lib.rs

//! HIR (previously known as descriptors) provides a high-level object oriented
//! access to Rust code.
//!
//! The principal difference between HIR and syntax trees is that HIR is bound
//! to a particular crate instance. That is, it has cfg flags and features
//! applied. So, the relation between syntax and HIR is many-to-one.
//!
//! HIR is the public API of the all of the compiler logic above syntax trees.
//! It is written in "OO" style. Each type is self contained (as in, it knows its
//! parents and full context). It should be "clean code".
//!
//! `hir_*` crates are the implementation of the compiler logic.
//! They are written in "ECS" style, with relatively little abstractions.
//! Many types are not self-contained, and explicitly use local indexes, arenas, etc.
//!
//! `hir` is what insulates the "we don't know how to actually write an incremental compiler"
//! from the ide with completions, hovers, etc. It is a (soft, internal) boundary:
//! <https://www.tedinski.com/2018/02/06/system-boundaries.html>.

#![warn(rust_2018_idioms, unused_lifetimes)]
#![cfg_attr(feature = "in-rust-tree", feature(rustc_private))]
#![recursion_limit = "512"]

mod semantics;
mod source_analyzer;

mod attrs;
mod from_id;
mod has_source;

pub mod db;
pub mod diagnostics;
pub mod symbols;
pub mod term_search;

mod display;

use std::{iter, mem::discriminant, ops::ControlFlow};

use arrayvec::ArrayVec;
use base_db::{CrateDisplayName, CrateId, CrateOrigin, FileId};
use either::Either;
use hir_def::{
    body::{BodyDiagnostic, SyntheticSyntax},
    data::adt::VariantData,
    generics::{LifetimeParamData, TypeOrConstParamData, TypeParamProvenance},
    hir::{BindingAnnotation, BindingId, ExprOrPatId, LabelId, Pat},
    item_tree::ItemTreeNode,
    lang_item::LangItemTarget,
    layout::{self, ReprOptions, TargetDataLayout},
    nameres::{self, diagnostics::DefDiagnostic},
    path::ImportAlias,
    per_ns::PerNs,
    resolver::{HasResolver, Resolver},
    src::HasSource as _,
    AssocItemId, AssocItemLoc, AttrDefId, ConstId, ConstParamId, CrateRootModuleId, DefWithBodyId,
    EnumId, EnumVariantId, ExternCrateId, FunctionId, GenericDefId, GenericParamId, HasModule,
    ImplId, InTypeConstId, ItemContainerId, LifetimeParamId, LocalFieldId, Lookup, MacroExpander,
    ModuleId, StaticId, StructId, TraitAliasId, TraitId, TupleId, TypeAliasId, TypeOrConstParamId,
    TypeParamId, UnionId,
};
use hir_expand::{attrs::collect_attrs, name::name, proc_macro::ProcMacroKind, MacroCallKind};
use hir_ty::{
    all_super_traits, autoderef, check_orphan_rules,
    consteval::{try_const_usize, unknown_const_as_generic, ConstExt},
    db::InternedClosure,
    diagnostics::BodyValidationDiagnostic,
    known_const_to_ast,
    layout::{Layout as TyLayout, RustcEnumVariantIdx, RustcFieldIdx, TagEncoding},
    method_resolution::{self, TyFingerprint},
    mir::{interpret_mir, MutBorrowKind},
    primitive::UintTy,
    traits::FnTrait,
    AliasTy, CallableDefId, CallableSig, Canonical, CanonicalVarKinds, Cast, ClosureId, GenericArg,
    GenericArgData, Interner, ParamKind, QuantifiedWhereClause, Scalar, Substitution,
    TraitEnvironment, TraitRefExt, Ty, TyBuilder, TyDefId, TyExt, TyKind, ValueTyDefId,
    WhereClause,
};
use itertools::Itertools;
use nameres::diagnostics::DefDiagnosticKind;
use rustc_hash::FxHashSet;
use span::Edition;
use stdx::{impl_from, never};
use syntax::{
    ast::{self, HasAttrs as _, HasName},
    format_smolstr, AstNode, AstPtr, SmolStr, SyntaxNode, SyntaxNodePtr, TextRange, T,
};
use triomphe::Arc;

use crate::db::{DefDatabase, HirDatabase};

pub use crate::{
    attrs::{resolve_doc_path_on, HasAttrs},
    diagnostics::*,
    has_source::HasSource,
    semantics::{
        DescendPreference, PathResolution, Semantics, SemanticsImpl, SemanticsScope, TypeInfo,
        VisibleTraits,
    },
};

// 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 {
    cfg::{CfgAtom, CfgExpr, CfgOptions},
    hir_def::{
        attr::{builtin::AttributeTemplate, AttrSourceMap, Attrs, AttrsWithOwner},
        data::adt::StructKind,
        find_path::PrefixKind,
        import_map,
        lang_item::LangItem,
        nameres::{DefMap, ModuleSource},
        path::{ModPath, PathKind},
        per_ns::Namespace,
        type_ref::{Mutability, TypeRef},
        visibility::Visibility,
        // FIXME: This is here since some queries take it as input that are used
        // outside of hir.
        {AdtId, MacroId, ModuleDefId},
    },
    hir_expand::{
        attrs::{Attr, AttrId},
        change::ChangeWithProcMacros,
        hygiene::{marks_rev, SyntaxContextExt},
        name::{known, Name},
        proc_macro::ProcMacros,
        tt, ExpandResult, HirFileId, HirFileIdExt, InFile, InMacroFile, InRealFile, MacroFileId,
        MacroFileIdExt,
    },
    hir_ty::{
        consteval::ConstEvalError,
        display::{ClosureStyle, HirDisplay, HirDisplayError, HirWrite},
        layout::LayoutError,
        mir::{MirEvalError, MirLowerError},
        PointerCast, Safety,
    },
    // FIXME: Properly encapsulate mir
    hir_ty::{mir, Interner as ChalkTyInterner},
};

// 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::{
        name::AsName,
        span_map::{ExpansionSpanMap, RealSpanMap, SpanMap, SpanMapRef},
    },
};

/// 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 origin(self, db: &dyn HirDatabase) -> CrateOrigin {
        db.crate_graph()[self.id].origin.clone()
    }

    pub fn is_builtin(self, db: &dyn HirDatabase) -> bool {
        matches!(self.origin(db), CrateOrigin::Lang(_))
    }

    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()
    }

    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 transitive_reverse_dependencies(
        self,
        db: &dyn HirDatabase,
    ) -> impl Iterator<Item = Crate> {
        db.crate_graph().transitive_rev_deps(self.id).map(|id| Crate { id })
    }

    pub fn root_module(self) -> Module {
        Module { id: CrateRootModuleId::from(self.id).into() }
    }

    pub fn modules(self, db: &dyn HirDatabase) -> Vec<Module> {
        let def_map = db.crate_def_map(self.id);
        def_map.modules().map(|(id, _)| def_map.module_id(id).into()).collect()
    }

    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 version(self, db: &dyn HirDatabase) -> Option<String> {
        db.crate_graph()[self.id].version.clone()
    }

    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, Macro>> {
        let _p = tracing::span!(tracing::Level::INFO, "query_external_importables");
        import_map::search_dependencies(db, self.into(), &query).into_iter().map(|item| {
            match ItemInNs::from(item) {
                ItemInNs::Types(mod_id) | ItemInNs::Values(mod_id) => Either::Left(mod_id),
                ItemInNs::Macros(mac_id) => Either::Right(mac_id),
            }
        })
    }

    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().into()));
        let doc_url = attrs.by_key("doc").find_string_value_in_tt("html_root_url");
        doc_url.map(|s| s.trim_matches('"').trim_end_matches('/').to_owned() + "/")
    }

    pub fn cfg(&self, db: &dyn HirDatabase) -> CfgOptions {
        db.crate_graph()[self.id].cfg_options.clone()
    }

    pub fn potential_cfg(&self, db: &dyn HirDatabase) -> CfgOptions {
        let data = &db.crate_graph()[self.id];
        data.potential_cfg_options.clone().unwrap_or_else(|| data.cfg_options.clone())
    }
}

#[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),
    TraitAlias(TraitAlias),
    TypeAlias(TypeAlias),
    BuiltinType(BuiltinType),
    Macro(Macro),
}
impl_from!(
    Module,
    Function,
    Adt(Struct, Enum, Union),
    Variant,
    Const,
    Static,
    Trait,
    TraitAlias,
    TypeAlias,
    BuiltinType,
    Macro
    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::TraitAlias(it) => Some(it.module(db)),
            ModuleDef::TypeAlias(it) => Some(it.module(db)),
            ModuleDef::Macro(it) => Some(it.module(db)),
            ModuleDef::BuiltinType(_) => None,
        }
    }

    pub fn canonical_path(&self, db: &dyn HirDatabase) -> Option<String> {
        let mut segments = vec![self.name(db)?];
        for m in self.module(db)?.path_to_root(db) {
            segments.extend(m.name(db))
        }
        segments.reverse();
        Some(segments.iter().map(|it| it.display(db.upcast())).join("::"))
    }

    pub fn canonical_module_path(
        &self,
        db: &dyn HirDatabase,
    ) -> Option<impl Iterator<Item = Module>> {
        self.module(db).map(|it| it.path_to_root(db).into_iter().rev())
    }

    pub fn name(self, db: &dyn HirDatabase) -> Option<Name> {
        let name = match self {
            ModuleDef::Module(it) => it.name(db)?,
            ModuleDef::Const(it) => it.name(db)?,
            ModuleDef::Adt(it) => it.name(db),
            ModuleDef::Trait(it) => it.name(db),
            ModuleDef::TraitAlias(it) => it.name(db),
            ModuleDef::Function(it) => it.name(db),
            ModuleDef::Variant(it) => it.name(db),
            ModuleDef::TypeAlias(it) => it.name(db),
            ModuleDef::Static(it) => it.name(db),
            ModuleDef::Macro(it) => it.name(db),
            ModuleDef::BuiltinType(it) => it.name(),
        };
        Some(name)
    }

    pub fn diagnostics(self, db: &dyn HirDatabase, style_lints: bool) -> Vec<AnyDiagnostic> {
        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::TraitAlias(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(),
            ModuleDef::Variant(it) => it.id.into(),
            ModuleDef::BuiltinType(_) | ModuleDef::Macro(_) => return Vec::new(),
        };

        let mut acc = Vec::new();

        match self.as_def_with_body() {
            Some(def) => {
                def.diagnostics(db, &mut acc, style_lints);
            }
            None => {
                for diag in hir_ty::diagnostics::incorrect_case(db, id) {
                    acc.push(diag.into())
                }
            }
        }

        acc
    }

    pub fn as_def_with_body(self) -> Option<DefWithBody> {
        match self {
            ModuleDef::Function(it) => Some(it.into()),
            ModuleDef::Const(it) => Some(it.into()),
            ModuleDef::Static(it) => Some(it.into()),
            ModuleDef::Variant(it) => Some(it.into()),

            ModuleDef::Module(_)
            | ModuleDef::Adt(_)
            | ModuleDef::Trait(_)
            | ModuleDef::TraitAlias(_)
            | ModuleDef::TypeAlias(_)
            | ModuleDef::Macro(_)
            | ModuleDef::BuiltinType(_) => None,
        }
    }

    pub fn attrs(&self, db: &dyn HirDatabase) -> Option<AttrsWithOwner> {
        Some(match self {
            ModuleDef::Module(it) => it.attrs(db),
            ModuleDef::Function(it) => it.attrs(db),
            ModuleDef::Adt(it) => it.attrs(db),
            ModuleDef::Variant(it) => it.attrs(db),
            ModuleDef::Const(it) => it.attrs(db),
            ModuleDef::Static(it) => it.attrs(db),
            ModuleDef::Trait(it) => it.attrs(db),
            ModuleDef::TraitAlias(it) => it.attrs(db),
            ModuleDef::TypeAlias(it) => it.attrs(db),
            ModuleDef::Macro(it) => it.attrs(db),
            ModuleDef::BuiltinType(_) => return None,
        })
    }
}

impl HasVisibility for ModuleDef {
    fn visibility(&self, db: &dyn HirDatabase) -> Visibility {
        match *self {
            ModuleDef::Module(it) => it.visibility(db),
            ModuleDef::Function(it) => it.visibility(db),
            ModuleDef::Adt(it) => it.visibility(db),
            ModuleDef::Const(it) => it.visibility(db),
            ModuleDef::Static(it) => it.visibility(db),
            ModuleDef::Trait(it) => it.visibility(db),
            ModuleDef::TraitAlias(it) => it.visibility(db),
            ModuleDef::TypeAlias(it) => it.visibility(db),
            ModuleDef::Variant(it) => it.visibility(db),
            ModuleDef::Macro(it) => it.visibility(db),
            ModuleDef::BuiltinType(_) => Visibility::Public,
        }
    }
}

impl Module {
    /// Name of this module.
    pub fn name(self, db: &dyn HirDatabase) -> Option<Name> {
        self.id.name(db.upcast())
    }

    /// 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.crate_root().into() }
    }

    pub fn is_crate_root(self) -> bool {
        DefMap::ROOT == self.id.local_id
    }

    /// 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
            .values()
            .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) })
    }

    /// Finds nearest non-block ancestor `Module` (`self` included).
    pub fn nearest_non_block_module(self, db: &dyn HirDatabase) -> Module {
        let mut id = self.id;
        while id.is_block_module() {
            id = id.containing_module(db.upcast()).expect("block without parent module");
        }
        Module { 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()
    }

    /// Fills `acc` with the module's diagnostics.
    pub fn diagnostics(
        self,
        db: &dyn HirDatabase,
        acc: &mut Vec<AnyDiagnostic>,
        style_lints: bool,
    ) {
        let name = self.name(db);
        let _p = tracing::span!(tracing::Level::INFO, "Module::diagnostics", ?name);
        let def_map = self.id.def_map(db.upcast());
        for diag in def_map.diagnostics() {
            if diag.in_module != self.id.local_id {
                // FIXME: This is accidentally quadratic.
                continue;
            }
            emit_def_diagnostic(db, acc, diag);
        }

        for def in self.declarations(db) {
            match def {
                ModuleDef::Module(m) => {
                    // Only add diagnostics from inline modules
                    if def_map[m.id.local_id].origin.is_inline() {
                        m.diagnostics(db, acc, style_lints)
                    }
                    acc.extend(def.diagnostics(db, style_lints))
                }
                ModuleDef::Trait(t) => {
                    for diag in db.trait_data_with_diagnostics(t.id).1.iter() {
                        emit_def_diagnostic(db, acc, diag);
                    }

                    for item in t.items(db) {
                        item.diagnostics(db, acc, style_lints);
                    }

                    acc.extend(def.diagnostics(db, style_lints))
                }
                ModuleDef::Adt(adt) => {
                    match adt {
                        Adt::Struct(s) => {
                            for diag in db.struct_data_with_diagnostics(s.id).1.iter() {
                                emit_def_diagnostic(db, acc, diag);
                            }
                        }
                        Adt::Union(u) => {
                            for diag in db.union_data_with_diagnostics(u.id).1.iter() {
                                emit_def_diagnostic(db, acc, diag);
                            }
                        }
                        Adt::Enum(e) => {
                            for v in e.variants(db) {
                                acc.extend(ModuleDef::Variant(v).diagnostics(db, style_lints));
                                for diag in db.enum_variant_data_with_diagnostics(v.id).1.iter() {
                                    emit_def_diagnostic(db, acc, diag);
                                }
                            }
                        }
                    }
                    acc.extend(def.diagnostics(db, style_lints))
                }
                ModuleDef::Macro(m) => emit_macro_def_diagnostics(db, acc, m),
                _ => acc.extend(def.diagnostics(db, style_lints)),
            }
        }
        self.legacy_macros(db).into_iter().for_each(|m| emit_macro_def_diagnostics(db, acc, m));

        let inherent_impls = db.inherent_impls_in_crate(self.id.krate());

        let mut impl_assoc_items_scratch = vec![];
        for impl_def in self.impl_defs(db) {
            let loc = impl_def.id.lookup(db.upcast());
            let tree = loc.id.item_tree(db.upcast());
            let node = &tree[loc.id.value];
            let file_id = loc.id.file_id();
            if file_id.macro_file().map_or(false, |it| it.is_builtin_derive(db.upcast())) {
                // these expansion come from us, diagnosing them is a waste of resources
                // FIXME: Once we diagnose the inputs to builtin derives, we should at least extract those diagnostics somehow
                continue;
            }
            let ast_id_map = db.ast_id_map(file_id);

            for diag in db.impl_data_with_diagnostics(impl_def.id).1.iter() {
                emit_def_diagnostic(db, acc, diag);
            }

            if inherent_impls.invalid_impls().contains(&impl_def.id) {
                acc.push(IncoherentImpl { impl_: ast_id_map.get(node.ast_id()), file_id }.into())
            }

            if !impl_def.check_orphan_rules(db) {
                acc.push(TraitImplOrphan { impl_: ast_id_map.get(node.ast_id()), file_id }.into())
            }

            let trait_ = impl_def.trait_(db);
            let trait_is_unsafe = trait_.map_or(false, |t| t.is_unsafe(db));
            let impl_is_negative = impl_def.is_negative(db);
            let impl_is_unsafe = impl_def.is_unsafe(db);

            let drop_maybe_dangle = (|| {
                // FIXME: This can be simplified a lot by exposing hir-ty's utils.rs::Generics helper
                let trait_ = trait_?;
                let drop_trait = db.lang_item(self.krate().into(), LangItem::Drop)?.as_trait()?;
                if drop_trait != trait_.into() {
                    return None;
                }
                let parent = impl_def.id.into();
                let generic_params = db.generic_params(parent);
                let lifetime_params = generic_params.lifetimes.iter().map(|(local_id, _)| {
                    GenericParamId::LifetimeParamId(LifetimeParamId { parent, local_id })
                });
                let type_params = generic_params
                    .iter()
                    .filter(|(_, it)| it.type_param().is_some())
                    .map(|(local_id, _)| {
                        GenericParamId::TypeParamId(TypeParamId::from_unchecked(
                            TypeOrConstParamId { parent, local_id },
                        ))
                    });
                let res = type_params
                    .chain(lifetime_params)
                    .any(|p| db.attrs(AttrDefId::GenericParamId(p)).by_key("may_dangle").exists());
                Some(res)
            })()
            .unwrap_or(false);

            match (impl_is_unsafe, trait_is_unsafe, impl_is_negative, drop_maybe_dangle) {
                // unsafe negative impl
                (true, _, true, _) |
                // unsafe impl for safe trait
                (true, false, _, false) => acc.push(TraitImplIncorrectSafety { impl_: ast_id_map.get(node.ast_id()), file_id, should_be_safe: true }.into()),
                // safe impl for unsafe trait
                (false, true, false, _) |
                // safe impl of dangling drop
                (false, false, _, true) => acc.push(TraitImplIncorrectSafety { impl_: ast_id_map.get(node.ast_id()), file_id, should_be_safe: false }.into()),
                _ => (),
            };

            // Negative impls can't have items, don't emit missing items diagnostic for them
            if let (false, Some(trait_)) = (impl_is_negative, trait_) {
                let items = &db.trait_data(trait_.into()).items;
                let required_items = items.iter().filter(|&(_, assoc)| match *assoc {
                    AssocItemId::FunctionId(it) => !db.function_data(it).has_body(),
                    AssocItemId::ConstId(id) => Const::from(id).value(db).is_none(),
                    AssocItemId::TypeAliasId(it) => db.type_alias_data(it).type_ref.is_none(),
                });
                impl_assoc_items_scratch.extend(db.impl_data(impl_def.id).items.iter().filter_map(
                    |&item| {
                        Some((
                            item,
                            match item {
                                AssocItemId::FunctionId(it) => db.function_data(it).name.clone(),
                                AssocItemId::ConstId(it) => {
                                    db.const_data(it).name.as_ref()?.clone()
                                }
                                AssocItemId::TypeAliasId(it) => db.type_alias_data(it).name.clone(),
                            },
                        ))
                    },
                ));

                let redundant = impl_assoc_items_scratch
                    .iter()
                    .filter(|(id, name)| {
                        !items.iter().any(|(impl_name, impl_item)| {
                            discriminant(impl_item) == discriminant(id) && impl_name == name
                        })
                    })
                    .map(|(item, name)| (name.clone(), AssocItem::from(*item)));
                for (name, assoc_item) in redundant {
                    acc.push(
                        TraitImplRedundantAssocItems {
                            trait_,
                            file_id,
                            impl_: ast_id_map.get(node.ast_id()),
                            assoc_item: (name, assoc_item),
                        }
                        .into(),
                    )
                }

                let missing: Vec<_> = required_items
                    .filter(|(name, id)| {
                        !impl_assoc_items_scratch.iter().any(|(impl_item, impl_name)| {
                            discriminant(impl_item) == discriminant(id) && impl_name == name
                        })
                    })
                    .map(|(name, item)| (name.clone(), AssocItem::from(*item)))
                    .collect();
                if !missing.is_empty() {
                    acc.push(
                        TraitImplMissingAssocItems {
                            impl_: ast_id_map.get(node.ast_id()),
                            file_id,
                            missing,
                        }
                        .into(),
                    )
                }
                impl_assoc_items_scratch.clear();
            }

            for &item in &db.impl_data(impl_def.id).items {
                AssocItem::from(item).diagnostics(db, acc, style_lints);
            }
        }
    }

    pub fn declarations(self, db: &dyn HirDatabase) -> Vec<ModuleDef> {
        let def_map = self.id.def_map(db.upcast());
        let scope = &def_map[self.id.local_id].scope;
        scope
            .declarations()
            .map(ModuleDef::from)
            .chain(scope.unnamed_consts().map(|id| ModuleDef::Const(Const::from(id))))
            .collect()
    }

    pub fn legacy_macros(self, db: &dyn HirDatabase) -> Vec<Macro> {
        let def_map = self.id.def_map(db.upcast());
        let scope = &def_map[self.id.local_id].scope;
        scope.legacy_macros().flat_map(|(_, it)| it).map(|&it| it.into()).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>,
        prefer_no_std: bool,
        prefer_prelude: bool,
    ) -> Option<ModPath> {
        hir_def::find_path::find_path(
            db,
            item.into().into(),
            self.into(),
            prefer_no_std,
            prefer_prelude,
        )
    }

    /// 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,
        prefer_no_std: bool,
        prefer_prelude: bool,
    ) -> Option<ModPath> {
        hir_def::find_path::find_path_prefixed(
            db,
            item.into().into(),
            self.into(),
            prefix_kind,
            prefer_no_std,
            prefer_prelude,
        )
    }
}

fn emit_macro_def_diagnostics(db: &dyn HirDatabase, acc: &mut Vec<AnyDiagnostic>, m: Macro) {
    let id = db.macro_def(m.id);
    if let hir_expand::db::TokenExpander::DeclarativeMacro(expander) = db.macro_expander(id) {
        if let Some(e) = expander.mac.err() {
            let Some(ast) = id.ast_id().left() else {
                never!("declarative expander for non decl-macro: {:?}", e);
                return;
            };
            emit_def_diagnostic_(
                db,
                acc,
                &DefDiagnosticKind::MacroDefError { ast, message: e.to_string() },
            );
        }
    }
}

fn emit_def_diagnostic(db: &dyn HirDatabase, acc: &mut Vec<AnyDiagnostic>, diag: &DefDiagnostic) {
    emit_def_diagnostic_(db, acc, &diag.kind)
}

fn emit_def_diagnostic_(
    db: &dyn HirDatabase,
    acc: &mut Vec<AnyDiagnostic>,
    diag: &DefDiagnosticKind,
) {
    match diag {
        DefDiagnosticKind::UnresolvedModule { ast: declaration, candidates } => {
            let decl = declaration.to_ptr(db.upcast());
            acc.push(
                UnresolvedModule {
                    decl: InFile::new(declaration.file_id, decl),
                    candidates: candidates.clone(),
                }
                .into(),
            )
        }
        DefDiagnosticKind::UnresolvedExternCrate { ast } => {
            let item = ast.to_ptr(db.upcast());
            acc.push(UnresolvedExternCrate { decl: InFile::new(ast.file_id, item) }.into());
        }

        DefDiagnosticKind::UnresolvedImport { id, index } => {
            let file_id = id.file_id();
            let item_tree = id.item_tree(db.upcast());
            let import = &item_tree[id.value];

            let use_tree = import.use_tree_to_ast(db.upcast(), file_id, *index);
            acc.push(
                UnresolvedImport { decl: InFile::new(file_id, AstPtr::new(&use_tree)) }.into(),
            );
        }

        DefDiagnosticKind::UnconfiguredCode { ast, cfg, opts } => {
            let item = ast.to_ptr(db.upcast());
            acc.push(
                InactiveCode { node: ast.with_value(item), cfg: cfg.clone(), opts: opts.clone() }
                    .into(),
            );
        }
        DefDiagnosticKind::UnresolvedProcMacro { ast, krate } => {
            let (node, precise_location, macro_name, kind) = precise_macro_call_location(ast, db);
            acc.push(
                UnresolvedProcMacro { node, precise_location, macro_name, kind, krate: *krate }
                    .into(),
            );
        }
        DefDiagnosticKind::UnresolvedMacroCall { ast, path } => {
            let (node, precise_location, _, _) = precise_macro_call_location(ast, db);
            acc.push(
                UnresolvedMacroCall {
                    macro_call: node,
                    precise_location,
                    path: path.clone(),
                    is_bang: matches!(ast, MacroCallKind::FnLike { .. }),
                }
                .into(),
            );
        }
        DefDiagnosticKind::MacroError { ast, message } => {
            let (node, precise_location, _, _) = precise_macro_call_location(ast, db);
            acc.push(MacroError { node, precise_location, message: message.clone() }.into());
        }
        DefDiagnosticKind::MacroExpansionParseError { ast, errors } => {
            let (node, precise_location, _, _) = precise_macro_call_location(ast, db);
            acc.push(
                MacroExpansionParseError { node, precise_location, errors: errors.clone() }.into(),
            );
        }
        DefDiagnosticKind::UnimplementedBuiltinMacro { ast } => {
            let node = ast.to_node(db.upcast());
            // Must have a name, otherwise we wouldn't emit it.
            let name = node.name().expect("unimplemented builtin macro with no name");
            acc.push(
                UnimplementedBuiltinMacro {
                    node: ast.with_value(SyntaxNodePtr::from(AstPtr::new(&name))),
                }
                .into(),
            );
        }
        DefDiagnosticKind::InvalidDeriveTarget { ast, id } => {
            let node = ast.to_node(db.upcast());
            let derive = node.attrs().nth(*id);
            match derive {
                Some(derive) => {
                    acc.push(
                        InvalidDeriveTarget {
                            node: ast.with_value(SyntaxNodePtr::from(AstPtr::new(&derive))),
                        }
                        .into(),
                    );
                }
                None => stdx::never!("derive diagnostic on item without derive attribute"),
            }
        }
        DefDiagnosticKind::MalformedDerive { ast, id } => {
            let node = ast.to_node(db.upcast());
            let derive = node.attrs().nth(*id);
            match derive {
                Some(derive) => {
                    acc.push(
                        MalformedDerive {
                            node: ast.with_value(SyntaxNodePtr::from(AstPtr::new(&derive))),
                        }
                        .into(),
                    );
                }
                None => stdx::never!("derive diagnostic on item without derive attribute"),
            }
        }
        DefDiagnosticKind::MacroDefError { ast, message } => {
            let node = ast.to_node(db.upcast());
            acc.push(
                MacroDefError {
                    node: InFile::new(ast.file_id, AstPtr::new(&node)),
                    name: node.name().map(|it| it.syntax().text_range()),
                    message: message.clone(),
                }
                .into(),
            );
        }
    }
}

fn precise_macro_call_location(
    ast: &MacroCallKind,
    db: &dyn HirDatabase,
) -> (InFile<SyntaxNodePtr>, Option<TextRange>, Option<String>, MacroKind) {
    // FIXME: maybe we actually want slightly different ranges for the different macro diagnostics
    // - e.g. the full attribute for macro errors, but only the name for name resolution
    match ast {
        MacroCallKind::FnLike { ast_id, .. } => {
            let node = ast_id.to_node(db.upcast());
            (
                ast_id.with_value(SyntaxNodePtr::from(AstPtr::new(&node))),
                node.path()
                    .and_then(|it| it.segment())
                    .and_then(|it| it.name_ref())
                    .map(|it| it.syntax().text_range()),
                node.path().and_then(|it| it.segment()).map(|it| it.to_string()),
                MacroKind::ProcMacro,
            )
        }
        MacroCallKind::Derive { ast_id, derive_attr_index, derive_index } => {
            let node = ast_id.to_node(db.upcast());
            // Compute the precise location of the macro name's token in the derive
            // list.
            let token = (|| {
                let derive_attr = collect_attrs(&node)
                    .nth(derive_attr_index.ast_index())
                    .and_then(|x| Either::left(x.1))?;
                let token_tree = derive_attr.meta()?.token_tree()?;
                let group_by = token_tree
                    .syntax()
                    .children_with_tokens()
                    .filter_map(|elem| match elem {
                        syntax::NodeOrToken::Token(tok) => Some(tok),
                        _ => None,
                    })
                    .group_by(|t| t.kind() == T![,]);
                let (_, mut group) = group_by
                    .into_iter()
                    .filter(|&(comma, _)| !comma)
                    .nth(*derive_index as usize)?;
                group.find(|t| t.kind() == T![ident])
            })();
            (
                ast_id.with_value(SyntaxNodePtr::from(AstPtr::new(&node))),
                token.as_ref().map(|tok| tok.text_range()),
                token.as_ref().map(ToString::to_string),
                MacroKind::Derive,
            )
        }
        MacroCallKind::Attr { ast_id, invoc_attr_index, .. } => {
            let node = ast_id.to_node(db.upcast());
            let attr = collect_attrs(&node)
                .nth(invoc_attr_index.ast_index())
                .and_then(|x| Either::left(x.1))
                .unwrap_or_else(|| {
                    panic!("cannot find attribute #{}", invoc_attr_index.ast_index())
                });

            (
                ast_id.with_value(SyntaxNodePtr::from(AstPtr::new(&attr))),
                Some(attr.syntax().text_range()),
                attr.path()
                    .and_then(|path| path.segment())
                    .and_then(|seg| seg.name_ref())
                    .as_ref()
                    .map(ToString::to_string),
                MacroKind::Attr,
            )
        }
    }
}

impl HasVisibility for Module {
    fn visibility(&self, db: &dyn HirDatabase) -> Visibility {
        let def_map = self.id.def_map(db.upcast());
        let module_data = &def_map[self.id.local_id];
        module_data.visibility
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct Field {
    pub(crate) parent: VariantDef,
    pub(crate) id: LocalFieldId,
}

#[derive(Debug, PartialEq, Eq, Copy, Clone, Hash)]
pub struct TupleField {
    pub owner: DefWithBodyId,
    pub tuple: TupleId,
    pub index: u32,
}

impl TupleField {
    pub fn name(&self) -> Name {
        Name::new_tuple_field(self.index as usize)
    }

    pub fn ty(&self, db: &dyn HirDatabase) -> Type {
        let ty = db.infer(self.owner).tuple_field_access_types[&self.tuple]
            .as_slice(Interner)
            .get(self.index as usize)
            .and_then(|arg| arg.ty(Interner))
            .cloned()
            .unwrap_or_else(|| TyKind::Error.intern(Interner));
        Type { env: db.trait_environment_for_body(self.owner), ty }
    }
}

#[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()
    }

    pub fn index(&self) -> usize {
        u32::from(self.id.into_raw()) as usize
    }

    /// Returns the type as in the signature of the struct (i.e., with
    /// placeholder types for type parameters). Only use this in the context of
    /// the field definition.
    pub fn 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.id.into(),
        };
        let substs = TyBuilder::placeholder_subst(db, generic_def_id);
        let ty = db.field_types(var_id)[self.id].clone().substitute(Interner, &substs);
        Type::new(db, var_id, ty)
    }

    // FIXME: Find better API to also handle const generics
    pub fn ty_with_args(&self, db: &dyn HirDatabase, generics: impl Iterator<Item = Type>) -> Type {
        let var_id = self.parent.into();
        let def_id: AdtId = match self.parent {
            VariantDef::Struct(it) => it.id.into(),
            VariantDef::Union(it) => it.id.into(),
            VariantDef::Variant(it) => it.parent_enum(db).id.into(),
        };
        let mut generics = generics.map(|it| it.ty);
        let substs = TyBuilder::subst_for_def(db, def_id, None)
            .fill(|x| match x {
                ParamKind::Type => {
                    generics.next().unwrap_or_else(|| TyKind::Error.intern(Interner)).cast(Interner)
                }
                ParamKind::Const(ty) => unknown_const_as_generic(ty.clone()),
            })
            .build();
        let ty = db.field_types(var_id)[self.id].clone().substitute(Interner, &substs);
        Type::new(db, var_id, ty)
    }

    pub fn layout(&self, db: &dyn HirDatabase) -> Result<Layout, LayoutError> {
        db.layout_of_ty(
            self.ty(db).ty,
            db.trait_environment(match hir_def::VariantId::from(self.parent) {
                hir_def::VariantId::EnumVariantId(id) => GenericDefId::EnumVariantId(id),
                hir_def::VariantId::StructId(id) => GenericDefId::AdtId(id.into()),
                hir_def::VariantId::UnionId(id) => GenericDefId::AdtId(id.into()),
            }),
        )
        .map(|layout| Layout(layout, db.target_data_layout(self.krate(db).into()).unwrap()))
    }

    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 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)
    }

    pub fn constructor_ty(self, db: &dyn HirDatabase) -> Type {
        Type::from_value_def(db, self.id)
    }

    pub fn repr(self, db: &dyn HirDatabase) -> Option<ReprOptions> {
        db.struct_data(self.id).repr
    }

    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()
    }

    pub fn is_unstable(self, db: &dyn HirDatabase) -> bool {
        db.attrs(self.id.into()).is_unstable()
    }
}

impl HasVisibility for Struct {
    fn visibility(&self, db: &dyn HirDatabase) -> Visibility {
        db.struct_data(self.id).visibility.resolve(db.upcast(), &self.id.resolver(db.upcast()))
    }
}

#[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)
    }

    pub fn constructor_ty(self, db: &dyn HirDatabase) -> Type {
        Type::from_value_def(db, 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()
    }

    pub fn is_unstable(self, db: &dyn HirDatabase) -> bool {
        db.attrs(self.id.into()).is_unstable()
    }
}

impl HasVisibility for Union {
    fn visibility(&self, db: &dyn HirDatabase) -> Visibility {
        db.union_data(self.id).visibility.resolve(db.upcast(), &self.id.resolver(db.upcast()))
    }
}

#[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 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 { id }).collect()
    }

    pub fn repr(self, db: &dyn HirDatabase) -> Option<ReprOptions> {
        db.enum_data(self.id).repr
    }

    pub fn ty(self, db: &dyn HirDatabase) -> Type {
        Type::from_def(db, self.id)
    }

    /// The type of the enum variant bodies.
    pub fn variant_body_ty(self, db: &dyn HirDatabase) -> Type {
        Type::new_for_crate(
            self.id.lookup(db.upcast()).container.krate(),
            TyBuilder::builtin(match db.enum_data(self.id).variant_body_type() {
                layout::IntegerType::Pointer(sign) => match sign {
                    true => hir_def::builtin_type::BuiltinType::Int(
                        hir_def::builtin_type::BuiltinInt::Isize,
                    ),
                    false => hir_def::builtin_type::BuiltinType::Uint(
                        hir_def::builtin_type::BuiltinUint::Usize,
                    ),
                },
                layout::IntegerType::Fixed(i, sign) => match sign {
                    true => hir_def::builtin_type::BuiltinType::Int(match i {
                        layout::Integer::I8 => hir_def::builtin_type::BuiltinInt::I8,
                        layout::Integer::I16 => hir_def::builtin_type::BuiltinInt::I16,
                        layout::Integer::I32 => hir_def::builtin_type::BuiltinInt::I32,
                        layout::Integer::I64 => hir_def::builtin_type::BuiltinInt::I64,
                        layout::Integer::I128 => hir_def::builtin_type::BuiltinInt::I128,
                    }),
                    false => hir_def::builtin_type::BuiltinType::Uint(match i {
                        layout::Integer::I8 => hir_def::builtin_type::BuiltinUint::U8,
                        layout::Integer::I16 => hir_def::builtin_type::BuiltinUint::U16,
                        layout::Integer::I32 => hir_def::builtin_type::BuiltinUint::U32,
                        layout::Integer::I64 => hir_def::builtin_type::BuiltinUint::U64,
                        layout::Integer::I128 => hir_def::builtin_type::BuiltinUint::U128,
                    }),
                },
            }),
        )
    }

    /// Returns true if at least one variant of this enum is a non-unit variant.
    pub fn is_data_carrying(self, db: &dyn HirDatabase) -> bool {
        self.variants(db).iter().any(|v| !matches!(v.kind(db), StructKind::Unit))
    }

    pub fn layout(self, db: &dyn HirDatabase) -> Result<Layout, LayoutError> {
        Adt::from(self).layout(db)
    }

    pub fn is_unstable(self, db: &dyn HirDatabase) -> bool {
        db.attrs(self.id.into()).is_unstable()
    }
}

impl HasVisibility for Enum {
    fn visibility(&self, db: &dyn HirDatabase) -> Visibility {
        db.enum_data(self.id).visibility.resolve(db.upcast(), &self.id.resolver(db.upcast()))
    }
}

impl From<&Variant> for DefWithBodyId {
    fn from(&v: &Variant) -> Self {
        DefWithBodyId::VariantId(v.into())
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct Variant {
    pub(crate) id: EnumVariantId,
}

impl Variant {
    pub fn module(self, db: &dyn HirDatabase) -> Module {
        Module { id: self.id.module(db.upcast()) }
    }

    pub fn parent_enum(self, db: &dyn HirDatabase) -> Enum {
        self.id.lookup(db.upcast()).parent.into()
    }

    pub fn constructor_ty(self, db: &dyn HirDatabase) -> Type {
        Type::from_value_def(db, self.id)
    }

    pub fn name(self, db: &dyn HirDatabase) -> Name {
        db.enum_variant_data(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_variant_data(self.id).variant_data.clone()
    }

    pub fn value(self, db: &dyn HirDatabase) -> Option<ast::Expr> {
        self.source(db)?.value.expr()
    }

    pub fn eval(self, db: &dyn HirDatabase) -> Result<i128, ConstEvalError> {
        db.const_eval_discriminant(self.into())
    }

    pub fn layout(&self, db: &dyn HirDatabase) -> Result<Layout, LayoutError> {
        let parent_enum = self.parent_enum(db);
        let parent_layout = parent_enum.layout(db)?;
        Ok(match &parent_layout.0.variants {
            layout::Variants::Multiple { variants, .. } => Layout(
                {
                    let lookup = self.id.lookup(db.upcast());
                    let rustc_enum_variant_idx = RustcEnumVariantIdx(lookup.index as usize);
                    Arc::new(variants[rustc_enum_variant_idx].clone())
                },
                db.target_data_layout(parent_enum.krate(db).into()).unwrap(),
            ),
            _ => parent_layout,
        })
    }

    pub fn is_unstable(self, db: &dyn HirDatabase) -> bool {
        db.attrs(self.id.into()).is_unstable()
    }
}

/// Variants inherit visibility from the parent enum.
impl HasVisibility for Variant {
    fn visibility(&self, db: &dyn HirDatabase) -> Visibility {
        self.parent_enum(db).visibility(db)
    }
}

/// 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| match ty.skip_binders().data(Interner) {
            GenericArgData::Ty(it) => it.is_unknown(),
            _ => false,
        })
    }

    pub fn layout(self, db: &dyn HirDatabase) -> Result<Layout, LayoutError> {
        if db.generic_params(self.into()).iter().count() != 0 {
            return Err(LayoutError::HasPlaceholder);
        }
        let krate = self.krate(db).id;
        db.layout_of_adt(
            self.into(),
            Substitution::empty(Interner),
            db.trait_environment(self.into()),
        )
        .map(|layout| Layout(layout, db.target_data_layout(krate).unwrap()))
    }

    /// 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)
    }

    /// Turns this ADT into a type with the given type parameters. This isn't
    /// the greatest API, FIXME find a better one.
    pub fn ty_with_args(self, db: &dyn HirDatabase, args: impl Iterator<Item = Type>) -> Type {
        let id = AdtId::from(self);
        let mut it = args.map(|t| t.ty);
        let ty = TyBuilder::def_ty(db, id.into(), None)
            .fill(|x| {
                let r = it.next().unwrap_or_else(|| TyKind::Error.intern(Interner));
                match x {
                    ParamKind::Type => r.cast(Interner),
                    ParamKind::Const(ty) => unknown_const_as_generic(ty.clone()),
                }
            })
            .build();
        Type::new(db, id, ty)
    }

    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 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),
        }
    }

    /// Returns the lifetime of the DataType
    pub fn lifetime(&self, db: &dyn HirDatabase) -> Option<LifetimeParamData> {
        let resolver = match self {
            Adt::Struct(s) => s.id.resolver(db.upcast()),
            Adt::Union(u) => u.id.resolver(db.upcast()),
            Adt::Enum(e) => e.id.resolver(db.upcast()),
        };
        resolver
            .generic_params()
            .and_then(|gp| {
                gp.lifetimes
                    .iter()
                    // there should only be a single lifetime
                    // but `Arena` requires to use an iterator
                    .nth(0)
            })
            .map(|arena| arena.1.clone())
    }

    pub fn as_enum(&self) -> Option<Enum> {
        if let Self::Enum(v) = self {
            Some(*v)
        } else {
            None
        }
    }
}

impl HasVisibility for Adt {
    fn visibility(&self, db: &dyn HirDatabase) -> Visibility {
        match self {
            Adt::Struct(it) => it.visibility(db),
            Adt::Union(it) => it.visibility(db),
            Adt::Enum(it) => it.visibility(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),
    Variant(Variant),
    InTypeConst(InTypeConst),
}
impl_from!(Function, Const, Static, Variant, InTypeConst 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),
            DefWithBody::Variant(v) => v.module(db),
            DefWithBody::InTypeConst(c) => c.module(db),
        }
    }

    pub fn name(self, db: &dyn HirDatabase) -> Option<Name> {
        match self {
            DefWithBody::Function(f) => Some(f.name(db)),
            DefWithBody::Static(s) => Some(s.name(db)),
            DefWithBody::Const(c) => c.name(db),
            DefWithBody::Variant(v) => Some(v.name(db)),
            DefWithBody::InTypeConst(_) => None,
        }
    }

    /// Returns the type this def's body has to evaluate to.
    pub fn body_type(self, db: &dyn HirDatabase) -> Type {
        match self {
            DefWithBody::Function(it) => it.ret_type(db),
            DefWithBody::Static(it) => it.ty(db),
            DefWithBody::Const(it) => it.ty(db),
            DefWithBody::Variant(it) => it.parent_enum(db).variant_body_ty(db),
            DefWithBody::InTypeConst(it) => Type::new_with_resolver_inner(
                db,
                &DefWithBodyId::from(it.id).resolver(db.upcast()),
                TyKind::Error.intern(Interner),
            ),
        }
    }

    fn id(&self) -> DefWithBodyId {
        match self {
            DefWithBody::Function(it) => it.id.into(),
            DefWithBody::Static(it) => it.id.into(),
            DefWithBody::Const(it) => it.id.into(),
            DefWithBody::Variant(it) => it.into(),
            DefWithBody::InTypeConst(it) => it.id.into(),
        }
    }

    /// A textual representation of the HIR of this def's body for debugging purposes.
    pub fn debug_hir(self, db: &dyn HirDatabase) -> String {
        let body = db.body(self.id());
        body.pretty_print(db.upcast(), self.id())
    }

    /// A textual representation of the MIR of this def's body for debugging purposes.
    pub fn debug_mir(self, db: &dyn HirDatabase) -> String {
        let body = db.mir_body(self.id());
        match body {
            Ok(body) => body.pretty_print(db),
            Err(e) => format!("error:\n{e:?}"),
        }
    }

    pub fn diagnostics(
        self,
        db: &dyn HirDatabase,
        acc: &mut Vec<AnyDiagnostic>,
        style_lints: bool,
    ) {
        db.unwind_if_cancelled();
        let krate = self.module(db).id.krate();

        let (body, source_map) = db.body_with_source_map(self.into());

        for (_, def_map) in body.blocks(db.upcast()) {
            Module { id: def_map.module_id(DefMap::ROOT) }.diagnostics(db, acc, style_lints);
        }

        for diag in source_map.diagnostics() {
            acc.push(match diag {
                BodyDiagnostic::InactiveCode { node, cfg, opts } => {
                    InactiveCode { node: *node, cfg: cfg.clone(), opts: opts.clone() }.into()
                }
                BodyDiagnostic::MacroError { node, message } => MacroError {
                    node: (*node).map(|it| it.into()),
                    precise_location: None,
                    message: message.to_string(),
                }
                .into(),
                BodyDiagnostic::UnresolvedProcMacro { node, krate } => UnresolvedProcMacro {
                    node: (*node).map(|it| it.into()),
                    precise_location: None,
                    macro_name: None,
                    kind: MacroKind::ProcMacro,
                    krate: *krate,
                }
                .into(),
                BodyDiagnostic::UnresolvedMacroCall { node, path } => UnresolvedMacroCall {
                    macro_call: (*node).map(|ast_ptr| ast_ptr.into()),
                    precise_location: None,
                    path: path.clone(),
                    is_bang: true,
                }
                .into(),
                BodyDiagnostic::UnreachableLabel { node, name } => {
                    UnreachableLabel { node: *node, name: name.clone() }.into()
                }
                BodyDiagnostic::UndeclaredLabel { node, name } => {
                    UndeclaredLabel { node: *node, name: name.clone() }.into()
                }
            });
        }

        let infer = db.infer(self.into());
        for d in &infer.diagnostics {
            acc.extend(AnyDiagnostic::inference_diagnostic(db, self.into(), d, &source_map));
        }
        for (pat_or_expr, mismatch) in infer.type_mismatches() {
            let expr_or_pat = match pat_or_expr {
                ExprOrPatId::ExprId(expr) => source_map.expr_syntax(expr).map(Either::Left),
                ExprOrPatId::PatId(pat) => source_map.pat_syntax(pat).map(Either::Right),
            };
            let expr_or_pat = match expr_or_pat {
                Ok(Either::Left(expr)) => expr.map(AstPtr::wrap_left),
                Ok(Either::Right(InFile { file_id, value: pat })) => {
                    // cast from Either<Pat, SelfParam> -> Either<_, Pat>
                    let Some(ptr) = AstPtr::try_from_raw(pat.syntax_node_ptr()) else {
                        continue;
                    };
                    InFile { file_id, value: ptr }
                }
                Err(SyntheticSyntax) => continue,
            };

            acc.push(
                TypeMismatch {
                    expr_or_pat,
                    expected: Type::new(db, DefWithBodyId::from(self), mismatch.expected.clone()),
                    actual: Type::new(db, DefWithBodyId::from(self), mismatch.actual.clone()),
                }
                .into(),
            );
        }

        for expr in hir_ty::diagnostics::missing_unsafe(db, self.into()) {
            match source_map.expr_syntax(expr) {
                Ok(expr) => acc.push(MissingUnsafe { expr }.into()),
                Err(SyntheticSyntax) => {
                    // FIXME: Here and elsewhere in this file, the `expr` was
                    // desugared, report or assert that this doesn't happen.
                }
            }
        }

        if let Ok(borrowck_results) = db.borrowck(self.into()) {
            for borrowck_result in borrowck_results.iter() {
                let mir_body = &borrowck_result.mir_body;
                for moof in &borrowck_result.moved_out_of_ref {
                    let span: InFile<SyntaxNodePtr> = match moof.span {
                        mir::MirSpan::ExprId(e) => match source_map.expr_syntax(e) {
                            Ok(s) => s.map(|it| it.into()),
                            Err(_) => continue,
                        },
                        mir::MirSpan::PatId(p) => match source_map.pat_syntax(p) {
                            Ok(s) => s.map(|it| it.into()),
                            Err(_) => continue,
                        },
                        mir::MirSpan::SelfParam => match source_map.self_param_syntax() {
                            Some(s) => s.map(|it| it.into()),
                            None => continue,
                        },
                        mir::MirSpan::Unknown => continue,
                    };
                    acc.push(
                        MovedOutOfRef { ty: Type::new_for_crate(krate, moof.ty.clone()), span }
                            .into(),
                    )
                }
                let mol = &borrowck_result.mutability_of_locals;
                for (binding_id, binding_data) in body.bindings.iter() {
                    if binding_data.problems.is_some() {
                        // We should report specific diagnostics for these problems, not `need-mut` and `unused-mut`.
                        continue;
                    }
                    let Some(&local) = mir_body.binding_locals.get(binding_id) else {
                        continue;
                    };
                    if body[binding_id]
                        .definitions
                        .iter()
                        .any(|&pat| source_map.pat_syntax(pat).is_err())
                    {
                        // Skip synthetic bindings
                        continue;
                    }
                    let mut need_mut = &mol[local];
                    if body[binding_id].name.as_str() == Some("self")
                        && need_mut == &mir::MutabilityReason::Unused
                    {
                        need_mut = &mir::MutabilityReason::Not;
                    }
                    let local = Local { parent: self.into(), binding_id };
                    match (need_mut, local.is_mut(db)) {
                        (mir::MutabilityReason::Unused, _) => {
                            let should_ignore = matches!(body[binding_id].name.as_str(), Some(it) if it.starts_with('_'));
                            if !should_ignore {
                                acc.push(UnusedVariable { local }.into())
                            }
                        }
                        (mir::MutabilityReason::Mut { .. }, true)
                        | (mir::MutabilityReason::Not, false) => (),
                        (mir::MutabilityReason::Mut { spans }, false) => {
                            for span in spans {
                                let span: InFile<SyntaxNodePtr> = match span {
                                    mir::MirSpan::ExprId(e) => match source_map.expr_syntax(*e) {
                                        Ok(s) => s.map(|it| it.into()),
                                        Err(_) => continue,
                                    },
                                    mir::MirSpan::PatId(p) => match source_map.pat_syntax(*p) {
                                        Ok(s) => s.map(|it| it.into()),
                                        Err(_) => continue,
                                    },
                                    mir::MirSpan::SelfParam => match source_map.self_param_syntax()
                                    {
                                        Some(s) => s.map(|it| it.into()),
                                        None => continue,
                                    },
                                    mir::MirSpan::Unknown => continue,
                                };
                                acc.push(NeedMut { local, span }.into());
                            }
                        }
                        (mir::MutabilityReason::Not, true) => {
                            if !infer.mutated_bindings_in_closure.contains(&binding_id) {
                                let should_ignore = matches!(body[binding_id].name.as_str(), Some(it) if it.starts_with('_'));
                                if !should_ignore {
                                    acc.push(UnusedMut { local }.into())
                                }
                            }
                        }
                    }
                }
            }
        }

        for diagnostic in BodyValidationDiagnostic::collect(db, self.into(), style_lints) {
            acc.extend(AnyDiagnostic::body_validation_diagnostic(db, diagnostic, &source_map));
        }

        let def: ModuleDef = match self {
            DefWithBody::Function(it) => it.into(),
            DefWithBody::Static(it) => it.into(),
            DefWithBody::Const(it) => it.into(),
            DefWithBody::Variant(it) => it.into(),
            // FIXME: don't ignore diagnostics for in type const
            DefWithBody::InTypeConst(_) => return,
        };
        for diag in hir_ty::diagnostics::incorrect_case(db, def.into()) {
            acc.push(diag.into())
        }
    }
}
#[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.module(db.upcast()).into()
    }

    pub fn name(self, db: &dyn HirDatabase) -> Name {
        db.function_data(self.id).name.clone()
    }

    pub fn ty(self, db: &dyn HirDatabase) -> Type {
        Type::from_value_def(db, self.id)
    }

    /// Get this function's return type
    pub fn ret_type(self, db: &dyn HirDatabase) -> Type {
        let resolver = self.id.resolver(db.upcast());
        let substs = TyBuilder::placeholder_subst(db, self.id);
        let callable_sig = db.callable_item_signature(self.id.into()).substitute(Interner, &substs);
        let ty = callable_sig.ret().clone();
        Type::new_with_resolver_inner(db, &resolver, ty)
    }

    // FIXME: Find better API to also handle const generics
    pub fn ret_type_with_args(
        self,
        db: &dyn HirDatabase,
        generics: impl Iterator<Item = Type>,
    ) -> Type {
        let resolver = self.id.resolver(db.upcast());
        let parent_id: Option<GenericDefId> = match self.id.lookup(db.upcast()).container {
            ItemContainerId::ImplId(it) => Some(it.into()),
            ItemContainerId::TraitId(it) => Some(it.into()),
            ItemContainerId::ModuleId(_) | ItemContainerId::ExternBlockId(_) => None,
        };
        let mut generics = generics.map(|it| it.ty);
        let mut filler = |x: &_| match x {
            ParamKind::Type => {
                generics.next().unwrap_or_else(|| TyKind::Error.intern(Interner)).cast(Interner)
            }
            ParamKind::Const(ty) => unknown_const_as_generic(ty.clone()),
        };

        let parent_substs =
            parent_id.map(|id| TyBuilder::subst_for_def(db, id, None).fill(&mut filler).build());
        let substs = TyBuilder::subst_for_def(db, self.id, parent_substs).fill(&mut filler).build();

        let callable_sig = db.callable_item_signature(self.id.into()).substitute(Interner, &substs);
        let ty = callable_sig.ret().clone();
        Type::new_with_resolver_inner(db, &resolver, ty)
    }

    pub fn async_ret_type(self, db: &dyn HirDatabase) -> Option<Type> {
        if !self.is_async(db) {
            return None;
        }
        let resolver = self.id.resolver(db.upcast());
        let substs = TyBuilder::placeholder_subst(db, self.id);
        let callable_sig = db.callable_item_signature(self.id.into()).substitute(Interner, &substs);
        let ret_ty = callable_sig.ret().clone();
        for pred in ret_ty.impl_trait_bounds(db).into_iter().flatten() {
            if let WhereClause::AliasEq(output_eq) = pred.into_value_and_skipped_binders().0 {
                return Type::new_with_resolver_inner(db, &resolver, output_eq.ty).into();
            }
        }
        never!("Async fn ret_type should be impl Future");
        None
    }

    pub fn has_self_param(self, db: &dyn HirDatabase) -> bool {
        db.function_data(self.id).has_self_param()
    }

    pub fn self_param(self, db: &dyn HirDatabase) -> Option<SelfParam> {
        self.has_self_param(db).then_some(SelfParam { func: self.id })
    }

    pub fn assoc_fn_params(self, db: &dyn HirDatabase) -> Vec<Param> {
        let environment = db.trait_environment(self.id.into());
        let substs = TyBuilder::placeholder_subst(db, self.id);
        let callable_sig = db.callable_item_signature(self.id.into()).substitute(Interner, &substs);
        callable_sig
            .params()
            .iter()
            .enumerate()
            .map(|(idx, ty)| {
                let ty = Type { env: environment.clone(), ty: ty.clone() };
                Param { func: self, ty, idx }
            })
            .collect()
    }

    pub fn num_params(self, db: &dyn HirDatabase) -> usize {
        db.function_data(self.id).params.len()
    }

    pub fn method_params(self, db: &dyn HirDatabase) -> Option<Vec<Param>> {
        self.self_param(db)?;
        Some(self.params_without_self(db))
    }

    pub fn params_without_self(self, db: &dyn HirDatabase) -> Vec<Param> {
        let environment = db.trait_environment(self.id.into());
        let substs = TyBuilder::placeholder_subst(db, self.id);
        let callable_sig = db.callable_item_signature(self.id.into()).substitute(Interner, &substs);
        let skip = if db.function_data(self.id).has_self_param() { 1 } else { 0 };
        callable_sig
            .params()
            .iter()
            .enumerate()
            .skip(skip)
            .map(|(idx, ty)| {
                let ty = Type { env: environment.clone(), ty: ty.clone() };
                Param { func: self, ty, idx }
            })
            .collect()
    }

    // FIXME: Find better API to also handle const generics
    pub fn params_without_self_with_args(
        self,
        db: &dyn HirDatabase,
        generics: impl Iterator<Item = Type>,
    ) -> Vec<Param> {
        let environment = db.trait_environment(self.id.into());
        let parent_id: Option<GenericDefId> = match self.id.lookup(db.upcast()).container {
            ItemContainerId::ImplId(it) => Some(it.into()),
            ItemContainerId::TraitId(it) => Some(it.into()),
            ItemContainerId::ModuleId(_) | ItemContainerId::ExternBlockId(_) => None,
        };
        let mut generics = generics.map(|it| it.ty);
        let parent_substs = parent_id.map(|id| {
            TyBuilder::subst_for_def(db, id, None)
                .fill(|x| match x {
                    ParamKind::Type => generics
                        .next()
                        .unwrap_or_else(|| TyKind::Error.intern(Interner))
                        .cast(Interner),
                    ParamKind::Const(ty) => unknown_const_as_generic(ty.clone()),
                })
                .build()
        });

        let substs = TyBuilder::subst_for_def(db, self.id, parent_substs)
            .fill(|_| {
                let ty = generics.next().unwrap_or_else(|| TyKind::Error.intern(Interner));
                GenericArg::new(Interner, GenericArgData::Ty(ty))
            })
            .build();
        let callable_sig = db.callable_item_signature(self.id.into()).substitute(Interner, &substs);
        let skip = if db.function_data(self.id).has_self_param() { 1 } else { 0 };
        callable_sig
            .params()
            .iter()
            .enumerate()
            .skip(skip)
            .map(|(idx, ty)| {
                let ty = Type { env: environment.clone(), ty: ty.clone() };
                Param { func: self, ty, idx }
            })
            .collect()
    }

    pub fn is_const(self, db: &dyn HirDatabase) -> bool {
        db.function_data(self.id).has_const_kw()
    }

    pub fn is_async(self, db: &dyn HirDatabase) -> bool {
        db.function_data(self.id).has_async_kw()
    }

    /// Does this function have `#[test]` attribute?
    pub fn is_test(self, db: &dyn HirDatabase) -> bool {
        db.function_data(self.id).attrs.is_test()
    }

    /// is this a `fn main` or a function with an `export_name` of `main`?
    pub fn is_main(self, db: &dyn HirDatabase) -> bool {
        if !self.module(db).is_crate_root() {
            return false;
        }
        let data = db.function_data(self.id);

        data.name.to_smol_str() == "main" || data.attrs.export_name() == Some("main")
    }

    /// Does this function have the ignore attribute?
    pub fn is_ignore(self, db: &dyn HirDatabase) -> bool {
        db.function_data(self.id).attrs.is_ignore()
    }

    /// Does this function have `#[bench]` attribute?
    pub fn is_bench(self, db: &dyn HirDatabase) -> bool {
        db.function_data(self.id).attrs.is_bench()
    }

    /// Is this function marked as unstable with `#[feature]` attribute?
    pub fn is_unstable(self, db: &dyn HirDatabase) -> bool {
        db.function_data(self.id).attrs.is_unstable()
    }

    pub fn is_unsafe_to_call(self, db: &dyn HirDatabase) -> bool {
        hir_ty::is_fn_unsafe_to_call(db, self.id)
    }

    /// 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()
    }

    pub fn as_proc_macro(self, db: &dyn HirDatabase) -> Option<Macro> {
        let function_data = db.function_data(self.id);
        let attrs = &function_data.attrs;
        // FIXME: Store this in FunctionData flags?
        if !(attrs.is_proc_macro()
            || attrs.is_proc_macro_attribute()
            || attrs.is_proc_macro_derive())
        {
            return None;
        }
        let def_map = db.crate_def_map(HasModule::krate(&self.id, db.upcast()));
        def_map.fn_as_proc_macro(self.id).map(|id| Macro { id: id.into() })
    }

    pub fn eval(
        self,
        db: &dyn HirDatabase,
        span_formatter: impl Fn(FileId, TextRange) -> String,
    ) -> String {
        let body = match db.monomorphized_mir_body(
            self.id.into(),
            Substitution::empty(Interner),
            db.trait_environment(self.id.into()),
        ) {
            Ok(body) => body,
            Err(e) => {
                let mut r = String::new();
                _ = e.pretty_print(&mut r, db, &span_formatter);
                return r;
            }
        };
        let (result, output) = interpret_mir(db, body, false, None);
        let mut text = match result {
            Ok(_) => "pass".to_owned(),
            Err(e) => {
                let mut r = String::new();
                _ = e.pretty_print(&mut r, db, &span_formatter);
                r
            }
        };
        let stdout = output.stdout().into_owned();
        if !stdout.is_empty() {
            text += "\n--------- stdout ---------\n";
            text += &stdout;
        }
        let stderr = output.stdout().into_owned();
        if !stderr.is_empty() {
            text += "\n--------- stderr ---------\n";
            text += &stderr;
        }
        text
    }
}

// Note: logically, this belongs to `hir_ty`, but we are not using it there yet.
#[derive(Clone, Copy, PartialEq, Eq)]
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(Clone, PartialEq, Eq, Hash, Debug)]
pub struct Param {
    func: Function,
    /// The index in parameter list, including self parameter.
    idx: usize,
    ty: Type,
}

impl Param {
    pub fn parent_fn(&self) -> Function {
        self.func
    }

    pub fn index(&self) -> usize {
        self.idx
    }

    pub fn ty(&self) -> &Type {
        &self.ty
    }

    pub fn name(&self, db: &dyn HirDatabase) -> Option<Name> {
        Some(self.as_local(db)?.name(db))
    }

    pub fn as_local(&self, db: &dyn HirDatabase) -> Option<Local> {
        let parent = DefWithBodyId::FunctionId(self.func.into());
        let body = db.body(parent);
        if let Some(self_param) = body.self_param.filter(|_| self.idx == 0) {
            Some(Local { parent, binding_id: self_param })
        } else if let Pat::Bind { id, .. } =
            &body[body.params[self.idx - body.self_param.is_some() as usize]]
        {
            Some(Local { parent, binding_id: *id })
        } else {
            None
        }
    }

    pub fn pattern_source(&self, db: &dyn HirDatabase) -> Option<ast::Pat> {
        self.source(db).and_then(|p| p.value.pat())
    }

    pub fn source(&self, db: &dyn HirDatabase) -> Option<InFile<ast::Param>> {
        let InFile { file_id, value } = self.func.source(db)?;
        let params = value.param_list()?;
        if params.self_param().is_some() {
            params.params().nth(self.idx.checked_sub(params.self_param().is_some() as usize)?)
        } else {
            params.params().nth(self.idx)
        }
        .map(|value| InFile { file_id, value })
    }
}

#[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)
    }

    pub fn source(&self, db: &dyn HirDatabase) -> Option<InFile<ast::SelfParam>> {
        let InFile { file_id, value } = Function::from(self.func).source(db)?;
        value
            .param_list()
            .and_then(|params| params.self_param())
            .map(|value| InFile { file_id, value })
    }

    pub fn parent_fn(&self) -> Function {
        Function::from(self.func)
    }

    pub fn ty(&self, db: &dyn HirDatabase) -> Type {
        let substs = TyBuilder::placeholder_subst(db, self.func);
        let callable_sig =
            db.callable_item_signature(self.func.into()).substitute(Interner, &substs);
        let environment = db.trait_environment(self.func.into());
        let ty = callable_sig.params()[0].clone();
        Type { env: environment, ty }
    }

    // FIXME: Find better API to also handle const generics
    pub fn ty_with_args(&self, db: &dyn HirDatabase, generics: impl Iterator<Item = Type>) -> Type {
        let parent_id: GenericDefId = match self.func.lookup(db.upcast()).container {
            ItemContainerId::ImplId(it) => it.into(),
            ItemContainerId::TraitId(it) => it.into(),
            ItemContainerId::ModuleId(_) | ItemContainerId::ExternBlockId(_) => {
                panic!("Never get here")
            }
        };

        let mut generics = generics.map(|it| it.ty);
        let mut filler = |x: &_| match x {
            ParamKind::Type => {
                generics.next().unwrap_or_else(|| TyKind::Error.intern(Interner)).cast(Interner)
            }
            ParamKind::Const(ty) => unknown_const_as_generic(ty.clone()),
        };

        let parent_substs = TyBuilder::subst_for_def(db, parent_id, None).fill(&mut filler).build();
        let substs =
            TyBuilder::subst_for_def(db, self.func, Some(parent_substs)).fill(&mut filler).build();
        let callable_sig =
            db.callable_item_signature(self.func.into()).substitute(Interner, &substs);
        let environment = db.trait_environment(self.func.into());
        let ty = callable_sig.params()[0].clone();
        Type { env: environment, ty }
    }
}

impl HasVisibility for Function {
    fn visibility(&self, db: &dyn HirDatabase) -> Visibility {
        db.function_visibility(self.id)
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct ExternCrateDecl {
    pub(crate) id: ExternCrateId,
}

impl ExternCrateDecl {
    pub fn module(self, db: &dyn HirDatabase) -> Module {
        self.id.module(db.upcast()).into()
    }

    pub fn resolved_crate(self, db: &dyn HirDatabase) -> Option<Crate> {
        db.extern_crate_decl_data(self.id).crate_id.map(Into::into)
    }

    pub fn name(self, db: &dyn HirDatabase) -> Name {
        db.extern_crate_decl_data(self.id).name.clone()
    }

    pub fn alias(self, db: &dyn HirDatabase) -> Option<ImportAlias> {
        db.extern_crate_decl_data(self.id).alias.clone()
    }

    /// Returns the name under which this crate is made accessible, taking `_` into account.
    pub fn alias_or_name(self, db: &dyn HirDatabase) -> Option<Name> {
        let extern_crate_decl_data = db.extern_crate_decl_data(self.id);
        match &extern_crate_decl_data.alias {
            Some(ImportAlias::Underscore) => None,
            Some(ImportAlias::Alias(alias)) => Some(alias.clone()),
            None => Some(extern_crate_decl_data.name.clone()),
        }
    }
}

impl HasVisibility for ExternCrateDecl {
    fn visibility(&self, db: &dyn HirDatabase) -> Visibility {
        db.extern_crate_decl_data(self.id)
            .visibility
            .resolve(db.upcast(), &self.id.resolver(db.upcast()))
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct InTypeConst {
    pub(crate) id: InTypeConstId,
}

impl InTypeConst {
    pub fn module(self, db: &dyn HirDatabase) -> Module {
        Module { id: self.id.lookup(db.upcast()).owner.module(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.module(db.upcast()) }
    }

    pub fn name(self, db: &dyn HirDatabase) -> Option<Name> {
        db.const_data(self.id).name.clone()
    }

    pub fn value(self, db: &dyn HirDatabase) -> Option<ast::Expr> {
        self.source(db)?.value.body()
    }

    pub fn ty(self, db: &dyn HirDatabase) -> Type {
        Type::from_value_def(db, self.id)
    }

    pub fn render_eval(self, db: &dyn HirDatabase) -> Result<String, ConstEvalError> {
        let c = db.const_eval(self.id.into(), Substitution::empty(Interner), None)?;
        let data = &c.data(Interner);
        if let TyKind::Scalar(s) = data.ty.kind(Interner) {
            if matches!(s, Scalar::Int(_) | Scalar::Uint(_)) {
                if let hir_ty::ConstValue::Concrete(c) = &data.value {
                    if let hir_ty::ConstScalar::Bytes(b, _) = &c.interned {
                        let value = u128::from_le_bytes(mir::pad16(b, false));
                        let value_signed =
                            i128::from_le_bytes(mir::pad16(b, matches!(s, Scalar::Int(_))));
                        if value >= 10 {
                            return Ok(format!("{} ({:#X})", value_signed, value));
                        } else {
                            return Ok(format!("{}", value_signed));
                        }
                    }
                }
            }
        }
        if let Ok(s) = mir::render_const_using_debug_impl(db, self.id, &c) {
            Ok(s)
        } else {
            Ok(format!("{}", c.display(db)))
        }
    }
}

impl HasVisibility for Const {
    fn visibility(&self, db: &dyn HirDatabase) -> Visibility {
        db.const_visibility(self.id)
    }
}

#[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.module(db.upcast()) }
    }

    pub fn name(self, db: &dyn HirDatabase) -> Name {
        db.static_data(self.id).name.clone()
    }

    pub fn is_mut(self, db: &dyn HirDatabase) -> bool {
        db.static_data(self.id).mutable
    }

    pub fn value(self, db: &dyn HirDatabase) -> Option<ast::Expr> {
        self.source(db)?.value.body()
    }

    pub fn ty(self, db: &dyn HirDatabase) -> Type {
        Type::from_value_def(db, self.id)
    }
}

impl HasVisibility for Static {
    fn visibility(&self, db: &dyn HirDatabase) -> Visibility {
        db.static_data(self.id).visibility.resolve(db.upcast(), &self.id.resolver(db.upcast()))
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct Trait {
    pub(crate) id: TraitId,
}

impl Trait {
    pub fn lang(db: &dyn HirDatabase, krate: Crate, name: &Name) -> Option<Trait> {
        db.lang_item(krate.into(), LangItem::from_name(name)?)
            .and_then(LangItemTarget::as_trait)
            .map(Into::into)
    }

    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 items_with_supertraits(self, db: &dyn HirDatabase) -> Vec<AssocItem> {
        let traits = all_super_traits(db.upcast(), self.into());
        traits.iter().flat_map(|tr| Trait::from(*tr).items(db)).collect()
    }

    pub fn is_auto(self, db: &dyn HirDatabase) -> bool {
        db.trait_data(self.id).is_auto
    }

    pub fn is_unsafe(&self, db: &dyn HirDatabase) -> bool {
        db.trait_data(self.id).is_unsafe
    }

    pub fn type_or_const_param_count(
        &self,
        db: &dyn HirDatabase,
        count_required_only: bool,
    ) -> usize {
        db.generic_params(GenericDefId::from(self.id))
            .type_or_consts
            .iter()
            .filter(|(_, ty)| !matches!(ty, TypeOrConstParamData::TypeParamData(ty) if ty.provenance != TypeParamProvenance::TypeParamList))
            .filter(|(_, ty)| !count_required_only || !ty.has_default())
            .count()
    }
}

impl HasVisibility for Trait {
    fn visibility(&self, db: &dyn HirDatabase) -> Visibility {
        db.trait_data(self.id).visibility.resolve(db.upcast(), &self.id.resolver(db.upcast()))
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct TraitAlias {
    pub(crate) id: TraitAliasId,
}

impl TraitAlias {
    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_alias_data(self.id).name.clone()
    }
}

impl HasVisibility for TraitAlias {
    fn visibility(&self, db: &dyn HirDatabase) -> Visibility {
        db.trait_alias_data(self.id).visibility.resolve(db.upcast(), &self.id.resolver(db.upcast()))
    }
}

#[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| match ty.skip_binders().data(Interner) {
            GenericArgData::Ty(it) => it.is_unknown(),
            _ => false,
        })
    }

    pub fn module(self, db: &dyn HirDatabase) -> Module {
        Module { id: self.id.module(db.upcast()) }
    }

    pub fn type_ref(self, db: &dyn HirDatabase) -> Option<TypeRef> {
        db.type_alias_data(self.id).type_ref.as_deref().cloned()
    }

    pub fn ty(self, db: &dyn HirDatabase) -> Type {
        Type::from_def(db, 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 str() -> BuiltinType {
        BuiltinType { inner: hir_def::builtin_type::BuiltinType::Str }
    }

    pub fn ty(self, db: &dyn HirDatabase) -> Type {
        Type::new_for_crate(db.crate_graph().iter().next().unwrap(), TyBuilder::builtin(self.inner))
    }

    pub fn name(self) -> Name {
        self.inner.as_name()
    }

    pub fn is_int(&self) -> bool {
        matches!(self.inner, hir_def::builtin_type::BuiltinType::Int(_))
    }

    pub fn is_uint(&self) -> bool {
        matches!(self.inner, hir_def::builtin_type::BuiltinType::Uint(_))
    }

    pub fn is_float(&self) -> bool {
        matches!(self.inner, hir_def::builtin_type::BuiltinType::Float(_))
    }

    pub fn is_char(&self) -> bool {
        matches!(self.inner, hir_def::builtin_type::BuiltinType::Char)
    }

    pub fn is_bool(&self) -> bool {
        matches!(self.inner, hir_def::builtin_type::BuiltinType::Bool)
    }

    pub fn is_str(&self) -> bool {
        matches!(self.inner, hir_def::builtin_type::BuiltinType::Str)
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum MacroKind {
    /// `macro_rules!` or Macros 2.0 macro.
    Declarative,
    /// A built-in or custom derive.
    Derive,
    /// A built-in function-like macro.
    BuiltIn,
    /// A procedural attribute macro.
    Attr,
    /// A function-like procedural macro.
    ProcMacro,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct Macro {
    pub(crate) id: MacroId,
}

impl Macro {
    pub fn module(self, db: &dyn HirDatabase) -> Module {
        Module { id: self.id.module(db.upcast()) }
    }

    pub fn name(self, db: &dyn HirDatabase) -> Name {
        match self.id {
            MacroId::Macro2Id(id) => db.macro2_data(id).name.clone(),
            MacroId::MacroRulesId(id) => db.macro_rules_data(id).name.clone(),
            MacroId::ProcMacroId(id) => db.proc_macro_data(id).name.clone(),
        }
    }

    pub fn is_macro_export(self, db: &dyn HirDatabase) -> bool {
        matches!(self.id, MacroId::MacroRulesId(id) if db.macro_rules_data(id).macro_export)
    }

    pub fn kind(&self, db: &dyn HirDatabase) -> MacroKind {
        match self.id {
            MacroId::Macro2Id(it) => match it.lookup(db.upcast()).expander {
                MacroExpander::Declarative => MacroKind::Declarative,
                MacroExpander::BuiltIn(_) | MacroExpander::BuiltInEager(_) => MacroKind::BuiltIn,
                MacroExpander::BuiltInAttr(_) => MacroKind::Attr,
                MacroExpander::BuiltInDerive(_) => MacroKind::Derive,
            },
            MacroId::MacroRulesId(it) => match it.lookup(db.upcast()).expander {
                MacroExpander::Declarative => MacroKind::Declarative,
                MacroExpander::BuiltIn(_) | MacroExpander::BuiltInEager(_) => MacroKind::BuiltIn,
                MacroExpander::BuiltInAttr(_) => MacroKind::Attr,
                MacroExpander::BuiltInDerive(_) => MacroKind::Derive,
            },
            MacroId::ProcMacroId(it) => match it.lookup(db.upcast()).kind {
                ProcMacroKind::CustomDerive => MacroKind::Derive,
                ProcMacroKind::FuncLike => MacroKind::ProcMacro,
                ProcMacroKind::Attr => MacroKind::Attr,
            },
        }
    }

    pub fn is_fn_like(&self, db: &dyn HirDatabase) -> bool {
        match self.kind(db) {
            MacroKind::Declarative | MacroKind::BuiltIn | MacroKind::ProcMacro => true,
            MacroKind::Attr | MacroKind::Derive => false,
        }
    }

    pub fn is_builtin_derive(&self, db: &dyn HirDatabase) -> bool {
        match self.id {
            MacroId::Macro2Id(it) => {
                matches!(it.lookup(db.upcast()).expander, MacroExpander::BuiltInDerive(_))
            }
            MacroId::MacroRulesId(it) => {
                matches!(it.lookup(db.upcast()).expander, MacroExpander::BuiltInDerive(_))
            }
            MacroId::ProcMacroId(_) => false,
        }
    }

    pub fn is_env_or_option_env(&self, db: &dyn HirDatabase) -> bool {
        match self.id {
            MacroId::Macro2Id(it) => {
                matches!(it.lookup(db.upcast()).expander, MacroExpander::BuiltInEager(eager) if eager.is_env_or_option_env())
            }
            MacroId::MacroRulesId(_) | MacroId::ProcMacroId(_) => false,
        }
    }

    pub fn is_attr(&self, db: &dyn HirDatabase) -> bool {
        matches!(self.kind(db), MacroKind::Attr)
    }

    pub fn is_derive(&self, db: &dyn HirDatabase) -> bool {
        matches!(self.kind(db), MacroKind::Derive)
    }
}

impl HasVisibility for Macro {
    fn visibility(&self, db: &dyn HirDatabase) -> Visibility {
        match self.id {
            MacroId::Macro2Id(id) => {
                let data = db.macro2_data(id);
                let visibility = &data.visibility;
                visibility.resolve(db.upcast(), &self.id.resolver(db.upcast()))
            }
            MacroId::MacroRulesId(_) => Visibility::Public,
            MacroId::ProcMacroId(_) => Visibility::Public,
        }
    }
}

#[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
pub enum ItemInNs {
    Types(ModuleDef),
    Values(ModuleDef),
    Macros(Macro),
}

impl From<Macro> for ItemInNs {
    fn from(it: Macro) -> Self {
        Self::Macros(it)
    }
}

impl From<ModuleDef> for ItemInNs {
    fn from(module_def: ModuleDef) -> Self {
        match module_def {
            ModuleDef::Static(_) | ModuleDef::Const(_) | ModuleDef::Function(_) => {
                ItemInNs::Values(module_def)
            }
            _ => ItemInNs::Types(module_def),
        }
    }
}

impl ItemInNs {
    pub fn as_module_def(self) -> Option<ModuleDef> {
        match self {
            ItemInNs::Types(id) | ItemInNs::Values(id) => Some(id),
            ItemInNs::Macros(_) => None,
        }
    }

    /// Returns the crate defining this item (or `None` if `self` is built-in).
    pub fn krate(&self, db: &dyn HirDatabase) -> Option<Crate> {
        match self {
            ItemInNs::Types(did) | ItemInNs::Values(did) => did.module(db).map(|m| m.krate()),
            ItemInNs::Macros(id) => Some(id.module(db).krate()),
        }
    }

    pub fn attrs(&self, db: &dyn HirDatabase) -> Option<AttrsWithOwner> {
        match self {
            ItemInNs::Types(it) | ItemInNs::Values(it) => it.attrs(db),
            ItemInNs::Macros(it) => Some(it.attrs(db)),
        }
    }
}

/// Invariant: `inner.as_extern_assoc_item(db).is_some()`
/// We do not actively enforce this invariant.
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
pub enum ExternAssocItem {
    Function(Function),
    Static(Static),
    TypeAlias(TypeAlias),
}

pub trait AsExternAssocItem {
    fn as_extern_assoc_item(self, db: &dyn HirDatabase) -> Option<ExternAssocItem>;
}

impl AsExternAssocItem for Function {
    fn as_extern_assoc_item(self, db: &dyn HirDatabase) -> Option<ExternAssocItem> {
        as_extern_assoc_item(db, ExternAssocItem::Function, self.id)
    }
}

impl AsExternAssocItem for Static {
    fn as_extern_assoc_item(self, db: &dyn HirDatabase) -> Option<ExternAssocItem> {
        as_extern_assoc_item(db, ExternAssocItem::Static, self.id)
    }
}

impl AsExternAssocItem for TypeAlias {
    fn as_extern_assoc_item(self, db: &dyn HirDatabase) -> Option<ExternAssocItem> {
        as_extern_assoc_item(db, ExternAssocItem::TypeAlias, self.id)
    }
}

/// 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, Clone)]
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,
        }
    }
}

impl AsAssocItem for DefWithBody {
    fn as_assoc_item(self, db: &dyn HirDatabase) -> Option<AssocItem> {
        match self {
            DefWithBody::Function(it) => it.as_assoc_item(db),
            DefWithBody::Const(it) => it.as_assoc_item(db),
            DefWithBody::Static(_) | DefWithBody::Variant(_) | DefWithBody::InTypeConst(_) => None,
        }
    }
}

fn as_assoc_item<'db, ID, DEF, LOC>(
    db: &(dyn HirDatabase + 'db),
    ctor: impl FnOnce(DEF) -> AssocItem,
    id: ID,
) -> Option<AssocItem>
where
    ID: Lookup<Database<'db> = dyn DefDatabase + 'db, Data = AssocItemLoc<LOC>>,
    DEF: From<ID>,
    LOC: ItemTreeNode,
{
    match id.lookup(db.upcast()).container {
        ItemContainerId::TraitId(_) | ItemContainerId::ImplId(_) => Some(ctor(DEF::from(id))),
        ItemContainerId::ModuleId(_) | ItemContainerId::ExternBlockId(_) => None,
    }
}

fn as_extern_assoc_item<'db, ID, DEF, LOC>(
    db: &(dyn HirDatabase + 'db),
    ctor: impl FnOnce(DEF) -> ExternAssocItem,
    id: ID,
) -> Option<ExternAssocItem>
where
    ID: Lookup<Database<'db> = dyn DefDatabase + 'db, Data = AssocItemLoc<LOC>>,
    DEF: From<ID>,
    LOC: ItemTreeNode,
{
    match id.lookup(db.upcast()).container {
        ItemContainerId::ExternBlockId(_) => Some(ctor(DEF::from(id))),
        ItemContainerId::TraitId(_) | ItemContainerId::ImplId(_) | ItemContainerId::ModuleId(_) => {
            None
        }
    }
}

impl ExternAssocItem {
    pub fn name(self, db: &dyn HirDatabase) -> Name {
        match self {
            Self::Function(it) => it.name(db),
            Self::Static(it) => it.name(db),
            Self::TypeAlias(it) => it.name(db),
        }
    }

    pub fn module(self, db: &dyn HirDatabase) -> Module {
        match self {
            Self::Function(f) => f.module(db),
            Self::Static(c) => c.module(db),
            Self::TypeAlias(t) => t.module(db),
        }
    }

    pub fn as_function(self) -> Option<Function> {
        match self {
            Self::Function(v) => Some(v),
            _ => None,
        }
    }

    pub fn as_static(self) -> Option<Static> {
        match self {
            Self::Static(v) => Some(v),
            _ => None,
        }
    }

    pub fn as_type_alias(self) -> Option<TypeAlias> {
        match self {
            Self::TypeAlias(v) => Some(v),
            _ => 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 {
            ItemContainerId::TraitId(id) => AssocItemContainer::Trait(id.into()),
            ItemContainerId::ImplId(id) => AssocItemContainer::Impl(id.into()),
            ItemContainerId::ModuleId(_) | ItemContainerId::ExternBlockId(_) => {
                panic!("invalid AssocItem")
            }
        }
    }

    pub fn container_trait(self, db: &dyn HirDatabase) -> Option<Trait> {
        match self.container(db) {
            AssocItemContainer::Trait(t) => Some(t),
            _ => None,
        }
    }

    pub fn implemented_trait(self, db: &dyn HirDatabase) -> Option<Trait> {
        match self.container(db) {
            AssocItemContainer::Impl(i) => i.trait_(db),
            _ => None,
        }
    }

    pub fn container_or_implemented_trait(self, db: &dyn HirDatabase) -> Option<Trait> {
        match self.container(db) {
            AssocItemContainer::Trait(t) => Some(t),
            AssocItemContainer::Impl(i) => i.trait_(db),
        }
    }

    pub fn implementing_ty(self, db: &dyn HirDatabase) -> Option<Type> {
        match self.container(db) {
            AssocItemContainer::Impl(i) => Some(i.self_ty(db)),
            _ => None,
        }
    }

    pub fn as_function(self) -> Option<Function> {
        match self {
            Self::Function(v) => Some(v),
            _ => None,
        }
    }

    pub fn as_const(self) -> Option<Const> {
        match self {
            Self::Const(v) => Some(v),
            _ => None,
        }
    }

    pub fn as_type_alias(self) -> Option<TypeAlias> {
        match self {
            Self::TypeAlias(v) => Some(v),
            _ => None,
        }
    }

    pub fn diagnostics(
        self,
        db: &dyn HirDatabase,
        acc: &mut Vec<AnyDiagnostic>,
        style_lints: bool,
    ) {
        match self {
            AssocItem::Function(func) => {
                DefWithBody::from(func).diagnostics(db, acc, style_lints);
            }
            AssocItem::Const(const_) => {
                DefWithBody::from(const_).diagnostics(db, acc, style_lints);
            }
            AssocItem::TypeAlias(type_alias) => {
                for diag in hir_ty::diagnostics::incorrect_case(db, type_alias.id.into()) {
                    acc.push(diag.into());
                }
            }
        }
    }
}

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),
        }
    }
}

impl From<AssocItem> for ModuleDef {
    fn from(assoc: AssocItem) -> Self {
        match assoc {
            AssocItem::Function(it) => ModuleDef::Function(it),
            AssocItem::Const(it) => ModuleDef::Const(it),
            AssocItem::TypeAlias(it) => ModuleDef::TypeAlias(it),
        }
    }
}

#[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
pub enum GenericDef {
    Function(Function),
    Adt(Adt),
    Trait(Trait),
    TraitAlias(TraitAlias),
    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,
    TraitAlias,
    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.type_or_consts.iter().map(|(local_id, _)| {
            let toc = TypeOrConstParam { id: TypeOrConstParamId { parent: self.into(), local_id } };
            match toc.split(db) {
                Either::Left(it) => GenericParam::ConstParam(it),
                Either::Right(it) => GenericParam::TypeParam(it),
            }
        });
        self.lifetime_params(db)
            .into_iter()
            .map(GenericParam::LifetimeParam)
            .chain(ty_params)
            .collect()
    }

    pub fn lifetime_params(self, db: &dyn HirDatabase) -> Vec<LifetimeParam> {
        let generics = db.generic_params(self.into());
        generics
            .lifetimes
            .iter()
            .map(|(local_id, _)| LifetimeParam {
                id: LifetimeParamId { parent: self.into(), local_id },
            })
            .collect()
    }

    pub fn type_or_const_params(self, db: &dyn HirDatabase) -> Vec<TypeOrConstParam> {
        let generics = db.generic_params(self.into());
        generics
            .type_or_consts
            .iter()
            .map(|(local_id, _)| TypeOrConstParam {
                id: TypeOrConstParamId { parent: self.into(), local_id },
            })
            .collect()
    }
}

/// A single local definition.
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
pub struct Local {
    pub(crate) parent: DefWithBodyId,
    pub(crate) binding_id: BindingId,
}

pub struct LocalSource {
    pub local: Local,
    pub source: InFile<Either<ast::IdentPat, ast::SelfParam>>,
}

impl LocalSource {
    pub fn as_ident_pat(&self) -> Option<&ast::IdentPat> {
        match &self.source.value {
            Either::Left(it) => Some(it),
            Either::Right(_) => None,
        }
    }

    pub fn into_ident_pat(self) -> Option<ast::IdentPat> {
        match self.source.value {
            Either::Left(it) => Some(it),
            Either::Right(_) => None,
        }
    }

    pub fn original_file(&self, db: &dyn HirDatabase) -> FileId {
        self.source.file_id.original_file(db.upcast())
    }

    pub fn file(&self) -> HirFileId {
        self.source.file_id
    }

    pub fn name(&self) -> Option<InFile<ast::Name>> {
        self.source.as_ref().map(|it| it.name()).transpose()
    }

    pub fn syntax(&self) -> &SyntaxNode {
        self.source.value.syntax()
    }

    pub fn syntax_ptr(self) -> InFile<SyntaxNodePtr> {
        self.source.map(|it| SyntaxNodePtr::new(it.syntax()))
    }
}

impl Local {
    pub fn is_param(self, db: &dyn HirDatabase) -> bool {
        // FIXME: This parses!
        let src = self.primary_source(db);
        match src.source.value {
            Either::Left(pat) => pat
                .syntax()
                .ancestors()
                .map(|it| it.kind())
                .take_while(|&kind| ast::Pat::can_cast(kind) || ast::Param::can_cast(kind))
                .any(ast::Param::can_cast),
            Either::Right(_) => true,
        }
    }

    pub fn as_self_param(self, db: &dyn HirDatabase) -> Option<SelfParam> {
        match self.parent {
            DefWithBodyId::FunctionId(func) if self.is_self(db) => Some(SelfParam { func }),
            _ => None,
        }
    }

    pub fn name(self, db: &dyn HirDatabase) -> Name {
        let body = db.body(self.parent);
        body[self.binding_id].name.clone()
    }

    pub fn is_self(self, db: &dyn HirDatabase) -> bool {
        self.name(db) == name![self]
    }

    pub fn is_mut(self, db: &dyn HirDatabase) -> bool {
        let body = db.body(self.parent);
        body[self.binding_id].mode == BindingAnnotation::Mutable
    }

    pub fn is_ref(self, db: &dyn HirDatabase) -> bool {
        let body = db.body(self.parent);
        matches!(body[self.binding_id].mode, BindingAnnotation::Ref | BindingAnnotation::RefMut)
    }

    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 = self.parent;
        let infer = db.infer(def);
        let ty = infer[self.binding_id].clone();
        Type::new(db, def, ty)
    }

    /// All definitions for this local. Example: `let (a$0, _) | (_, a$0) = it;`
    pub fn sources(self, db: &dyn HirDatabase) -> Vec<LocalSource> {
        let (body, source_map) = db.body_with_source_map(self.parent);
        match body.self_param.zip(source_map.self_param_syntax()) {
            Some((param, source)) if param == self.binding_id => {
                let root = source.file_syntax(db.upcast());
                vec![LocalSource {
                    local: self,
                    source: source.map(|ast| Either::Right(ast.to_node(&root))),
                }]
            }
            _ => body[self.binding_id]
                .definitions
                .iter()
                .map(|&definition| {
                    let src = source_map.pat_syntax(definition).unwrap(); // Hmm...
                    let root = src.file_syntax(db.upcast());
                    LocalSource {
                        local: self,
                        source: src.map(|ast| match ast.to_node(&root) {
                            ast::Pat::IdentPat(it) => Either::Left(it),
                            _ => unreachable!("local with non ident-pattern"),
                        }),
                    }
                })
                .collect(),
        }
    }

    /// The leftmost definition for this local. Example: `let (a$0, _) | (_, a) = it;`
    pub fn primary_source(self, db: &dyn HirDatabase) -> LocalSource {
        let (body, source_map) = db.body_with_source_map(self.parent);
        match body.self_param.zip(source_map.self_param_syntax()) {
            Some((param, source)) if param == self.binding_id => {
                let root = source.file_syntax(db.upcast());
                LocalSource {
                    local: self,
                    source: source.map(|ast| Either::Right(ast.to_node(&root))),
                }
            }
            _ => body[self.binding_id]
                .definitions
                .first()
                .map(|&definition| {
                    let src = source_map.pat_syntax(definition).unwrap(); // Hmm...
                    let root = src.file_syntax(db.upcast());
                    LocalSource {
                        local: self,
                        source: src.map(|ast| match ast.to_node(&root) {
                            ast::Pat::IdentPat(it) => Either::Left(it),
                            _ => unreachable!("local with non ident-pattern"),
                        }),
                    }
                })
                .unwrap(),
        }
    }
}

#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
pub struct DeriveHelper {
    pub(crate) derive: MacroId,
    pub(crate) idx: u32,
}

impl DeriveHelper {
    pub fn derive(&self) -> Macro {
        Macro { id: self.derive }
    }

    pub fn name(&self, db: &dyn HirDatabase) -> Name {
        match self.derive {
            MacroId::Macro2Id(it) => db
                .macro2_data(it)
                .helpers
                .as_deref()
                .and_then(|it| it.get(self.idx as usize))
                .cloned(),
            MacroId::MacroRulesId(_) => None,
            MacroId::ProcMacroId(proc_macro) => db
                .proc_macro_data(proc_macro)
                .helpers
                .as_deref()
                .and_then(|it| it.get(self.idx as usize))
                .cloned(),
        }
        .unwrap_or_else(Name::missing)
    }
}

// FIXME: Wrong name? This is could also be a registered attribute
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
pub struct BuiltinAttr {
    krate: Option<CrateId>,
    idx: u32,
}

impl BuiltinAttr {
    // FIXME: consider crates\hir_def\src\nameres\attr_resolution.rs?
    pub(crate) fn by_name(db: &dyn HirDatabase, krate: Crate, name: &str) -> Option<Self> {
        if let builtin @ Some(_) = Self::builtin(name) {
            return builtin;
        }
        let idx =
            db.crate_def_map(krate.id).registered_attrs().iter().position(|it| it == name)? as u32;
        Some(BuiltinAttr { krate: Some(krate.id), idx })
    }

    fn builtin(name: &str) -> Option<Self> {
        hir_def::attr::builtin::find_builtin_attr_idx(name)
            .map(|idx| BuiltinAttr { krate: None, idx: idx as u32 })
    }

    pub fn name(&self, db: &dyn HirDatabase) -> SmolStr {
        // FIXME: Return a `Name` here
        match self.krate {
            Some(krate) => db.crate_def_map(krate).registered_attrs()[self.idx as usize].clone(),
            None => SmolStr::new(hir_def::attr::builtin::INERT_ATTRIBUTES[self.idx as usize].name),
        }
    }

    pub fn template(&self, _: &dyn HirDatabase) -> Option<AttributeTemplate> {
        match self.krate {
            Some(_) => None,
            None => Some(hir_def::attr::builtin::INERT_ATTRIBUTES[self.idx as usize].template),
        }
    }
}

#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
pub struct ToolModule {
    krate: Option<CrateId>,
    idx: u32,
}

impl ToolModule {
    // FIXME: consider crates\hir_def\src\nameres\attr_resolution.rs?
    pub(crate) fn by_name(db: &dyn HirDatabase, krate: Crate, name: &str) -> Option<Self> {
        if let builtin @ Some(_) = Self::builtin(name) {
            return builtin;
        }
        let idx =
            db.crate_def_map(krate.id).registered_tools().iter().position(|it| it == name)? as u32;
        Some(ToolModule { krate: Some(krate.id), idx })
    }

    fn builtin(name: &str) -> Option<Self> {
        hir_def::attr::builtin::TOOL_MODULES
            .iter()
            .position(|&tool| tool == name)
            .map(|idx| ToolModule { krate: None, idx: idx as u32 })
    }

    pub fn name(&self, db: &dyn HirDatabase) -> SmolStr {
        // FIXME: Return a `Name` here
        match self.krate {
            Some(krate) => db.crate_def_map(krate).registered_tools()[self.idx as usize].clone(),
            None => SmolStr::new(hir_def::attr::builtin::TOOL_MODULES[self.idx as usize]),
        }
    }
}

#[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);
        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);
        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),
    ConstParam(ConstParam),
    LifetimeParam(LifetimeParam),
}
impl_from!(TypeParam, ConstParam, LifetimeParam for GenericParam);

impl GenericParam {
    pub fn module(self, db: &dyn HirDatabase) -> Module {
        match self {
            GenericParam::TypeParam(it) => it.module(db),
            GenericParam::ConstParam(it) => it.module(db),
            GenericParam::LifetimeParam(it) => it.module(db),
        }
    }

    pub fn name(self, db: &dyn HirDatabase) -> Name {
        match self {
            GenericParam::TypeParam(it) => it.name(db),
            GenericParam::ConstParam(it) => it.name(db),
            GenericParam::LifetimeParam(it) => it.name(db),
        }
    }

    pub fn parent(self) -> GenericDef {
        match self {
            GenericParam::TypeParam(it) => it.id.parent().into(),
            GenericParam::ConstParam(it) => it.id.parent().into(),
            GenericParam::LifetimeParam(it) => it.id.parent.into(),
        }
    }
}

#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
pub struct TypeParam {
    pub(crate) id: TypeParamId,
}

impl TypeParam {
    pub fn merge(self) -> TypeOrConstParam {
        TypeOrConstParam { id: self.id.into() }
    }

    pub fn name(self, db: &dyn HirDatabase) -> Name {
        self.merge().name(db)
    }

    pub fn module(self, db: &dyn HirDatabase) -> Module {
        self.id.parent().module(db.upcast()).into()
    }

    /// Is this type parameter implicitly introduced (eg. `Self` in a trait or an `impl Trait`
    /// argument)?
    pub fn is_implicit(self, db: &dyn HirDatabase) -> bool {
        let params = db.generic_params(self.id.parent());
        let data = &params.type_or_consts[self.id.local_id()];
        match data.type_param().unwrap().provenance {
            hir_def::generics::TypeParamProvenance::TypeParamList => false,
            hir_def::generics::TypeParamProvenance::TraitSelf
            | hir_def::generics::TypeParamProvenance::ArgumentImplTrait => true,
        }
    }

    pub fn ty(self, db: &dyn HirDatabase) -> Type {
        let resolver = self.id.parent().resolver(db.upcast());
        let ty =
            TyKind::Placeholder(hir_ty::to_placeholder_idx(db, self.id.into())).intern(Interner);
        Type::new_with_resolver_inner(db, &resolver, ty)
    }

    /// FIXME: this only lists trait bounds from the item defining the type
    /// parameter, not additional bounds that might be added e.g. by a method if
    /// the parameter comes from an impl!
    pub fn trait_bounds(self, db: &dyn HirDatabase) -> Vec<Trait> {
        db.generic_predicates_for_param(self.id.parent(), self.id.into(), None)
            .iter()
            .filter_map(|pred| match &pred.skip_binders().skip_binders() {
                hir_ty::WhereClause::Implemented(trait_ref) => {
                    Some(Trait::from(trait_ref.hir_trait_id()))
                }
                _ => None,
            })
            .collect()
    }

    pub fn default(self, db: &dyn HirDatabase) -> Option<Type> {
        let ty = generic_arg_from_param(db, self.id.into())?;
        let resolver = self.id.parent().resolver(db.upcast());
        match ty.data(Interner) {
            GenericArgData::Ty(it) if *it.kind(Interner) != TyKind::Error => {
                Some(Type::new_with_resolver_inner(db, &resolver, it.clone()))
            }
            _ => None,
        }
    }

    pub fn is_unstable(self, db: &dyn HirDatabase) -> bool {
        db.attrs(GenericParamId::from(self.id).into()).is_unstable()
    }
}

#[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 merge(self) -> TypeOrConstParam {
        TypeOrConstParam { id: self.id.into() }
    }

    pub fn name(self, db: &dyn HirDatabase) -> Name {
        let params = db.generic_params(self.id.parent());
        match params.type_or_consts[self.id.local_id()].name() {
            Some(it) => it.clone(),
            None => {
                never!();
                Name::missing()
            }
        }
    }

    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 {
        Type::new(db, self.id.parent(), db.const_param_ty(self.id))
    }

    pub fn default(self, db: &dyn HirDatabase) -> Option<ast::ConstArg> {
        let arg = generic_arg_from_param(db, self.id.into())?;
        known_const_to_ast(arg.constant(Interner)?, db)
    }
}

fn generic_arg_from_param(db: &dyn HirDatabase, id: TypeOrConstParamId) -> Option<GenericArg> {
    let params = db.generic_defaults(id.parent);
    let local_idx = hir_ty::param_idx(db, id)?;
    let ty = params.get(local_idx)?.clone();
    let subst = TyBuilder::placeholder_subst(db, id.parent);
    Some(ty.substitute(Interner, &subst))
}

#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
pub struct TypeOrConstParam {
    pub(crate) id: TypeOrConstParamId,
}

impl TypeOrConstParam {
    pub fn name(self, db: &dyn HirDatabase) -> Name {
        let params = db.generic_params(self.id.parent);
        match params.type_or_consts[self.id.local_id].name() {
            Some(n) => n.clone(),
            _ => Name::missing(),
        }
    }

    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 split(self, db: &dyn HirDatabase) -> Either<ConstParam, TypeParam> {
        let params = db.generic_params(self.id.parent);
        match &params.type_or_consts[self.id.local_id] {
            hir_def::generics::TypeOrConstParamData::TypeParamData(_) => {
                Either::Right(TypeParam { id: TypeParamId::from_unchecked(self.id) })
            }
            hir_def::generics::TypeOrConstParamData::ConstParamData(_) => {
                Either::Left(ConstParam { id: ConstParamId::from_unchecked(self.id) })
            }
        }
    }

    pub fn ty(self, db: &dyn HirDatabase) -> Type {
        match self.split(db) {
            Either::Left(it) => it.ty(db),
            Either::Right(it) => it.ty(db),
        }
    }

    pub fn as_type_param(self, db: &dyn HirDatabase) -> Option<TypeParam> {
        let params = db.generic_params(self.id.parent);
        match &params.type_or_consts[self.id.local_id] {
            hir_def::generics::TypeOrConstParamData::TypeParamData(_) => {
                Some(TypeParam { id: TypeParamId::from_unchecked(self.id) })
            }
            hir_def::generics::TypeOrConstParamData::ConstParamData(_) => None,
        }
    }

    pub fn as_const_param(self, db: &dyn HirDatabase) -> Option<ConstParam> {
        let params = db.generic_params(self.id.parent);
        match &params.type_or_consts[self.id.local_id] {
            hir_def::generics::TypeOrConstParamData::TypeParamData(_) => None,
            hir_def::generics::TypeOrConstParamData::ConstParamData(_) => {
                Some(ConstParam { id: ConstParamId::from_unchecked(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 all_for_type(db: &dyn HirDatabase, Type { ty, env }: Type) -> Vec<Impl> {
        let def_crates = match method_resolution::def_crates(db, &ty, env.krate) {
            Some(def_crates) => def_crates,
            None => return Vec::new(),
        };

        let filter = |impl_def: &Impl| {
            let self_ty = impl_def.self_ty(db);
            let rref = self_ty.remove_ref();
            ty.equals_ctor(rref.as_ref().map_or(&self_ty.ty, |it| &it.ty))
        };

        let fp = TyFingerprint::for_inherent_impl(&ty);
        let fp = match fp {
            Some(fp) => fp,
            None => return Vec::new(),
        };

        let mut all = Vec::new();
        def_crates.iter().for_each(|&id| {
            all.extend(
                db.inherent_impls_in_crate(id)
                    .for_self_ty(&ty)
                    .iter()
                    .cloned()
                    .map(Self::from)
                    .filter(filter),
            )
        });

        for id in def_crates
            .iter()
            .flat_map(|&id| Crate { id }.transitive_reverse_dependencies(db))
            .map(|Crate { id }| id)
        {
            all.extend(
                db.trait_impls_in_crate(id)
                    .for_self_ty_without_blanket_impls(fp)
                    .map(Self::from)
                    .filter(filter),
            );
        }

        if let Some(block) =
            ty.adt_id(Interner).and_then(|def| def.0.module(db.upcast()).containing_block())
        {
            if let Some(inherent_impls) = db.inherent_impls_in_block(block) {
                all.extend(
                    inherent_impls.for_self_ty(&ty).iter().cloned().map(Self::from).filter(filter),
                );
            }
            if let Some(trait_impls) = db.trait_impls_in_block(block) {
                all.extend(
                    trait_impls
                        .for_self_ty_without_blanket_impls(fp)
                        .map(Self::from)
                        .filter(filter),
                );
            }
        }

        all
    }

    pub fn all_for_trait(db: &dyn HirDatabase, trait_: Trait) -> Vec<Impl> {
        let module = trait_.module(db);
        let krate = module.krate();
        let mut all = Vec::new();
        for Crate { id } in krate.transitive_reverse_dependencies(db) {
            let impls = db.trait_impls_in_crate(id);
            all.extend(impls.for_trait(trait_.id).map(Self::from))
        }
        if let Some(block) = module.id.containing_block() {
            if let Some(trait_impls) = db.trait_impls_in_block(block) {
                all.extend(trait_impls.for_trait(trait_.id).map(Self::from));
            }
        }
        all
    }

    pub fn trait_(self, db: &dyn HirDatabase) -> Option<Trait> {
        let trait_ref = db.impl_trait(self.id)?;
        let id = trait_ref.skip_binders().hir_trait_id();
        Some(Trait { id })
    }

    pub fn trait_ref(self, db: &dyn HirDatabase) -> Option<TraitRef> {
        let substs = TyBuilder::placeholder_subst(db, self.id);
        let trait_ref = db.impl_trait(self.id)?.substitute(Interner, &substs);
        let resolver = self.id.resolver(db.upcast());
        Some(TraitRef::new_with_resolver(db, &resolver, trait_ref))
    }

    pub fn self_ty(self, db: &dyn HirDatabase) -> Type {
        let resolver = self.id.resolver(db.upcast());
        let substs = TyBuilder::placeholder_subst(db, self.id);
        let ty = db.impl_self_ty(self.id).substitute(Interner, &substs);
        Type::new_with_resolver_inner(db, &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 is_unsafe(self, db: &dyn HirDatabase) -> bool {
        db.impl_data(self.id).is_unsafe
    }

    pub fn module(self, db: &dyn HirDatabase) -> Module {
        self.id.lookup(db.upcast()).container.into()
    }

    pub fn as_builtin_derive_path(self, db: &dyn HirDatabase) -> Option<InMacroFile<ast::Path>> {
        let src = self.source(db)?;

        let macro_file = src.file_id.macro_file()?;
        let loc = macro_file.macro_call_id.lookup(db.upcast());
        let (derive_attr, derive_index) = match loc.kind {
            MacroCallKind::Derive { ast_id, derive_attr_index, derive_index } => {
                let module_id = self.id.lookup(db.upcast()).container;
                (
                    db.crate_def_map(module_id.krate())[module_id.local_id]
                        .scope
                        .derive_macro_invoc(ast_id, derive_attr_index)?,
                    derive_index,
                )
            }
            _ => return None,
        };
        let file_id = MacroFileId { macro_call_id: derive_attr };
        let path = db
            .parse_macro_expansion(file_id)
            .value
            .0
            .syntax_node()
            .children()
            .nth(derive_index as usize)
            .and_then(<ast::Attr as AstNode>::cast)
            .and_then(|it| it.path())?;
        Some(InMacroFile { file_id, value: path })
    }

    pub fn check_orphan_rules(self, db: &dyn HirDatabase) -> bool {
        check_orphan_rules(db, self.id)
    }
}

#[derive(Clone, PartialEq, Eq, Debug, Hash)]
pub struct TraitRef {
    env: Arc<TraitEnvironment>,
    trait_ref: hir_ty::TraitRef,
}

impl TraitRef {
    pub(crate) fn new_with_resolver(
        db: &dyn HirDatabase,
        resolver: &Resolver,
        trait_ref: hir_ty::TraitRef,
    ) -> TraitRef {
        let env = resolver
            .generic_def()
            .map_or_else(|| TraitEnvironment::empty(resolver.krate()), |d| db.trait_environment(d));
        TraitRef { env, trait_ref }
    }

    pub fn trait_(&self) -> Trait {
        let id = self.trait_ref.hir_trait_id();
        Trait { id }
    }

    pub fn self_ty(&self) -> Type {
        let ty = self.trait_ref.self_type_parameter(Interner);
        Type { env: self.env.clone(), ty }
    }

    /// Returns `idx`-th argument of this trait reference if it is a type argument. Note that the
    /// first argument is the `Self` type.
    pub fn get_type_argument(&self, idx: usize) -> Option<Type> {
        self.trait_ref
            .substitution
            .as_slice(Interner)
            .get(idx)
            .and_then(|arg| arg.ty(Interner))
            .cloned()
            .map(|ty| Type { env: self.env.clone(), ty })
    }
}

#[derive(Clone, Debug, PartialEq, Eq, Hash)]
pub struct Closure {
    id: ClosureId,
    subst: Substitution,
}

impl From<Closure> for ClosureId {
    fn from(value: Closure) -> Self {
        value.id
    }
}

impl Closure {
    fn as_ty(self) -> Ty {
        TyKind::Closure(self.id, self.subst).intern(Interner)
    }

    pub fn display_with_id(&self, db: &dyn HirDatabase) -> String {
        self.clone().as_ty().display(db).with_closure_style(ClosureStyle::ClosureWithId).to_string()
    }

    pub fn display_with_impl(&self, db: &dyn HirDatabase) -> String {
        self.clone().as_ty().display(db).with_closure_style(ClosureStyle::ImplFn).to_string()
    }

    pub fn captured_items(&self, db: &dyn HirDatabase) -> Vec<ClosureCapture> {
        let owner = db.lookup_intern_closure((self.id).into()).0;
        let infer = &db.infer(owner);
        let info = infer.closure_info(&self.id);
        info.0
            .iter()
            .cloned()
            .map(|capture| ClosureCapture { owner, closure: self.id, capture })
            .collect()
    }

    pub fn capture_types(&self, db: &dyn HirDatabase) -> Vec<Type> {
        let owner = db.lookup_intern_closure((self.id).into()).0;
        let infer = &db.infer(owner);
        let (captures, _) = infer.closure_info(&self.id);
        captures
            .iter()
            .map(|capture| Type {
                env: db.trait_environment_for_body(owner),
                ty: capture.ty(&self.subst),
            })
            .collect()
    }

    pub fn fn_trait(&self, db: &dyn HirDatabase) -> FnTrait {
        let owner = db.lookup_intern_closure((self.id).into()).0;
        let infer = &db.infer(owner);
        let info = infer.closure_info(&self.id);
        info.1
    }
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct ClosureCapture {
    owner: DefWithBodyId,
    closure: ClosureId,
    capture: hir_ty::CapturedItem,
}

impl ClosureCapture {
    pub fn local(&self) -> Local {
        Local { parent: self.owner, binding_id: self.capture.local() }
    }

    pub fn kind(&self) -> CaptureKind {
        match self.capture.kind() {
            hir_ty::CaptureKind::ByRef(
                hir_ty::mir::BorrowKind::Shallow | hir_ty::mir::BorrowKind::Shared,
            ) => CaptureKind::SharedRef,
            hir_ty::CaptureKind::ByRef(hir_ty::mir::BorrowKind::Mut {
                kind: MutBorrowKind::ClosureCapture,
            }) => CaptureKind::UniqueSharedRef,
            hir_ty::CaptureKind::ByRef(hir_ty::mir::BorrowKind::Mut {
                kind: MutBorrowKind::Default | MutBorrowKind::TwoPhasedBorrow,
            }) => CaptureKind::MutableRef,
            hir_ty::CaptureKind::ByValue => CaptureKind::Move,
        }
    }

    pub fn display_place(&self, db: &dyn HirDatabase) -> String {
        self.capture.display_place(self.owner, db)
    }
}

pub enum CaptureKind {
    SharedRef,
    UniqueSharedRef,
    MutableRef,
    Move,
}

#[derive(Clone, PartialEq, Eq, Debug, Hash)]
pub struct Type {
    env: Arc<TraitEnvironment>,
    ty: Ty,
}

impl Type {
    pub(crate) fn new_with_resolver(db: &dyn HirDatabase, resolver: &Resolver, ty: Ty) -> Type {
        Type::new_with_resolver_inner(db, resolver, ty)
    }

    pub(crate) fn new_with_resolver_inner(
        db: &dyn HirDatabase,
        resolver: &Resolver,
        ty: Ty,
    ) -> Type {
        let environment = resolver
            .generic_def()
            .map_or_else(|| TraitEnvironment::empty(resolver.krate()), |d| db.trait_environment(d));
        Type { env: environment, ty }
    }

    pub(crate) fn new_for_crate(krate: CrateId, ty: Ty) -> Type {
        Type { env: TraitEnvironment::empty(krate), ty }
    }

    pub fn reference(inner: &Type, m: Mutability) -> Type {
        inner.derived(
            TyKind::Ref(
                if m.is_mut() { hir_ty::Mutability::Mut } else { hir_ty::Mutability::Not },
                hir_ty::static_lifetime(),
                inner.ty.clone(),
            )
            .intern(Interner),
        )
    }

    fn new(db: &dyn HirDatabase, lexical_env: impl HasResolver, ty: Ty) -> Type {
        let resolver = lexical_env.resolver(db.upcast());
        let environment = resolver
            .generic_def()
            .map_or_else(|| TraitEnvironment::empty(resolver.krate()), |d| db.trait_environment(d));
        Type { env: environment, ty }
    }

    fn from_def(db: &dyn HirDatabase, def: impl Into<TyDefId> + HasResolver) -> Type {
        let ty = db.ty(def.into());
        let substs = TyBuilder::unknown_subst(
            db,
            match def.into() {
                TyDefId::AdtId(it) => GenericDefId::AdtId(it),
                TyDefId::TypeAliasId(it) => GenericDefId::TypeAliasId(it),
                TyDefId::BuiltinType(_) => return Type::new(db, def, ty.skip_binders().clone()),
            },
        );
        Type::new(db, def, ty.substitute(Interner, &substs))
    }

    fn from_value_def(db: &dyn HirDatabase, def: impl Into<ValueTyDefId> + HasResolver) -> Type {
        let Some(ty) = db.value_ty(def.into()) else {
            return Type::new(db, def, TyKind::Error.intern(Interner));
        };
        let substs = TyBuilder::unknown_subst(
            db,
            match def.into() {
                ValueTyDefId::ConstId(it) => GenericDefId::ConstId(it),
                ValueTyDefId::FunctionId(it) => GenericDefId::FunctionId(it),
                ValueTyDefId::StructId(it) => GenericDefId::AdtId(AdtId::StructId(it)),
                ValueTyDefId::UnionId(it) => GenericDefId::AdtId(AdtId::UnionId(it)),
                ValueTyDefId::EnumVariantId(it) => GenericDefId::EnumVariantId(it),
                ValueTyDefId::StaticId(_) => return Type::new(db, def, ty.skip_binders().clone()),
            },
        );
        Type::new(db, def, ty.substitute(Interner, &substs))
    }

    pub fn new_slice(ty: Type) -> Type {
        Type { env: ty.env, ty: TyBuilder::slice(ty.ty) }
    }

    pub fn new_tuple(krate: CrateId, tys: &[Type]) -> Type {
        let tys = tys.iter().map(|it| it.ty.clone());
        Type { env: TraitEnvironment::empty(krate), ty: TyBuilder::tuple_with(tys) }
    }

    pub fn is_unit(&self) -> bool {
        matches!(self.ty.kind(Interner), TyKind::Tuple(0, ..))
    }

    pub fn is_bool(&self) -> bool {
        matches!(self.ty.kind(Interner), TyKind::Scalar(Scalar::Bool))
    }

    pub fn is_never(&self) -> bool {
        matches!(self.ty.kind(Interner), TyKind::Never)
    }

    pub fn is_mutable_reference(&self) -> bool {
        matches!(self.ty.kind(Interner), TyKind::Ref(hir_ty::Mutability::Mut, ..))
    }

    pub fn is_reference(&self) -> bool {
        matches!(self.ty.kind(Interner), TyKind::Ref(..))
    }

    pub fn contains_reference(&self, db: &dyn HirDatabase) -> bool {
        return go(db, self.env.krate, &self.ty);

        fn go(db: &dyn HirDatabase, krate: CrateId, ty: &Ty) -> bool {
            match ty.kind(Interner) {
                // Reference itself
                TyKind::Ref(_, _, _) => true,

                // For non-phantom_data adts we check variants/fields as well as generic parameters
                TyKind::Adt(adt_id, substitution)
                    if !db.adt_datum(krate, *adt_id).flags.phantom_data =>
                {
                    let adt_datum = &db.adt_datum(krate, *adt_id);
                    let adt_datum_bound =
                        adt_datum.binders.clone().substitute(Interner, substitution);
                    adt_datum_bound
                        .variants
                        .into_iter()
                        .flat_map(|variant| variant.fields.into_iter())
                        .any(|ty| go(db, krate, &ty))
                        || substitution
                            .iter(Interner)
                            .filter_map(|x| x.ty(Interner))
                            .any(|ty| go(db, krate, ty))
                }
                // And for `PhantomData<T>`, we check `T`.
                TyKind::Adt(_, substitution)
                | TyKind::Tuple(_, substitution)
                | TyKind::OpaqueType(_, substitution)
                | TyKind::AssociatedType(_, substitution)
                | TyKind::FnDef(_, substitution) => substitution
                    .iter(Interner)
                    .filter_map(|x| x.ty(Interner))
                    .any(|ty| go(db, krate, ty)),

                // For `[T]` or `*T` we check `T`
                TyKind::Array(ty, _) | TyKind::Slice(ty) | TyKind::Raw(_, ty) => go(db, krate, ty),

                // Consider everything else as not reference
                _ => false,
            }
        }
    }

    pub fn as_reference(&self) -> Option<(Type, Mutability)> {
        let (ty, _lt, m) = self.ty.as_reference()?;
        let m = Mutability::from_mutable(matches!(m, hir_ty::Mutability::Mut));
        Some((self.derived(ty.clone()), m))
    }

    pub fn is_slice(&self) -> bool {
        matches!(self.ty.kind(Interner), TyKind::Slice(..))
    }

    pub fn is_usize(&self) -> bool {
        matches!(self.ty.kind(Interner), TyKind::Scalar(Scalar::Uint(UintTy::Usize)))
    }

    pub fn is_float(&self) -> bool {
        matches!(self.ty.kind(Interner), TyKind::Scalar(Scalar::Float(_)))
    }

    pub fn is_char(&self) -> bool {
        matches!(self.ty.kind(Interner), TyKind::Scalar(Scalar::Char))
    }

    pub fn is_int_or_uint(&self) -> bool {
        matches!(self.ty.kind(Interner), TyKind::Scalar(Scalar::Int(_) | Scalar::Uint(_)))
    }

    pub fn is_scalar(&self) -> bool {
        matches!(self.ty.kind(Interner), TyKind::Scalar(_))
    }

    pub fn is_tuple(&self) -> bool {
        matches!(self.ty.kind(Interner), TyKind::Tuple(..))
    }

    pub fn remove_ref(&self) -> Option<Type> {
        match &self.ty.kind(Interner) {
            TyKind::Ref(.., ty) => Some(self.derived(ty.clone())),
            _ => None,
        }
    }

    pub fn as_slice(&self) -> Option<Type> {
        match &self.ty.kind(Interner) {
            TyKind::Slice(ty) => Some(self.derived(ty.clone())),
            _ => None,
        }
    }

    pub fn strip_references(&self) -> Type {
        self.derived(self.ty.strip_references().clone())
    }

    pub fn strip_reference(&self) -> Type {
        self.derived(self.ty.strip_reference().clone())
    }

    pub fn is_unknown(&self) -> bool {
        self.ty.is_unknown()
    }

    /// Checks that particular type `ty` implements `std::future::IntoFuture` or
    /// `std::future::Future`.
    /// This function is used in `.await` syntax completion.
    pub fn impls_into_future(&self, db: &dyn HirDatabase) -> bool {
        let trait_ = db
            .lang_item(self.env.krate, LangItem::IntoFutureIntoFuture)
            .and_then(|it| {
                let into_future_fn = it.as_function()?;
                let assoc_item = as_assoc_item(db, AssocItem::Function, into_future_fn)?;
                let into_future_trait = assoc_item.container_or_implemented_trait(db)?;
                Some(into_future_trait.id)
            })
            .or_else(|| {
                let future_trait = db.lang_item(self.env.krate, LangItem::Future)?;
                future_trait.as_trait()
            });

        let trait_ = match trait_ {
            Some(it) => it,
            None => return false,
        };

        let canonical_ty =
            Canonical { value: self.ty.clone(), binders: CanonicalVarKinds::empty(Interner) };
        method_resolution::implements_trait(&canonical_ty, db, &self.env, 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 fnonce_trait = match FnTrait::FnOnce.get_id(db, self.env.krate) {
            Some(it) => it,
            None => return false,
        };

        let canonical_ty =
            Canonical { value: self.ty.clone(), binders: CanonicalVarKinds::empty(Interner) };
        method_resolution::implements_trait_unique(&canonical_ty, db, &self.env, fnonce_trait)
    }

    // FIXME: Find better API that also handles const generics
    pub fn impls_trait(&self, db: &dyn HirDatabase, trait_: Trait, args: &[Type]) -> bool {
        let mut it = args.iter().map(|t| t.ty.clone());
        let trait_ref = TyBuilder::trait_ref(db, trait_.id)
            .push(self.ty.clone())
            .fill(|x| {
                match x {
                    ParamKind::Type => {
                        it.next().unwrap_or_else(|| TyKind::Error.intern(Interner)).cast(Interner)
                    }
                    ParamKind::Const(ty) => {
                        // FIXME: this code is not covered in tests.
                        unknown_const_as_generic(ty.clone())
                    }
                }
            })
            .build();

        let goal = Canonical {
            value: hir_ty::InEnvironment::new(&self.env.env, trait_ref.cast(Interner)),
            binders: CanonicalVarKinds::empty(Interner),
        };

        db.trait_solve(self.env.krate, self.env.block, goal).is_some()
    }

    pub fn normalize_trait_assoc_type(
        &self,
        db: &dyn HirDatabase,
        args: &[Type],
        alias: TypeAlias,
    ) -> Option<Type> {
        let mut args = args.iter();
        let trait_id = match alias.id.lookup(db.upcast()).container {
            ItemContainerId::TraitId(id) => id,
            _ => unreachable!("non assoc type alias reached in normalize_trait_assoc_type()"),
        };
        let parent_subst = TyBuilder::subst_for_def(db, trait_id, None)
            .push(self.ty.clone())
            .fill(|it| {
                // FIXME: this code is not covered in tests.
                match it {
                    ParamKind::Type => args.next().unwrap().ty.clone().cast(Interner),
                    ParamKind::Const(ty) => unknown_const_as_generic(ty.clone()),
                }
            })
            .build();
        // FIXME: We don't handle GATs yet.
        let projection = TyBuilder::assoc_type_projection(db, alias.id, Some(parent_subst)).build();

        let ty = db.normalize_projection(projection, self.env.clone());
        if ty.is_unknown() {
            None
        } else {
            Some(self.derived(ty))
        }
    }

    pub fn is_copy(&self, db: &dyn HirDatabase) -> bool {
        let lang_item = db.lang_item(self.env.krate, LangItem::Copy);
        let copy_trait = match lang_item {
            Some(LangItemTarget::Trait(it)) => it,
            _ => return false,
        };
        self.impls_trait(db, copy_trait.into(), &[])
    }

    pub fn as_callable(&self, db: &dyn HirDatabase) -> Option<Callable> {
        let mut the_ty = &self.ty;
        let callee = match self.ty.kind(Interner) {
            TyKind::Ref(_, _, ty) if ty.as_closure().is_some() => {
                the_ty = ty;
                Callee::Closure(ty.as_closure().unwrap())
            }
            TyKind::Closure(id, _) => Callee::Closure(*id),
            TyKind::Function(_) => Callee::FnPtr,
            TyKind::FnDef(..) => Callee::Def(self.ty.callable_def(db)?),
            _ => {
                let sig = hir_ty::callable_sig_from_fnonce(&self.ty, self.env.clone(), db)?;
                return Some(Callable {
                    ty: self.clone(),
                    sig,
                    callee: Callee::Other,
                    is_bound_method: false,
                });
            }
        };

        let sig = the_ty.callable_sig(db)?;
        Some(Callable { ty: self.clone(), sig, callee, is_bound_method: false })
    }

    pub fn is_closure(&self) -> bool {
        matches!(self.ty.kind(Interner), TyKind::Closure { .. })
    }

    pub fn as_closure(&self) -> Option<Closure> {
        match self.ty.kind(Interner) {
            TyKind::Closure(id, subst) => Some(Closure { id: *id, subst: subst.clone() }),
            _ => None,
        }
    }

    pub fn is_fn(&self) -> bool {
        matches!(self.ty.kind(Interner), TyKind::FnDef(..) | TyKind::Function { .. })
    }

    pub fn is_array(&self) -> bool {
        matches!(self.ty.kind(Interner), TyKind::Array(..))
    }

    pub fn is_packed(&self, db: &dyn HirDatabase) -> bool {
        let adt_id = match *self.ty.kind(Interner) {
            TyKind::Adt(hir_ty::AdtId(adt_id), ..) => adt_id,
            _ => return false,
        };

        let adt = adt_id.into();
        match adt {
            Adt::Struct(s) => s.repr(db).unwrap_or_default().pack.is_some(),
            _ => false,
        }
    }

    pub fn is_raw_ptr(&self) -> bool {
        matches!(self.ty.kind(Interner), TyKind::Raw(..))
    }

    pub fn remove_raw_ptr(&self) -> Option<Type> {
        if let TyKind::Raw(_, ty) = self.ty.kind(Interner) {
            Some(self.derived(ty.clone()))
        } else {
            None
        }
    }

    pub fn contains_unknown(&self) -> bool {
        // FIXME: When we get rid of `ConstScalar::Unknown`, we can just look at precomputed
        // `TypeFlags` in `TyData`.
        return go(&self.ty);

        fn go(ty: &Ty) -> bool {
            match ty.kind(Interner) {
                TyKind::Error => true,

                TyKind::Adt(_, substs)
                | TyKind::AssociatedType(_, substs)
                | TyKind::Tuple(_, substs)
                | TyKind::OpaqueType(_, substs)
                | TyKind::FnDef(_, substs)
                | TyKind::Closure(_, substs) => {
                    substs.iter(Interner).filter_map(|a| a.ty(Interner)).any(go)
                }

                TyKind::Array(_ty, len) if len.is_unknown() => true,
                TyKind::Array(ty, _)
                | TyKind::Slice(ty)
                | TyKind::Raw(_, ty)
                | TyKind::Ref(_, _, ty) => go(ty),

                TyKind::Scalar(_)
                | TyKind::Str
                | TyKind::Never
                | TyKind::Placeholder(_)
                | TyKind::BoundVar(_)
                | TyKind::InferenceVar(_, _)
                | TyKind::Dyn(_)
                | TyKind::Function(_)
                | TyKind::Alias(_)
                | TyKind::Foreign(_)
                | TyKind::Coroutine(..)
                | TyKind::CoroutineWitness(..) => false,
            }
        }
    }

    pub fn fields(&self, db: &dyn HirDatabase) -> Vec<(Field, Type)> {
        let (variant_id, substs) = match self.ty.kind(Interner) {
            TyKind::Adt(hir_ty::AdtId(AdtId::StructId(s)), substs) => ((*s).into(), substs),
            TyKind::Adt(hir_ty::AdtId(AdtId::UnionId(u)), 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().substitute(Interner, substs);
                (def, self.derived(ty))
            })
            .collect()
    }

    pub fn tuple_fields(&self, _db: &dyn HirDatabase) -> Vec<Type> {
        if let TyKind::Tuple(_, substs) = &self.ty.kind(Interner) {
            substs
                .iter(Interner)
                .map(|ty| self.derived(ty.assert_ty_ref(Interner).clone()))
                .collect()
        } else {
            Vec::new()
        }
    }

    pub fn as_array(&self, db: &dyn HirDatabase) -> Option<(Type, usize)> {
        if let TyKind::Array(ty, len) = &self.ty.kind(Interner) {
            try_const_usize(db, len).map(|it| (self.derived(ty.clone()), it as usize))
        } else {
            None
        }
    }

    pub fn fingerprint_for_trait_impl(&self) -> Option<TyFingerprint> {
        TyFingerprint::for_trait_impl(&self.ty)
    }

    pub(crate) fn canonical(&self) -> Canonical<Ty> {
        hir_ty::replace_errors_with_variables(&self.ty)
    }

    /// Returns types that this type dereferences to (including this type itself). The returned
    /// iterator won't yield the same type more than once even if the deref chain contains a cycle.
    pub fn autoderef(&self, db: &dyn HirDatabase) -> impl Iterator<Item = Type> + '_ {
        self.autoderef_(db).map(move |ty| self.derived(ty))
    }

    fn autoderef_(&self, db: &dyn HirDatabase) -> impl Iterator<Item = Ty> {
        // There should be no inference vars in types passed here
        let canonical = hir_ty::replace_errors_with_variables(&self.ty);
        autoderef(db, self.env.clone(), canonical)
    }

    // 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> {
        let mut slot = None;
        self.iterate_assoc_items_dyn(db, krate, &mut |assoc_item_id| {
            slot = callback(assoc_item_id.into());
            slot.is_some()
        });
        slot
    }

    fn iterate_assoc_items_dyn(
        &self,
        db: &dyn HirDatabase,
        krate: Crate,
        callback: &mut dyn FnMut(AssocItemId) -> bool,
    ) {
        let def_crates = match method_resolution::def_crates(db, &self.ty, krate.id) {
            Some(it) => it,
            None => return,
        };
        for krate in def_crates {
            let impls = db.inherent_impls_in_crate(krate);

            for impl_def in impls.for_self_ty(&self.ty) {
                for &item in db.impl_data(*impl_def).items.iter() {
                    if callback(item) {
                        return;
                    }
                }
            }
        }
    }

    /// Iterates its type arguments
    ///
    /// It iterates the actual type arguments when concrete types are used
    /// and otherwise the generic names.
    /// It does not include `const` arguments.
    ///
    /// For code, such as:
    /// ```text
    /// struct Foo<T, U>
    ///
    /// impl<U> Foo<String, U>
    /// ```
    ///
    /// It iterates:
    /// ```text
    /// - "String"
    /// - "U"
    /// ```
    pub fn type_arguments(&self) -> impl Iterator<Item = Type> + '_ {
        self.ty
            .strip_references()
            .as_adt()
            .map(|(_, substs)| substs)
            .or_else(|| self.ty.strip_references().as_tuple())
            .into_iter()
            .flat_map(|substs| substs.iter(Interner))
            .filter_map(|arg| arg.ty(Interner).cloned())
            .map(move |ty| self.derived(ty))
    }

    /// Iterates its type and const arguments
    ///
    /// It iterates the actual type and const arguments when concrete types
    /// are used and otherwise the generic names.
    ///
    /// For code, such as:
    /// ```text
    /// struct Foo<T, const U: usize, const X: usize>
    ///
    /// impl<U> Foo<String, U, 12>
    /// ```
    ///
    /// It iterates:
    /// ```text
    /// - "String"
    /// - "U"
    /// - "12"
    /// ```
    pub fn type_and_const_arguments<'a>(
        &'a self,
        db: &'a dyn HirDatabase,
    ) -> impl Iterator<Item = SmolStr> + 'a {
        self.ty
            .strip_references()
            .as_adt()
            .into_iter()
            .flat_map(|(_, substs)| substs.iter(Interner))
            .filter_map(|arg| {
                // arg can be either a `Ty` or `constant`
                if let Some(ty) = arg.ty(Interner) {
                    Some(format_smolstr!("{}", ty.display(db)))
                } else {
                    arg.constant(Interner).map(|const_| format_smolstr!("{}", const_.display(db)))
                }
            })
    }

    /// Combines lifetime indicators, type and constant parameters into a single `Iterator`
    pub fn generic_parameters<'a>(
        &'a self,
        db: &'a dyn HirDatabase,
    ) -> impl Iterator<Item = SmolStr> + 'a {
        // iterate the lifetime
        self.as_adt()
            .and_then(|a| a.lifetime(db).map(|lt| lt.name.to_smol_str()))
            .into_iter()
            // add the type and const parameters
            .chain(self.type_and_const_arguments(db))
    }

    pub fn iterate_method_candidates_with_traits<T>(
        &self,
        db: &dyn HirDatabase,
        scope: &SemanticsScope<'_>,
        traits_in_scope: &FxHashSet<TraitId>,
        with_local_impls: Option<Module>,
        name: Option<&Name>,
        mut callback: impl FnMut(Function) -> Option<T>,
    ) -> Option<T> {
        let _p = tracing::span!(tracing::Level::INFO, "iterate_method_candidates");
        let mut slot = None;

        self.iterate_method_candidates_dyn(
            db,
            scope,
            traits_in_scope,
            with_local_impls,
            name,
            &mut |assoc_item_id| {
                if let AssocItemId::FunctionId(func) = assoc_item_id {
                    if let Some(res) = callback(func.into()) {
                        slot = Some(res);
                        return ControlFlow::Break(());
                    }
                }
                ControlFlow::Continue(())
            },
        );
        slot
    }

    pub fn iterate_method_candidates<T>(
        &self,
        db: &dyn HirDatabase,
        scope: &SemanticsScope<'_>,
        with_local_impls: Option<Module>,
        name: Option<&Name>,
        callback: impl FnMut(Function) -> Option<T>,
    ) -> Option<T> {
        self.iterate_method_candidates_with_traits(
            db,
            scope,
            &scope.visible_traits().0,
            with_local_impls,
            name,
            callback,
        )
    }

    fn iterate_method_candidates_dyn(
        &self,
        db: &dyn HirDatabase,
        scope: &SemanticsScope<'_>,
        traits_in_scope: &FxHashSet<TraitId>,
        with_local_impls: Option<Module>,
        name: Option<&Name>,
        callback: &mut dyn FnMut(AssocItemId) -> ControlFlow<()>,
    ) {
        let _p = tracing::span!(
            tracing::Level::INFO,
            "iterate_method_candidates_dyn",
            with_local_impls = traits_in_scope.len(),
            traits_in_scope = traits_in_scope.len(),
            ?name,
        )
        .entered();
        // There should be no inference vars in types passed here
        let canonical = hir_ty::replace_errors_with_variables(&self.ty);

        let krate = scope.krate();
        let environment = scope
            .resolver()
            .generic_def()
            .map_or_else(|| TraitEnvironment::empty(krate.id), |d| db.trait_environment(d));

        method_resolution::iterate_method_candidates_dyn(
            &canonical,
            db,
            environment,
            traits_in_scope,
            with_local_impls.and_then(|b| b.id.containing_block()).into(),
            name,
            method_resolution::LookupMode::MethodCall,
            &mut |_adj, id, _| callback(id),
        );
    }

    #[tracing::instrument(skip_all, fields(name = ?name))]
    pub fn iterate_path_candidates<T>(
        &self,
        db: &dyn HirDatabase,
        scope: &SemanticsScope<'_>,
        traits_in_scope: &FxHashSet<TraitId>,
        with_local_impls: Option<Module>,
        name: Option<&Name>,
        mut callback: impl FnMut(AssocItem) -> Option<T>,
    ) -> Option<T> {
        let _p = tracing::span!(tracing::Level::INFO, "iterate_path_candidates");
        let mut slot = None;
        self.iterate_path_candidates_dyn(
            db,
            scope,
            traits_in_scope,
            with_local_impls,
            name,
            &mut |assoc_item_id| {
                if let Some(res) = callback(assoc_item_id.into()) {
                    slot = Some(res);
                    return ControlFlow::Break(());
                }
                ControlFlow::Continue(())
            },
        );
        slot
    }

    #[tracing::instrument(skip_all, fields(name = ?name))]
    fn iterate_path_candidates_dyn(
        &self,
        db: &dyn HirDatabase,
        scope: &SemanticsScope<'_>,
        traits_in_scope: &FxHashSet<TraitId>,
        with_local_impls: Option<Module>,
        name: Option<&Name>,
        callback: &mut dyn FnMut(AssocItemId) -> ControlFlow<()>,
    ) {
        let canonical = hir_ty::replace_errors_with_variables(&self.ty);

        let krate = scope.krate();
        let environment = scope
            .resolver()
            .generic_def()
            .map_or_else(|| TraitEnvironment::empty(krate.id), |d| db.trait_environment(d));

        method_resolution::iterate_path_candidates(
            &canonical,
            db,
            environment,
            traits_in_scope,
            with_local_impls.and_then(|b| b.id.containing_block()).into(),
            name,
            callback,
        );
    }

    pub fn as_adt(&self) -> Option<Adt> {
        let (adt, _subst) = self.ty.as_adt()?;
        Some(adt.into())
    }

    pub fn as_builtin(&self) -> Option<BuiltinType> {
        self.ty.as_builtin().map(|inner| BuiltinType { inner })
    }

    pub fn as_dyn_trait(&self) -> Option<Trait> {
        self.ty.dyn_trait().map(Into::into)
    }

    /// If a type can be represented as `dyn Trait`, returns all traits accessible via this type,
    /// or an empty iterator otherwise.
    pub fn applicable_inherent_traits<'a>(
        &'a self,
        db: &'a dyn HirDatabase,
    ) -> impl Iterator<Item = Trait> + 'a {
        let _p = tracing::span!(tracing::Level::INFO, "applicable_inherent_traits");
        self.autoderef_(db)
            .filter_map(|ty| ty.dyn_trait())
            .flat_map(move |dyn_trait_id| hir_ty::all_super_traits(db.upcast(), dyn_trait_id))
            .map(Trait::from)
    }

    pub fn env_traits<'a>(&'a self, db: &'a dyn HirDatabase) -> impl Iterator<Item = Trait> + 'a {
        let _p = tracing::span!(tracing::Level::INFO, "env_traits");
        self.autoderef_(db)
            .filter(|ty| matches!(ty.kind(Interner), TyKind::Placeholder(_)))
            .flat_map(|ty| {
                self.env
                    .traits_in_scope_from_clauses(ty)
                    .flat_map(|t| hir_ty::all_super_traits(db.upcast(), t))
            })
            .map(Trait::from)
    }

    pub fn as_impl_traits(&self, db: &dyn HirDatabase) -> Option<impl Iterator<Item = Trait>> {
        self.ty.impl_trait_bounds(db).map(|it| {
            it.into_iter().filter_map(|pred| match pred.skip_binders() {
                hir_ty::WhereClause::Implemented(trait_ref) => {
                    Some(Trait::from(trait_ref.hir_trait_id()))
                }
                _ => None,
            })
        })
    }

    pub fn as_associated_type_parent_trait(&self, db: &dyn HirDatabase) -> Option<Trait> {
        self.ty.associated_type_parent_trait(db).map(Into::into)
    }

    fn derived(&self, ty: Ty) -> Type {
        Type { env: self.env.clone(), ty }
    }

    /// Visits every type, including generic arguments, in this type. `cb` is called with type
    /// itself first, and then with its generic arguments.
    pub fn walk(&self, db: &dyn HirDatabase, mut cb: impl FnMut(Type)) {
        fn walk_substs(
            db: &dyn HirDatabase,
            type_: &Type,
            substs: &Substitution,
            cb: &mut impl FnMut(Type),
        ) {
            for ty in substs.iter(Interner).filter_map(|a| a.ty(Interner)) {
                walk_type(db, &type_.derived(ty.clone()), cb);
            }
        }

        fn walk_bounds(
            db: &dyn HirDatabase,
            type_: &Type,
            bounds: &[QuantifiedWhereClause],
            cb: &mut impl FnMut(Type),
        ) {
            for pred in bounds {
                if let WhereClause::Implemented(trait_ref) = pred.skip_binders() {
                    cb(type_.clone());
                    // skip the self type. it's likely the type we just got the bounds from
                    for ty in
                        trait_ref.substitution.iter(Interner).skip(1).filter_map(|a| a.ty(Interner))
                    {
                        walk_type(db, &type_.derived(ty.clone()), cb);
                    }
                }
            }
        }

        fn walk_type(db: &dyn HirDatabase, type_: &Type, cb: &mut impl FnMut(Type)) {
            let ty = type_.ty.strip_references();
            match ty.kind(Interner) {
                TyKind::Adt(_, substs) => {
                    cb(type_.derived(ty.clone()));
                    walk_substs(db, type_, substs, cb);
                }
                TyKind::AssociatedType(_, substs) => {
                    if ty.associated_type_parent_trait(db).is_some() {
                        cb(type_.derived(ty.clone()));
                    }
                    walk_substs(db, type_, substs, cb);
                }
                TyKind::OpaqueType(_, subst) => {
                    if let Some(bounds) = ty.impl_trait_bounds(db) {
                        walk_bounds(db, &type_.derived(ty.clone()), &bounds, cb);
                    }

                    walk_substs(db, type_, subst, cb);
                }
                TyKind::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.substitution, cb);
                }
                TyKind::Placeholder(_) => {
                    if let Some(bounds) = ty.impl_trait_bounds(db) {
                        walk_bounds(db, &type_.derived(ty.clone()), &bounds, cb);
                    }
                }
                TyKind::Dyn(bounds) => {
                    walk_bounds(
                        db,
                        &type_.derived(ty.clone()),
                        bounds.bounds.skip_binders().interned(),
                        cb,
                    );
                }

                TyKind::Ref(_, _, ty)
                | TyKind::Raw(_, ty)
                | TyKind::Array(ty, _)
                | TyKind::Slice(ty) => {
                    walk_type(db, &type_.derived(ty.clone()), cb);
                }

                TyKind::FnDef(_, substs)
                | TyKind::Tuple(_, substs)
                | TyKind::Closure(.., substs) => {
                    walk_substs(db, type_, substs, cb);
                }
                TyKind::Function(hir_ty::FnPointer { substitution, .. }) => {
                    walk_substs(db, type_, &substitution.0, cb);
                }

                _ => {}
            }
        }

        walk_type(db, self, &mut cb);
    }
    /// Check if type unifies with another type.
    ///
    /// Note that we consider placeholder types to unify with everything.
    /// For example `Option<T>` and `Option<U>` unify although there is unresolved goal `T = U`.
    pub fn could_unify_with(&self, db: &dyn HirDatabase, other: &Type) -> bool {
        let tys = hir_ty::replace_errors_with_variables(&(self.ty.clone(), other.ty.clone()));
        hir_ty::could_unify(db, self.env.clone(), &tys)
    }

    /// Check if type unifies with another type eagerly making sure there are no unresolved goals.
    ///
    /// This means that placeholder types are not considered to unify if there are any bounds set on
    /// them. For example `Option<T>` and `Option<U>` do not unify as we cannot show that `T = U`
    pub fn could_unify_with_deeply(&self, db: &dyn HirDatabase, other: &Type) -> bool {
        let tys = hir_ty::replace_errors_with_variables(&(self.ty.clone(), other.ty.clone()));
        hir_ty::could_unify_deeply(db, self.env.clone(), &tys)
    }

    pub fn could_coerce_to(&self, db: &dyn HirDatabase, to: &Type) -> bool {
        let tys = hir_ty::replace_errors_with_variables(&(self.ty.clone(), to.ty.clone()));
        hir_ty::could_coerce(db, self.env.clone(), &tys)
    }

    pub fn as_type_param(&self, db: &dyn HirDatabase) -> Option<TypeParam> {
        match self.ty.kind(Interner) {
            TyKind::Placeholder(p) => Some(TypeParam {
                id: TypeParamId::from_unchecked(hir_ty::from_placeholder_idx(db, *p)),
            }),
            _ => None,
        }
    }

    /// Returns unique `GenericParam`s contained in this type.
    pub fn generic_params(&self, db: &dyn HirDatabase) -> FxHashSet<GenericParam> {
        hir_ty::collect_placeholders(&self.ty, db)
            .into_iter()
            .map(|id| TypeOrConstParam { id }.split(db).either_into())
            .collect()
    }

    pub fn layout(&self, db: &dyn HirDatabase) -> Result<Layout, LayoutError> {
        db.layout_of_ty(self.ty.clone(), self.env.clone())
            .map(|layout| Layout(layout, db.target_data_layout(self.env.krate).unwrap()))
    }
}

// FIXME: Document this
#[derive(Debug)]
pub struct Callable {
    ty: Type,
    sig: CallableSig,
    callee: Callee,
    /// Whether this is a method that was called with method call syntax.
    pub(crate) is_bound_method: bool,
}

#[derive(Debug)]
enum Callee {
    Def(CallableDefId),
    Closure(ClosureId),
    FnPtr,
    Other,
}

pub enum CallableKind {
    Function(Function),
    TupleStruct(Struct),
    TupleEnumVariant(Variant),
    Closure,
    FnPtr,
    /// Some other type that implements `FnOnce`.
    Other,
}

impl Callable {
    pub fn kind(&self) -> CallableKind {
        use Callee::*;
        match self.callee {
            Def(CallableDefId::FunctionId(it)) => CallableKind::Function(it.into()),
            Def(CallableDefId::StructId(it)) => CallableKind::TupleStruct(it.into()),
            Def(CallableDefId::EnumVariantId(it)) => CallableKind::TupleEnumVariant(it.into()),
            Closure(_) => CallableKind::Closure,
            FnPtr => CallableKind::FnPtr,
            Other => CallableKind::Other,
        }
    }
    pub fn receiver_param(&self, db: &dyn HirDatabase) -> Option<(SelfParam, Type)> {
        let func = match self.callee {
            Callee::Def(CallableDefId::FunctionId(it)) if self.is_bound_method => it,
            _ => return None,
        };
        let func = Function { id: func };
        Some((func.self_param(db)?, self.ty.derived(self.sig.params()[0].clone())))
    }
    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 map_param = |it: ast::Param| it.pat().map(Either::Right);
        let patterns = match self.callee {
            Callee::Def(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(map_param))
                })
            }
            Callee::Closure(closure_id) => match closure_source(db, closure_id) {
                Some(src) => src.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(map_param))
                }),
                None => None,
            },
            _ => 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())
    }
    pub fn sig(&self) -> &CallableSig {
        &self.sig
    }
}

fn closure_source(db: &dyn HirDatabase, closure: ClosureId) -> Option<ast::ClosureExpr> {
    let InternedClosure(owner, expr_id) = db.lookup_intern_closure(closure.into());
    let (_, source_map) = db.body_with_source_map(owner);
    let ast = source_map.expr_syntax(expr_id).ok()?;
    let root = ast.file_syntax(db.upcast());
    let expr = ast.value.to_node(&root);
    match expr {
        ast::Expr::ClosureExpr(it) => Some(it),
        _ => None,
    }
}

#[derive(Clone, Debug, Eq, PartialEq)]
pub struct Layout(Arc<TyLayout>, Arc<TargetDataLayout>);

impl Layout {
    pub fn size(&self) -> u64 {
        self.0.size.bytes()
    }

    pub fn align(&self) -> u64 {
        self.0.align.abi.bytes()
    }

    pub fn niches(&self) -> Option<u128> {
        Some(self.0.largest_niche?.available(&*self.1))
    }

    pub fn field_offset(&self, field: Field) -> Option<u64> {
        match self.0.fields {
            layout::FieldsShape::Primitive => None,
            layout::FieldsShape::Union(_) => Some(0),
            layout::FieldsShape::Array { stride, count } => {
                let i = u64::try_from(field.index()).ok()?;
                (i < count).then_some((stride * i).bytes())
            }
            layout::FieldsShape::Arbitrary { ref offsets, .. } => {
                Some(offsets.get(RustcFieldIdx(field.id))?.bytes())
            }
        }
    }

    pub fn tuple_field_offset(&self, field: usize) -> Option<u64> {
        match self.0.fields {
            layout::FieldsShape::Primitive => None,
            layout::FieldsShape::Union(_) => Some(0),
            layout::FieldsShape::Array { stride, count } => {
                let i = u64::try_from(field).ok()?;
                (i < count).then_some((stride * i).bytes())
            }
            layout::FieldsShape::Arbitrary { ref offsets, .. } => {
                Some(offsets.get(RustcFieldIdx::new(field))?.bytes())
            }
        }
    }

    pub fn enum_tag_size(&self) -> Option<usize> {
        let tag_size =
            if let layout::Variants::Multiple { tag, tag_encoding, .. } = &self.0.variants {
                match tag_encoding {
                    TagEncoding::Direct => tag.size(&*self.1).bytes_usize(),
                    TagEncoding::Niche { .. } => 0,
                }
            } else {
                return None;
            };
        Some(tag_size)
    }
}

#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub enum BindingMode {
    Move,
    Ref(Mutability),
}

/// For IDE only
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
pub enum ScopeDef {
    ModuleDef(ModuleDef),
    GenericParam(GenericParam),
    ImplSelfType(Impl),
    AdtSelfType(Adt),
    Local(Local),
    Label(Label),
    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::ModuleDef(ModuleDef::Macro(macro_def_id.into())));
        }

        if items.is_empty() {
            items.push(ScopeDef::Unknown);
        }

        items
    }

    pub fn attrs(&self, db: &dyn HirDatabase) -> Option<AttrsWithOwner> {
        match self {
            ScopeDef::ModuleDef(it) => it.attrs(db),
            ScopeDef::GenericParam(it) => Some(it.attrs(db)),
            ScopeDef::ImplSelfType(_)
            | ScopeDef::AdtSelfType(_)
            | ScopeDef::Local(_)
            | ScopeDef::Label(_)
            | ScopeDef::Unknown => None,
        }
    }

    pub fn krate(&self, db: &dyn HirDatabase) -> Option<Crate> {
        match self {
            ScopeDef::ModuleDef(it) => it.module(db).map(|m| m.krate()),
            ScopeDef::GenericParam(it) => Some(it.module(db).krate()),
            ScopeDef::ImplSelfType(_) => None,
            ScopeDef::AdtSelfType(it) => Some(it.module(db).krate()),
            ScopeDef::Local(it) => Some(it.module(db).krate()),
            ScopeDef::Label(it) => Some(it.module(db).krate()),
            ScopeDef::Unknown => None,
        }
    }
}

impl From<ItemInNs> for ScopeDef {
    fn from(item: ItemInNs) -> Self {
        match item {
            ItemInNs::Types(id) => ScopeDef::ModuleDef(id),
            ItemInNs::Values(id) => ScopeDef::ModuleDef(id),
            ItemInNs::Macros(id) => ScopeDef::ModuleDef(ModuleDef::Macro(id)),
        }
    }
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct Adjustment {
    pub source: Type,
    pub target: Type,
    pub kind: Adjust,
}

#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
pub enum Adjust {
    /// Go from ! to any type.
    NeverToAny,
    /// Dereference once, producing a place.
    Deref(Option<OverloadedDeref>),
    /// Take the address and produce either a `&` or `*` pointer.
    Borrow(AutoBorrow),
    Pointer(PointerCast),
}

#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
pub enum AutoBorrow {
    /// Converts from T to &T.
    Ref(Mutability),
    /// Converts from T to *T.
    RawPtr(Mutability),
}

#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
pub struct OverloadedDeref(pub Mutability);

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)
    }
}

/// Trait for obtaining the defining crate of an item.
pub trait HasCrate {
    fn krate(&self, db: &dyn HirDatabase) -> Crate;
}

impl<T: hir_def::HasModule> HasCrate for T {
    fn krate(&self, db: &dyn HirDatabase) -> Crate {
        self.module(db.upcast()).krate().into()
    }
}

impl HasCrate for AssocItem {
    fn krate(&self, db: &dyn HirDatabase) -> Crate {
        self.module(db).krate()
    }
}

impl HasCrate for Struct {
    fn krate(&self, db: &dyn HirDatabase) -> Crate {
        self.module(db).krate()
    }
}

impl HasCrate for Union {
    fn krate(&self, db: &dyn HirDatabase) -> Crate {
        self.module(db).krate()
    }
}

impl HasCrate for Enum {
    fn krate(&self, db: &dyn HirDatabase) -> Crate {
        self.module(db).krate()
    }
}

impl HasCrate for Field {
    fn krate(&self, db: &dyn HirDatabase) -> Crate {
        self.parent_def(db).module(db).krate()
    }
}

impl HasCrate for Variant {
    fn krate(&self, db: &dyn HirDatabase) -> Crate {
        self.module(db).krate()
    }
}

impl HasCrate for Function {
    fn krate(&self, db: &dyn HirDatabase) -> Crate {
        self.module(db).krate()
    }
}

impl HasCrate for Const {
    fn krate(&self, db: &dyn HirDatabase) -> Crate {
        self.module(db).krate()
    }
}

impl HasCrate for TypeAlias {
    fn krate(&self, db: &dyn HirDatabase) -> Crate {
        self.module(db).krate()
    }
}

impl HasCrate for Type {
    fn krate(&self, _db: &dyn HirDatabase) -> Crate {
        self.env.krate.into()
    }
}

impl HasCrate for Macro {
    fn krate(&self, db: &dyn HirDatabase) -> Crate {
        self.module(db).krate()
    }
}

impl HasCrate for Trait {
    fn krate(&self, db: &dyn HirDatabase) -> Crate {
        self.module(db).krate()
    }
}

impl HasCrate for TraitAlias {
    fn krate(&self, db: &dyn HirDatabase) -> Crate {
        self.module(db).krate()
    }
}

impl HasCrate for Static {
    fn krate(&self, db: &dyn HirDatabase) -> Crate {
        self.module(db).krate()
    }
}

impl HasCrate for Adt {
    fn krate(&self, db: &dyn HirDatabase) -> Crate {
        self.module(db).krate()
    }
}

impl HasCrate for Module {
    fn krate(&self, _: &dyn HirDatabase) -> Crate {
        Module::krate(*self)
    }
}

pub trait HasContainer {
    fn container(&self, db: &dyn HirDatabase) -> ItemContainer;
}

impl HasContainer for ExternCrateDecl {
    fn container(&self, db: &dyn HirDatabase) -> ItemContainer {
        container_id_to_hir(self.id.lookup(db.upcast()).container.into())
    }
}

impl HasContainer for Module {
    fn container(&self, db: &dyn HirDatabase) -> ItemContainer {
        // FIXME: handle block expressions as modules (their parent is in a different DefMap)
        let def_map = self.id.def_map(db.upcast());
        match def_map[self.id.local_id].parent {
            Some(parent_id) => ItemContainer::Module(Module { id: def_map.module_id(parent_id) }),
            None => ItemContainer::Crate(def_map.krate()),
        }
    }
}

impl HasContainer for Function {
    fn container(&self, db: &dyn HirDatabase) -> ItemContainer {
        container_id_to_hir(self.id.lookup(db.upcast()).container)
    }
}

impl HasContainer for Struct {
    fn container(&self, db: &dyn HirDatabase) -> ItemContainer {
        ItemContainer::Module(Module { id: self.id.lookup(db.upcast()).container })
    }
}

impl HasContainer for Union {
    fn container(&self, db: &dyn HirDatabase) -> ItemContainer {
        ItemContainer::Module(Module { id: self.id.lookup(db.upcast()).container })
    }
}

impl HasContainer for Enum {
    fn container(&self, db: &dyn HirDatabase) -> ItemContainer {
        ItemContainer::Module(Module { id: self.id.lookup(db.upcast()).container })
    }
}

impl HasContainer for TypeAlias {
    fn container(&self, db: &dyn HirDatabase) -> ItemContainer {
        container_id_to_hir(self.id.lookup(db.upcast()).container)
    }
}

impl HasContainer for Const {
    fn container(&self, db: &dyn HirDatabase) -> ItemContainer {
        container_id_to_hir(self.id.lookup(db.upcast()).container)
    }
}

impl HasContainer for Static {
    fn container(&self, db: &dyn HirDatabase) -> ItemContainer {
        container_id_to_hir(self.id.lookup(db.upcast()).container)
    }
}

impl HasContainer for Trait {
    fn container(&self, db: &dyn HirDatabase) -> ItemContainer {
        ItemContainer::Module(Module { id: self.id.lookup(db.upcast()).container })
    }
}

impl HasContainer for TraitAlias {
    fn container(&self, db: &dyn HirDatabase) -> ItemContainer {
        ItemContainer::Module(Module { id: self.id.lookup(db.upcast()).container })
    }
}

fn container_id_to_hir(c: ItemContainerId) -> ItemContainer {
    match c {
        ItemContainerId::ExternBlockId(_id) => ItemContainer::ExternBlock(),
        ItemContainerId::ModuleId(id) => ItemContainer::Module(Module { id }),
        ItemContainerId::ImplId(id) => ItemContainer::Impl(Impl { id }),
        ItemContainerId::TraitId(id) => ItemContainer::Trait(Trait { id }),
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum ItemContainer {
    Trait(Trait),
    Impl(Impl),
    Module(Module),
    ExternBlock(),
    Crate(CrateId),
}

/// Subset of `ide_db::Definition` that doc links can resolve to.
pub enum DocLinkDef {
    ModuleDef(ModuleDef),
    Field(Field),
    SelfType(Trait),
}