1 files changed, 2097 insertions, 29 deletions

diff --git a/crates/hir/src/lib.rs b/crates/hir/src/lib.rs
index 69fcdab07..58adc8fd3 100644
--- a/crates/hir/src/lib.rs
+++ b/crates/hir/src/lib.rs
@@ -20,49 +20,2117 @@
 #![recursion_limit = "512"]
 
 mod semantics;
-pub mod db;
 mod source_analyzer;
 
-pub mod diagnostics;
-
 mod from_id;
-mod code_model;
 mod attrs;
 mod has_source;
 
+pub mod diagnostics;
+pub mod db;
+
+use std::{iter, sync::Arc};
+
+use arrayvec::ArrayVec;
+use base_db::{CrateDisplayName, CrateId, Edition, FileId};
+use either::Either;
+use hir_def::{
+    adt::{ReprKind, VariantData},
+    expr::{BindingAnnotation, LabelId, Pat, PatId},
+    item_tree::ItemTreeNode,
+    lang_item::LangItemTarget,
+    per_ns::PerNs,
+    resolver::{HasResolver, Resolver},
+    src::HasSource as _,
+    AdtId, AssocContainerId, AssocItemId, AssocItemLoc, AttrDefId, ConstId, ConstParamId,
+    DefWithBodyId, EnumId, FunctionId, GenericDefId, HasModule, ImplId, LifetimeParamId,
+    LocalEnumVariantId, LocalFieldId, Lookup, ModuleId, StaticId, StructId, TraitId, TypeAliasId,
+    TypeParamId, UnionId,
+};
+use hir_expand::{diagnostics::DiagnosticSink, name::name, MacroDefKind};
+use hir_ty::{
+    autoderef,
+    display::{write_bounds_like_dyn_trait_with_prefix, HirDisplayError, HirFormatter},
+    method_resolution,
+    traits::{FnTrait, Solution, SolutionVariables},
+    AliasTy, BoundVar, CallableDefId, CallableSig, Canonical, DebruijnIndex, GenericPredicate,
+    InEnvironment, Obligation, ProjectionPredicate, ProjectionTy, Scalar, Substs, TraitEnvironment,
+    Ty, TyDefId, TyVariableKind,
+};
+use rustc_hash::FxHashSet;
+use stdx::{format_to, impl_from};
+use syntax::{
+    ast::{self, AttrsOwner, NameOwner},
+    AstNode, SmolStr,
+};
+use tt::{Ident, Leaf, Literal, TokenTree};
+
+use crate::db::{DefDatabase, HirDatabase};
+
 pub use crate::{
     attrs::{HasAttrs, Namespace},
-    code_model::{
-        Access, Adt, AsAssocItem, AssocItem, AssocItemContainer, BuiltinType, Callable,
-        CallableKind, Const, ConstParam, Crate, CrateDependency, DefWithBody, Enum, Field,
-        FieldSource, Function, GenericDef, GenericParam, HasVisibility, Impl, Label, LifetimeParam,
-        Local, MacroDef, Module, ModuleDef, ScopeDef, Static, Struct, Trait, Type, TypeAlias,
-        TypeParam, Union, Variant, VariantDef,
-    },
     has_source::HasSource,
     semantics::{PathResolution, Semantics, SemanticsScope},
 };
 
-pub use hir_def::{
-    adt::StructKind,
-    attr::{Attrs, Documentation},
-    body::scope::ExprScopes,
-    find_path::PrefixKind,
-    import_map,
-    item_scope::ItemInNs,
-    nameres::ModuleSource,
-    path::{ModPath, PathKind},
-    type_ref::{Mutability, TypeRef},
-    visibility::Visibility,
-};
-pub use hir_expand::{
-    name::{known, AsName, Name},
-    ExpandResult, HirFileId, InFile, MacroCallId, MacroCallLoc, /* FIXME */ MacroDefId,
-    MacroFile, Origin,
+// Be careful with these re-exports.
+//
+// `hir` is the boundary between the compiler and the IDE. It should try hard to
+// isolate the compiler from the ide, to allow the two to be refactored
+// independently. Re-exporting something from the compiler is the sure way to
+// breach the boundary.
+//
+// Generally, a refactoring which *removes* a name from this list is a good
+// idea!
+pub use {
+    hir_def::{
+        adt::StructKind,
+        attr::{Attrs, Documentation},
+        body::scope::ExprScopes,
+        find_path::PrefixKind,
+        import_map,
+        item_scope::ItemInNs,
+        nameres::ModuleSource,
+        path::{ModPath, PathKind},
+        type_ref::{Mutability, TypeRef},
+        visibility::Visibility,
+    },
+    hir_expand::{
+        name::{known, Name},
+        ExpandResult, HirFileId, InFile, MacroCallId, MacroCallLoc, /* FIXME */ MacroDefId,
+        MacroFile, Origin,
+    },
+    hir_ty::display::HirDisplay,
 };
-pub use hir_ty::display::HirDisplay;
 
 // These are negative re-exports: pub using these names is forbidden, they
 // should remain private to hir internals.
 #[allow(unused)]
-use {hir_def::path::Path, hir_expand::hygiene::Hygiene};
+use {
+    hir_def::path::Path,
+    hir_expand::{hygiene::Hygiene, name::AsName},
+};
+
+/// 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 def_map = db.crate_def_map(self.id);
+        Module { id: def_map.module_id(def_map.root()) }
+    }
+
+    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<CrateDisplayName> {
+        db.crate_graph()[self.id].display_name.clone()
+    }
+
+    pub fn query_external_importables(
+        self,
+        db: &dyn DefDatabase,
+        query: import_map::Query,
+    ) -> impl Iterator<Item = Either<ModuleDef, MacroDef>> {
+        import_map::search_dependencies(db, self.into(), query).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()
+    }
+
+    /// Try to get the root URL of the documentation of a crate.
+    pub fn get_html_root_url(self: &Crate, db: &dyn HirDatabase) -> Option<String> {
+        // Look for #![doc(html_root_url = "...")]
+        let attrs = db.attrs(AttrDefId::ModuleId(self.root_module(db).into()));
+        let doc_attr_q = attrs.by_key("doc");
+
+        if !doc_attr_q.exists() {
+            return None;
+        }
+
+        let doc_url = doc_attr_q.tt_values().map(|tt| {
+            let name = tt.token_trees.iter()
+                .skip_while(|tt| !matches!(tt, TokenTree::Leaf(Leaf::Ident(Ident{text: ref ident, ..})) if ident == "html_root_url"))
+                .skip(2)
+                .next();
+
+            match name {
+                Some(TokenTree::Leaf(Leaf::Literal(Literal{ref text, ..}))) => Some(text),
+                _ => None
+            }
+        }).flat_map(|t| t).next();
+
+        doc_url.map(|s| s.trim_matches('"').trim_end_matches('/').to_owned() + "/")
+    }
+}
+
+#[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.
+    Variant(Variant),
+    Const(Const),
+    Static(Static),
+    Trait(Trait),
+    TypeAlias(TypeAlias),
+    BuiltinType(BuiltinType),
+}
+impl_from!(
+    Module,
+    Function,
+    Adt(Struct, Enum, Union),
+    Variant,
+    Const,
+    Static,
+    Trait,
+    TypeAlias,
+    BuiltinType
+    for ModuleDef
+);
+
+impl From<VariantDef> for ModuleDef {
+    fn from(var: VariantDef) -> Self {
+        match var {
+            VariantDef::Struct(t) => Adt::from(t).into(),
+            VariantDef::Union(t) => Adt::from(t).into(),
+            VariantDef::Variant(t) => t.into(),
+        }
+    }
+}
+
+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::Variant(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 canonical_path(&self, db: &dyn HirDatabase) -> Option<String> {
+        let mut segments = Vec::new();
+        segments.push(self.name(db)?.to_string());
+        for m in self.module(db)?.path_to_root(db) {
+            segments.extend(m.name(db).map(|it| it.to_string()))
+        }
+        segments.reverse();
+        Some(segments.join("::"))
+    }
+
+    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::Variant(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::Variant(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.name()),
+        }
+    }
+
+    pub fn diagnostics(self, db: &dyn HirDatabase, sink: &mut DiagnosticSink) {
+        let id = match self {
+            ModuleDef::Adt(it) => match it {
+                Adt::Struct(it) => it.id.into(),
+                Adt::Enum(it) => it.id.into(),
+                Adt::Union(it) => it.id.into(),
+            },
+            ModuleDef::Trait(it) => it.id.into(),
+            ModuleDef::Function(it) => it.id.into(),
+            ModuleDef::TypeAlias(it) => it.id.into(),
+            ModuleDef::Module(it) => it.id.into(),
+            ModuleDef::Const(it) => it.id.into(),
+            ModuleDef::Static(it) => it.id.into(),
+            _ => return,
+        };
+
+        let module = match self.module(db) {
+            Some(it) => it,
+            None => return,
+        };
+
+        hir_ty::diagnostics::validate_module_item(db, module.id.krate(), id, sink)
+    }
+}
+
+impl Module {
+    /// Name of this module.
+    pub fn name(self, db: &dyn HirDatabase) -> Option<Name> {
+        let def_map = self.id.def_map(db.upcast());
+        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());
+        Module { id: def_map.module_id(def_map.root()) }
+    }
+
+    /// Iterates over all child modules.
+    pub fn children(self, db: &dyn HirDatabase) -> impl Iterator<Item = Module> {
+        let def_map = self.id.def_map(db.upcast());
+        let children = def_map[self.id.local_id]
+            .children
+            .iter()
+            .map(|(_, module_id)| Module { id: def_map.module_id(*module_id) })
+            .collect::<Vec<_>>();
+        children.into_iter()
+    }
+
+    /// Finds a parent module.
+    pub fn parent(self, db: &dyn HirDatabase) -> Option<Module> {
+        // FIXME: handle block expressions as modules (their parent is in a different DefMap)
+        let def_map = self.id.def_map(db.upcast());
+        let parent_id = def_map[self.id.local_id].parent?;
+        Some(Module { id: def_map.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)> {
+        self.id.def_map(db.upcast())[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> {
+        self.id.def_map(db.upcast())[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").detail(|| {
+            format!("{:?}", self.name(db).map_or("<unknown>".into(), |name| name.to_string()))
+        });
+        let def_map = self.id.def_map(db.upcast());
+        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 def_map[m.id.local_id].origin.is_inline() {
+                        m.diagnostics(db, sink)
+                    }
+                }
+                _ => {
+                    decl.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 = self.id.def_map(db.upcast());
+        def_map[self.id.local_id].scope.declarations().map(ModuleDef::from).collect()
+    }
+
+    pub fn impl_defs(self, db: &dyn HirDatabase) -> Vec<Impl> {
+        let def_map = self.id.def_map(db.upcast());
+        def_map[self.id.local_id].scope.impls().map(Impl::from).collect()
+    }
+
+    /// 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<ModPath> {
+        hir_def::find_path::find_path(db, item.into(), self.into())
+    }
+
+    /// Finds a path that can be used to refer to the given item from within
+    /// this module, if possible. This is used for returning import paths for use-statements.
+    pub fn find_use_path_prefixed(
+        self,
+        db: &dyn DefDatabase,
+        item: impl Into<ItemInNs>,
+        prefix_kind: PrefixKind,
+    ) -> Option<ModPath> {
+        hir_def::find_path::find_path_prefixed(db, item.into(), self.into(), prefix_kind)
+    }
+}
+
+#[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::Variant(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 }
+    }
+
+    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.krate(), self.id)
+    }
+
+    pub fn repr(self, db: &dyn HirDatabase) -> Option<ReprKind> {
+        db.struct_data(self.id).repr.clone()
+    }
+
+    pub fn kind(self, db: &dyn HirDatabase) -> StructKind {
+        self.variant_data(db).kind()
+    }
+
+    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 }
+    }
+
+    pub fn ty(self, db: &dyn HirDatabase) -> Type {
+        Type::from_def(db, self.id.lookup(db.upcast()).container.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 }
+    }
+
+    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<Variant> {
+        db.enum_data(self.id).variants.iter().map(|(id, _)| Variant { parent: self, id }).collect()
+    }
+
+    pub fn ty(self, db: &dyn HirDatabase) -> Type {
+        Type::from_def(db, self.id.lookup(db.upcast()).container.krate(), self.id)
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Variant {
+    pub(crate) parent: Enum,
+    pub(crate) id: LocalEnumVariantId,
+}
+
+impl Variant {
+    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),
+    Variant(Variant),
+}
+impl_from!(Struct, Union, Variant 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::Variant(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::Variant(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::Variant(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::Variant(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()
+    }
+
+    /// Get this function's return type
+    pub fn ret_type(self, db: &dyn HirDatabase) -> Type {
+        let resolver = self.id.resolver(db.upcast());
+        let krate = self.id.lookup(db.upcast()).container.module(db.upcast()).krate();
+        let ret_type = &db.function_data(self.id).ret_type;
+        let ctx = hir_ty::TyLoweringContext::new(db, &resolver);
+        let ty = Ty::from_hir_ext(&ctx, ret_type).0;
+        Type::new_with_resolver_inner(db, krate, &resolver, ty)
+    }
+
+    pub fn self_param(self, db: &dyn HirDatabase) -> Option<SelfParam> {
+        if !db.function_data(self.id).has_self_param {
+            return None;
+        }
+        Some(SelfParam { func: self.id })
+    }
+
+    pub fn assoc_fn_params(self, db: &dyn HirDatabase) -> Vec<Param> {
+        let resolver = self.id.resolver(db.upcast());
+        let krate = self.id.lookup(db.upcast()).container.module(db.upcast()).krate();
+        let ctx = hir_ty::TyLoweringContext::new(db, &resolver);
+        let environment = TraitEnvironment::lower(db, &resolver);
+        db.function_data(self.id)
+            .params
+            .iter()
+            .map(|type_ref| {
+                let ty = Type {
+                    krate,
+                    ty: InEnvironment {
+                        value: Ty::from_hir_ext(&ctx, type_ref).0,
+                        environment: environment.clone(),
+                    },
+                };
+                Param { ty }
+            })
+            .collect()
+    }
+    pub fn method_params(self, db: &dyn HirDatabase) -> Option<Vec<Param>> {
+        if self.self_param(db).is_none() {
+            return None;
+        }
+        let mut res = self.assoc_fn_params(db);
+        res.remove(0);
+        Some(res)
+    }
+
+    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) {
+        let krate = self.module(db).id.krate();
+        hir_def::diagnostics::validate_body(db.upcast(), self.id.into(), sink);
+        hir_ty::diagnostics::validate_module_item(db, krate, self.id.into(), sink);
+        hir_ty::diagnostics::validate_body(db, self.id.into(), sink);
+    }
+
+    /// Whether this function declaration has a definition.
+    ///
+    /// This is false in the case of required (not provided) trait methods.
+    pub fn has_body(self, db: &dyn HirDatabase) -> bool {
+        db.function_data(self.id).has_body
+    }
+
+    /// A textual representation of the HIR of this function for debugging purposes.
+    pub fn debug_hir(self, db: &dyn HirDatabase) -> String {
+        let body = db.body(self.id.into());
+
+        let mut result = String::new();
+        format_to!(result, "HIR expressions in the body of `{}`:\n", self.name(db));
+        for (id, expr) in body.exprs.iter() {
+            format_to!(result, "{:?}: {:?}\n", id, expr);
+        }
+
+        result
+    }
+}
+
+// Note: logically, this belongs to `hir_ty`, but we are not using it there yet.
+pub enum Access {
+    Shared,
+    Exclusive,
+    Owned,
+}
+
+impl From<hir_ty::Mutability> for Access {
+    fn from(mutability: hir_ty::Mutability) -> Access {
+        match mutability {
+            hir_ty::Mutability::Not => Access::Shared,
+            hir_ty::Mutability::Mut => Access::Exclusive,
+        }
+    }
+}
+
+#[derive(Debug)]
+pub struct Param {
+    ty: Type,
+}
+
+impl Param {
+    pub fn ty(&self) -> &Type {
+        &self.ty
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct SelfParam {
+    func: FunctionId,
+}
+
+impl SelfParam {
+    pub fn access(self, db: &dyn HirDatabase) -> Access {
+        let func_data = db.function_data(self.func);
+        func_data
+            .params
+            .first()
+            .map(|param| match *param {
+                TypeRef::Reference(.., mutability) => match mutability {
+                    hir_def::type_ref::Mutability::Shared => Access::Shared,
+                    hir_def::type_ref::Mutability::Mut => Access::Exclusive,
+                },
+                _ => Access::Owned,
+            })
+            .unwrap_or(Access::Owned)
+    }
+}
+
+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 }
+    }
+
+    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 BuiltinType {
+    pub(crate) inner: hir_def::builtin_type::BuiltinType,
+}
+
+impl BuiltinType {
+    pub fn ty(self, db: &dyn HirDatabase, module: Module) -> Type {
+        let resolver = module.id.resolver(db.upcast());
+        Type::new_with_resolver(db, &resolver, Ty::builtin(self.inner))
+            .expect("crate not present in resolver")
+    }
+
+    pub fn name(self) -> Name {
+        self.inner.as_name()
+    }
+}
+
+#[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 def_map = db.crate_def_map(krate);
+        let module_id = def_map.root();
+        Some(Module { id: def_map.module_id(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::ProcMacro(_))
+    }
+
+    /// Indicate it is a derive macro
+    pub fn is_derive_macro(&self) -> bool {
+        matches!(self.id.kind, MacroDefKind::ProcMacro(_) | 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),
+}
+#[derive(Debug)]
+pub enum AssocItemContainer {
+    Trait(Trait),
+    Impl(Impl),
+}
+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)
+    }
+}
+impl AsAssocItem for ModuleDef {
+    fn as_assoc_item(self, db: &dyn HirDatabase) -> Option<AssocItem> {
+        match self {
+            ModuleDef::Function(it) => it.as_assoc_item(db),
+            ModuleDef::Const(it) => it.as_assoc_item(db),
+            ModuleDef::TypeAlias(it) => it.as_assoc_item(db),
+            _ => None,
+        }
+    }
+}
+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::ModuleId(_) => None,
+    }
+}
+
+impl AssocItem {
+    pub fn name(self, db: &dyn HirDatabase) -> Option<Name> {
+        match self {
+            AssocItem::Function(it) => Some(it.name(db)),
+            AssocItem::Const(it) => it.name(db),
+            AssocItem::TypeAlias(it) => Some(it.name(db)),
+        }
+    }
+    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::Impl(id.into()),
+            AssocContainerId::ModuleId(_) => panic!("invalid AssocItem"),
+        }
+    }
+
+    pub fn containing_trait(self, db: &dyn HirDatabase) -> Option<Trait> {
+        match self.container(db) {
+            AssocItemContainer::Trait(t) => Some(t),
+            _ => None,
+        }
+    }
+}
+
+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),
+    Impl(Impl),
+    // enum variants cannot have generics themselves, but their parent enums
+    // can, and this makes some code easier to write
+    Variant(Variant),
+    // 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,
+    Impl,
+    Variant,
+    Const
+    for GenericDef
+);
+
+impl GenericDef {
+    pub fn params(self, db: &dyn HirDatabase) -> Vec<GenericParam> {
+        let generics = db.generic_params(self.into());
+        let ty_params = generics
+            .types
+            .iter()
+            .map(|(local_id, _)| TypeParam { id: TypeParamId { parent: self.into(), local_id } })
+            .map(GenericParam::TypeParam);
+        let lt_params = generics
+            .lifetimes
+            .iter()
+            .map(|(local_id, _)| LifetimeParam {
+                id: LifetimeParamId { parent: self.into(), local_id },
+            })
+            .map(GenericParam::LifetimeParam);
+        let const_params = generics
+            .consts
+            .iter()
+            .map(|(local_id, _)| ConstParam { id: ConstParamId { parent: self.into(), local_id } })
+            .map(GenericParam::ConstParam);
+        ty_params.chain(lt_params).chain(const_params).collect()
+    }
+
+    pub fn type_params(self, db: &dyn HirDatabase) -> Vec<TypeParam> {
+        let generics = 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());
+        matches!(&body[self.pat_id], Pat::Bind { mode: BindingAnnotation::Mutable, .. })
+    }
+
+    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 Label {
+    pub(crate) parent: DefWithBodyId,
+    pub(crate) label_id: LabelId,
+}
+
+impl Label {
+    pub fn module(self, db: &dyn HirDatabase) -> Module {
+        self.parent(db).module(db)
+    }
+
+    pub fn parent(self, _db: &dyn HirDatabase) -> DefWithBody {
+        self.parent.into()
+    }
+
+    pub fn name(self, db: &dyn HirDatabase) -> Name {
+        let body = db.body(self.parent.into());
+        body[self.label_id].name.clone()
+    }
+
+    pub fn source(self, db: &dyn HirDatabase) -> InFile<ast::Label> {
+        let (_body, source_map) = db.body_with_source_map(self.parent.into());
+        let src = source_map.label_syntax(self.label_id);
+        let root = src.file_syntax(db.upcast());
+        src.map(|ast| ast.to_node(&root))
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum GenericParam {
+    TypeParam(TypeParam),
+    LifetimeParam(LifetimeParam),
+    ConstParam(ConstParam),
+}
+impl_from!(TypeParam, LifetimeParam, ConstParam for GenericParam);
+
+impl GenericParam {
+    pub fn module(self, db: &dyn HirDatabase) -> Module {
+        match self {
+            GenericParam::TypeParam(it) => it.module(db),
+            GenericParam::LifetimeParam(it) => it.module(db),
+            GenericParam::ConstParam(it) => it.module(db),
+        }
+    }
+
+    pub fn name(self, db: &dyn HirDatabase) -> Name {
+        match self {
+            GenericParam::TypeParam(it) => it.name(db),
+            GenericParam::LifetimeParam(it) => it.name(db),
+            GenericParam::ConstParam(it) => it.name(db),
+        }
+    }
+}
+
+#[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 krate = self.id.parent.module(db.upcast()).krate();
+        let ty = Ty::Placeholder(self.id);
+        Type::new_with_resolver_inner(db, krate, &resolver, ty)
+    }
+
+    pub fn trait_bounds(self, db: &dyn HirDatabase) -> Vec<Trait> {
+        db.generic_predicates_for_param(self.id)
+            .into_iter()
+            .filter_map(|pred| match &pred.value {
+                hir_ty::GenericPredicate::Implemented(trait_ref) => {
+                    Some(Trait::from(trait_ref.trait_))
+                }
+                _ => None,
+            })
+            .collect()
+    }
+
+    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 krate = self.id.parent.module(db.upcast()).krate();
+        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::new_with_resolver_inner(db, krate, &resolver, ty))
+    }
+}
+
+impl HirDisplay for TypeParam {
+    fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
+        write!(f, "{}", self.name(f.db))?;
+        let bounds = f.db.generic_predicates_for_param(self.id);
+        let substs = Substs::type_params(f.db, self.id.parent);
+        let predicates = bounds.iter().cloned().map(|b| b.subst(&substs)).collect::<Vec<_>>();
+        if !(predicates.is_empty() || f.omit_verbose_types()) {
+            write_bounds_like_dyn_trait_with_prefix(":", &predicates, f)?;
+        }
+        Ok(())
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub struct LifetimeParam {
+    pub(crate) id: LifetimeParamId,
+}
+
+impl LifetimeParam {
+    pub fn name(self, db: &dyn HirDatabase) -> Name {
+        let params = db.generic_params(self.id.parent);
+        params.lifetimes[self.id.local_id].name.clone()
+    }
+
+    pub fn module(self, db: &dyn HirDatabase) -> Module {
+        self.id.parent.module(db.upcast()).into()
+    }
+
+    pub fn parent(self, _db: &dyn HirDatabase) -> GenericDef {
+        self.id.parent.into()
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub struct ConstParam {
+    pub(crate) id: ConstParamId,
+}
+
+impl ConstParam {
+    pub fn name(self, db: &dyn HirDatabase) -> Name {
+        let params = db.generic_params(self.id.parent);
+        params.consts[self.id.local_id].name.clone()
+    }
+
+    pub fn module(self, db: &dyn HirDatabase) -> Module {
+        self.id.parent.module(db.upcast()).into()
+    }
+
+    pub fn parent(self, _db: &dyn HirDatabase) -> GenericDef {
+        self.id.parent.into()
+    }
+
+    pub fn ty(self, db: &dyn HirDatabase) -> Type {
+        let def = self.id.parent;
+        let krate = def.module(db.upcast()).krate();
+        Type::new(db, krate, def, db.const_param_ty(self.id))
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Impl {
+    pub(crate) id: ImplId,
+}
+
+impl Impl {
+    pub fn all_in_crate(db: &dyn HirDatabase, krate: Crate) -> Vec<Impl> {
+        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<Impl> {
+        let impls = db.trait_impls_in_crate(krate.id);
+        impls.for_trait(trait_.id).map(Self::from).collect()
+    }
+
+    // FIXME: the return type is wrong. This should be a hir version of
+    // `TraitRef` (ie, resolved `TypeRef`).
+    pub fn target_trait(self, db: &dyn HirDatabase) -> Option<TypeRef> {
+        db.impl_data(self.id).target_trait.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 krate = self.id.lookup(db.upcast()).container.krate();
+        let ctx = hir_ty::TyLoweringContext::new(db, &resolver);
+        let ty = Ty::from_hir(&ctx, &impl_data.target_type);
+        Type::new_with_resolver_inner(db, krate, &resolver, ty)
+    }
+
+    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.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);
+
+        // FIXME: handle `cfg_attr`
+        let attr = item
+            .value
+            .attrs()
+            .filter_map(|it| {
+                let 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::Tuple(0, ..))
+    }
+    pub fn is_bool(&self) -> bool {
+        matches!(self.ty.value, Ty::Scalar(Scalar::Bool))
+    }
+
+    pub fn is_mutable_reference(&self) -> bool {
+        matches!(self.ty.value, Ty::Ref(hir_ty::Mutability::Mut, ..))
+    }
+
+    pub fn remove_ref(&self) -> Option<Type> {
+        match &self.ty.value {
+            Ty::Ref(.., substs) => Some(self.derived(substs[0].clone())),
+            _ => None,
+        }
+    }
+
+    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 {
+        // No special case for the type of async block, since Chalk can figure it out.
+
+        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,
+        )
+    }
+
+    /// Checks that particular type `ty` implements `std::ops::FnOnce`.
+    ///
+    /// This function can be used to check if a particular type is callable, since FnOnce is a
+    /// supertrait of Fn and FnMut, so all callable types implements at least FnOnce.
+    pub fn impls_fnonce(&self, db: &dyn HirDatabase) -> bool {
+        let krate = self.krate;
+
+        let fnonce_trait = match FnTrait::FnOnce.get_id(db, krate) {
+            Some(it) => it,
+            None => return false,
+        };
+
+        let canonical_ty = Canonical { value: self.ty.value.clone(), kinds: Arc::new([]) };
+        method_resolution::implements_trait_unique(
+            &canonical_ty,
+            db,
+            self.ty.environment.clone(),
+            krate,
+            fnonce_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 normalize_trait_assoc_type(
+        &self,
+        db: &dyn HirDatabase,
+        trait_: Trait,
+        args: &[Type],
+        alias: TypeAlias,
+    ) -> Option<Type> {
+        let subst = Substs::build_for_def(db, trait_.id)
+            .push(self.ty.value.clone())
+            .fill(args.iter().map(|t| t.ty.value.clone()))
+            .build();
+        let predicate = ProjectionPredicate {
+            projection_ty: ProjectionTy { associated_ty: alias.id, parameters: subst },
+            ty: Ty::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)),
+        };
+        let goal = Canonical {
+            value: InEnvironment::new(
+                self.ty.environment.clone(),
+                Obligation::Projection(predicate),
+            ),
+            kinds: Arc::new([TyVariableKind::General]),
+        };
+
+        match db.trait_solve(self.krate, goal)? {
+            Solution::Unique(SolutionVariables(subst)) => {
+                subst.value.first().map(|ty| self.derived(ty.clone()))
+            }
+            Solution::Ambig(_) => None,
+        }
+    }
+
+    pub fn is_copy(&self, db: &dyn HirDatabase) -> bool {
+        let lang_item = db.lang_item(self.krate, SmolStr::new("copy"));
+        let copy_trait = match lang_item {
+            Some(LangItemTarget::TraitId(it)) => it,
+            _ => return false,
+        };
+        self.impls_trait(db, copy_trait.into(), &[])
+    }
+
+    pub fn as_callable(&self, db: &dyn HirDatabase) -> Option<Callable> {
+        let def = match self.ty.value {
+            Ty::FnDef(def, _) => 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::Closure { .. })
+    }
+
+    pub fn is_fn(&self) -> bool {
+        matches!(&self.ty.value, Ty::FnDef(..) | Ty::Function { .. })
+    }
+
+    pub fn is_packed(&self, db: &dyn HirDatabase) -> bool {
+        let adt_id = match self.ty.value {
+            Ty::Adt(hir_ty::AdtId(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::Raw(..))
+    }
+
+    pub fn contains_unknown(&self) -> bool {
+        return go(&self.ty.value);
+
+        fn go(ty: &Ty) -> bool {
+            match ty {
+                Ty::Unknown => true,
+                _ => ty.substs().map_or(false, |substs| substs.iter().any(go)),
+            }
+        }
+    }
+
+    pub fn fields(&self, db: &dyn HirDatabase) -> Vec<(Field, Type)> {
+        let (variant_id, substs) = match self.ty.value {
+            Ty::Adt(hir_ty::AdtId(AdtId::StructId(s)), ref substs) => (s.into(), substs),
+            Ty::Adt(hir_ty::AdtId(AdtId::UnionId(u)), ref substs) => (u.into(), substs),
+            _ => return Vec::new(),
+        };
+
+        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(substs);
+                (def, self.derived(ty))
+            })
+            .collect()
+    }
+
+    pub fn tuple_fields(&self, _db: &dyn HirDatabase) -> Vec<Type> {
+        if let Ty::Tuple(_, substs) = &self.ty.value {
+            substs.iter().map(|ty| self.derived(ty.clone())).collect()
+        } else {
+            Vec::new()
+        }
+    }
+
+    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 type_parameters(&self) -> impl Iterator<Item = Type> + '_ {
+        self.ty
+            .value
+            .strip_references()
+            .substs()
+            .into_iter()
+            .flat_map(|substs| substs.iter())
+            .map(move |ty| self.derived(ty.clone()))
+    }
+
+    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 {
+        let rref = other.remove_ref();
+        self.ty.value.equals_ctor(rref.as_ref().map_or(&other.ty.value, |it| &it.ty.value))
+    }
+
+    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::Adt(..) => {
+                    cb(type_.derived(ty.clone()));
+                }
+                Ty::AssociatedType(..) => {
+                    if let Some(_) = ty.associated_type_parent_trait(db) {
+                        cb(type_.derived(ty.clone()));
+                    }
+                }
+                Ty::OpaqueType(..) => {
+                    if let Some(bounds) = ty.impl_trait_bounds(db) {
+                        walk_bounds(db, &type_.derived(ty.clone()), &bounds, cb);
+                    }
+                }
+                Ty::Alias(AliasTy::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);
+                }
+
+                _ => {}
+            }
+            if let Some(substs) = ty.substs() {
+                walk_substs(db, type_, &substs, 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: CallableSig,
+    def: Option<CallableDefId>,
+    pub(crate) is_bound_method: bool,
+}
+
+pub enum CallableKind {
+    Function(Function),
+    TupleStruct(Struct),
+    TupleEnumVariant(Variant),
+    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, PartialEq, Eq, Hash)]
+pub enum ScopeDef {
+    ModuleDef(ModuleDef),
+    MacroDef(MacroDef),
+    GenericParam(GenericParam),
+    ImplSelfType(Impl),
+    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
+    }
+}
+
+impl From<ItemInNs> for ScopeDef {
+    fn from(item: ItemInNs) -> Self {
+        match item {
+            ItemInNs::Types(id) => ScopeDef::ModuleDef(id.into()),
+            ItemInNs::Values(id) => ScopeDef::ModuleDef(id.into()),
+            ItemInNs::Macros(id) => ScopeDef::MacroDef(id.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)
+    }
+}