1 files changed, 1712 insertions, 0 deletions

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)
+    }
+}