Field { parent: variant_id.into(), id: local_id };
+                    let ty = ty.clone().subst(&a_ty.parameters);
+                    (def, self.derived(ty))
+                })
+                .collect();
+        };
+        Vec::new()
+    }
+
+    pub fn tuple_fields(&self, _db: &dyn HirDatabase) -> Vec<Type> {
+        let mut res = Vec::new();
+        if let Ty::Apply(a_ty) = &self.ty.value {
+            if let TypeCtor::Tuple { .. } = a_ty.ctor {
+                for ty in a_ty.parameters.iter() {
+                    let ty = ty.clone();
+                    res.push(self.derived(ty));
+                }
+            }
+        };
+        res
+    }
+
+    pub fn autoderef<'a>(&'a self, db: &'a dyn HirDatabase) -> impl Iterator<Item = Type> + 'a {
+        // There should be no inference vars in types passed here
+        // FIXME check that?
+        let canonical = Canonical { value: self.ty.value.clone(), kinds: Arc::new([]) };
+        let environment = self.ty.environment.clone();
+        let ty = InEnvironment { value: canonical, environment };
+        autoderef(db, Some(self.krate), ty)
+            .map(|canonical| canonical.value)
+            .map(move |ty| self.derived(ty))
+    }
+
+    // This would be nicer if it just returned an iterator, but that runs into
+    // lifetime problems, because we need to borrow temp `CrateImplDefs`.
+    pub fn iterate_assoc_items<T>(
+        self,
+        db: &dyn HirDatabase,
+        krate: Crate,
+        mut callback: impl FnMut(AssocItem) -> Option<T>,
+    ) -> Option<T> {
+        for krate in self.ty.value.def_crates(db, krate.id)? {
+            let impls = db.inherent_impls_in_crate(krate);
+
+            for impl_def in impls.for_self_ty(&self.ty.value) {
+                for &item in db.impl_data(*impl_def).items.iter() {
+                    if let Some(result) = callback(item.into()) {
+                        return Some(result);
+                    }
+                }
+            }
+        }
+        None
+    }
+
+    pub fn iterate_method_candidates<T>(
+        &self,
+        db: &dyn HirDatabase,
+        krate: Crate,
+        traits_in_scope: &FxHashSet<TraitId>,
+        name: Option<&Name>,
+        mut callback: impl FnMut(&Ty, Function) -> Option<T>,
+    ) -> Option<T> {
+        // There should be no inference vars in types passed here
+        // FIXME check that?
+        // FIXME replace Unknown by bound vars here
+        let canonical = Canonical { value: self.ty.value.clone(), kinds: Arc::new([]) };
+
+        let env = self.ty.environment.clone();
+        let krate = krate.id;
+
+        method_resolution::iterate_method_candidates(
+            &canonical,
+            db,
+            env,
+            krate,
+            traits_in_scope,
+            name,
+            method_resolution::LookupMode::MethodCall,
+            |ty, it| match it {
+                AssocItemId::FunctionId(f) => callback(ty, f.into()),
+                _ => None,
+            },
+        )
+    }
+
+    pub fn iterate_path_candidates<T>(
+        &self,
+        db: &dyn HirDatabase,
+        krate: Crate,
+        traits_in_scope: &FxHashSet<TraitId>,
+        name: Option<&Name>,
+        mut callback: impl FnMut(&Ty, AssocItem) -> Option<T>,
+    ) -> Option<T> {
+        // There should be no inference vars in types passed here
+        // FIXME check that?
+        // FIXME replace Unknown by bound vars here
+        let canonical = Canonical { value: self.ty.value.clone(), kinds: Arc::new([]) };
+
+        let env = self.ty.environment.clone();
+        let krate = krate.id;
+
+        method_resolution::iterate_method_candidates(
+            &canonical,
+            db,
+            env,
+            krate,
+            traits_in_scope,
+            name,
+            method_resolution::LookupMode::Path,
+            |ty, it| callback(ty, it.into()),
+        )
+    }
+
+    pub fn as_adt(&self) -> Option<Adt> {
+        let (adt, _subst) = self.ty.value.as_adt()?;
+        Some(adt.into())
+    }
+
+    pub fn as_dyn_trait(&self) -> Option<Trait> {
+        self.ty.value.dyn_trait().map(Into::into)
+    }
+
+    pub fn as_impl_traits(&self, db: &dyn HirDatabase) -> Option<Vec<Trait>> {
+        self.ty.value.impl_trait_bounds(db).map(|it| {
+            it.into_iter()
+                .filter_map(|pred| match pred {
+                    hir_ty::GenericPredicate::Implemented(trait_ref) => {
+                        Some(Trait::from(trait_ref.trait_))
+                    }
+                    _ => None,
+                })
+                .collect()
+        })
+    }
+
+    pub fn as_associated_type_parent_trait(&self, db: &dyn HirDatabase) -> Option<Trait> {
+        self.ty.value.associated_type_parent_trait(db).map(Into::into)
+    }
+
+    // FIXME: provide required accessors such that it becomes implementable from outside.
+    pub fn is_equal_for_find_impls(&self, other: &Type) -> bool {
+        match (&self.ty.value, &other.ty.value) {
+            (Ty::Apply(a_original_ty), Ty::Apply(ApplicationTy { ctor, parameters })) => match ctor
+            {
+                TypeCtor::Ref(..) => match parameters.as_single() {
+                    Ty::Apply(a_ty) => a_original_ty.ctor == a_ty.ctor,
+                    _ => false,
+                },
+                _ => a_original_ty.ctor == *ctor,
+            },
+            _ => false,
+        }
+    }
+
+    fn derived(&self, ty: Ty) -> Type {
+        Type {
+            krate: self.krate,
+            ty: InEnvironment { value: ty, environment: self.ty.environment.clone() },
+        }
+    }
+
+    pub fn walk(&self, db: &dyn HirDatabase, mut cb: impl FnMut(Type)) {
+        // TypeWalk::walk for a Ty at first visits parameters and only after that the Ty itself.
+        // We need a different order here.
+
+        fn walk_substs(
+            db: &dyn HirDatabase,
+            type_: &Type,
+            substs: &Substs,
+            cb: &mut impl FnMut(Type),
+        ) {
+            for ty in substs.iter() {
+                walk_type(db, &type_.derived(ty.clone()), cb);
+            }
+        }
+
+        fn walk_bounds(
+            db: &dyn HirDatabase,
+            type_: &Type,
+            bounds: &[GenericPredicate],
+            cb: &mut impl FnMut(Type),
+        ) {
+            for pred in bounds {
+                match pred {
+                    GenericPredicate::Implemented(trait_ref) => {
+                        cb(type_.clone());
+                        walk_substs(db, type_, &trait_ref.substs, cb);
+                    }
+                    _ => (),
+                }
+            }
+        }
+
+        fn walk_type(db: &dyn HirDatabase, type_: &Type, cb: &mut impl FnMut(Type)) {
+            let ty = type_.ty.value.strip_references();
+            match ty {
+                Ty::Apply(ApplicationTy { ctor, parameters }) => {
+                    match ctor {
+                        TypeCtor::Adt(_) => {
+                            cb(type_.derived(ty.clone()));
+                        }
+                        TypeCtor::AssociatedType(_) => {
+                            if let Some(_) = ty.associated_type_parent_trait(db) {
+                                cb(type_.derived(ty.clone()));
+                            }
+                        }
+                        _ => (),
+                    }
+
+                    // adt params, tuples, etc...
+                    walk_substs(db, type_, parameters, cb);
+                }
+                Ty::Opaque(opaque_ty) => {
+                    if let Some(bounds) = ty.impl_trait_bounds(db) {
+                        walk_bounds(db, &type_.derived(ty.clone()), &bounds, cb);
+                    }
+
+                    walk_substs(db, type_, &opaque_ty.parameters, cb);
+                }
+                Ty::Placeholder(_) => {
+                    if let Some(bounds) = ty.impl_trait_bounds(db) {
+                        walk_bounds(db, &type_.derived(ty.clone()), &bounds, cb);
+                    }
+                }
+                Ty::Dyn(bounds) => {
+                    walk_bounds(db, &type_.derived(ty.clone()), bounds.as_ref(), cb);
+                }
+
+                _ => (),
+            }
+        }
+
+        walk_type(db, self, &mut cb);
+    }
+}
+
+impl HirDisplay for Type {
+    fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
+        self.ty.value.hir_fmt(f)
+    }
+}
+
+// FIXME: closures
+#[derive(Debug)]
+pub struct Callable {
+    ty: Type,
+    sig: FnSig,
+    def: Option<CallableDefId>,
+    pub(crate) is_bound_method: bool,
+}
+
+pub enum CallableKind {
+    Function(Function),
+    TupleStruct(Struct),
+    TupleEnumVariant(EnumVariant),
+    Closure,
+}
+
+impl Callable {
+    pub fn kind(&self) -> CallableKind {
+        match self.def {
+            Some(CallableDefId::FunctionId(it)) => CallableKind::Function(it.into()),
+            Some(CallableDefId::StructId(it)) => CallableKind::TupleStruct(it.into()),
+            Some(CallableDefId::EnumVariantId(it)) => CallableKind::TupleEnumVariant(it.into()),
+            None => CallableKind::Closure,
+        }
+    }
+    pub fn receiver_param(&self, db: &dyn HirDatabase) -> Option<ast::SelfParam> {
+        let func = match self.def {
+            Some(CallableDefId::FunctionId(it)) if self.is_bound_method => it,
+            _ => return None,
+        };
+        let src = func.lookup(db.upcast()).source(db.upcast());
+        let param_list = src.value.param_list()?;
+        param_list.self_param()
+    }
+    pub fn n_params(&self) -> usize {
+        self.sig.params().len() - if self.is_bound_method { 1 } else { 0 }
+    }
+    pub fn params(
+        &self,
+        db: &dyn HirDatabase,
+    ) -> Vec<(Option<Either<ast::SelfParam, ast::Pat>>, Type)> {
+        let types = self
+            .sig
+            .params()
+            .iter()
+            .skip(if self.is_bound_method { 1 } else { 0 })
+            .map(|ty| self.ty.derived(ty.clone()));
+        let patterns = match self.def {
+            Some(CallableDefId::FunctionId(func)) => {
+                let src = func.lookup(db.upcast()).source(db.upcast());
+                src.value.param_list().map(|param_list| {
+                    param_list
+                        .self_param()
+                        .map(|it| Some(Either::Left(it)))
+                        .filter(|_| !self.is_bound_method)
+                        .into_iter()
+                        .chain(param_list.params().map(|it| it.pat().map(Either::Right)))
+                })
+            }
+            _ => None,
+        };
+        patterns.into_iter().flatten().chain(iter::repeat(None)).zip(types).collect()
+    }
+    pub fn return_type(&self) -> Type {
+        self.ty.derived(self.sig.ret().clone())
+    }
+}
+
+/// For IDE only
+#[derive(Debug)]
+pub enum ScopeDef {
+    ModuleDef(ModuleDef),
+    MacroDef(MacroDef),
+    GenericParam(TypeParam),
+    ImplSelfType(ImplDef),
+    AdtSelfType(Adt),
+    Local(Local),
+    Unknown,
+}
+
+impl ScopeDef {
+    pub fn all_items(def: PerNs) -> ArrayVec<[Self; 3]> {
+        let mut items = ArrayVec::new();
+
+        match (def.take_types(), def.take_values()) {
+            (Some(m1), None) => items.push(ScopeDef::ModuleDef(m1.into())),
+            (None, Some(m2)) => items.push(ScopeDef::ModuleDef(m2.into())),
+            (Some(m1), Some(m2)) => {
+                // Some items, like unit structs and enum variants, are
+                // returned as both a type and a value. Here we want
+                // to de-duplicate them.
+                if m1 != m2 {
+                    items.push(ScopeDef::ModuleDef(m1.into()));
+                    items.push(ScopeDef::ModuleDef(m2.into()));
+                } else {
+                    items.push(ScopeDef::ModuleDef(m1.into()));
+                }
+            }
+            (None, None) => {}
+        };
+
+        if let Some(macro_def_id) = def.take_macros() {
+            items.push(ScopeDef::MacroDef(macro_def_id.into()));
+        }
+
+        if items.is_empty() {
+            items.push(ScopeDef::Unknown);
+        }
+
+        items
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum AttrDef {
+    Module(Module),
+    Field(Field),
+    Adt(Adt),
+    Function(Function),
+    EnumVariant(EnumVariant),
+    Static(Static),
+    Const(Const),
+    Trait(Trait),
+    TypeAlias(TypeAlias),
+    MacroDef(MacroDef),
+}
+
+impl_from!(
+    Module,
+    Field,
+    Adt(Struct, Enum, Union),
+    EnumVariant,
+    Static,
+    Const,
+    Function,
+    Trait,
+    TypeAlias,
+    MacroDef
+    for AttrDef
+);
+
+pub trait HasAttrs {
+    fn attrs(self, db: &dyn HirDatabase) -> Attrs;
+}
+
+impl<T: Into<AttrDef>> HasAttrs for T {
+    fn attrs(self, db: &dyn HirDatabase) -> Attrs {
+        let def: AttrDef = self.into();
+        db.attrs(def.into())
+    }
+}
+
+pub trait Docs {
+    fn docs(&self, db: &dyn HirDatabase) -> Option<Documentation>;
+}
+impl<T: Into<AttrDef> + Copy> Docs for T {
+    fn docs(&self, db: &dyn HirDatabase) -> Option<Documentation> {
+        let def: AttrDef = (*self).into();
+        db.documentation(def.into())
+    }
+}
+
+pub trait HasVisibility {
+    fn visibility(&self, db: &dyn HirDatabase) -> Visibility;
+    fn is_visible_from(&self, db: &dyn HirDatabase, module: Module) -> bool {
+        let vis = self.visibility(db);
+        vis.is_visible_from(db.upcast(), module.id)
+    }
+}
diff --git a/crates/hir/src/db.rs b/crates/hir/src/db.rs
new file mode 100644
index 000000000..07333c453
--- /dev/null
+++ b/crates/hir/src/db.rs
@@ -0,0 +1,21 @@
+//! FIXME: write short doc here
+
+pub use hir_def::db::{
+    AttrsQuery, BodyQuery, BodyWithSourceMapQuery, ConstDataQuery, CrateDefMapQueryQuery,
+    CrateLangItemsQuery, DefDatabase, DefDatabaseStorage, DocumentationQuery, EnumDataQuery,
+    ExprScopesQuery, FunctionDataQuery, GenericParamsQuery, ImplDataQuery, ImportMapQuery,
+    InternConstQuery, InternDatabase, InternDatabaseStorage, InternEnumQuery, InternFunctionQuery,
+    InternImplQuery, InternStaticQuery, InternStructQuery, InternTraitQuery, InternTypeAliasQuery,
+    InternUnionQuery, ItemTreeQuery, LangItemQuery, ModuleLangItemsQuery, StaticDataQuery,
+    StructDataQuery, TraitDataQuery, TypeAliasDataQuery, UnionDataQuery,
+};
+pub use hir_expand::db::{
+    AstDatabase, AstDatabaseStorage, AstIdMapQuery, InternEagerExpansionQuery, InternMacroQuery,
+    MacroArgTextQuery, MacroDefQuery, MacroExpandQuery, ParseMacroQuery,
+};
+pub use hir_ty::db::*;
+
+#[test]
+fn hir_database_is_object_safe() {
+    fn _assert_object_safe(_: &dyn HirDatabase) {}
+}
diff --git a/crates/hir/src/diagnostics.rs b/crates/hir/src/diagnostics.rs
new file mode 100644
index 000000000..363164b9b
--- /dev/null
+++ b/crates/hir/src/diagnostics.rs
@@ -0,0 +1,6 @@
+//! FIXME: write short doc here
+pub use hir_def::diagnostics::UnresolvedModule;
+pub use hir_expand::diagnostics::{Diagnostic, DiagnosticSink, DiagnosticSinkBuilder};
+pub use hir_ty::diagnostics::{
+    MismatchedArgCount, MissingFields, MissingMatchArms, MissingOkInTailExpr, NoSuchField,
+};
diff --git a/crates/hir/src/from_id.rs b/crates/hir/src/from_id.rs
new file mode 100644
index 000000000..a53ac1e08
--- /dev/null
+++ b/crates/hir/src/from_id.rs
@@ -0,0 +1,247 @@
+//! Utility module for converting between hir_def ids and code_model wrappers.
+//!
+//! It's unclear if we need this long-term, but it's definitelly useful while we
+//! are splitting the hir.
+
+use hir_def::{
+    expr::PatId, AdtId, AssocItemId, AttrDefId, DefWithBodyId, EnumVariantId, FieldId,
+    GenericDefId, ModuleDefId, VariantId,
+};
+
+use crate::{
+    code_model::ItemInNs, Adt, AssocItem, AttrDef, DefWithBody, EnumVariant, Field, GenericDef,
+    Local, MacroDef, ModuleDef, VariantDef,
+};
+
+macro_rules! from_id {
+    ($(($id:path, $ty:path)),*) => {$(
+        impl From<$id> for $ty {
+            fn from(id: $id) -> $ty {
+                $ty { id }
+            }
+        }
+        impl From<$ty> for $id {
+            fn from(ty: $ty) -> $id {
+                ty.id
+            }
+        }
+    )*}
+}
+
+from_id![
+    (base_db::CrateId, crate::Crate),
+    (hir_def::ModuleId, crate::Module),
+    (hir_def::StructId, crate::Struct),
+    (hir_def::UnionId, crate::Union),
+    (hir_def::EnumId, crate::Enum),
+    (hir_def::TypeAliasId, crate::TypeAlias),
+    (hir_def::TraitId, crate::Trait),
+    (hir_def::StaticId, crate::Static),
+    (hir_def::ConstId, crate::Const),
+    (hir_def::FunctionId, crate::Function),
+    (hir_def::ImplId, crate::ImplDef),
+    (hir_def::TypeParamId, crate::TypeParam),
+    (hir_expand::MacroDefId, crate::MacroDef)
+];
+
+impl From<AdtId> for Adt {
+    fn from(id: AdtId) -> Self {
+        match id {
+            AdtId::StructId(it) => Adt::Struct(it.into()),
+            AdtId::UnionId(it) => Adt::Union(it.into()),
+            AdtId::EnumId(it) => Adt::Enum(it.into()),
+        }
+    }
+}
+
+impl From<Adt> for AdtId {
+    fn from(id: Adt) -> Self {
+        match id {
+            Adt::Struct(it) => AdtId::StructId(it.id),
+            Adt::Union(it) => AdtId::UnionId(it.id),
+            Adt::Enum(it) => AdtId::EnumId(it.id),
+        }
+    }
+}
+
+impl From<EnumVariantId> for EnumVariant {
+    fn from(id: EnumVariantId) -> Self {
+        EnumVariant { parent: id.parent.into(), id: id.local_id }
+    }
+}
+
+impl From<EnumVariant> for EnumVariantId {
+    fn from(def: EnumVariant) -> Self {
+        EnumVariantId { parent: def.parent.id, local_id: def.id }
+    }
+}
+
+impl From<ModuleDefId> for ModuleDef {
+    fn from(id: ModuleDefId) -> Self {
+        match id {
+            ModuleDefId::ModuleId(it) => ModuleDef::Module(it.into()),
+            ModuleDefId::FunctionId(it) => ModuleDef::Function(it.into()),
+            ModuleDefId::AdtId(it) => ModuleDef::Adt(it.into()),
+            ModuleDefId::EnumVariantId(it) => ModuleDef::EnumVariant(it.into()),
+            ModuleDefId::ConstId(it) => ModuleDef::Const(it.into()),
+            ModuleDefId::StaticId(it) => ModuleDef::Static(it.into()),
+            ModuleDefId::TraitId(it) => ModuleDef::Trait(it.into()),
+            ModuleDefId::TypeAliasId(it) => ModuleDef::TypeAlias(it.into()),
+            ModuleDefId::BuiltinType(it) => ModuleDef::BuiltinType(it),
+        }
+    }
+}
+
+impl From<ModuleDef> for ModuleDefId {
+    fn from(id: ModuleDef) -> Self {
+        match id {
+            ModuleDef::Module(it) => ModuleDefId::ModuleId(it.into()),
+            ModuleDef::Function(it) => ModuleDefId::FunctionId(it.into()),
+            ModuleDef::Adt(it) => ModuleDefId::AdtId(it.into()),
+            ModuleDef::EnumVariant(it) => ModuleDefId::EnumVariantId(it.into()),
+            ModuleDef::Const(it) => ModuleDefId::ConstId(it.into()),
+            ModuleDef::Static(it) => ModuleDefId::StaticId(it.into()),
+            ModuleDef::Trait(it) => ModuleDefId::TraitId(it.into()),
+            ModuleDef::TypeAlias(it) => ModuleDefId::TypeAliasId(it.into()),
+            ModuleDef::BuiltinType(it) => ModuleDefId::BuiltinType(it),
+        }
+    }
+}
+
+impl From<DefWithBody> for DefWithBodyId {
+    fn from(def: DefWithBody) -> Self {
+        match def {
+            DefWithBody::Function(it) => DefWithBodyId::FunctionId(it.id),
+            DefWithBody::Static(it) => DefWithBodyId::StaticId(it.id),
+            DefWithBody::Const(it) => DefWithBodyId::ConstId(it.id),
+        }
+    }
+}
+
+impl From<DefWithBodyId> for DefWithBody {
+    fn from(def: DefWithBodyId) -> Self {
+        match def {
+            DefWithBodyId::FunctionId(it) => DefWithBody::Function(it.into()),
+            DefWithBodyId::StaticId(it) => DefWithBody::Static(it.into()),
+            DefWithBodyId::ConstId(it) => DefWithBody::Const(it.into()),
+        }
+    }
+}
+
+impl From<AssocItemId> for AssocItem {
+    fn from(def: AssocItemId) -> Self {
+        match def {
+            AssocItemId::FunctionId(it) => AssocItem::Function(it.into()),
+            AssocItemId::TypeAliasId(it) => AssocItem::TypeAlias(it.into()),
+            AssocItemId::ConstId(it) => AssocItem::Const(it.into()),
+        }
+    }
+}
+
+impl From<GenericDef> for GenericDefId {
+    fn from(def: GenericDef) -> Self {
+        match def {
+            GenericDef::Function(it) => GenericDefId::FunctionId(it.id),
+            GenericDef::Adt(it) => GenericDefId::AdtId(it.into()),
+            GenericDef::Trait(it) => GenericDefId::TraitId(it.id),
+            GenericDef::TypeAlias(it) => GenericDefId::TypeAliasId(it.id),
+            GenericDef::ImplDef(it) => GenericDefId::ImplId(it.id),
+            GenericDef::EnumVariant(it) => {
+                GenericDefId::EnumVariantId(EnumVariantId { parent: it.parent.id, local_id: it.id })
+            }
+            GenericDef::Const(it) => GenericDefId::ConstId(it.id),
+        }
+    }
+}
+
+impl From<Adt> for GenericDefId {
+    fn from(id: Adt) -> Self {
+        match id {
+            Adt::Struct(it) => it.id.into(),
+            Adt::Union(it) => it.id.into(),
+            Adt::Enum(it) => it.id.into(),
+        }
+    }
+}
+
+impl From<VariantId> for VariantDef {
+    fn from(def: VariantId) -> Self {
+        match def {
+            VariantId::StructId(it) => VariantDef::Struct(it.into()),
+            VariantId::EnumVariantId(it) => VariantDef::EnumVariant(it.into()),
+            VariantId::UnionId(it) => VariantDef::Union(it.into()),
+        }
+    }
+}
+
+impl From<VariantDef> for VariantId {
+    fn from(def: VariantDef) -> Self {
+        match def {
+            VariantDef::Struct(it) => VariantId::StructId(it.id),
+            VariantDef::EnumVariant(it) => VariantId::EnumVariantId(it.into()),
+            VariantDef::Union(it) => VariantId::UnionId(it.id),
+        }
+    }
+}
+
+impl From<Field> for FieldId {
+    fn from(def: Field) -> Self {
+        FieldId { parent: def.parent.into(), local_id: def.id }
+    }
+}
+
+impl From<FieldId> for Field {
+    fn from(def: FieldId) -> Self {
+        Field { parent: def.parent.into(), id: def.local_id }
+    }
+}
+
+impl From<AttrDef> for AttrDefId {
+    fn from(def: AttrDef) -> Self {
+        match def {
+            AttrDef::Module(it) => AttrDefId::ModuleId(it.id),
+            AttrDef::Field(it) => AttrDefId::FieldId(it.into()),
+            AttrDef::Adt(it) => AttrDefId::AdtId(it.into()),
+            AttrDef::Function(it) => AttrDefId::FunctionId(it.id),
+            AttrDef::EnumVariant(it) => AttrDefId::EnumVariantId(it.into()),
+            AttrDef::Static(it) => AttrDefId::StaticId(it.id),
+            AttrDef::Const(it) => AttrDefId::ConstId(it.id),
+            AttrDef::Trait(it) => AttrDefId::TraitId(it.id),
+            AttrDef::TypeAlias(it) => AttrDefId::TypeAliasId(it.id),
+            AttrDef::MacroDef(it) => AttrDefId::MacroDefId(it.id),
+        }
+    }
+}
+
+impl From<AssocItem> for GenericDefId {
+    fn from(item: AssocItem) -> Self {
+        match item {
+            AssocItem::Function(f) => f.id.into(),
+            AssocItem::Const(c) => c.id.into(),
+            AssocItem::TypeAlias(t) => t.id.into(),
+        }
+    }
+}
+
+impl From<(DefWithBodyId, PatId)> for Local {
+    fn from((parent, pat_id): (DefWithBodyId, PatId)) -> Self {
+        Local { parent, pat_id }
+    }
+}
+
+impl From<MacroDef> for ItemInNs {
+    fn from(macro_def: MacroDef) -> Self {
+        ItemInNs::Macros(macro_def.into())
+    }
+}
+
+impl From<ModuleDef> for ItemInNs {
+    fn from(module_def: ModuleDef) -> Self {
+        match module_def {
+            ModuleDef::Static(_) | ModuleDef::Const(_) | ModuleDef::Function(_) => {
+                ItemInNs::Values(module_def.into())
+            }
+            _ => ItemInNs::Types(module_def.into()),
+        }
+    }
+}
diff --git a/crates/hir/src/has_source.rs b/crates/hir/src/has_source.rs
new file mode 100644
index 000000000..a50d4ff02
--- /dev/null
+++ b/crates/hir/src/has_source.rs
@@ -0,0 +1,135 @@
+//! FIXME: write short doc here
+
+use either::Either;
+use hir_def::{
+    nameres::{ModuleOrigin, ModuleSource},
+    src::{HasChildSource, HasSource as _},
+    Lookup, VariantId,
+};
+use syntax::ast;
+
+use crate::{
+    db::HirDatabase, Const, Enum, EnumVariant, Field, FieldSource, Function, ImplDef, MacroDef,
+    Module, Static, Struct, Trait, TypeAlias, TypeParam, Union,
+};
+
+pub use hir_expand::InFile;
+
+pub trait HasSource {
+    type Ast;
+    fn source(self, db: &dyn HirDatabase) -> InFile<Self::Ast>;
+}
+
+/// NB: Module is !HasSource, because it has two source nodes at the same time:
+/// definition and declaration.
+impl Module {
+    /// Returns a node which defines this module. That is, a file or a `mod foo {}` with items.
+    pub fn definition_source(self, db: &dyn HirDatabase) -> InFile<ModuleSource> {
+        let def_map = db.crate_def_map(self.id.krate);
+        def_map[self.id.local_id].definition_source(db.upcast())
+    }
+
+    pub fn is_mod_rs(self, db: &dyn HirDatabase) -> bool {
+        let def_map = db.crate_def_map(self.id.krate);
+        match def_map[self.id.local_id].origin {
+            ModuleOrigin::File { is_mod_rs, .. } => is_mod_rs,
+            _ => false,
+        }
+    }
+
+    /// Returns a node which declares this module, either a `mod foo;` or a `mod foo {}`.
+    /// `None` for the crate root.
+    pub fn declaration_source(self, db: &dyn HirDatabase) -> Option<InFile<ast::Module>> {
+        let def_map = db.crate_def_map(self.id.krate);
+        def_map[self.id.local_id].declaration_source(db.upcast())
+    }
+}
+
+impl HasSource for Field {
+    type Ast = FieldSource;
+    fn source(self, db: &dyn HirDatabase) -> InFile<FieldSource> {
+        let var = VariantId::from(self.parent);
+        let src = var.child_source(db.upcast());
+        src.map(|it| match it[self.id].clone() {
+            Either::Left(it) => FieldSource::Pos(it),
+            Either::Right(it) => FieldSource::Named(it),
+        })
+    }
+}
+impl HasSource for Struct {
+    type Ast = ast::Struct;
+    fn source(self, db: &dyn HirDatabase) -> InFile<ast::Struct> {
+        self.id.lookup(db.upcast()).source(db.upcast())
+    }
+}
+impl HasSource for Union {
+    type Ast = ast::Union;
+    fn source(self, db: &dyn HirDatabase) -> InFile<ast::Union> {
+        self.id.lookup(db.upcast()).source(db.upcast())
+    }
+}
+impl HasSource for Enum {
+    type Ast = ast::Enum;
+    fn source(self, db: &dyn HirDatabase) -> InFile<ast::Enum> {
+        self.id.lookup(db.upcast()).source(db.upcast())
+    }
+}
+impl HasSource for EnumVariant {
+    type Ast = ast::Variant;
+    fn source(self, db: &dyn HirDatabase) -> InFile<ast::Variant> {
+        self.parent.id.child_source(db.upcast()).map(|map| map[self.id].clone())
+    }
+}
+impl HasSource for Function {
+    type Ast = ast::Fn;
+    fn source(self, db: &dyn HirDatabase) -> InFile<ast::Fn> {
+        self.id.lookup(db.upcast()).source(db.upcast())
+    }
+}
+impl HasSource for Const {
+    type Ast = ast::Const;
+    fn source(self, db: &dyn HirDatabase) -> InFile<ast::Const> {
+        self.id.lookup(db.upcast()).source(db.upcast())
+    }
+}
+impl HasSource for Static {
+    type Ast = ast::Static;
+    fn source(self, db: &dyn HirDatabase) -> InFile<ast::Static> {
+        self.id.lookup(db.upcast()).source(db.upcast())
+    }
+}
+impl HasSource for Trait {
+    type Ast = ast::Trait;
+    fn source(self, db: &dyn HirDatabase) -> InFile<ast::Trait> {
+        self.id.lookup(db.upcast()).source(db.upcast())
+    }
+}
+impl HasSource for TypeAlias {
+    type Ast = ast::TypeAlias;
+    fn source(self, db: &dyn HirDatabase) -> InFile<ast::TypeAlias> {
+        self.id.lookup(db.upcast()).source(db.upcast())
+    }
+}
+impl HasSource for MacroDef {
+    type Ast = ast::MacroCall;
+    fn source(self, db: &dyn HirDatabase) -> InFile<ast::MacroCall> {
+        InFile {
+            file_id: self.id.ast_id.expect("MacroDef without ast_id").file_id,
+            value: self.id.ast_id.expect("MacroDef without ast_id").to_node(db.upcast()),
+        }
+    }
+}
+impl HasSource for ImplDef {
+    type Ast = ast::Impl;
+    fn source(self, db: &dyn HirDatabase) -> InFile<ast::Impl> {
+        self.id.lookup(db.upcast()).source(db.upcast())
+    }
+}
+
+impl HasSource for TypeParam {
+    type Ast = Either<ast::Trait, ast::TypeParam>;
+    fn source(self, db: &dyn HirDatabase) -> InFile<Self::Ast> {
+        let child_source = self.id.parent.child_source(db.upcast());
+        child_source.map(|it| it[self.id.local_id].clone())
+    }
+}
diff --git a/crates/hir/src/lib.rs b/crates/hir/src/lib.rs
new file mode 100644
index 000000000..24a0f6b4b
--- /dev/null
+++ b/crates/hir/src/lib.rs
@@ -0,0 +1,59 @@
+//! HIR (previously known as descriptors) provides a high-level object oriented
+//! access to Rust code.
+//!
+//! The principal difference between HIR and syntax trees is that HIR is bound
+//! to a particular crate instance. That is, it has cfg flags and features
+//! applied. So, the relation between syntax and HIR is many-to-one.
+//!
+//! HIR is the public API of the all of the compiler logic above syntax trees.
+//! It is written in "OO" style. Each type is self contained (as in, it knows it's
+//! parents and full context). It should be "clean code".
+//!
+//! `hir_*` crates are the implementation of the compiler logic.
+//! They are written in "ECS" style, with relatively little abstractions.
+//! Many types are not self-contained, and explicitly use local indexes, arenas, etc.
+//!
+//! `hir` is what insulates the "we don't know how to actually write an incremental compiler"
+//! from the ide with completions, hovers, etc. It is a (soft, internal) boundary:
+//! https://www.tedinski.com/2018/02/06/system-boundaries.html.
+
+#![recursion_limit = "512"]
+
+mod semantics;
+pub mod db;
+mod source_analyzer;
+
+pub mod diagnostics;
+
+mod from_id;
+mod code_model;
+
+mod has_source;
+
+pub use crate::{
+    code_model::{
+        Adt, AsAssocItem, AssocItem, AssocItemContainer, AttrDef, Callable, CallableKind, Const,
+        Crate, CrateDependency, DefWithBody, Docs, Enum, EnumVariant, Field, FieldSource, Function,
+        GenericDef, HasAttrs, HasVisibility, ImplDef, Local, MacroDef, Module, ModuleDef, ScopeDef,
+        Static, Struct, Trait, Type, TypeAlias, TypeParam, Union, VariantDef, Visibility,
+    },
+    has_source::HasSource,
+    semantics::{original_range, PathResolution, Semantics, SemanticsScope},
+};
+
+pub use hir_def::{
+    adt::StructKind,
+    attr::Attrs,
+    body::scope::ExprScopes,
+    builtin_type::BuiltinType,
+    docs::Documentation,
+    nameres::ModuleSource,
+    path::{ModPath, Path, PathKind},
+    type_ref::{Mutability, TypeRef},
+};
+pub use hir_expand::{
+    hygiene::Hygiene, name::Name, HirFileId, InFile, MacroCallId, MacroCallLoc,
+    MacroDefId, /* FIXME */
+    MacroFile, Origin,
+};
+pub use hir_ty::display::HirDisplay;
diff --git a/crates/hir/src/semantics.rs b/crates/hir/src/semantics.rs
new file mode 100644
index 000000000..1467d825d
--- /dev/null
+++ b/crates/hir/src/semantics.rs
@@ -0,0 +1,840 @@
+//! See `Semantics`.
+
+mod source_to_def;
+
+use std::{cell::RefCell, fmt, iter::successors};
+
+use base_db::{FileId, FileRange};
+use hir_def::{
+    resolver::{self, HasResolver, Resolver},
+    AsMacroCall, FunctionId, TraitId, VariantId,
+};
+use hir_expand::{hygiene::Hygiene, name::AsName, ExpansionInfo};
+use hir_ty::associated_type_shorthand_candidates;
+use itertools::Itertools;
+use rustc_hash::{FxHashMap, FxHashSet};
+use syntax::{
+    algo::{find_node_at_offset, skip_trivia_token},
+    ast, AstNode, Direction, SyntaxNode, SyntaxToken, TextRange, TextSize,
+};
+
+use crate::{
+    db::HirDatabase,
+    diagnostics::Diagnostic,
+    semantics::source_to_def::{ChildContainer, SourceToDefCache, SourceToDefCtx},
+    source_analyzer::{resolve_hir_path, resolve_hir_path_qualifier, SourceAnalyzer},
+    AssocItem, Callable, Crate, Field, Function, HirFileId, ImplDef, InFile, Local, MacroDef,
+    Module, ModuleDef, Name, Origin, Path, ScopeDef, Trait, Type, TypeAlias, TypeParam, TypeRef,
+    VariantDef,
+};
+use resolver::TypeNs;
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum PathResolution {
+    /// An item
+    Def(ModuleDef),
+    /// A local binding (only value namespace)
+    Local(Local),
+    /// A generic parameter
+    TypeParam(TypeParam),
+    SelfType(ImplDef),
+    Macro(MacroDef),
+    AssocItem(AssocItem),
+}
+
+impl PathResolution {
+    fn in_type_ns(&self) -> Option<TypeNs> {
+        match self {
+            PathResolution::Def(ModuleDef::Adt(adt)) => Some(TypeNs::AdtId((*adt).into())),
+            PathResolution::Def(ModuleDef::BuiltinType(builtin)) => {
+                Some(TypeNs::BuiltinType(*builtin))
+            }
+            PathResolution::Def(ModuleDef::Const(_))
+            | PathResolution::Def(ModuleDef::EnumVariant(_))
+            | PathResolution::Def(ModuleDef::Function(_))
+            | PathResolution::Def(ModuleDef::Module(_))
+            | PathResolution::Def(ModuleDef::Static(_))
+            | PathResolution::Def(ModuleDef::Trait(_)) => None,
+            PathResolution::Def(ModuleDef::TypeAlias(alias)) => {
+                Some(TypeNs::TypeAliasId((*alias).into()))
+            }
+            PathResolution::Local(_) | PathResolution::Macro(_) => None,
+            PathResolution::TypeParam(param) => Some(TypeNs::GenericParam((*param).into())),
+            PathResolution::SelfType(impl_def) => Some(TypeNs::SelfType((*impl_def).into())),
+            PathResolution::AssocItem(AssocItem::Const(_))
+            | PathResolution::AssocItem(AssocItem::Function(_)) => None,
+            PathResolution::AssocItem(AssocItem::TypeAlias(alias)) => {
+                Some(TypeNs::TypeAliasId((*alias).into()))
+            }
+        }
+    }
+
+    /// Returns an iterator over associated types that may be specified after this path (using
+    /// `Ty::Assoc` syntax).
+    pub fn assoc_type_shorthand_candidates<R>(
+        &self,
+        db: &dyn HirDatabase,
+        mut cb: impl FnMut(TypeAlias) -> Option<R>,
+    ) -> Option<R> {
+        associated_type_shorthand_candidates(db, self.in_type_ns()?, |_, _, id| cb(id.into()))
+    }
+}
+
+/// Primary API to get semantic information, like types, from syntax trees.
+pub struct Semantics<'db, DB> {
+    pub db: &'db DB,
+    imp: SemanticsImpl<'db>,
+}
+
+pub struct SemanticsImpl<'db> {
+    pub db: &'db dyn HirDatabase,
+    s2d_cache: RefCell<SourceToDefCache>,
+    expansion_info_cache: RefCell<FxHashMap<HirFileId, Option<ExpansionInfo>>>,
+    cache: RefCell<FxHashMap<SyntaxNode, HirFileId>>,
+}
+
+impl<DB> fmt::Debug for Semantics<'_, DB> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "Semantics {{ ... }}")
+    }
+}
+
+impl<'db, DB: HirDatabase> Semantics<'db, DB> {
+    pub fn new(db: &DB) -> Semantics<DB> {
+        let impl_ = SemanticsImpl::new(db);
+        Semantics { db, imp: impl_ }
+    }
+
+    pub fn parse(&self, file_id: FileId) -> ast::SourceFile {
+        self.imp.parse(file_id)
+    }
+
+    pub fn expand(&self, macro_call: &ast::MacroCall) -> Option<SyntaxNode> {
+        self.imp.expand(macro_call)
+    }
+
+    pub fn expand_hypothetical(
+        &self,
+        actual_macro_call: &ast::MacroCall,
+        hypothetical_args: &ast::TokenTree,
+        token_to_map: SyntaxToken,
+    ) -> Option<(SyntaxNode, SyntaxToken)> {
+        self.imp.expand_hypothetical(actual_macro_call, hypothetical_args, token_to_map)
+    }
+
+    pub fn descend_into_macros(&self, token: SyntaxToken) -> SyntaxToken {
+        self.imp.descend_into_macros(token)
+    }
+
+    pub fn descend_node_at_offset<N: ast::AstNode>(
+        &self,
+        node: &SyntaxNode,
+        offset: TextSize,
+    ) -> Option<N> {
+        self.imp.descend_node_at_offset(node, offset).find_map(N::cast)
+    }
+
+    pub fn original_range(&self, node: &SyntaxNode) -> FileRange {
+        self.imp.original_range(node)
+    }
+
+    pub fn diagnostics_display_range(&self, diagnostics: &dyn Diagnostic) -> FileRange {
+        self.imp.diagnostics_display_range(diagnostics)
+    }
+
+    pub fn ancestors_with_macros(&self, node: SyntaxNode) -> impl Iterator<Item = SyntaxNode> + '_ {
+        self.imp.ancestors_with_macros(node)
+    }
+
+    pub fn ancestors_at_offset_with_macros(
+        &self,
+        node: &SyntaxNode,
+        offset: TextSize,
+    ) -> impl Iterator<Item = SyntaxNode> + '_ {
+        self.imp.ancestors_at_offset_with_macros(node, offset)
+    }
+
+    /// Find a AstNode by offset inside SyntaxNode, if it is inside *Macrofile*,
+    /// search up until it is of the target AstNode type
+    pub fn find_node_at_offset_with_macros<N: AstNode>(
+        &self,
+        node: &SyntaxNode,
+        offset: TextSize,
+    ) -> Option<N> {
+        self.imp.ancestors_at_offset_with_macros(node, offset).find_map(N::cast)
+    }
+
+    /// Find a AstNode by offset inside SyntaxNode, if it is inside *MacroCall*,
+    /// descend it and find again
+    pub fn find_node_at_offset_with_descend<N: AstNode>(
+        &self,
+        node: &SyntaxNode,
+        offset: TextSize,
+    ) -> Option<N> {
+        if let Some(it) = find_node_at_offset(&node, offset) {
+            return Some(it);
+        }
+
+        self.imp.descend_node_at_offset(node, offset).find_map(N::cast)
+    }
+
+    pub fn type_of_expr(&self, expr: &ast::Expr) -> Option<Type> {
+        self.imp.type_of_expr(expr)
+    }
+
+    pub fn type_of_pat(&self, pat: &ast::Pat) -> Option<Type> {
+        self.imp.type_of_pat(pat)
+    }
+
+    pub fn type_of_self(&self, param: &ast::SelfParam) -> Option<Type> {
+        self.imp.type_of_self(param)
+    }
+
+    pub fn resolve_method_call(&self, call: &ast::MethodCallExpr) -> Option<Function> {
+        self.imp.resolve_method_call(call).map(Function::from)
+    }
+
+    pub fn resolve_method_call_as_callable(&self, call: &ast::MethodCallExpr) -> Option<Callable> {
+        self.imp.resolve_method_call_as_callable(call)
+    }
+
+    pub fn resolve_field(&self, field: &ast::FieldExpr) -> Option<Field> {
+        self.imp.resolve_field(field)
+    }
+
+    pub fn resolve_record_field(
+        &self,
+        field: &ast::RecordExprField,
+    ) -> Option<(Field, Option<Local>)> {
+        self.imp.resolve_record_field(field)
+    }
+
+    pub fn resolve_record_field_pat(&self, field: &ast::RecordPatField) -> Option<Field> {
+        self.imp.resolve_record_field_pat(field)
+    }
+
+    pub fn resolve_macro_call(&self, macro_call: &ast::MacroCall) -> Option<MacroDef> {
+        self.imp.resolve_macro_call(macro_call)
+    }
+
+    pub fn resolve_path(&self, path: &ast::Path) -> Option<PathResolution> {
+        self.imp.resolve_path(path)
+    }
+
+    pub fn resolve_extern_crate(&self, extern_crate: &ast::ExternCrate) -> Option<Crate> {
+        self.imp.resolve_extern_crate(extern_crate)
+    }
+
+    pub fn resolve_variant(&self, record_lit: ast::RecordExpr) -> Option<VariantDef> {
+        self.imp.resolve_variant(record_lit).map(VariantDef::from)
+    }
+
+    pub fn lower_path(&self, path: &ast::Path) -> Option<Path> {
+        self.imp.lower_path(path)
+    }
+
+    pub fn resolve_bind_pat_to_const(&self, pat: &ast::IdentPat) -> Option<ModuleDef> {
+        self.imp.resolve_bind_pat_to_const(pat)
+    }
+
+    // FIXME: use this instead?
+    // pub fn resolve_name_ref(&self, name_ref: &ast::NameRef) -> Option<???>;
+
+    pub fn record_literal_missing_fields(&self, literal: &ast::RecordExpr) -> Vec<(Field, Type)> {
+        self.imp.record_literal_missing_fields(literal)
+    }
+
+    pub fn record_pattern_missing_fields(&self, pattern: &ast::RecordPat) -> Vec<(Field, Type)> {
+        self.imp.record_pattern_missing_fields(pattern)
+    }
+
+    pub fn to_def<T: ToDef>(&self, src: &T) -> Option<T::Def> {
+        let src = self.imp.find_file(src.syntax().clone()).with_value(src).cloned();
+        T::to_def(&self.imp, src)
+    }
+
+    pub fn to_module_def(&self, file: FileId) -> Option<Module> {
+        self.imp.to_module_def(file)
+    }
+
+    pub fn scope(&self, node: &SyntaxNode) -> SemanticsScope<'db> {
+        self.imp.scope(node)
+    }
+
+    pub fn scope_at_offset(&self, node: &SyntaxNode, offset: TextSize) -> SemanticsScope<'db> {
+        self.imp.scope_at_offset(node, offset)
+    }
+
+    pub fn scope_for_def(&self, def: Trait) -> SemanticsScope<'db> {
+        self.imp.scope_for_def(def)
+    }
+
+    pub fn assert_contains_node(&self, node: &SyntaxNode) {
+        self.imp.assert_contains_node(node)
+    }
+
+    pub fn is_unsafe_method_call(&self, method_call_expr: ast::MethodCallExpr) -> bool {
+        self.imp.is_unsafe_method_call(method_call_expr)
+    }
+
+    pub fn is_unsafe_ref_expr(&self, ref_expr: &ast::RefExpr) -> bool {
+        self.imp.is_unsafe_ref_expr(ref_expr)
+    }
+
+    pub fn is_unsafe_ident_pat(&self, ident_pat: &ast::IdentPat) -> bool {
+        self.imp.is_unsafe_ident_pat(ident_pat)
+    }
+}
+
+impl<'db> SemanticsImpl<'db> {
+    fn new(db: &'db dyn HirDatabase) -> Self {
+        SemanticsImpl {
+            db,
+            s2d_cache: Default::default(),
+            cache: Default::default(),
+            expansion_info_cache: Default::default(),
+        }
+    }
+
+    fn parse(&self, file_id: FileId) -> ast::SourceFile {
+        let tree = self.db.parse(file_id).tree();
+        self.cache(tree.syntax().clone(), file_id.into());
+        tree
+    }
+
+    fn expand(&self, macro_call: &ast::MacroCall) -> Option<SyntaxNode> {
+        let macro_call = self.find_file(macro_call.syntax().clone()).with_value(macro_call);
+        let sa = self.analyze2(macro_call.map(|it| it.syntax()), None);
+        let file_id = sa.expand(self.db, macro_call)?;
+        let node = self.db.parse_or_expand(file_id)?;
+        self.cache(node.clone(), file_id);
+        Some(node)
+    }
+
+    fn expand_hypothetical(
+        &self,
+        actual_macro_call: &ast::MacroCall,
+        hypothetical_args: &ast::TokenTree,
+        token_to_map: SyntaxToken,
+    ) -> Option<(SyntaxNode, SyntaxToken)> {
+        let macro_call =
+            self.find_file(actual_macro_call.syntax().clone()).with_value(actual_macro_call);
+        let sa = self.analyze2(macro_call.map(|it| it.syntax()), None);
+        let krate = sa.resolver.krate()?;
+        let macro_call_id = macro_call.as_call_id(self.db.upcast(), krate, |path| {
+            sa.resolver.resolve_path_as_macro(self.db.upcast(), &path)
+        })?;
+        hir_expand::db::expand_hypothetical(
+            self.db.upcast(),
+            macro_call_id,
+            hypothetical_args,
+            token_to_map,
+        )
+    }
+
+    fn descend_into_macros(&self, token: SyntaxToken) -> SyntaxToken {
+        let _p = profile::span("descend_into_macros");
+        let parent = token.parent();
+        let parent = self.find_file(parent);
+        let sa = self.analyze2(parent.as_ref(), None);
+
+        let token = successors(Some(parent.with_value(token)), |token| {
+            self.db.check_canceled();
+            let macro_call = token.value.ancestors().find_map(ast::MacroCall::cast)?;
+            let tt = macro_call.token_tree()?;
+            if !tt.syntax().text_range().contains_range(token.value.text_range()) {
+                return None;
+            }
+            let file_id = sa.expand(self.db, token.with_value(&macro_call))?;
+            let token = self
+                .expansion_info_cache
+                .borrow_mut()
+                .entry(file_id)
+                .or_insert_with(|| file_id.expansion_info(self.db.upcast()))
+                .as_ref()?
+                .map_token_down(token.as_ref())?;
+
+            self.cache(find_root(&token.value.parent()), token.file_id);
+
+            Some(token)
+        })
+        .last()
+        .unwrap();
+
+        token.value
+    }
+
+    fn descend_node_at_offset(
+        &self,
+        node: &SyntaxNode,
+        offset: TextSize,
+    ) -> impl Iterator<Item = SyntaxNode> + '_ {
+        // Handle macro token cases
+        node.token_at_offset(offset)
+            .map(|token| self.descend_into_macros(token))
+            .map(|it| self.ancestors_with_macros(it.parent()))
+            .flatten()
+    }
+
+    fn original_range(&self, node: &SyntaxNode) -> FileRange {
+        let node = self.find_file(node.clone());
+        original_range(self.db, node.as_ref())
+    }
+
+    fn diagnostics_display_range(&self, diagnostics: &dyn Diagnostic) -> FileRange {
+        let src = diagnostics.display_source();
+        let root = self.db.parse_or_expand(src.file_id).unwrap();
+        let node = src.value.to_node(&root);
+        self.cache(root, src.file_id);
+        original_range(self.db, src.with_value(&node))
+    }
+
+    fn ancestors_with_macros(&self, node: SyntaxNode) -> impl Iterator<Item = SyntaxNode> + '_ {
+        let node = self.find_file(node);
+        node.ancestors_with_macros(self.db.upcast()).map(|it| it.value)
+    }
+
+    fn ancestors_at_offset_with_macros(
+        &self,
+        node: &SyntaxNode,
+        offset: TextSize,
+    ) -> impl Iterator<Item = SyntaxNode> + '_ {
+        node.token_at_offset(offset)
+            .map(|token| self.ancestors_with_macros(token.parent()))
+            .kmerge_by(|node1, node2| node1.text_range().len() < node2.text_range().len())
+    }
+
+    fn type_of_expr(&self, expr: &ast::Expr) -> Option<Type> {
+        self.analyze(expr.syntax()).type_of_expr(self.db, &expr)
+    }
+
+    fn type_of_pat(&self, pat: &ast::Pat) -> Option<Type> {
+        self.analyze(pat.syntax()).type_of_pat(self.db, &pat)
+    }
+
+    fn type_of_self(&self, param: &ast::SelfParam) -> Option<Type> {
+        self.analyze(param.syntax()).type_of_self(self.db, &param)
+    }
+
+    fn resolve_method_call(&self, call: &ast::MethodCallExpr) -> Option<FunctionId> {
+        self.analyze(call.syntax()).resolve_method_call(self.db, call)
+    }
+
+    fn resolve_method_call_as_callable(&self, call: &ast::MethodCallExpr) -> Option<Callable> {
+        // FIXME: this erases Substs
+        let func = self.resolve_method_call(call)?;
+        let ty = self.db.value_ty(func.into());
+        let resolver = self.analyze(call.syntax()).resolver;
+        let ty = Type::new_with_resolver(self.db, &resolver, ty.value)?;
+        let mut res = ty.as_callable(self.db)?;
+        res.is_bound_method = true;
+        Some(res)
+    }
+
+    fn resolve_field(&self, field: &ast::FieldExpr) -> Option<Field> {
+        self.analyze(field.syntax()).resolve_field(self.db, field)
+    }
+
+    fn resolve_record_field(&self, field: &ast::RecordExprField) -> Option<(Field, Option<Local>)> {
+        self.analyze(field.syntax()).resolve_record_field(self.db, field)
+    }
+
+    fn resolve_record_field_pat(&self, field: &ast::RecordPatField) -> Option<Field> {
+        self.analyze(field.syntax()).resolve_record_field_pat(self.db, field)
+    }
+
+    fn resolve_macro_call(&self, macro_call: &ast::MacroCall) -> Option<MacroDef> {
+        let sa = self.analyze(macro_call.syntax());
+        let macro_call = self.find_file(macro_call.syntax().clone()).with_value(macro_call);
+        sa.resolve_macro_call(self.db, macro_call)
+    }
+
+    fn resolve_path(&self, path: &ast::Path) -> Option<PathResolution> {
+        self.analyze(path.syntax()).resolve_path(self.db, path)
+    }
+
+    fn resolve_extern_crate(&self, extern_crate: &ast::ExternCrate) -> Option<Crate> {
+        let krate = self.scope(extern_crate.syntax()).krate()?;
+        krate.dependencies(self.db).into_iter().find_map(|dep| {
+            if dep.name == extern_crate.name_ref()?.as_name() {
+                Some(dep.krate)
+            } else {
+                None
+            }
+        })
+    }
+
+    fn resolve_variant(&self, record_lit: ast::RecordExpr) -> Option<VariantId> {
+        self.analyze(record_lit.syntax()).resolve_variant(self.db, record_lit)
+    }
+
+    fn lower_path(&self, path: &ast::Path) -> Option<Path> {
+        let src = self.find_file(path.syntax().clone());
+        Path::from_src(path.clone(), &Hygiene::new(self.db.upcast(), src.file_id.into()))
+    }
+
+    fn resolve_bind_pat_to_const(&self, pat: &ast::IdentPat) -> Option<ModuleDef> {
+        self.analyze(pat.syntax()).resolve_bind_pat_to_const(self.db, pat)
+    }
+
+    fn record_literal_missing_fields(&self, literal: &ast::RecordExpr) -> Vec<(Field, Type)> {
+        self.analyze(literal.syntax())
+            .record_literal_missing_fields(self.db, literal)
+            .unwrap_or_default()
+    }
+
+    fn record_pattern_missing_fields(&self, pattern: &ast::RecordPat) -> Vec<(Field, Type)> {
+        self.analyze(pattern.syntax())
+            .record_pattern_missing_fields(self.db, pattern)
+            .unwrap_or_default()
+    }
+
+    fn with_ctx<F: FnOnce(&mut SourceToDefCtx) -> T, T>(&self, f: F) -> T {
+        let mut cache = self.s2d_cache.borrow_mut();
+        let mut ctx = SourceToDefCtx { db: self.db, cache: &mut *cache };
+        f(&mut ctx)
+    }
+
+    fn to_module_def(&self, file: FileId) -> Option<Module> {
+        self.with_ctx(|ctx| ctx.file_to_def(file)).map(Module::from)
+    }
+
+    fn scope(&self, node: &SyntaxNode) -> SemanticsScope<'db> {
+        let node = self.find_file(node.clone());
+        let resolver = self.analyze2(node.as_ref(), None).resolver;
+        SemanticsScope { db: self.db, resolver }
+    }
+
+    fn scope_at_offset(&self, node: &SyntaxNode, offset: TextSize) -> SemanticsScope<'db> {
+        let node = self.find_file(node.clone());
+        let resolver = self.analyze2(node.as_ref(), Some(offset)).resolver;
+        SemanticsScope { db: self.db, resolver }
+    }
+
+    fn scope_for_def(&self, def: Trait) -> SemanticsScope<'db> {
+        let resolver = def.id.resolver(self.db.upcast());
+        SemanticsScope { db: self.db, resolver }
+    }
+
+    fn analyze(&self, node: &SyntaxNode) -> SourceAnalyzer {
+        let src = self.find_file(node.clone());
+        self.analyze2(src.as_ref(), None)
+    }
+
+    fn analyze2(&self, src: InFile<&SyntaxNode>, offset: Option<TextSize>) -> SourceAnalyzer {
+        let _p = profile::span("Semantics::analyze2");
+
+        let container = match self.with_ctx(|ctx| ctx.find_container(src)) {
+            Some(it) => it,
+            None => return SourceAnalyzer::new_for_resolver(Resolver::default(), src),
+        };
+
+        let resolver = match container {
+            ChildContainer::DefWithBodyId(def) => {
+                return SourceAnalyzer::new_for_body(self.db, def, src, offset)
+            }
+            ChildContainer::TraitId(it) => it.resolver(self.db.upcast()),
+            ChildContainer::ImplId(it) => it.resolver(self.db.upcast()),
+            ChildContainer::ModuleId(it) => it.resolver(self.db.upcast()),
+            ChildContainer::EnumId(it) => it.resolver(self.db.upcast()),
+            ChildContainer::VariantId(it) => it.resolver(self.db.upcast()),
+            ChildContainer::TypeAliasId(it) => it.resolver(self.db.upcast()),
+            ChildContainer::GenericDefId(it) => it.resolver(self.db.upcast()),
+        };
+        SourceAnalyzer::new_for_resolver(resolver, src)
+    }
+
+    fn cache(&self, root_node: SyntaxNode, file_id: HirFileId) {
+        assert!(root_node.parent().is_none());
+        let mut cache = self.cache.borrow_mut();
+        let prev = cache.insert(root_node, file_id);
+        assert!(prev == None || prev == Some(file_id))
+    }
+
+    fn assert_contains_node(&self, node: &SyntaxNode) {
+        self.find_file(node.clone());
+    }
+
+    fn lookup(&self, root_node: &SyntaxNode) -> Option<HirFileId> {
+        let cache = self.cache.borrow();
+        cache.get(root_node).copied()
+    }
+
+    fn find_file(&self, node: SyntaxNode) -> InFile<SyntaxNode> {
+        let root_node = find_root(&node);
+        let file_id = self.lookup(&root_node).unwrap_or_else(|| {
+            panic!(
+                "\n\nFailed to lookup {:?} in this Semantics.\n\
+                 Make sure to use only query nodes, derived from this instance of Semantics.\n\
+                 root node:   {:?}\n\
+                 known nodes: {}\n\n",
+                node,
+                root_node,
+                self.cache
+                    .borrow()
+                    .keys()
+                    .map(|it| format!("{:?}", it))
+                    .collect::<Vec<_>>()
+                    .join(", ")
+            )
+        });
+        InFile::new(file_id, node)
+    }
+
+    pub fn is_unsafe_method_call(&self, method_call_expr: ast::MethodCallExpr) -> bool {
+        method_call_expr
+            .expr()
+            .and_then(|expr| {
+                let field_expr = if let ast::Expr::FieldExpr(field_expr) = expr {
+                    field_expr
+                } else {
+                    return None;
+                };
+                let ty = self.type_of_expr(&field_expr.expr()?)?;
+                if !ty.is_packed(self.db) {
+                    return None;
+                }
+
+                let func = self.resolve_method_call(&method_call_expr).map(Function::from)?;
+                let is_unsafe = func.has_self_param(self.db)
+                    && matches!(func.params(self.db).first(), Some(TypeRef::Reference(..)));
+                Some(is_unsafe)
+            })
+            .unwrap_or(false)
+    }
+
+    pub fn is_unsafe_ref_expr(&self, ref_expr: &ast::RefExpr) -> bool {
+        ref_expr
+            .expr()
+            .and_then(|expr| {
+                let field_expr = match expr {
+                    ast::Expr::FieldExpr(field_expr) => field_expr,
+                    _ => return None,
+                };
+                let expr = field_expr.expr()?;
+                self.type_of_expr(&expr)
+            })
+            // Binding a reference to a packed type is possibly unsafe.
+            .map(|ty| ty.is_packed(self.db))
+            .unwrap_or(false)
+
+        // FIXME This needs layout computation to be correct. It will highlight
+        // more than it should with the current implementation.
+    }
+
+    pub fn is_unsafe_ident_pat(&self, ident_pat: &ast::IdentPat) -> bool {
+        if !ident_pat.ref_token().is_some() {
+            return false;
+        }
+
+        ident_pat
+            .syntax()
+            .parent()
+            .and_then(|parent| {
+                // `IdentPat` can live under `RecordPat` directly under `RecordPatField` or
+                // `RecordPatFieldList`. `RecordPatField` also lives under `RecordPatFieldList`,
+                // so this tries to lookup the `IdentPat` anywhere along that structure to the
+                // `RecordPat` so we can get the containing type.
+                let record_pat = ast::RecordPatField::cast(parent.clone())
+                    .and_then(|record_pat| record_pat.syntax().parent())
+                    .or_else(|| Some(parent.clone()))
+                    .and_then(|parent| {
+                        ast::RecordPatFieldList::cast(parent)?
+                            .syntax()
+                            .parent()
+                            .and_then(ast::RecordPat::cast)
+                    });
+
+                // If this doesn't match a `RecordPat`, fallback to a `LetStmt` to see if
+                // this is initialized from a `FieldExpr`.
+                if let Some(record_pat) = record_pat {
+                    self.type_of_pat(&ast::Pat::RecordPat(record_pat))
+                } else if let Some(let_stmt) = ast::LetStmt::cast(parent) {
+                    let field_expr = match let_stmt.initializer()? {
+                        ast::Expr::FieldExpr(field_expr) => field_expr,
+                        _ => return None,
+                    };
+
+                    self.type_of_expr(&field_expr.expr()?)
+                } else {
+                    None
+                }
+            })
+            // Binding a reference to a packed type is possibly unsafe.
+            .map(|ty| ty.is_packed(self.db))
+            .unwrap_or(false)
+    }
+}
+
+pub trait ToDef: AstNode + Clone {
+    type Def;
+
+    fn to_def(sema: &SemanticsImpl, src: InFile<Self>) -> Option<Self::Def>;
+}
+
+macro_rules! to_def_impls {
+    ($(($def:path, $ast:path, $meth:ident)),* ,) => {$(
+        impl ToDef for $ast {
+            type Def = $def;
+            fn to_def(sema: &SemanticsImpl, src: InFile<Self>) -> Option<Self::Def> {
+                sema.with_ctx(|ctx| ctx.$meth(src)).map(<$def>::from)
+            }
+        }
+    )*}
+}
+
+to_def_impls![
+    (crate::Module, ast::Module, module_to_def),
+    (crate::Struct, ast::Struct, struct_to_def),
+    (crate::Enum, ast::Enum, enum_to_def),
+    (crate::Union, ast::Union, union_to_def),
+    (crate::Trait, ast::Trait, trait_to_def),
+    (crate::ImplDef, ast::Impl, impl_to_def),
+    (crate::TypeAlias, ast::TypeAlias, type_alias_to_def),
+    (crate::Const, ast::Const, const_to_def),
+    (crate::Static, ast::Static, static_to_def),
+    (crate::Function, ast::Fn, fn_to_def),
+    (crate::Field, ast::RecordField, record_field_to_def),
+    (crate::Field, ast::TupleField, tuple_field_to_def),
+    (crate::EnumVariant, ast::Variant, enum_variant_to_def),
+    (crate::TypeParam, ast::TypeParam, type_param_to_def),
+    (crate::MacroDef, ast::MacroCall, macro_call_to_def), // this one is dubious, not all calls are macros
+    (crate::Local, ast::IdentPat, bind_pat_to_def),
+];
+
+fn find_root(node: &SyntaxNode) -> SyntaxNode {
+    node.ancestors().last().unwrap()
+}
+
+#[derive(Debug)]
+pub struct SemanticsScope<'a> {
+    pub db: &'a dyn HirDatabase,
+    resolver: Resolver,
+}
+
+impl<'a> SemanticsScope<'a> {
+    pub fn module(&self) -> Option<Module> {
+        Some(Module { id: self.resolver.module()? })
+    }
+
+    pub fn krate(&self) -> Option<Crate> {
+        Some(Crate { id: self.resolver.krate()? })
+    }
+
+    /// Note: `FxHashSet<TraitId>` should be treated as an opaque type, passed into `Type
+    // FIXME: rename to visible_traits to not repeat scope?
+    pub fn traits_in_scope(&self) -> FxHashSet<TraitId> {
+        let resolver = &self.resolver;
+        resolver.traits_in_scope(self.db.upcast())
+    }
+
+    pub fn process_all_names(&self, f: &mut dyn FnMut(Name, ScopeDef)) {
+        let resolver = &self.resolver;
+
+        resolver.process_all_names(self.db.upcast(), &mut |name, def| {
+            let def = match def {
+                resolver::ScopeDef::PerNs(it) => {
+                    let items = ScopeDef::all_items(it);
+                    for item in items {
+                        f(name.clone(), item);
+                    }
+                    return;
+                }
+                resolver::ScopeDef::ImplSelfType(it) => ScopeDef::ImplSelfType(it.into()),
+                resolver::ScopeDef::AdtSelfType(it) => ScopeDef::AdtSelfType(it.into()),
+                resolver::ScopeDef::GenericParam(id) => ScopeDef::GenericParam(TypeParam { id }),
+                resolver::ScopeDef::Local(pat_id) => {
+                    let parent = resolver.body_owner().unwrap().into();
+                    ScopeDef::Local(Local { parent, pat_id })
+                }
+            };
+            f(name, def)
+        })
+    }
+
+    pub fn resolve_hir_path(&self, path: &Path) -> Option<PathResolution> {
+        resolve_hir_path(self.db, &self.resolver, path)
+    }
+
+    /// Resolves a path where we know it is a qualifier of another path.
+    ///
+    /// For example, if we have:
+    /// ```
+    /// mod my {
+    ///     pub mod foo {
+    ///         struct Bar;
+    ///     }
+    ///
+    ///     pub fn foo() {}
+    /// }
+    /// ```
+    /// then we know that `foo` in `my::foo::Bar` refers to the module, not the function.
+    pub fn resolve_hir_path_qualifier(&self, path: &Path) -> Option<PathResolution> {
+        resolve_hir_path_qualifier(self.db, &self.resolver, path)
+    }
+}
+
+// FIXME: Change `HasSource` trait to work with `Semantics` and remove this?
+pub fn original_range(db: &dyn HirDatabase, node: InFile<&SyntaxNode>) -> FileRange {
+    if let Some(range) = original_range_opt(db, node) {
+        let original_file = range.file_id.original_file(db.upcast());
+        if range.file_id == original_file.into() {
+            return FileRange { file_id: original_file, range: range.value };
+        }
+
+        log::error!("Fail to mapping up more for {:?}", range);
+        return FileRange { file_id: range.file_id.original_file(db.upcast()), range: range.value };
+    }
+
+    // Fall back to whole macro call
+    if let Some(expansion) = node.file_id.expansion_info(db.upcast()) {
+        if let Some(call_node) = expansion.call_node() {
+            return FileRange {
+                file_id: call_node.file_id.original_file(db.upcast()),
+                range: call_node.value.text_range(),
+            };
+        }
+    }
+
+    FileRange { file_id: node.file_id.original_file(db.upcast()), range: node.value.text_range() }
+}
+
+fn original_range_opt(
+    db: &dyn HirDatabase,
+    node: InFile<&SyntaxNode>,
+) -> Option<InFile<TextRange>> {
+    let expansion = node.file_id.expansion_info(db.upcast())?;
+
+    // the input node has only one token ?
+    let single = skip_trivia_token(node.value.first_token()?, Direction::Next)?
+        == skip_trivia_token(node.value.last_token()?, Direction::Prev)?;
+
+    Some(node.value.descendants().find_map(|it| {
+        let first = skip_trivia_token(it.first_token()?, Direction::Next)?;
+        let first = ascend_call_token(db, &expansion, node.with_value(first))?;
+
+        let last = skip_trivia_token(it.last_token()?, Direction::Prev)?;
+        let last = ascend_call_token(db, &expansion, node.with_value(last))?;
+
+        if (!single && first == last) || (first.file_id != last.file_id) {
+            return None;
+        }
+
+        Some(first.with_value(first.value.text_range().cover(last.value.text_range())))
+    })?)
+}
+
+fn ascend_call_token(
+    db: &dyn HirDatabase,
+    expansion: &ExpansionInfo,
+    token: InFile<SyntaxToken>,
+) -> Option<InFile<SyntaxToken>> {
+    let (mapped, origin) = expansion.map_token_up(token.as_ref())?;
+    if origin != Origin::Call {
+        return None;
+    }
+    if let Some(info) = mapped.file_id.expansion_info(db.upcast()) {
+        return ascend_call_token(db, &info, mapped);
+    }
+    Some(mapped)
+}
diff --git a/crates/hir/src/semantics/source_to_def.rs b/crates/hir/src/semantics/source_to_def.rs
new file mode 100644
index 000000000..5918b9541
--- /dev/null
+++ b/crates/hir/src/semantics/source_to_def.rs
@@ -0,0 +1,275 @@
+//! Maps *syntax* of various definitions to their semantic ids.
+
+use base_db::FileId;
+use hir_def::{
+    child_by_source::ChildBySource,
+    dyn_map::DynMap,
+    expr::PatId,
+    keys::{self, Key},
+    ConstId, DefWithBodyId, EnumId, EnumVariantId, FieldId, FunctionId, GenericDefId, ImplId,
+    ModuleId, StaticId, StructId, TraitId, TypeAliasId, TypeParamId, UnionId, VariantId,
+};
+use hir_expand::{name::AsName, AstId, MacroDefKind};
+use rustc_hash::FxHashMap;
+use stdx::impl_from;
+use syntax::{
+    ast::{self, NameOwner},
+    match_ast, AstNode, SyntaxNode,
+};
+
+use crate::{db::HirDatabase, InFile, MacroDefId};
+
+pub(super) type SourceToDefCache = FxHashMap<ChildContainer, DynMap>;
+
+pub(super) struct SourceToDefCtx<'a, 'b> {
+    pub(super) db: &'b dyn HirDatabase,
+    pub(super) cache: &'a mut SourceToDefCache,
+}
+
+impl SourceToDefCtx<'_, '_> {
+    pub(super) fn file_to_def(&mut self, file: FileId) -> Option<ModuleId> {
+        let _p = profile::span("SourceBinder::to_module_def");
+        let (krate, local_id) = self.db.relevant_crates(file).iter().find_map(|&crate_id| {
+            let crate_def_map = self.db.crate_def_map(crate_id);
+            let local_id = crate_def_map.modules_for_file(file).next()?;
+            Some((crate_id, local_id))
+        })?;
+        Some(ModuleId { krate, local_id })
+    }
+
+    pub(super) fn module_to_def(&mut self, src: InFile<ast::Module>) -> Option<ModuleId> {
+        let _p = profile::span("module_to_def");
+        let parent_declaration = src
+            .as_ref()
+            .map(|it| it.syntax())
+            .cloned()
+            .ancestors_with_macros(self.db.upcast())
+            .skip(1)
+            .find_map(|it| {
+                let m = ast::Module::cast(it.value.clone())?;
+                Some(it.with_value(m))
+            });
+
+        let parent_module = match parent_declaration {
+            Some(parent_declaration) => self.module_to_def(parent_declaration),
+            None => {
+                let file_id = src.file_id.original_file(self.db.upcast());
+                self.file_to_def(file_id)
+            }
+        }?;
+
+        let child_name = src.value.name()?.as_name();
+        let def_map = self.db.crate_def_map(parent_module.krate);
+        let child_id = *def_map[parent_module.local_id].children.get(&child_name)?;
+        Some(ModuleId { krate: parent_module.krate, local_id: child_id })
+    }
+
+    pub(super) fn trait_to_def(&mut self, src: InFile<ast::Trait>) -> Option<TraitId> {
+        self.to_def(src, keys::TRAIT)
+    }
+    pub(super) fn impl_to_def(&mut self, src: InFile<ast::Impl>) -> Option<ImplId> {
+        self.to_def(src, keys::IMPL)
+    }
+    pub(super) fn fn_to_def(&mut self, src: InFile<ast::Fn>) -> Option<FunctionId> {
+        self.to_def(src, keys::FUNCTION)
+    }
+    pub(super) fn struct_to_def(&mut self, src: InFile<ast::Struct>) -> Option<StructId> {
+        self.to_def(src, keys::STRUCT)
+    }
+    pub(super) fn enum_to_def(&mut self, src: InFile<ast::Enum>) -> Option<EnumId> {
+        self.to_def(src, keys::ENUM)
+    }
+    pub(super) fn union_to_def(&mut self, src: InFile<ast::Union>) -> Option<UnionId> {
+        self.to_def(src, keys::UNION)
+    }
+    pub(super) fn static_to_def(&mut self, src: InFile<ast::Static>) -> Option<StaticId> {
+        self.to_def(src, keys::STATIC)
+    }
+    pub(super) fn const_to_def(&mut self, src: InFile<ast::Const>) -> Option<ConstId> {
+        self.to_def(src, keys::CONST)
+    }
+    pub(super) fn type_alias_to_def(&mut self, src: InFile<ast::TypeAlias>) -> Option<TypeAliasId> {
+        self.to_def(src, keys::TYPE_ALIAS)
+    }
+    pub(super) fn record_field_to_def(&mut self, src: InFile<ast::RecordField>) -> Option<FieldId> {
+        self.to_def(src, keys::RECORD_FIELD)
+    }
+    pub(super) fn tuple_field_to_def(&mut self, src: InFile<ast::TupleField>) -> Option<FieldId> {
+        self.to_def(src, keys::TUPLE_FIELD)
+    }
+    pub(super) fn enum_variant_to_def(
+        &mut self,
+        src: InFile<ast::Variant>,
+    ) -> Option<EnumVariantId> {
+        self.to_def(src, keys::VARIANT)
+    }
+    pub(super) fn bind_pat_to_def(
+        &mut self,
+        src: InFile<ast::IdentPat>,
+    ) -> Option<(DefWithBodyId, PatId)> {
+        let container = self.find_pat_container(src.as_ref().map(|it| it.syntax()))?;
+        let (_body, source_map) = self.db.body_with_source_map(container);
+        let src = src.map(ast::Pat::from);
+        let pat_id = source_map.node_pat(src.as_ref())?;
+        Some((container, pat_id))
+    }
+
+    fn to_def<Ast: AstNode + 'static, ID: Copy + 'static>(
+        &mut self,
+        src: InFile<Ast>,
+        key: Key<Ast, ID>,
+    ) -> Option<ID> {
+        let container = self.find_container(src.as_ref().map(|it| it.syntax()))?;
+        let db = self.db;
+        let dyn_map =
+            &*self.cache.entry(container).or_insert_with(|| container.child_by_source(db));
+        dyn_map[key].get(&src).copied()
+    }
+
+    pub(super) fn type_param_to_def(&mut self, src: InFile<ast::TypeParam>) -> Option<TypeParamId> {
+        let container: ChildContainer =
+            self.find_type_param_container(src.as_ref().map(|it| it.syntax()))?.into();
+        let db = self.db;
+        let dyn_map =
+            &*self.cache.entry(container).or_insert_with(|| container.child_by_source(db));
+        dyn_map[keys::TYPE_PARAM].get(&src).copied()
+    }
+
+    // FIXME: use DynMap as well?
+    pub(super) fn macro_call_to_def(&mut self, src: InFile<ast::MacroCall>) -> Option<MacroDefId> {
+        let kind = MacroDefKind::Declarative;
+        let file_id = src.file_id.original_file(self.db.upcast());
+        let krate = self.file_to_def(file_id)?.krate;
+        let file_ast_id = self.db.ast_id_map(src.file_id).ast_id(&src.value);
+        let ast_id = Some(AstId::new(src.file_id, file_ast_id));
+        Some(MacroDefId { krate: Some(krate), ast_id, kind, local_inner: false })
+    }
+
+    pub(super) fn find_container(&mut self, src: InFile<&SyntaxNode>) -> Option<ChildContainer> {
+        for container in src.cloned().ancestors_with_macros(self.db.upcast()).skip(1) {
+            let res: ChildContainer = match_ast! {
+                match (container.value) {
+                    ast::Module(it) => {
+                        let def = self.module_to_def(container.with_value(it))?;
+                        def.into()
+                    },
+                    ast::Trait(it) => {
+                        let def = self.trait_to_def(container.with_value(it))?;
+                        def.into()
+                    },
+                    ast::Impl(it) => {
+                        let def = self.impl_to_def(container.with_value(it))?;
+                        def.into()
+                    },
+                    ast::Fn(it) => {
+                        let def = self.fn_to_def(container.with_value(it))?;
+                        DefWithBodyId::from(def).into()
+                    },
+                    ast::Struct(it) => {
+                        let def = self.struct_to_def(container.with_value(it))?;
+                        VariantId::from(def).into()
+                    },
+                    ast::Enum(it) => {
+                        let def = self.enum_to_def(container.with_value(it))?;
+                        def.into()
+                    },
+                    ast::Union(it) => {
+                        let def = self.union_to_def(container.with_value(it))?;
+                        VariantId::from(def).into()
+                    },
+                    ast::Static(it) => {
+                        let def = self.static_to_def(container.with_value(it))?;
+                        DefWithBodyId::from(def).into()
+                    },
+                    ast::Const(it) => {
+                        let def = self.const_to_def(container.with_value(it))?;
+                        DefWithBodyId::from(def).into()
+                    },
+                    ast::TypeAlias(it) => {
+                        let def = self.type_alias_to_def(container.with_value(it))?;
+                        def.into()
+                    },
+                    _ => continue,
+                }
+            };
+            return Some(res);
+        }
+
+        let def = self.file_to_def(src.file_id.original_file(self.db.upcast()))?;
+        Some(def.into())
+    }
+
+    fn find_type_param_container(&mut self, src: InFile<&SyntaxNode>) -> Option<GenericDefId> {
+        for container in src.cloned().ancestors_with_macros(self.db.upcast()).skip(1) {
+            let res: GenericDefId = match_ast! {
+                match (container.value) {
+                    ast::Fn(it) => self.fn_to_def(container.with_value(it))?.into(),
+                    ast::Struct(it) => self.struct_to_def(container.with_value(it))?.into(),
+                    ast::Enum(it) => self.enum_to_def(container.with_value(it))?.into(),
+                    ast::Trait(it) => self.trait_to_def(container.with_value(it))?.into(),
+                    ast::TypeAlias(it) => self.type_alias_to_def(container.with_value(it))?.into(),
+                    ast::Impl(it) => self.impl_to_def(container.with_value(it))?.into(),
+                    _ => continue,
+                }
+            };
+            return Some(res);
+        }
+        None
+    }
+
+    fn find_pat_container(&mut self, src: InFile<&SyntaxNode>) -> Option<DefWithBodyId> {
+        for container in src.cloned().ancestors_with_macros(self.db.upcast()).skip(1) {
+            let res: DefWithBodyId = match_ast! {
+                match (container.value) {
+                    ast::Const(it) => self.const_to_def(container.with_value(it))?.into(),
+                    ast::Static(it) => self.static_to_def(container.with_value(it))?.into(),
+                    ast::Fn(it) => self.fn_to_def(container.with_value(it))?.into(),
+                    _ => continue,
+                }
+            };
+            return Some(res);
+        }
+        None
+    }
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
+pub(crate) enum ChildContainer {
+    DefWithBodyId(DefWithBodyId),
+    ModuleId(ModuleId),
+    TraitId(TraitId),
+    ImplId(ImplId),
+    EnumId(EnumId),
+    VariantId(VariantId),
+    TypeAliasId(TypeAliasId),
+    /// XXX: this might be the same def as, for example an `EnumId`. However,
+    /// here the children generic parameters, and not, eg enum variants.
+    GenericDefId(GenericDefId),
+}
+impl_from! {
+    DefWithBodyId,
+    ModuleId,
+    TraitId,
+    ImplId,
+    EnumId,
+    VariantId,
+    TypeAliasId,
+    GenericDefId
+    for ChildContainer
+}
+
+impl ChildContainer {
+    fn child_by_source(self, db: &dyn HirDatabase) -> DynMap {
+        let db = db.upcast();
+        match self {
+            ChildContainer::DefWithBodyId(it) => it.child_by_source(db),
+            ChildContainer::ModuleId(it) => it.child_by_source(db),
+            ChildContainer::TraitId(it) => it.child_by_source(db),
+            ChildContainer::ImplId(it) => it.child_by_source(db),
+            ChildContainer::EnumId(it) => it.child_by_source(db),
+            ChildContainer::VariantId(it) => it.child_by_source(db),
+            ChildContainer::TypeAliasId(_) => DynMap::default(),
+            ChildContainer::GenericDefId(it) => it.child_by_source(db),
+        }
+    }
+}
diff --git a/crates/hir/src/source_analyzer.rs b/crates/hir/src/source_analyzer.rs
new file mode 100644
index 000000000..8750584f9
--- /dev/null
+++ b/crates/hir/src/source_analyzer.rs
@@ -0,0 +1,534 @@
+//! Lookup hir elements using positions in the source code. This is a lossy
+//! transformation: in general, a single source might correspond to several
+//! modules, functions, etc, due to macros, cfgs and `#[path=]` attributes on
+//! modules.
+//!
+//! So, this modules should not be used during hir construction, it exists
+//! purely for "IDE needs".
+use std::{iter::once, sync::Arc};
+
+use hir_def::{
+    body::{
+        scope::{ExprScopes, ScopeId},
+        Body, BodySourceMap,
+    },
+    expr::{ExprId, Pat, PatId},
+    resolver::{resolver_for_scope, Resolver, TypeNs, ValueNs},
+    AsMacroCall, DefWithBodyId, FieldId, FunctionId, LocalFieldId, VariantId,
+};
+use hir_expand::{hygiene::Hygiene, name::AsName, HirFileId, InFile};
+use hir_ty::{
+    diagnostics::{record_literal_missing_fields, record_pattern_missing_fields},
+    InferenceResult, Substs, Ty,
+};
+use syntax::{
+    ast::{self, AstNode},
+    SyntaxNode, TextRange, TextSize,
+};
+
+use crate::{
+    db::HirDatabase, semantics::PathResolution, Adt, Const, EnumVariant, Field, Function, Local,
+    MacroDef, ModPath, ModuleDef, Path, PathKind, Static, Struct, Trait, Type, TypeAlias,
+    TypeParam,
+};
+use base_db::CrateId;
+
+/// `SourceAnalyzer` is a convenience wrapper which exposes HIR API in terms of
+/// original source files. It should not be used inside the HIR itself.
+#[derive(Debug)]
+pub(crate) struct SourceAnalyzer {
+    file_id: HirFileId,
+    pub(crate) resolver: Resolver,
+    body: Option<Arc<Body>>,
+    body_source_map: Option<Arc<BodySourceMap>>,
+    infer: Option<Arc<InferenceResult>>,
+    scopes: Option<Arc<ExprScopes>>,
+}
+
+impl SourceAnalyzer {
+    pub(crate) fn new_for_body(
+        db: &dyn HirDatabase,
+        def: DefWithBodyId,
+        node: InFile<&SyntaxNode>,
+        offset: Option<TextSize>,
+    ) -> SourceAnalyzer {
+        let (body, source_map) = db.body_with_source_map(def);
+        let scopes = db.expr_scopes(def);
+        let scope = match offset {
+            None => scope_for(&scopes, &source_map, node),
+            Some(offset) => scope_for_offset(db, &scopes, &source_map, node.with_value(offset)),
+        };
+        let resolver = resolver_for_scope(db.upcast(), def, scope);
+        SourceAnalyzer {
+            resolver,
+            body: Some(body),
+            body_source_map: Some(source_map),
+            infer: Some(db.infer(def)),
+            scopes: Some(scopes),
+            file_id: node.file_id,
+        }
+    }
+
+    pub(crate) fn new_for_resolver(
+        resolver: Resolver,
+        node: InFile<&SyntaxNode>,
+    ) -> SourceAnalyzer {
+        SourceAnalyzer {
+            resolver,
+            body: None,
+            body_source_map: None,
+            infer: None,
+            scopes: None,
+            file_id: node.file_id,
+        }
+    }
+
+    fn expr_id(&self, db: &dyn HirDatabase, expr: &ast::Expr) -> Option<ExprId> {
+        let src = match expr {
+            ast::Expr::MacroCall(call) => {
+                self.expand_expr(db, InFile::new(self.file_id, call.clone()))?
+            }
+            _ => InFile::new(self.file_id, expr.clone()),
+        };
+        let sm = self.body_source_map.as_ref()?;
+        sm.node_expr(src.as_ref())
+    }
+
+    fn pat_id(&self, pat: &ast::Pat) -> Option<PatId> {
+        // FIXME: macros, see `expr_id`
+        let src = InFile { file_id: self.file_id, value: pat };
+        self.body_source_map.as_ref()?.node_pat(src)
+    }
+
+    fn expand_expr(
+        &self,
+        db: &dyn HirDatabase,
+        expr: InFile<ast::MacroCall>,
+    ) -> Option<InFile<ast::Expr>> {
+        let macro_file = self.body_source_map.as_ref()?.node_macro_file(expr.as_ref())?;
+        let expanded = db.parse_or_expand(macro_file)?;
+
+        let res = match ast::MacroCall::cast(expanded.clone()) {
+            Some(call) => self.expand_expr(db, InFile::new(macro_file, call))?,
+            _ => InFile::new(macro_file, ast::Expr::cast(expanded)?),
+        };
+        Some(res)
+    }
+
+    pub(crate) fn type_of_expr(&self, db: &dyn HirDatabase, expr: &ast::Expr) -> Option<Type> {
+        let expr_id = self.expr_id(db, expr)?;
+        let ty = self.infer.as_ref()?[expr_id].clone();
+        Type::new_with_resolver(db, &self.resolver, ty)
+    }
+
+    pub(crate) fn type_of_pat(&self, db: &dyn HirDatabase, pat: &ast::Pat) -> Option<Type> {
+        let pat_id = self.pat_id(pat)?;
+        let ty = self.infer.as_ref()?[pat_id].clone();
+        Type::new_with_resolver(db, &self.resolver, ty)
+    }
+
+    pub(crate) fn type_of_self(
+        &self,
+        db: &dyn HirDatabase,
+        param: &ast::SelfParam,
+    ) -> Option<Type> {
+        let src = InFile { file_id: self.file_id, value: param };
+        let pat_id = self.body_source_map.as_ref()?.node_self_param(src)?;
+        let ty = self.infer.as_ref()?[pat_id].clone();
+        Type::new_with_resolver(db, &self.resolver, ty)
+    }
+
+    pub(crate) fn resolve_method_call(
+        &self,
+        db: &dyn HirDatabase,
+        call: &ast::MethodCallExpr,
+    ) -> Option<FunctionId> {
+        let expr_id = self.expr_id(db, &call.clone().into())?;
+        self.infer.as_ref()?.method_resolution(expr_id)
+    }
+
+    pub(crate) fn resolve_field(
+        &self,
+        db: &dyn HirDatabase,
+        field: &ast::FieldExpr,
+    ) -> Option<Field> {
+        let expr_id = self.expr_id(db, &field.clone().into())?;
+        self.infer.as_ref()?.field_resolution(expr_id).map(|it| it.into())
+    }
+
+    pub(crate) fn resolve_record_field(
+        &self,
+        db: &dyn HirDatabase,
+        field: &ast::RecordExprField,
+    ) -> Option<(Field, Option<Local>)> {
+        let expr = field.expr()?;
+        let expr_id = self.expr_id(db, &expr)?;
+        let local = if field.name_ref().is_some() {
+            None
+        } else {
+            let local_name = field.field_name()?.as_name();
+            let path = ModPath::from_segments(PathKind::Plain, once(local_name));
+            match self.resolver.resolve_path_in_value_ns_fully(db.upcast(), &path) {
+                Some(ValueNs::LocalBinding(pat_id)) => {
+                    Some(Local { pat_id, parent: self.resolver.body_owner()? })
+                }
+                _ => None,
+            }
+        };
+        let struct_field = self.infer.as_ref()?.record_field_resolution(expr_id)?;
+        Some((struct_field.into(), local))
+    }
+
+    pub(crate) fn resolve_record_field_pat(
+        &self,
+        _db: &dyn HirDatabase,
+        field: &ast::RecordPatField,
+    ) -> Option<Field> {
+        let pat_id = self.pat_id(&field.pat()?)?;
+        let struct_field = self.infer.as_ref()?.record_field_pat_resolution(pat_id)?;
+        Some(struct_field.into())
+    }
+
+    pub(crate) fn resolve_macro_call(
+        &self,
+        db: &dyn HirDatabase,
+        macro_call: InFile<&ast::MacroCall>,
+    ) -> Option<MacroDef> {
+        let hygiene = Hygiene::new(db.upcast(), macro_call.file_id);
+        let path = macro_call.value.path().and_then(|ast| Path::from_src(ast, &hygiene))?;
+        self.resolver.resolve_path_as_macro(db.upcast(), path.mod_path()).map(|it| it.into())
+    }
+
+    pub(crate) fn resolve_bind_pat_to_const(
+        &self,
+        db: &dyn HirDatabase,
+        pat: &ast::IdentPat,
+    ) -> Option<ModuleDef> {
+        let pat_id = self.pat_id(&pat.clone().into())?;
+        let body = self.body.as_ref()?;
+        let path = match &body[pat_id] {
+            Pat::Path(path) => path,
+            _ => return None,
+        };
+        let res = resolve_hir_path(db, &self.resolver, &path)?;
+        match res {
+            PathResolution::Def(def) => Some(def),
+            _ => None,
+        }
+    }
+
+    pub(crate) fn resolve_path(
+        &self,
+        db: &dyn HirDatabase,
+        path: &ast::Path,
+    ) -> Option<PathResolution> {
+        if let Some(path_expr) = path.syntax().parent().and_then(ast::PathExpr::cast) {
+            let expr_id = self.expr_id(db, &path_expr.into())?;
+            if let Some(assoc) = self.infer.as_ref()?.assoc_resolutions_for_expr(expr_id) {
+                return Some(PathResolution::AssocItem(assoc.into()));
+            }
+            if let Some(VariantId::EnumVariantId(variant)) =
+                self.infer.as_ref()?.variant_resolution_for_expr(expr_id)
+            {
+                return Some(PathResolution::Def(ModuleDef::EnumVariant(variant.into())));
+            }
+        }
+
+        if let Some(path_pat) = path.syntax().parent().and_then(ast::PathPat::cast) {
+            let pat_id = self.pat_id(&path_pat.into())?;
+            if let Some(assoc) = self.infer.as_ref()?.assoc_resolutions_for_pat(pat_id) {
+                return Some(PathResolution::AssocItem(assoc.into()));
+            }
+            if let Some(VariantId::EnumVariantId(variant)) =
+                self.infer.as_ref()?.variant_resolution_for_pat(pat_id)
+            {
+                return Some(PathResolution::Def(ModuleDef::EnumVariant(variant.into())));
+            }
+        }
+
+        if let Some(rec_lit) = path.syntax().parent().and_then(ast::RecordExpr::cast) {
+            let expr_id = self.expr_id(db, &rec_lit.into())?;
+            if let Some(VariantId::EnumVariantId(variant)) =
+                self.infer.as_ref()?.variant_resolution_for_expr(expr_id)
+            {
+                return Some(PathResolution::Def(ModuleDef::EnumVariant(variant.into())));
+            }
+        }
+
+        if let Some(rec_pat) = path.syntax().parent().and_then(ast::RecordPat::cast) {
+            let pat_id = self.pat_id(&rec_pat.into())?;
+            if let Some(VariantId::EnumVariantId(variant)) =
+                self.infer.as_ref()?.variant_resolution_for_pat(pat_id)
+            {
+                return Some(PathResolution::Def(ModuleDef::EnumVariant(variant.into())));
+            }
+        }
+
+        // This must be a normal source file rather than macro file.
+        let hir_path = Path::from_src(path.clone(), &Hygiene::new(db.upcast(), self.file_id))?;
+
+        // Case where path is a qualifier of another path, e.g. foo::bar::Baz where we
+        // trying to resolve foo::bar.
+        if let Some(outer_path) = path.syntax().parent().and_then(ast::Path::cast) {
+            if let Some(qualifier) = outer_path.qualifier() {
+                if path == &qualifier {
+                    return resolve_hir_path_qualifier(db, &self.resolver, &hir_path);
+                }
+            }
+        }
+
+        resolve_hir_path(db, &self.resolver, &hir_path)
+    }
+
+    pub(crate) fn record_literal_missing_fields(
+        &self,
+        db: &dyn HirDatabase,
+        literal: &ast::RecordExpr,
+    ) -> Option<Vec<(Field, Type)>> {
+        let krate = self.resolver.krate()?;
+        let body = self.body.as_ref()?;
+        let infer = self.infer.as_ref()?;
+
+        let expr_id = self.expr_id(db, &literal.clone().into())?;
+        let substs = match &infer.type_of_expr[expr_id] {
+            Ty::Apply(a_ty) => &a_ty.parameters,
+            _ => return None,
+        };
+
+        let (variant, missing_fields, _exhaustive) =
+            record_literal_missing_fields(db, infer, expr_id, &body[expr_id])?;
+        let res = self.missing_fields(db, krate, substs, variant, missing_fields);
+        Some(res)
+    }
+
+    pub(crate) fn record_pattern_missing_fields(
+        &self,
+        db: &dyn HirDatabase,
+        pattern: &ast::RecordPat,
+    ) -> Option<Vec<(Field, Type)>> {
+        let krate = self.resolver.krate()?;
+        let body = self.body.as_ref()?;
+        let infer = self.infer.as_ref()?;
+
+        let pat_id = self.pat_id(&pattern.clone().into())?;
+        let substs = match &infer.type_of_pat[pat_id] {
+            Ty::Apply(a_ty) => &a_ty.parameters,
+            _ => return None,
+        };
+
+        let (variant, missing_fields, _exhaustive) =
+            record_pattern_missing_fields(db, infer, pat_id, &body[pat_id])?;
+        let res = self.missing_fields(db, krate, substs, variant, missing_fields);
+        Some(res)
+    }
+
+    fn missing_fields(
+        &self,
+        db: &dyn HirDatabase,
+        krate: CrateId,
+        substs: &Substs,
+        variant: VariantId,
+        missing_fields: Vec<LocalFieldId>,
+    ) -> Vec<(Field, Type)> {
+        let field_types = db.field_types(variant);
+
+        missing_fields
+            .into_iter()
+            .map(|local_id| {
+                let field = FieldId { parent: variant, local_id };
+                let ty = field_types[local_id].clone().subst(substs);
+                (field.into(), Type::new_with_resolver_inner(db, krate, &self.resolver, ty))
+            })
+            .collect()
+    }
+
+    pub(crate) fn expand(
+        &self,
+        db: &dyn HirDatabase,
+        macro_call: InFile<&ast::MacroCall>,
+    ) -> Option<HirFileId> {
+        let krate = self.resolver.krate()?;
+        let macro_call_id = macro_call.as_call_id(db.upcast(), krate, |path| {
+            self.resolver.resolve_path_as_macro(db.upcast(), &path)
+        })?;
+        Some(macro_call_id.as_file()).filter(|it| it.expansion_level(db.upcast()) < 64)
+    }
+
+    pub(crate) fn resolve_variant(
+        &self,
+        db: &dyn HirDatabase,
+        record_lit: ast::RecordExpr,
+    ) -> Option<VariantId> {
+        let infer = self.infer.as_ref()?;
+        let expr_id = self.expr_id(db, &record_lit.into())?;
+        infer.variant_resolution_for_expr(expr_id)
+    }
+}
+
+fn scope_for(
+    scopes: &ExprScopes,
+    source_map: &BodySourceMap,
+    node: InFile<&SyntaxNode>,
+) -> Option<ScopeId> {
+    node.value
+        .ancestors()
+        .filter_map(ast::Expr::cast)
+        .filter_map(|it| source_map.node_expr(InFile::new(node.file_id, &it)))
+        .find_map(|it| scopes.scope_for(it))
+}
+
+fn scope_for_offset(
+    db: &dyn HirDatabase,
+    scopes: &ExprScopes,
+    source_map: &BodySourceMap,
+    offset: InFile<TextSize>,
+) -> Option<ScopeId> {
+    scopes
+        .scope_by_expr()
+        .iter()
+        .filter_map(|(id, scope)| {
+            let source = source_map.expr_syntax(*id).ok()?;
+            // FIXME: correctly handle macro expansion
+            if source.file_id != offset.file_id {
+                return None;
+            }
+            let root = source.file_syntax(db.upcast());
+            let node = source.value.to_node(&root);
+            Some((node.syntax().text_range(), scope))
+        })
+        // find containing scope
+        .min_by_key(|(expr_range, _scope)| {
+            (
+                !(expr_range.start() <= offset.value && offset.value <= expr_range.end()),
+                expr_range.len(),
+            )
+        })
+        .map(|(expr_range, scope)| {
+            adjust(db, scopes, source_map, expr_range, offset).unwrap_or(*scope)
+        })
+}
+
+// XXX: during completion, cursor might be outside of any particular
+// expression. Try to figure out the correct scope...
+fn adjust(
+    db: &dyn HirDatabase,
+    scopes: &ExprScopes,
+    source_map: &BodySourceMap,
+    expr_range: TextRange,
+    offset: InFile<TextSize>,
+) -> Option<ScopeId> {
+    let child_scopes = scopes
+        .scope_by_expr()
+        .iter()
+        .filter_map(|(id, scope)| {
+            let source = source_map.expr_syntax(*id).ok()?;
+            // FIXME: correctly handle macro expansion
+            if source.file_id != offset.file_id {
+                return None;
+            }
+            let root = source.file_syntax(db.upcast());
+            let node = source.value.to_node(&root);
+            Some((node.syntax().text_range(), scope))
+        })
+        .filter(|&(range, _)| {
+            range.start() <= offset.value && expr_range.contains_range(range) && range != expr_range
+        });
+
+    child_scopes
+        .max_by(|&(r1, _), &(r2, _)| {
+            if r1.contains_range(r2) {
+                std::cmp::Ordering::Greater
+            } else if r2.contains_range(r1) {
+                std::cmp::Ordering::Less
+            } else {
+                r1.start().cmp(&r2.start())
+            }
+        })
+        .map(|(_ptr, scope)| *scope)
+}
+
+pub(crate) fn resolve_hir_path(
+    db: &dyn HirDatabase,
+    resolver: &Resolver,
+    path: &Path,
+) -> Option<PathResolution> {
+    let types =
+        resolver.resolve_path_in_type_ns_fully(db.upcast(), path.mod_path()).map(|ty| match ty {
+            TypeNs::SelfType(it) => PathResolution::SelfType(it.into()),
+            TypeNs::GenericParam(id) => PathResolution::TypeParam(TypeParam { id }),
+            TypeNs::AdtSelfType(it) | TypeNs::AdtId(it) => {
+                PathResolution::Def(Adt::from(it).into())
+            }
+            TypeNs::EnumVariantId(it) => PathResolution::Def(EnumVariant::from(it).into()),
+            TypeNs::TypeAliasId(it) => PathResolution::Def(TypeAlias::from(it).into()),
+            TypeNs::BuiltinType(it) => PathResolution::Def(it.into()),
+            TypeNs::TraitId(it) => PathResolution::Def(Trait::from(it).into()),
+        });
+
+    let body_owner = resolver.body_owner();
+    let values =
+        resolver.resolve_path_in_value_ns_fully(db.upcast(), path.mod_path()).and_then(|val| {
+            let res = match val {
+                ValueNs::LocalBinding(pat_id) => {
+                    let var = Local { parent: body_owner?.into(), pat_id };
+                    PathResolution::Local(var)
+                }
+                ValueNs::FunctionId(it) => PathResolution::Def(Function::from(it).into()),
+                ValueNs::ConstId(it) => PathResolution::Def(Const::from(it).into()),
+                ValueNs::StaticId(it) => PathResolution::Def(Static::from(it).into()),
+                ValueNs::StructId(it) => PathResolution::Def(Struct::from(it).into()),
+                ValueNs::EnumVariantId(it) => PathResolution::Def(EnumVariant::from(it).into()),
+                ValueNs::ImplSelf(impl_id) => PathResolution::SelfType(impl_id.into()),
+            };
+            Some(res)
+        });
+
+    let items = resolver
+        .resolve_module_path_in_items(db.upcast(), path.mod_path())
+        .take_types()
+        .map(|it| PathResolution::Def(it.into()));
+
+    types.or(values).or(items).or_else(|| {
+        resolver
+            .resolve_path_as_macro(db.upcast(), path.mod_path())
+            .map(|def| PathResolution::Macro(def.into()))
+    })
+}
+
+/// Resolves a path where we know it is a qualifier of another path.
+///
+/// For example, if we have:
+/// ```
+/// mod my {
+///     pub mod foo {
+///         struct Bar;
+///     }
+///
+///     pub fn foo() {}
+/// }
+/// ```
+/// then we know that `foo` in `my::foo::Bar` refers to the module, not the function.
+pub(crate) fn resolve_hir_path_qualifier(
+    db: &dyn HirDatabase,
+    resolver: &Resolver,
+    path: &Path,
+) -> Option<PathResolution> {
+    let items = resolver
+        .resolve_module_path_in_items(db.upcast(), path.mod_path())
+        .take_types()
+        .map(|it| PathResolution::Def(it.into()));
+
+    if items.is_some() {
+        return items;
+    }
+
+    resolver.resolve_path_in_type_ns_fully(db.upcast(), path.mod_path()).map(|ty| match ty {
+        TypeNs::SelfType(it) => PathResolution::SelfType(it.into()),
+        TypeNs::GenericParam(id) => PathResolution::TypeParam(TypeParam { id }),
+        TypeNs::AdtSelfType(it) | TypeNs::AdtId(it) => PathResolution::Def(Adt::from(it).into()),
+        TypeNs::EnumVariantId(it) => PathResolution::Def(EnumVariant::from(it).into()),
+        TypeNs::TypeAliasId(it) => PathResolution::Def(TypeAlias::from(it).into()),
+        TypeNs::BuiltinType(it) => PathResolution::Def(it.into()),
+        TypeNs::TraitId(it) => PathResolution::Def(Trait::from(it).into()),
+    })
+}