cairo_lang_semantic/items/

imp.rs

use std::collections::BTreeSet;
use std::hash::Hash;
use std::mem;
use std::sync::Arc;

use cairo_lang_debug::DebugWithDb;
use cairo_lang_defs::db::DefsGroup;
use cairo_lang_defs::ids::{
    FunctionTitleId, GenericKind, GenericParamId, GenericParamLongId, ImplAliasId,
    ImplConstantDefId, ImplConstantDefLongId, ImplDefId, ImplFunctionId, ImplFunctionLongId,
    ImplImplDefId, ImplImplDefLongId, ImplItemId, ImplTypeDefId, ImplTypeDefLongId,
    LanguageElementId, LookupItemId, ModuleId, ModuleItemId, NamedLanguageElementId,
    NamedLanguageElementLongId, TopLevelLanguageElementId, TraitConstantId, TraitFunctionId,
    TraitId, TraitImplId, TraitTypeId, UseId,
};
use cairo_lang_diagnostics::{
    DiagnosticAdded, Diagnostics, Maybe, MaybeAsRef, ToMaybe, skip_diagnostic,
};
use cairo_lang_filesystem::db::FilesGroup;
use cairo_lang_filesystem::ids::{CrateId, CrateLongId, SmolStrId, Tracked, UnstableSalsaId};
use cairo_lang_proc_macros::{DebugWithDb, HeapSize, SemanticObject};
use cairo_lang_syntax as syntax;
use cairo_lang_syntax::node::ast::{
    OptionTypeClause, OptionWrappedGenericParamList, UnaryOperator,
};
use cairo_lang_syntax::node::helpers::GetIdentifier;
use cairo_lang_utils::ordered_hash_map::OrderedHashMap;
use cairo_lang_utils::ordered_hash_set::OrderedHashSet;
use cairo_lang_utils::unordered_hash_map::UnorderedHashMap;
use cairo_lang_utils::unordered_hash_set::UnorderedHashSet;
use cairo_lang_utils::{Intern, define_short_id, extract_matches, try_extract_matches};
use itertools::{Itertools, chain, izip};
use salsa::Database;
use syntax::attribute::structured::{Attribute, AttributeListStructurize};
use syntax::node::ast::{self, GenericArg, ImplItem, MaybeImplBody, OptionReturnTypeClause};
use syntax::node::helpers::OptionWrappedGenericParamListHelper;
use syntax::node::ids::SyntaxStablePtrId;
use syntax::node::{Terminal, TypedStablePtr, TypedSyntaxNode};

use super::constant::{
    ConstValue, ConstValueId, ConstantData, ImplConstantId, constant_semantic_data_cycle_helper,
    constant_semantic_data_helper,
};
use super::enm::SemanticEnumEx;
use super::feature_kind::{FeatureKind, HasFeatureKind};
use super::function_with_body::{FunctionBody, FunctionBodyData, get_inline_config};
use super::functions::{
    FunctionDeclarationData, GenericFunctionId, ImplGenericFunctionId, InlineConfiguration,
    forbid_inline_always_with_impl_generic_param,
};
use super::generics::{
    GenericArgumentHead, GenericParamImpl, GenericParamsData, displayable_concrete,
    generic_params_to_args, semantic_generic_params,
};
use super::impl_alias::{
    ImplAliasData, impl_alias_generic_params_data_helper, impl_alias_semantic_data_cycle_helper,
    impl_alias_semantic_data_helper,
};
use super::trt::{
    ConcreteTraitConstantId, ConcreteTraitGenericFunctionId, ConcreteTraitGenericFunctionLongId,
    ConcreteTraitImplId,
};
use super::type_aliases::{
    TypeAliasData, type_alias_generic_params_data_helper, type_alias_semantic_data_cycle_helper,
    type_alias_semantic_data_helper,
};
use super::visibility::peek_visible_in;
use super::{TraitOrImplContext, resolve_trait_path};
use crate::corelib::{CorelibSemantic, concrete_destruct_trait, concrete_drop_trait, core_crate};
use crate::db::get_resolver_data_options;
use crate::diagnostic::SemanticDiagnosticKind::{self, *};
use crate::diagnostic::{NotFoundItemType, SemanticDiagnostics, SemanticDiagnosticsBuilder};
use crate::expr::compute::{ComputationContext, ContextFunction, Environment, compute_root_expr};
use crate::expr::inference::canonic::ResultNoErrEx;
use crate::expr::inference::conform::InferenceConform;
use crate::expr::inference::infers::InferenceEmbeddings;
use crate::expr::inference::solver::{Ambiguity, SolutionSet, enrich_lookup_context_with_ty};
use crate::expr::inference::{
    ImplVarId, ImplVarTraitItemMappings, Inference, InferenceError, InferenceId, NegativeImplVarId,
};
use crate::items::function_with_body::get_implicit_precedence;
use crate::items::functions::ImplicitPrecedence;
use crate::items::generics::GenericParamSemantic;
use crate::items::impl_alias::ImplAliasSemantic;
use crate::items::implization::ImplizationSemantic;
use crate::items::macro_call::{MacroCallSemantic, module_macro_modules};
use crate::items::module::ModuleSemantic;
use crate::items::structure::StructSemantic;
use crate::items::trt::TraitSemantic;
use crate::items::us::{SemanticUseEx, UseSemantic};
use crate::resolve::{
    AsSegments, ResolutionContext, ResolvedConcreteItem, ResolvedGenericItem, Resolver,
    ResolverData,
};
use crate::substitution::{GenericSubstitution, SemanticRewriter};
use crate::types::{
    ImplTypeId, ShallowGenericArg, TypeHead, TypesSemantic, add_type_based_diagnostics,
    get_impl_at_context, maybe_resolve_shallow_generic_arg_type, resolve_type,
};
use crate::{
    ConcreteFunction, ConcreteTraitId, ConcreteTraitLongId, FunctionId, FunctionLongId,
    GenericArgumentId, GenericParam, Mutability, SemanticDiagnostic, TypeId, TypeLongId, semantic,
    semantic_object_for_id,
};

#[cfg(test)]
#[path = "imp_test.rs"]
mod test;

#[derive(Clone, Debug, Hash, PartialEq, Eq, SemanticObject, salsa::Update, HeapSize)]
pub struct ConcreteImplLongId<'db> {
    pub impl_def_id: ImplDefId<'db>,
    pub generic_args: Vec<GenericArgumentId<'db>>,
}
define_short_id!(ConcreteImplId, ConcreteImplLongId<'db>);
semantic_object_for_id!(ConcreteImplId, ConcreteImplLongId<'a>);
impl<'db> DebugWithDb<'db> for ConcreteImplLongId<'db> {
    type Db = dyn Database;

    fn fmt(&self, f: &mut std::fmt::Formatter<'_>, db: &'db dyn Database) -> std::fmt::Result {
        write!(
            f,
            "{}",
            displayable_concrete(db, &self.impl_def_id.full_path(db), &self.generic_args)
        )
    }
}
impl<'db> ConcreteImplId<'db> {
    pub fn impl_def_id(&self, db: &'db dyn Database) -> ImplDefId<'db> {
        self.long(db).impl_def_id
    }
    pub fn get_impl_function(
        &self,
        db: &'db dyn Database,
        function: TraitFunctionId<'db>,
    ) -> Maybe<Option<ImplFunctionId<'db>>> {
        db.impl_function_by_trait_function(self.impl_def_id(db), function)
    }
    pub fn name(&self, db: &'db dyn Database) -> SmolStrId<'db> {
        self.impl_def_id(db).name(db)
    }
    pub fn full_path(&self, db: &dyn Database) -> String {
        format!("{:?}", self.debug(db))
    }
    pub fn substitution(&self, db: &'db dyn Database) -> Maybe<GenericSubstitution<'db>> {
        Ok(GenericSubstitution::from_impl(ImplLongId::Concrete(*self).intern(db)).concat(
            GenericSubstitution::new(
                db.impl_def_generic_params(self.impl_def_id(db))?,
                &self.long(db).generic_args,
            ),
        ))
    }
    /// Returns true if the `impl` does not depend on any generics.
    pub fn is_fully_concrete(&self, db: &dyn Database) -> bool {
        self.long(db)
            .generic_args
            .iter()
            .all(|generic_argument_id| generic_argument_id.is_fully_concrete(db))
    }
    /// Returns true if the `impl` does not depend on impl or type variables.
    pub fn is_var_free(&self, db: &dyn Database) -> bool {
        self.long(db)
            .generic_args
            .iter()
            .all(|generic_argument_id| generic_argument_id.is_var_free(db))
    }
}

/// Represents a "callee" impl that can be referred to in the code.
/// Traits should be resolved to this.
#[derive(Clone, Debug, Hash, PartialEq, Eq, SemanticObject, salsa::Update, HeapSize)]
pub enum ImplLongId<'db> {
    Concrete(ConcreteImplId<'db>),
    GenericParameter(GenericParamId<'db>),
    ImplVar(ImplVarId<'db>),
    ImplImpl(ImplImplId<'db>),
    SelfImpl(ConcreteTraitId<'db>),
    GeneratedImpl(GeneratedImplId<'db>),
}
impl<'db> ImplLongId<'db> {
    /// Returns the [ImplHead] of an impl if available.
    pub fn head(&self, db: &'db dyn Database) -> Option<ImplHead<'db>> {
        Some(match self {
            ImplLongId::Concrete(concrete) => ImplHead::Concrete(concrete.impl_def_id(db)),
            ImplLongId::GenericParameter(_)
            | ImplLongId::ImplVar(_)
            | ImplLongId::ImplImpl(_)
            | ImplLongId::SelfImpl(_)
            | ImplLongId::GeneratedImpl(_) => {
                return None;
            }
        })
    }
    pub fn name(&self, db: &dyn Database) -> String {
        match self {
            ImplLongId::Concrete(concrete_impl) => concrete_impl.name(db).to_string(db),
            ImplLongId::GenericParameter(generic_param_impl) => {
                generic_param_impl.name(db).map(|n| n.long(db).as_str()).unwrap_or("_").to_string()
            }
            ImplLongId::ImplVar(var) => {
                format!("ImplVar({})", var.concrete_trait_id(db).full_path(db))
            }
            ImplLongId::ImplImpl(impl_impl) => format!(
                "{}::{}",
                impl_impl.impl_id().name(db),
                db.impl_impl_concrete_trait(*impl_impl)
                    .map(|trait_impl| trait_impl.full_path(db))
                    .unwrap_or_else(|_| "_".into())
            ),
            ImplLongId::SelfImpl(trait_impl) => trait_impl.name(db).to_string(db),
            ImplLongId::GeneratedImpl(generated_impl) => {
                format!("{:?}", generated_impl.debug(db))
            }
        }
    }
    pub fn format(&self, db: &dyn Database) -> String {
        format!("{:?}", self.debug(db))
    }

    /// Returns true if the `impl` does not depend on impl or type variables.
    pub fn is_var_free(&self, db: &dyn Database) -> bool {
        match self {
            ImplLongId::Concrete(concrete_impl_id) => concrete_impl_id.is_var_free(db),
            ImplLongId::SelfImpl(concrete_trait_id) => concrete_trait_id.is_var_free(db),
            ImplLongId::GenericParameter(_) => true,
            ImplLongId::ImplVar(_) => false,
            ImplLongId::ImplImpl(impl_impl) => impl_impl.impl_id().is_var_free(db),
            ImplLongId::GeneratedImpl(generated_impl) => {
                generated_impl.concrete_trait(db).is_var_free(db)
                    && generated_impl
                        .long(db)
                        .impl_items
                        .0
                        .values()
                        .all(|type_id| type_id.is_var_free(db))
            }
        }
    }

    /// Returns true if the `impl` does not depend on any generics.
    pub fn is_fully_concrete(&self, db: &dyn Database) -> bool {
        match self {
            ImplLongId::Concrete(concrete_impl_id) => concrete_impl_id.is_fully_concrete(db),
            ImplLongId::GenericParameter(_) => false,
            ImplLongId::ImplVar(_) => false,
            ImplLongId::ImplImpl(_) | ImplLongId::SelfImpl(_) => false,
            ImplLongId::GeneratedImpl(generated_impl) => {
                generated_impl.concrete_trait(db).is_fully_concrete(db)
                    && generated_impl
                        .long(db)
                        .impl_items
                        .0
                        .values()
                        .all(|type_id| type_id.is_fully_concrete(db))
            }
        }
    }
}
impl<'db> DebugWithDb<'db> for ImplLongId<'db> {
    type Db = dyn Database;

    fn fmt(&self, f: &mut std::fmt::Formatter<'_>, db: &'db dyn Database) -> std::fmt::Result {
        match self {
            ImplLongId::Concrete(concrete_impl_id) => {
                write!(f, "{:?}", concrete_impl_id.debug(db))
            }
            ImplLongId::GenericParameter(param) => write!(f, "{}", param.format(db).long(db)),
            ImplLongId::ImplVar(var) => write!(f, "?{}", var.long(db).id.0),
            ImplLongId::ImplImpl(impl_impl) => write!(f, "{:?}", impl_impl.debug(db)),
            ImplLongId::SelfImpl(trait_impl) => write!(f, "{:?}", trait_impl.debug(db)),
            ImplLongId::GeneratedImpl(generated_impl) => {
                write!(f, "{:?}", generated_impl.debug(db))
            }
        }
    }
}

define_short_id!(ImplId, ImplLongId<'db>);
semantic_object_for_id!(ImplId, ImplLongId<'a>);
impl<'db> ImplId<'db> {
    pub fn concrete_trait(&self, db: &'db dyn Database) -> Maybe<ConcreteTraitId<'db>> {
        db.impl_concrete_trait(*self)
    }

    /// Returns true if the `impl` does not depend on any generics.
    pub fn is_fully_concrete(&self, db: &dyn Database) -> bool {
        impl_is_fully_concrete(db, *self)
    }

    /// Returns true if the `impl` does not depend on impl or type variables.
    pub fn is_var_free(&self, db: &dyn Database) -> bool {
        impl_is_var_free(db, *self)
    }

    /// Returns the [ImplHead] of an impl if available.
    pub fn head(&self, db: &'db dyn Database) -> Option<ImplHead<'db>> {
        self.long(db).head(db)
    }

    /// Returns the name of the impl.
    pub fn name(&self, db: &dyn Database) -> String {
        self.long(db).name(db)
    }

    pub fn format(&self, db: &dyn Database) -> String {
        self.long(db).format(db)
    }
}

define_short_id!(GeneratedImplId, GeneratedImplLongId<'db>);
semantic_object_for_id!(GeneratedImplId, GeneratedImplLongId<'a>);

impl<'db> GeneratedImplId<'db> {
    pub fn concrete_trait(self, db: &'db dyn Database) -> ConcreteTraitId<'db> {
        self.long(db).concrete_trait
    }

    pub fn trait_id(&self, db: &'db dyn Database) -> TraitId<'db> {
        self.concrete_trait(db).trait_id(db)
    }
}

/// An impl that is generated by the compiler for a specific trait.
/// There can be only one such impl per concrete trait as otherwise there would be a
/// MultipleImplsFound ambiguity.
#[derive(Clone, Debug, Hash, PartialEq, Eq, SemanticObject, salsa::Update, HeapSize)]
pub struct GeneratedImplLongId<'db> {
    pub concrete_trait: ConcreteTraitId<'db>,
    /// The generic params required for the impl. Typically impls and negative impls.
    /// We save the params so that we can validate negative impls.
    pub generic_params: Vec<GenericParam<'db>>,
    pub impl_items: GeneratedImplItems<'db>,
}
#[derive(Clone, Debug, Default, PartialEq, Eq, Hash, SemanticObject, salsa::Update, HeapSize)]
pub struct GeneratedImplItems<'db>(pub OrderedHashMap<TraitTypeId<'db>, TypeId<'db>>);

pub enum GeneratedImplAssociatedTypes<'db> {
    /// The associated types are not yet resolved.
    Unresolved,
    /// The associated types are resolved.
    Resolved(OrderedHashMap<TraitTypeId<'db>, TypeId<'db>>),
}

impl<'db> DebugWithDb<'db> for GeneratedImplLongId<'db> {
    type Db = dyn Database;

    fn fmt(&self, f: &mut std::fmt::Formatter<'_>, db: &'db dyn Database) -> std::fmt::Result {
        write!(f, "Generated {:?}", self.concrete_trait.debug(db))
    }
}

/// An impl item of kind impl.
#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, SemanticObject, HeapSize, salsa::Update)]
pub struct ImplImplId<'db> {
    /// The impl the item impl is in.
    impl_id: ImplId<'db>,
    /// The trait impl this impl impl "implements".
    trait_impl_id: TraitImplId<'db>,
}

impl<'db> ImplImplId<'db> {
    /// Creates a new impl impl id. For an impl impl of a concrete impl, asserts that the
    /// trait impl belongs to the same trait that the impl implements (panics if not).
    pub fn new(impl_id: ImplId<'db>, trait_impl_id: TraitImplId<'db>, db: &dyn Database) -> Self {
        if let ImplLongId::Concrete(concrete_impl) = impl_id.long(db) {
            let impl_def_id = concrete_impl.impl_def_id(db);
            assert_eq!(Ok(trait_impl_id.trait_id(db)), db.impl_def_trait(impl_def_id));
        }

        ImplImplId { impl_id, trait_impl_id }
    }
    pub fn impl_id(&self) -> ImplId<'db> {
        self.impl_id
    }
    pub fn trait_impl_id(&self) -> TraitImplId<'db> {
        self.trait_impl_id
    }

    pub fn concrete_trait_impl_id(&self, db: &'db dyn Database) -> Maybe<ConcreteTraitImplId<'db>> {
        Ok(ConcreteTraitImplId::new_from_data(
            db,
            self.impl_id.concrete_trait(db)?,
            self.trait_impl_id,
        ))
    }

    pub fn full_path(&self, db: &dyn Database) -> String {
        format!("{:?}", self.debug(db))
    }
}
impl<'db> DebugWithDb<'db> for ImplImplId<'db> {
    type Db = dyn Database;

    fn fmt(&self, f: &mut std::fmt::Formatter<'_>, db: &'db dyn Database) -> std::fmt::Result {
        write!(f, "{:?}::{}", self.impl_id.debug(db), self.trait_impl_id.name(db).long(db))
    }
}

/// Represents a "callee" impl that can be referred to in the code.
/// Traits should be resolved to this.
#[derive(Clone, Debug, Hash, PartialEq, Eq, SemanticObject, salsa::Update, HeapSize)]
pub enum NegativeImplLongId<'db> {
    Solved(ConcreteTraitId<'db>),
    GenericParameter(GenericParamId<'db>),
    NegativeImplVar(NegativeImplVarId<'db>),
}

impl<'db> NegativeImplLongId<'db> {
    pub fn concrete_trait(&self, db: &'db dyn Database) -> Maybe<ConcreteTraitId<'db>> {
        match self {
            NegativeImplLongId::Solved(concrete_trait_id) => Ok(*concrete_trait_id),
            NegativeImplLongId::GenericParameter(param) => {
                let param_impl =
                    extract_matches!(db.generic_param_semantic(*param)?, GenericParam::NegImpl);
                param_impl.concrete_trait
            }
            NegativeImplLongId::NegativeImplVar(negative_impl_var_id) => {
                Ok(negative_impl_var_id.long(db).concrete_trait_id)
            }
        }
    }
    pub fn is_var_free(&self, db: &dyn Database) -> bool {
        match self {
            NegativeImplLongId::Solved(concrete_trait_id) => concrete_trait_id.is_var_free(db),
            NegativeImplLongId::GenericParameter(_) => true,
            NegativeImplLongId::NegativeImplVar(_) => false,
        }
    }
    pub fn is_fully_concrete(&self, db: &dyn Database) -> bool {
        match self {
            NegativeImplLongId::Solved(concrete_trait_id) => {
                concrete_trait_id.is_fully_concrete(db)
            }
            NegativeImplLongId::GenericParameter(_) | NegativeImplLongId::NegativeImplVar(_) => {
                false
            }
        }
    }
}

define_short_id!(NegativeImplId, NegativeImplLongId<'db>);
impl<'db> NegativeImplId<'db> {
    pub fn concrete_trait(&self, db: &'db dyn Database) -> Maybe<ConcreteTraitId<'db>> {
        self.long(db).concrete_trait(db)
    }
    pub fn is_var_free(&self, db: &dyn Database) -> bool {
        self.long(db).is_var_free(db)
    }
    pub fn is_fully_concrete(&self, db: &dyn Database) -> bool {
        self.long(db).is_fully_concrete(db)
    }
}
semantic_object_for_id!(NegativeImplId, NegativeImplLongId<'a>);

impl<'db> UnstableSalsaId for ImplId<'db> {
    fn get_internal_id(&self) -> salsa::Id {
        self.as_intern_id()
    }
}

/// Head of an impl.
///
/// A non-param non-variable impl has a head, which represents the kind of the root node in its tree
/// representation. This is used for caching queries for fast lookups when the impl is not
/// completely inferred yet.
#[derive(Clone, Debug, Hash, PartialEq, Eq, salsa::Update)]
pub enum ImplHead<'db> {
    Concrete(ImplDefId<'db>),
}

// === Impl Declaration ===

#[derive(Clone, Debug, PartialEq, Eq, DebugWithDb, salsa::Update)]
#[debug_db(dyn Database)]
struct ImplDeclarationData<'db> {
    diagnostics: Diagnostics<'db, SemanticDiagnostic<'db>>,
    /// The concrete trait this impl implements, or Err if it cannot be resolved.
    concrete_trait: Maybe<ConcreteTraitId<'db>>,
    attributes: Vec<Attribute<'db>>,
    resolver_data: Arc<ResolverData<'db>>,
}

/// Returns the generic parameters data of an impl definition.
#[salsa::tracked(returns(ref))]
fn impl_def_generic_params_data<'db>(
    db: &'db dyn Database,
    impl_def_id: ImplDefId<'db>,
) -> Maybe<GenericParamsData<'db>> {
    let module_id = impl_def_id.parent_module(db);
    let mut diagnostics = SemanticDiagnostics::new(module_id);

    let impl_ast = db.module_impl_by_id(impl_def_id)?;
    let inference_id =
        InferenceId::LookupItemGenerics(LookupItemId::ModuleItem(ModuleItemId::Impl(impl_def_id)));

    let mut resolver = Resolver::new(db, module_id, inference_id);
    resolver.set_feature_config(&impl_def_id, &impl_ast, &mut diagnostics);
    let generic_params = semantic_generic_params(
        db,
        &mut diagnostics,
        &mut resolver,
        module_id,
        &impl_ast.generic_params(db),
    );
    let inference = &mut resolver.inference();
    inference.finalize(&mut diagnostics, impl_ast.stable_ptr(db).untyped());
    let generic_params = inference.rewrite(generic_params).no_err();
    let resolver_data = Arc::new(resolver.data);
    Ok(GenericParamsData { generic_params, diagnostics: diagnostics.build(), resolver_data })
}

/// Implementation of [PrivImplSemantic::impl_def_substitution].
#[salsa::tracked(returns(ref))]
fn impl_def_substitution<'db>(
    db: &'db dyn Database,
    impl_def_id: ImplDefId<'db>,
) -> Maybe<GenericSubstitution<'db>> {
    let params = db.impl_def_generic_params(impl_def_id)?;
    let generic_args = generic_params_to_args(params, db);
    ConcreteImplLongId { impl_def_id, generic_args }.intern(db).substitution(db)
}

/// Implementation of [ImplSemantic::impl_def_trait].
#[salsa::tracked]
fn impl_def_trait<'db>(db: &'db dyn Database, impl_def_id: ImplDefId<'db>) -> Maybe<TraitId<'db>> {
    let module_id = impl_def_id.parent_module(db);
    let mut diagnostics = SemanticDiagnostics::new(module_id);

    let impl_ast = db.module_impl_by_id(impl_def_id)?;
    let inference_id = InferenceId::ImplDefTrait(impl_def_id);

    let mut resolver = Resolver::new(db, module_id, inference_id);
    resolver.set_feature_config(&impl_def_id, &impl_ast, &mut diagnostics);

    let trait_path_syntax = impl_ast.trait_path(db);

    resolve_trait_path(db, &mut diagnostics, &mut resolver, &trait_path_syntax)
}

/// Query implementation of [PrivImplSemantic::impl_def_shallow_trait_generic_args].
fn impl_def_shallow_trait_generic_args<'db>(
    db: &'db dyn Database,
    impl_def_id: ImplDefId<'db>,
) -> Maybe<&'db [(GenericParamId<'db>, ShallowGenericArg<'db>)]> {
    Ok(impl_def_shallow_trait_generic_args_helper(db, impl_def_id).maybe_as_ref()?)
}

/// Helper for [ImplSemantic::impl_def_shallow_trait_generic_args].
/// The actual query implementation, separated to allow returning a reference.
#[salsa::tracked(returns(ref))]
fn impl_def_shallow_trait_generic_args_helper<'db>(
    db: &'db dyn Database,
    impl_def_id: ImplDefId<'db>,
) -> Maybe<Vec<(GenericParamId<'db>, ShallowGenericArg<'db>)>> {
    let module_id = impl_def_id.parent_module(db);
    let mut diagnostics = SemanticDiagnostics::new(module_id);

    let impl_ast = db.module_impl_by_id(impl_def_id)?;
    let inference_id = InferenceId::ImplDefTrait(impl_def_id);

    let mut resolver = Resolver::new(db, module_id, inference_id);
    resolver.set_feature_config(&impl_def_id, &impl_ast, &mut diagnostics);

    if let OptionWrappedGenericParamList::WrappedGenericParamList(params_list) =
        impl_ast.generic_params(db)
    {
        params_list.generic_params(db).elements(db).for_each(|param_syntax| {
            let generic_param_id =
                GenericParamLongId(module_id, param_syntax.stable_ptr(db)).intern(db);
            resolver.add_generic_param(generic_param_id);
        })
    }
    let trait_path_syntax = impl_ast.trait_path(db);

    let ResolvedGenericItem::Trait(trait_id) = resolver.resolve_generic_path_with_args(
        &mut diagnostics,
        &trait_path_syntax,
        NotFoundItemType::Trait,
        ResolutionContext::Default,
    )?
    else {
        return Err(skip_diagnostic());
    };
    let generic_params = db
        .trait_generic_params_ids(trait_id)?
        .iter()
        .map(|param_syntax| {
            GenericParamLongId(trait_id.parent_module(db), param_syntax.stable_ptr(db)).intern(db)
        })
        .collect::<Vec<_>>();

    let elements = trait_path_syntax.segments(db).elements(db);
    let Some(last) = elements.last() else {
        return Ok(Vec::new());
    };
    match last {
        ast::PathSegment::Simple(_) => Ok(Vec::new()),
        ast::PathSegment::WithGenericArgs(path_segment_with_generic_args) => {
            let generic_args =
                path_segment_with_generic_args.generic_args(db).generic_args(db).elements_vec(db);

            let arg_syntax_per_param = resolver.get_arg_syntax_per_param(
                &mut diagnostics,
                &generic_params,
                &generic_args,
            )?;
            Ok(generic_params
                .iter()
                .filter_map(|generic_param| {
                    let expr = arg_syntax_per_param.get(generic_param)?;
                    let arg_ty = maybe_resolve_shallow_generic_arg_type(
                        db,
                        &mut diagnostics,
                        &mut resolver,
                        expr,
                    )?;
                    Some((*generic_param, arg_ty))
                })
                .collect::<Vec<_>>())
        }
    }
}

/// Query implementation of [PrivImplSemantic::impl_alias_trait_generic_args].
fn impl_alias_trait_generic_args<'db>(
    db: &'db dyn Database,
    impl_alias_id: ImplAliasId<'db>,
) -> Maybe<&'db [(GenericParamId<'db>, ShallowGenericArg<'db>)]> {
    Ok(impl_alias_trait_generic_args_helper(db, impl_alias_id).maybe_as_ref()?)
}

#[salsa::tracked(returns(ref))]
fn impl_alias_trait_generic_args_helper<'db>(
    db: &'db dyn Database,
    impl_alias_id: ImplAliasId<'db>,
) -> Maybe<Vec<(GenericParamId<'db>, ShallowGenericArg<'db>)>> {
    let module_id = impl_alias_id.parent_module(db);
    let mut diagnostics = SemanticDiagnostics::new(module_id);

    let impl_alias_ast = db.module_impl_alias_by_id(impl_alias_id)?;
    let inference_id = InferenceId::ImplAliasImplDef(impl_alias_id);

    let mut resolver = Resolver::new(db, module_id, inference_id);
    resolver.set_feature_config(&impl_alias_id, &impl_alias_ast, &mut diagnostics);

    if let OptionWrappedGenericParamList::WrappedGenericParamList(params_list) =
        impl_alias_ast.generic_params(db)
    {
        params_list.generic_params(db).elements(db).for_each(|param_syntax| {
            let generic_param_id =
                GenericParamLongId(module_id, param_syntax.stable_ptr(db)).intern(db);
            resolver.add_generic_param(generic_param_id);
        })
    }
    let rhs_syntax = impl_alias_ast.impl_path(db);
    let (shallow_args, rhs_generic_params) = match resolver.resolve_generic_path_with_args(
        &mut diagnostics,
        &rhs_syntax,
        NotFoundItemType::Impl,
        ResolutionContext::Default,
    ) {
        Ok(ResolvedGenericItem::Impl(impl_def_id)) => {
            let shallow_args = db.impl_def_shallow_trait_generic_args(impl_def_id)?.to_vec();
            let OptionWrappedGenericParamList::WrappedGenericParamList(params) =
                db.module_impl_by_id(impl_def_id)?.generic_params(db)
            else {
                return Ok(shallow_args);
            };
            (
                shallow_args,
                params
                    .generic_params(db)
                    .elements(db)
                    .map(|param_syntax| {
                        GenericParamLongId(
                            impl_def_id.parent_module(db),
                            param_syntax.stable_ptr(db),
                        )
                        .intern(db)
                    })
                    .collect::<Vec<_>>(),
            )
        }
        Ok(ResolvedGenericItem::GenericImplAlias(impl_alias)) => {
            let shallow_args = db.impl_alias_trait_generic_args(impl_alias)?.to_vec();
            let OptionWrappedGenericParamList::WrappedGenericParamList(params) =
                db.module_impl_alias_by_id(impl_alias)?.generic_params(db)
            else {
                return Ok(shallow_args);
            };
            (
                shallow_args,
                params
                    .generic_params(db)
                    .elements(db)
                    .map(|param_syntax| {
                        GenericParamLongId(
                            impl_alias.parent_module(db),
                            param_syntax.stable_ptr(db),
                        )
                        .intern(db)
                    })
                    .collect::<Vec<_>>(),
            )
        }
        _ => return Ok(Vec::new()),
    };

    let elements = rhs_syntax.segments(db).elements(db);
    let Some(last) = elements.last() else {
        return Ok(Vec::new());
    };

    match last {
        ast::PathSegment::Simple(_) => Ok(shallow_args),
        ast::PathSegment::WithGenericArgs(path_segment_with_generic_args) => {
            let generic_args =
                path_segment_with_generic_args.generic_args(db).generic_args(db).elements_vec(db);
            let arg_syntax_per_param = resolver.get_arg_syntax_per_param(
                &mut diagnostics,
                &rhs_generic_params,
                &generic_args,
            )?;

            Ok(shallow_args
                .iter()
                .filter_map(|(trait_param, arg)| {
                    let ShallowGenericArg::GenericParameter(arg) = arg else {
                        return Some((*trait_param, arg.clone()));
                    };

                    arg_syntax_per_param.get(arg).and_then(|expr| {
                        let arg_ty = maybe_resolve_shallow_generic_arg_type(
                            db,
                            &mut diagnostics,
                            &mut resolver,
                            expr,
                        )?;
                        Some((*trait_param, arg_ty))
                    })
                })
                .collect::<Vec<_>>())
        }
    }
}

/// Implementation of [ImplSemantic::impl_concrete_trait].
fn impl_concrete_trait<'db>(
    db: &'db dyn Database,
    impl_id: ImplId<'db>,
) -> Maybe<ConcreteTraitId<'db>> {
    match impl_id.long(db) {
        ImplLongId::Concrete(concrete_impl_id) => {
            let long_impl = concrete_impl_id.long(db);
            let substitution = GenericSubstitution::new(
                db.impl_def_generic_params(long_impl.impl_def_id)?,
                &long_impl.generic_args,
            );

            let impl_concrete_trait_id = db.impl_def_concrete_trait(long_impl.impl_def_id)?;
            substitution.substitute(db, impl_concrete_trait_id)
        }
        ImplLongId::GenericParameter(param) => {
            let param_impl =
                extract_matches!(db.generic_param_semantic(*param)?, GenericParam::Impl);
            param_impl.concrete_trait
        }
        ImplLongId::ImplVar(var) => Ok(var.long(db).concrete_trait_id),
        ImplLongId::ImplImpl(impl_impl) => db.impl_impl_concrete_trait(*impl_impl),
        ImplLongId::SelfImpl(concrete_trait_id) => Ok(*concrete_trait_id),
        ImplLongId::GeneratedImpl(generated_impl) => Ok(generated_impl.concrete_trait(db)),
    }
}

/// Query implementation of [ImplSemantic::impl_concrete_trait].
#[salsa::tracked]
fn impl_concrete_trait_tracked<'db>(
    db: &'db dyn Database,
    impl_id: ImplId<'db>,
) -> Maybe<ConcreteTraitId<'db>> {
    impl_concrete_trait(db, impl_id)
}

// --- Computation ---

/// Cycle handling for [impl_declaration_data].
fn impl_declaration_data_cycle<'db>(
    db: &'db dyn Database,
    _id: salsa::Id,
    impl_def_id: ImplDefId<'db>,
) -> Maybe<ImplDeclarationData<'db>> {
    impl_declaration_data_inner(db, impl_def_id, false)
}

/// Computes impl declaration data.
#[salsa::tracked(cycle_result=impl_declaration_data_cycle, returns(ref))]
fn impl_declaration_data<'db>(
    db: &'db dyn Database,
    impl_def_id: ImplDefId<'db>,
) -> Maybe<ImplDeclarationData<'db>> {
    impl_declaration_data_inner(db, impl_def_id, true)
}

/// Shared code for the query and cycle handling.
/// The cycle handling logic needs to pass resolve_trait=false to prevent the cycle.
fn impl_declaration_data_inner<'db>(
    db: &'db dyn Database,
    impl_def_id: ImplDefId<'db>,
    resolve_trait: bool,
) -> Maybe<ImplDeclarationData<'db>> {
    let mut diagnostics = SemanticDiagnostics::new(impl_def_id.parent_module(db));

    // TODO(spapini): when code changes in a file, all the AST items change (as they contain a path
    // to the green root that changes. Once ASTs are rooted on items, use a selector that picks only
    // the item instead of all the module data.
    let impl_ast = db.module_impl_by_id(impl_def_id)?;
    let inference_id = InferenceId::LookupItemDeclaration(LookupItemId::ModuleItem(
        ModuleItemId::Impl(impl_def_id),
    ));

    // Generic params.
    let generic_params_data = impl_def_generic_params_data(db, impl_def_id).maybe_as_ref()?;
    let mut resolver = Resolver::with_data(
        db,
        (*generic_params_data.resolver_data).clone_with_inference_id(db, inference_id),
    );
    resolver.set_feature_config(&impl_def_id, &impl_ast, &mut diagnostics);
    diagnostics.extend(generic_params_data.diagnostics.clone());
    let trait_path_syntax = impl_ast.trait_path(db);

    let concrete_trait = if resolve_trait {
        resolver
            .resolve_concrete_path(&mut diagnostics, &trait_path_syntax, NotFoundItemType::Trait)
            .and_then(|resolved_item| match resolved_item {
                ResolvedConcreteItem::Trait(id) | ResolvedConcreteItem::SelfTrait(id) => Ok(id),
                _ => Err(diagnostics
                    .report(trait_path_syntax.stable_ptr(db), SemanticDiagnosticKind::NotATrait)),
            })
    } else {
        Err(diagnostics.report(trait_path_syntax.stable_ptr(db), ImplRequirementCycle))
    };

    let info = db.core_info();

    // Check for reimplementation of compilers' Traits.
    if let Ok(concrete_trait) = concrete_trait
        && [
            info.type_eq_trt,
            info.fn_trt,
            info.fn_once_trt,
            info.felt252_dict_value_trt,
            info.numeric_literal_trt,
            info.string_literal_trt,
        ]
        .contains(&concrete_trait.trait_id(db))
        && impl_def_id.parent_module(db).owning_crate(db) != core_crate(db)
    {
        diagnostics.report(
            trait_path_syntax.stable_ptr(db),
            CompilerTraitReImplementation { trait_id: concrete_trait.trait_id(db) },
        );
    }

    // Check fully resolved.
    let inference = &mut resolver.inference();
    inference.finalize(&mut diagnostics, impl_ast.stable_ptr(db).untyped());

    let concrete_trait: Result<ConcreteTraitId<'_>, DiagnosticAdded> =
        inference.rewrite(concrete_trait).no_err();

    let attributes = impl_ast.attributes(db).structurize(db);
    let mut resolver_data = resolver.data;
    resolver_data.trait_or_impl_ctx = TraitOrImplContext::Impl(impl_def_id);
    Ok(ImplDeclarationData {
        diagnostics: diagnostics.build(),
        concrete_trait,
        attributes,
        resolver_data: Arc::new(resolver_data),
    })
}

// === Impl Definition ===

#[derive(Clone, Debug, PartialEq, Eq, DebugWithDb, salsa::Update)]
#[debug_db(dyn Database)]
struct ImplDefinitionData<'db> {
    /// The diagnostics here are "flat" - that is, only the diagnostics found on the impl level
    /// itself, and don't include the diagnostics of its items. The reason it's this way is that
    /// computing the items' diagnostics require a query about their impl, forming a cycle of
    /// queries. Adding the items' diagnostics only after the whole computation breaks this cycle.
    diagnostics: Diagnostics<'db, SemanticDiagnostic<'db>>,

    // AST maps.
    function_asts: OrderedHashMap<ImplFunctionId<'db>, ast::FunctionWithBody<'db>>,
    item_type_asts: OrderedHashMap<ImplTypeDefId<'db>, ast::ItemTypeAlias<'db>>,
    item_constant_asts: OrderedHashMap<ImplConstantDefId<'db>, ast::ItemConstant<'db>>,
    item_impl_asts: OrderedHashMap<ImplImplDefId<'db>, ast::ItemImplAlias<'db>>,

    /// Mapping of item names to their meta data info. All the IDs should appear in one of the AST
    /// maps above.
    item_id_by_name: OrderedHashMap<SmolStrId<'db>, ImplItemInfo<'db>>,

    /// Mapping of missing impl names item names to the trait id.
    implicit_impls_id_by_name: OrderedHashMap<SmolStrId<'db>, TraitImplId<'db>>,
}

impl<'db> ImplDefinitionData<'db> {
    /// Retrieves impl item information by its name.
    pub fn get_impl_item_info(&self, item_name: SmolStrId<'db>) -> Option<ImplItemInfo<'db>> {
        self.item_id_by_name.get(&item_name).cloned()
    }
}
/// Stores metadata for an impl item, including its ID and feature kind.
#[derive(Clone, Debug, PartialEq, Eq, salsa::Update)]
pub struct ImplItemInfo<'db> {
    /// The unique identifier of the impl item.
    pub id: ImplItemId<'db>,
    /// The feature kind associated with this impl item.
    pub feature_kind: FeatureKind<'db>,
}

impl<'db> HasFeatureKind<'db> for ImplItemInfo<'db> {
    /// Returns the feature kind of this impl item.
    fn feature_kind(&self) -> &FeatureKind<'db> {
        &self.feature_kind
    }
}

// --- Selectors ---

/// Implementation of [ImplSemantic::impl_semantic_definition_diagnostics].
fn impl_semantic_definition_diagnostics<'db>(
    db: &'db dyn Database,
    impl_def_id: ImplDefId<'db>,
) -> Diagnostics<'db, SemanticDiagnostic<'db>> {
    let mut diagnostics = SemanticDiagnostics::new(impl_def_id.parent_module(db));

    let Ok(data) = impl_definition_data(db, impl_def_id) else {
        return Diagnostics::default();
    };

    // The diagnostics from `priv_impl_definition_data` are only the diagnostics from the impl
    // level. They should be enriched with the items' diagnostics.
    diagnostics.extend(data.diagnostics.clone());
    for impl_function_id in data.function_asts.keys() {
        diagnostics.extend(db.impl_function_declaration_diagnostics(*impl_function_id));
        diagnostics.extend(db.impl_function_body_diagnostics(*impl_function_id));
    }
    for impl_item_type_id in data.item_type_asts.keys() {
        diagnostics.extend(db.impl_type_def_semantic_diagnostics(*impl_item_type_id));
        if let Ok(ty) = db.impl_type_def_resolved_type(*impl_item_type_id) {
            add_type_based_diagnostics(db, &mut diagnostics, ty, impl_item_type_id.stable_ptr(db));
        }
    }
    for impl_item_constant_id in data.item_constant_asts.keys() {
        diagnostics.extend(db.impl_constant_def_semantic_diagnostics(*impl_item_constant_id));
    }
    for impl_item_impl_id in data.item_impl_asts.keys() {
        diagnostics.extend(db.impl_impl_def_semantic_diagnostics(*impl_item_impl_id));
    }
    for implicit_impl_id in data.implicit_impls_id_by_name.values() {
        diagnostics
            .extend(db.implicit_impl_impl_semantic_diagnostics(impl_def_id, *implicit_impl_id));
    }
    // Diagnostics for special traits.
    if diagnostics.error_count == 0 {
        let concrete_trait =
            impl_declaration_data(db, impl_def_id).as_ref().unwrap().concrete_trait.unwrap();

        let trait_id = concrete_trait.trait_id(db);
        if trait_id == db.core_info().deref_trt {
            deref_impl_diagnostics(db, impl_def_id, concrete_trait, &mut diagnostics);
        }
    }
    diagnostics.build()
}

/// Query implementation of [ImplSemantic::impl_semantic_definition_diagnostics].
#[salsa::tracked]
fn impl_semantic_definition_diagnostics_tracked<'db>(
    db: &'db dyn Database,
    impl_def_id: ImplDefId<'db>,
) -> Diagnostics<'db, SemanticDiagnostic<'db>> {
    impl_semantic_definition_diagnostics(db, impl_def_id)
}

/// Represents a chain of dereferences.
#[derive(Clone, Debug, Eq, PartialEq, salsa::Update)]
pub struct DerefChain<'db> {
    pub derefs: Arc<Vec<DerefInfo<'db>>>,
}

/// Represents a single steps in a deref chain.
#[derive(Clone, Debug, Eq, PartialEq, salsa::Update)]
pub struct DerefInfo<'db> {
    /// The concrete `Deref::deref` or `MutDeref::mderef_mut` function.
    pub function_id: FunctionId<'db>,
    /// The mutability of the self argument of the deref function.
    pub self_mutability: Mutability,
    /// The target type of the deref function.
    pub target_ty: TypeId<'db>,
}

/// Cycle handling for [ImplSemantic::deref_chain].
fn deref_chain_cycle<'db>(
    _db: &dyn Database,
    _id: salsa::Id,
    _ty: TypeId<'db>,
    _crate_id: CrateId<'db>,
    _try_deref_mut: bool,
) -> Maybe<DerefChain<'db>> {
    // `SemanticDiagnosticKind::DerefCycle` will be reported by `deref_impl_diagnostics`.
    Maybe::Err(skip_diagnostic())
}

/// Query implementation of [ImplSemantic::deref_chain].
#[salsa::tracked(cycle_result=deref_chain_cycle, returns(ref))]
fn deref_chain<'db>(
    db: &'db dyn Database,
    ty: TypeId<'db>,
    crate_id: CrateId<'db>,
    try_deref_mut: bool,
) -> Maybe<DerefChain<'db>> {
    let mut opt_deref = None;
    if try_deref_mut {
        opt_deref = try_get_deref_func_and_target(db, ty, crate_id, true)?;
    }
    let self_mutability = if opt_deref.is_some() {
        Mutability::Reference
    } else {
        opt_deref = try_get_deref_func_and_target(db, ty, crate_id, false)?;
        Mutability::Immutable
    };

    let Some((function_id, target_ty)) = opt_deref else {
        return Ok(DerefChain { derefs: Arc::new(vec![]) });
    };

    let inner_chain = db.deref_chain(target_ty, crate_id, false)?;

    Ok(DerefChain {
        derefs: Arc::new(
            chain!(
                [DerefInfo { function_id, target_ty, self_mutability }],
                inner_chain.derefs.iter().cloned()
            )
            .collect(),
        ),
    })
}

/// Tries to find the deref function and the target type for a given type and deref trait.
fn try_get_deref_func_and_target<'db>(
    db: &'db dyn Database,
    ty: TypeId<'db>,
    crate_id: CrateId<'db>,
    is_mut_deref: bool,
) -> Result<Option<(FunctionId<'db>, TypeId<'db>)>, DiagnosticAdded> {
    let info = db.core_info();
    let (deref_trait_id, deref_method) = if is_mut_deref {
        (info.deref_mut_trt, info.deref_mut_fn)
    } else {
        (info.deref_trt, info.deref_fn)
    };

    let mut lookup_context = ImplLookupContext::new_from_crate(crate_id);
    enrich_lookup_context_with_ty(db, ty, &mut lookup_context);
    let concrete_trait = ConcreteTraitLongId {
        trait_id: deref_trait_id,
        generic_args: vec![GenericArgumentId::Type(ty)],
    }
    .intern(db);
    let Ok(deref_impl) = get_impl_at_context(db, lookup_context.intern(db), concrete_trait, None)
    else {
        return Ok(None);
    };
    let concrete_impl_id: ConcreteImplId<'db> = match deref_impl.long(db) {
        ImplLongId::Concrete(concrete_impl_id) => *concrete_impl_id,
        _ => panic!("Expected concrete impl"),
    };

    let function_id: FunctionId<'db> = FunctionLongId {
        function: ConcreteFunction {
            generic_function: GenericFunctionId::Impl(ImplGenericFunctionId {
                impl_id: deref_impl,
                function: deref_method,
            }),
            generic_args: vec![],
        },
    }
    .intern(db);

    let data = impl_definition_data(db, concrete_impl_id.impl_def_id(db)).maybe_as_ref()?;
    let Ok((impl_item_type_id, _)) = data.item_type_asts.iter().exactly_one() else {
        return Ok(None);
    };
    let ty = db.impl_type_def_resolved_type(*impl_item_type_id)?;
    let substitution: GenericSubstitution<'db> = concrete_impl_id.substitution(db)?;
    let ty: TypeId<'db> = substitution.substitute(db, ty)?;

    Ok(Some((function_id, ty)))
}

/// Reports diagnostic for a deref impl.
fn deref_impl_diagnostics<'db>(
    db: &'db dyn Database,
    mut impl_def_id: ImplDefId<'db>,
    concrete_trait: ConcreteTraitId<'db>,
    diagnostics: &mut SemanticDiagnostics<'db>,
) {
    let mut visited_impls: OrderedHashSet<ImplDefId<'_>> = OrderedHashSet::default();
    let deref_trait_id = concrete_trait.trait_id(db);

    let impl_module = impl_def_id.parent_module(db);

    let mut impl_in_valid_location = false;
    if impl_module == deref_trait_id.parent_module(db) {
        impl_in_valid_location = true;
    }

    let gargs = concrete_trait.generic_args(db);
    let deref_ty = extract_matches!(gargs[0], GenericArgumentId::Type);
    if let Some(module_id) = deref_ty.long(db).module_id(db)
        && module_id == impl_module
    {
        impl_in_valid_location = true;
    }

    if !impl_in_valid_location {
        diagnostics.report(
            impl_def_id.stable_ptr(db),
            SemanticDiagnosticKind::MustBeNextToTypeOrTrait { trait_id: deref_trait_id },
        );
        return;
    }

    loop {
        let Ok(impl_id) = get_impl_based_on_single_impl_type(db, impl_def_id, |ty| {
            ConcreteTraitLongId {
                trait_id: deref_trait_id,
                generic_args: vec![GenericArgumentId::Type(ty)],
            }
            .intern(db)
        }) else {
            // Inference errors are handled when the impl is in actual use. In here we only check
            // for cycles.
            return;
        };

        impl_def_id = match impl_id.long(db) {
            ImplLongId::Concrete(concrete_impl_id) => concrete_impl_id.impl_def_id(db),
            _ => return,
        };

        if !visited_impls.insert(impl_def_id) {
            let deref_chain = visited_impls
                .iter()
                .map(|visited_impl| {
                    format!("{:?}", db.impl_def_concrete_trait(*visited_impl).unwrap().debug(db))
                })
                .join(" -> ");
            diagnostics.report(
                impl_def_id.stable_ptr(db),
                SemanticDiagnosticKind::DerefCycle { deref_chain },
            );
            return;
        }
    }
}

/// Assuming that an impl has a single impl type, extracts the type, and then infers another impl
/// based on it. If the inference fails, returns the inference error and the impl type definition
/// for diagnostics.
fn get_impl_based_on_single_impl_type<'db>(
    db: &'db dyn Database,
    impl_def_id: ImplDefId<'db>,
    concrete_trait_id: impl FnOnce(TypeId<'db>) -> ConcreteTraitId<'db>,
) -> Result<ImplId<'db>, (InferenceError<'db>, ImplTypeDefId<'db>)> {
    let data = impl_definition_data(db, impl_def_id).clone().unwrap();
    let mut types_iter = data.item_type_asts.iter();
    let (impl_item_type_id, _) = types_iter.next().unwrap();
    if types_iter.next().is_some() {
        panic!(
            "get_impl_based_on_single_impl_type called with an impl that has more than one type"
        );
    }
    let ty = db.impl_type_def_resolved_type(*impl_item_type_id).unwrap();

    let module_id = impl_def_id.parent_module(db);
    let generic_params = db.impl_def_generic_params(impl_def_id).unwrap();
    let generic_params_ids =
        generic_params.iter().map(|generic_param| generic_param.id()).collect();
    let lookup_context = ImplLookupContext::new(module_id, generic_params_ids, db);
    get_impl_at_context(db, lookup_context.intern(db), concrete_trait_id(ty), None)
        .map_err(|err| (err, *impl_item_type_id))
}

/// Query implementation of [ImplSemantic::impl_functions].
#[salsa::tracked(returns(ref))]
fn impl_functions<'db>(
    db: &'db dyn Database,
    impl_def_id: ImplDefId<'db>,
) -> Maybe<OrderedHashMap<SmolStrId<'db>, ImplFunctionId<'db>>> {
    Ok(impl_definition_data(db, impl_def_id)
        .maybe_as_ref()?
        .function_asts
        .keys()
        .map(|function_id| {
            let function_long_id = function_id.long(db);
            (function_long_id.name(db), *function_id)
        })
        .collect())
}

/// Query implementation of [PrivImplSemantic::impl_function_by_trait_function].
#[salsa::tracked]
fn impl_function_by_trait_function<'db>(
    db: &'db dyn Database,
    impl_def_id: ImplDefId<'db>,
    trait_function_id: TraitFunctionId<'db>,
) -> Maybe<Option<ImplFunctionId<'db>>> {
    let name = trait_function_id.name(db);
    for impl_function_id in
        impl_definition_data(db, impl_def_id).maybe_as_ref()?.function_asts.keys()
    {
        if impl_function_id.long(db).name(db) == name {
            return Ok(Some(*impl_function_id));
        }
    }
    Ok(None)
}

/// Implementation of [ImplSemantic::impl_item_info_by_name].
fn impl_item_info_by_name<'db>(
    db: &'db dyn Database,
    impl_def_id: ImplDefId<'db>,
    name: SmolStrId<'db>,
) -> Maybe<Option<ImplItemInfo<'db>>> {
    let impl_definition_data = impl_definition_data(db, impl_def_id).maybe_as_ref()?;
    Ok(impl_definition_data.get_impl_item_info(name))
}

/// Query implementation of [ImplSemantic::impl_item_info_by_name].
#[salsa::tracked]
fn impl_item_info_by_name_tracked<'db>(
    db: &'db dyn Database,
    impl_def_id: ImplDefId<'db>,
    name: SmolStrId<'db>,
) -> Maybe<Option<ImplItemInfo<'db>>> {
    impl_item_info_by_name(db, impl_def_id, name)
}

/// Query implementation of [ImplSemantic::impl_all_used_uses].
#[salsa::tracked(returns(ref))]
fn impl_all_used_uses<'db>(
    db: &'db dyn Database,
    impl_def_id: ImplDefId<'db>,
) -> Maybe<OrderedHashSet<UseId<'db>>> {
    let mut all_used_uses = db.impl_def_resolver_data(impl_def_id)?.used_uses.clone();
    let data = impl_definition_data(db, impl_def_id).maybe_as_ref()?;
    for item in data.item_id_by_name.values() {
        for resolver_data in get_resolver_data_options(LookupItemId::ImplItem(item.id), db) {
            all_used_uses.extend(resolver_data.used_uses.iter().cloned());
        }
    }
    Ok(all_used_uses)
}

/// Query implementation of [PrivImplSemantic::impl_type_by_id].
#[salsa::tracked]
fn impl_type_by_id<'db>(
    db: &'db dyn Database,
    impl_type_id: ImplTypeDefId<'db>,
) -> Maybe<ast::ItemTypeAlias<'db>> {
    let impl_types = db.impl_types(impl_type_id.impl_def_id(db))?;
    impl_types.get(&impl_type_id).cloned().ok_or_else(skip_diagnostic)
}

/// Implementation of [ImplSemantic::impl_type_by_trait_type].
fn impl_type_by_trait_type<'db>(
    db: &'db dyn Database,
    impl_def_id: ImplDefId<'db>,
    trait_type_id: TraitTypeId<'db>,
) -> Maybe<ImplTypeDefId<'db>> {
    if trait_type_id.trait_id(db) != db.impl_def_trait(impl_def_id)? {
        unreachable!(
            "impl_type_by_trait_type called with a trait type that does not belong to the impl's \
             trait"
        )
    }
    // If the trait type's name is not found, then a missing item diagnostic is reported.
    db.impl_item_by_name(impl_def_id, trait_type_id.name(db))?
        .and_then(|item_id| try_extract_matches!(item_id, ImplItemId::Type))
        .ok_or_else(skip_diagnostic)
}

/// Query implementation of [ImplSemantic::impl_type_by_trait_type].
#[salsa::tracked]
fn impl_type_by_trait_type_tracked<'db>(
    db: &'db dyn Database,
    impl_def_id: ImplDefId<'db>,
    trait_type_id: TraitTypeId<'db>,
) -> Maybe<ImplTypeDefId<'db>> {
    impl_type_by_trait_type(db, impl_def_id, trait_type_id)
}

/// Query implementation of [PrivImplSemantic::impl_constant_by_trait_constant].
#[salsa::tracked]
fn impl_constant_by_trait_constant<'db>(
    db: &'db dyn Database,
    impl_def_id: ImplDefId<'db>,
    trait_constant_id: TraitConstantId<'db>,
) -> Maybe<ImplConstantDefId<'db>> {
    if trait_constant_id.trait_id(db) != db.impl_def_trait(impl_def_id)? {
        unreachable!(
            "impl_constant_by_trait_constant called with a trait constant that does not belong to \
             the impl's trait"
        )
    }
    // If the trait constant's name is not found, then a missing item diagnostic is reported.
    db.impl_item_by_name(impl_def_id, trait_constant_id.name(db))?
        .and_then(|item_id| try_extract_matches!(item_id, ImplItemId::Constant))
        .ok_or_else(skip_diagnostic)
}

/// Query implementation of [PrivImplSemantic::impl_impl_by_id].
#[salsa::tracked]
fn impl_impl_by_id<'db>(
    db: &'db dyn Database,
    impl_impl_id: ImplImplDefId<'db>,
) -> Maybe<ast::ItemImplAlias<'db>> {
    let impl_impls = db.impl_impls(impl_impl_id.impl_def_id(db))?;
    impl_impls.get(&impl_impl_id).cloned().ok_or_else(skip_diagnostic)
}

/// Query implementation of [PrivImplSemantic::impl_impl_by_trait_impl].
#[salsa::tracked]
fn impl_impl_by_trait_impl<'db>(
    db: &'db dyn Database,
    impl_def_id: ImplDefId<'db>,
    trait_impl_id: TraitImplId<'db>,
) -> Maybe<ImplImplDefId<'db>> {
    if trait_impl_id.trait_id(db) != db.impl_def_trait(impl_def_id)? {
        unreachable!(
            "impl_impl_by_trait_impl called with a trait impl that does not belong to the impl's \
             trait"
        )
    }
    // If the trait impl's name is not found, then a missing item diagnostic is reported.
    db.impl_item_by_name(impl_def_id, trait_impl_id.name(db))?
        .and_then(|item_id| try_extract_matches!(item_id, ImplItemId::Impl))
        .ok_or_else(skip_diagnostic)
}

/// Query implementation of [PrivImplSemantic::is_implicit_impl_impl].
#[salsa::tracked]
fn is_implicit_impl_impl<'db>(
    db: &'db dyn Database,
    impl_def_id: ImplDefId<'db>,
    trait_impl_id: TraitImplId<'db>,
) -> Maybe<bool> {
    if trait_impl_id.trait_id(db) != db.impl_def_trait(impl_def_id)? {
        unreachable!(
            "impl_impl_by_trait_impl called with a trait impl that does not belong to the impl's \
             trait"
        )
    }

    let name = trait_impl_id.name(db);
    // If the trait impl's name is not found, then a missing item diagnostic is reported.
    Ok(db.impl_implicit_impl_by_name(impl_def_id, name)?.is_some())
}

// --- Computation ---

/// Returns data about an impl definition.
#[salsa::tracked(returns(ref))]
fn impl_definition_data<'db>(
    db: &'db dyn Database,
    impl_def_id: ImplDefId<'db>,
) -> Maybe<ImplDefinitionData<'db>> {
    let module_id = impl_def_id.parent_module(db);
    let mut diagnostics = SemanticDiagnostics::new(module_id);

    let generic_params =
        impl_def_generic_params_data(db, impl_def_id).maybe_as_ref()?.generic_params.clone();
    let concrete_trait = impl_declaration_data(db, impl_def_id).maybe_as_ref()?.concrete_trait?;

    let impl_ast = db.module_impl_by_id(impl_def_id)?;

    let generic_params_ids =
        generic_params.iter().map(|generic_param| generic_param.id()).collect();
    let lookup_context = ImplLookupContext::new(module_id, generic_params_ids, db).intern(db);
    check_special_impls(
        db,
        &mut diagnostics,
        lookup_context,
        concrete_trait,
        impl_ast.stable_ptr(db).untyped(),
    )
    // Ignore the result.
    .ok();

    let mut function_asts = OrderedHashMap::default();
    let mut item_type_asts = OrderedHashMap::default();
    let mut item_constant_asts = OrderedHashMap::default();
    let mut item_impl_asts = OrderedHashMap::default();
    let mut item_id_by_name = OrderedHashMap::default();

    if let MaybeImplBody::Some(body) = impl_ast.body(db) {
        for item in body.items(db).elements(db) {
            match item {
                ImplItem::Module(module) => {
                    report_invalid_impl_item(db, &mut diagnostics, module.module_kw(db))
                }

                ImplItem::Use(use_item) => {
                    report_invalid_impl_item(db, &mut diagnostics, use_item.use_kw(db))
                }
                ImplItem::ExternFunction(extern_func) => {
                    report_invalid_impl_item(db, &mut diagnostics, extern_func.extern_kw(db))
                }
                ImplItem::ExternType(extern_type) => {
                    report_invalid_impl_item(db, &mut diagnostics, extern_type.extern_kw(db))
                }
                ImplItem::Trait(trt) => {
                    report_invalid_impl_item(db, &mut diagnostics, trt.trait_kw(db))
                }
                ImplItem::Struct(structure) => {
                    report_invalid_impl_item(db, &mut diagnostics, structure.struct_kw(db))
                }
                ImplItem::Enum(enm) => {
                    report_invalid_impl_item(db, &mut diagnostics, enm.enum_kw(db))
                }
                ImplItem::Function(func) => {
                    let impl_function_id =
                        ImplFunctionLongId(module_id, func.stable_ptr(db)).intern(db);
                    let name_node = func.declaration(db).name(db);
                    let name = name_node.text(db);
                    let feature_kind =
                        FeatureKind::from_ast(db, &mut diagnostics, &func.attributes(db));
                    if item_id_by_name
                        .insert(
                            name,
                            ImplItemInfo {
                                id: ImplItemId::Function(impl_function_id),
                                feature_kind,
                            },
                        )
                        .is_some()
                    {
                        diagnostics
                            .report(name_node.stable_ptr(db), NameDefinedMultipleTimes(name));
                    }
                    function_asts.insert(impl_function_id, func);
                }
                ImplItem::Type(ty) => {
                    let impl_type_id = ImplTypeDefLongId(module_id, ty.stable_ptr(db)).intern(db);
                    let name_node = ty.name(db);
                    let name = name_node.text(db);
                    let feature_kind =
                        FeatureKind::from_ast(db, &mut diagnostics, &ty.attributes(db));
                    if item_id_by_name
                        .insert(
                            name,
                            ImplItemInfo { id: ImplItemId::Type(impl_type_id), feature_kind },
                        )
                        .is_some()
                    {
                        diagnostics
                            .report(name_node.stable_ptr(db), NameDefinedMultipleTimes(name));
                    }
                    item_type_asts.insert(impl_type_id, ty);
                }
                ImplItem::Constant(constant) => {
                    let impl_constant_id =
                        ImplConstantDefLongId(module_id, constant.stable_ptr(db)).intern(db);
                    let name_node = constant.name(db);
                    let name = name_node.text(db);
                    let feature_kind =
                        FeatureKind::from_ast(db, &mut diagnostics, &constant.attributes(db));
                    if item_id_by_name
                        .insert(
                            name,
                            ImplItemInfo {
                                id: ImplItemId::Constant(impl_constant_id),
                                feature_kind,
                            },
                        )
                        .is_some()
                    {
                        diagnostics.report(
                            name_node.stable_ptr(db),
                            SemanticDiagnosticKind::NameDefinedMultipleTimes(name),
                        );
                    }
                    item_constant_asts.insert(impl_constant_id, constant);
                }
                ImplItem::Impl(imp) => {
                    let impl_impl_id = ImplImplDefLongId(module_id, imp.stable_ptr(db)).intern(db);
                    let name_node = imp.name(db);
                    let name = name_node.text(db);
                    let feature_kind =
                        FeatureKind::from_ast(db, &mut diagnostics, &imp.attributes(db));
                    if item_id_by_name
                        .insert(
                            name,
                            ImplItemInfo { id: ImplItemId::Impl(impl_impl_id), feature_kind },
                        )
                        .is_some()
                    {
                        diagnostics.report(
                            name_node.stable_ptr(db),
                            SemanticDiagnosticKind::NameDefinedMultipleTimes(name),
                        );
                    }
                    item_impl_asts.insert(impl_impl_id, imp);
                }
                // Report nothing, a parser diagnostic is reported.
                ImplItem::Missing(_) => {}
            }
        }
    }

    let mut implicit_impls_id_by_name = OrderedHashMap::default();

    let trait_id = concrete_trait.long(db).trait_id;
    for (name, trait_impl_id) in db.trait_impls(trait_id)?.iter() {
        if item_id_by_name.contains_key(name) {
            continue;
        }
        implicit_impls_id_by_name.insert(*name, *trait_impl_id);
    }

    // It is later verified that all items in this impl match items from `concrete_trait`.
    // To ensure exact match (up to trait functions with default implementation), it is sufficient
    // to verify here that all items in `concrete_trait` appear in this impl.
    let impl_item_names: OrderedHashSet<SmolStrId<'db>> = item_id_by_name.keys().copied().collect();

    let trait_required_item_names = db.trait_required_item_names(trait_id)?;
    let missing_items_in_impl =
        trait_required_item_names.difference(&impl_item_names).cloned().collect::<Vec<_>>();
    if !missing_items_in_impl.is_empty() {
        diagnostics.report(
            // TODO(yuval): change this to point to impl declaration (need to add ImplDeclaration
            // in cairo_spec).
            // TODO(TomerStarkware): make sure we do not report missing if the trait item is
            // unsupported in impl.
            impl_ast.name(db).stable_ptr(db),
            SemanticDiagnosticKind::MissingItemsInImpl(missing_items_in_impl),
        );
    }

    Ok(ImplDefinitionData {
        diagnostics: diagnostics.build(),
        function_asts,
        item_type_asts,
        item_id_by_name,
        item_constant_asts,
        item_impl_asts,
        implicit_impls_id_by_name,
    })
}

/// A helper function to report diagnostics of items in an impl (used in
/// priv_impl_definition_data).
fn report_invalid_impl_item<'db, Terminal: syntax::node::Terminal<'db>>(
    db: &'db dyn Database,
    diagnostics: &mut SemanticDiagnostics<'db>,
    kw_terminal: Terminal,
) {
    diagnostics
        .report(kw_terminal.as_syntax_node().stable_ptr(db), InvalidImplItem(kw_terminal.text(db)));
}

/// Handle special cases such as Copy and Drop checking.
fn check_special_impls<'db>(
    db: &'db dyn Database,
    diagnostics: &mut SemanticDiagnostics<'db>,
    lookup_context: ImplLookupContextId<'db>,
    concrete_trait: ConcreteTraitId<'db>,
    stable_ptr: SyntaxStablePtrId<'db>,
) -> Maybe<()> {
    let ConcreteTraitLongId { trait_id, generic_args } = concrete_trait.long(db);
    let info = db.core_info();
    let copy = info.copy_trt;
    let drop = info.drop_trt;

    if *trait_id == copy {
        let tys = get_inner_types(db, extract_matches!(generic_args[0], GenericArgumentId::Type))?;
        for inference_error in tys
            .into_iter()
            .map(|ty| db.type_info(lookup_context, ty))
            .flat_map(|info| info.copyable.err())
        {
            if matches!(
                inference_error,
                InferenceError::Ambiguity(Ambiguity::MultipleImplsFound { .. })
            ) {
                // Having multiple copy implementations for a member is not an actual error.
                continue;
            }
            return Err(diagnostics.report(stable_ptr, InvalidCopyTraitImpl(inference_error)));
        }
    }
    if *trait_id == drop {
        let tys = get_inner_types(db, extract_matches!(generic_args[0], GenericArgumentId::Type))?;
        for inference_error in tys
            .into_iter()
            .map(|ty| db.type_info(lookup_context, ty))
            .flat_map(|info| info.droppable.err())
        {
            if matches!(
                inference_error,
                InferenceError::Ambiguity(Ambiguity::MultipleImplsFound { .. })
            ) {
                // Having multiple drop implementations for a member is not an actual error.
                continue;
            }
            return Err(diagnostics.report(stable_ptr, InvalidDropTraitImpl(inference_error)));
        }
    }

    Ok(())
}

/// Retrieves all the inner types (members of a struct / tuple or variants of an enum).
///
/// These are the types that are required to implement some trait,
/// in order for the original type to be able to implement this trait.
///
/// For example, a struct containing a type T can implement Drop only if T implements Drop.
fn get_inner_types<'db>(db: &'db dyn Database, ty: TypeId<'db>) -> Maybe<Vec<TypeId<'db>>> {
    Ok(match ty.long(db) {
        TypeLongId::Concrete(concrete_type_id) => {
            // Look for Copy and Drop trait in the defining module.
            match concrete_type_id {
                crate::ConcreteTypeId::Struct(concrete_struct_id) => db
                    .concrete_struct_members(*concrete_struct_id)?
                    .values()
                    .map(|member| member.ty)
                    .collect(),
                crate::ConcreteTypeId::Enum(concrete_enum_id) => db
                    .concrete_enum_variants(*concrete_enum_id)?
                    .into_iter()
                    .map(|variant| variant.ty)
                    .collect(),
                crate::ConcreteTypeId::Extern(_) => vec![],
            }
        }
        TypeLongId::Tuple(tys) => tys.to_vec(),
        TypeLongId::Snapshot(_) | TypeLongId::Closure(_) => vec![],
        TypeLongId::GenericParameter(_) => {
            return Err(skip_diagnostic());
        }
        TypeLongId::Var(_) | TypeLongId::NumericLiteral(_) | TypeLongId::ImplType(_) => {
            panic!("Types should be fully resolved at this point.")
        }
        TypeLongId::Coupon(_) => vec![],
        TypeLongId::FixedSizeArray { type_id, .. } => vec![*type_id],
        TypeLongId::Missing(diag_added) => {
            return Err(*diag_added);
        }
    })
}

// === Trait Filter ===

/// A filter for trait lookup that is not based on current inference state. This is
/// used for caching queries.
#[derive(Clone, Debug, Hash, PartialEq, Eq)]
pub struct TraitFilter<'db> {
    pub trait_id: TraitId<'db>,
    /// The filter on the generic arguments.
    pub generics_filter: GenericsHeadFilter<'db>,
}

/// A lookup filter on generic arguments that is not based on current inference state.
/// This is used for caching queries.
#[derive(Clone, Debug, Hash, PartialEq, Eq, salsa::Update)]
pub enum GenericsHeadFilter<'db> {
    /// No filter is applied. When nothing is known about the generics, this will lead to a
    /// wider search.
    NoFilter,
    /// Generics exists and the first generic parameter has a filter.
    /// This is usually enough to considerably reduce the number of searched items.
    FirstGenericFilter(GenericArgumentHead<'db>),
    /// Generics must not exist.
    NoGenerics,
}

#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, HeapSize, salsa::Update)]
pub struct UninferredImplById<'db>(pub UninferredImpl<'db>);
impl<'db> Ord for UninferredImplById<'db> {
    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
        match (&self.0, &other.0) {
            (UninferredImpl::Def(impl_def_id), UninferredImpl::Def(other_impl_def_id)) => {
                impl_def_id.get_internal_id().cmp(&other_impl_def_id.get_internal_id())
            }
            (
                UninferredImpl::ImplAlias(impl_alias_id),
                UninferredImpl::ImplAlias(other_impl_alias_id),
            ) => impl_alias_id.get_internal_id().cmp(&other_impl_alias_id.get_internal_id()),
            (UninferredImpl::GenericParam(param), UninferredImpl::GenericParam(other_param)) => {
                param.get_internal_id().cmp(&other_param.get_internal_id())
            }
            (
                UninferredImpl::ImplImpl(impl_impl_id),
                UninferredImpl::ImplImpl(other_impl_impl_id),
            ) => {
                if impl_impl_id.impl_id() == other_impl_impl_id.impl_id() {
                    impl_impl_id
                        .trait_impl_id()
                        .get_internal_id()
                        .cmp(&other_impl_impl_id.trait_impl_id().get_internal_id())
                } else {
                    impl_impl_id
                        .impl_id()
                        .get_internal_id()
                        .cmp(&other_impl_impl_id.impl_id().get_internal_id())
                }
            }
            (
                UninferredImpl::GeneratedImpl(generated_impl),
                UninferredImpl::GeneratedImpl(other_generated_impl),
            ) => generated_impl.get_internal_id().cmp(&other_generated_impl.get_internal_id()),
            (UninferredImpl::Def(_), _) => std::cmp::Ordering::Less,
            (_, UninferredImpl::Def(_)) => std::cmp::Ordering::Greater,
            (UninferredImpl::ImplAlias(_), _) => std::cmp::Ordering::Less,
            (_, UninferredImpl::ImplAlias(_)) => std::cmp::Ordering::Greater,
            (UninferredImpl::GenericParam(_), _) => std::cmp::Ordering::Less,
            (_, UninferredImpl::GenericParam(_)) => std::cmp::Ordering::Greater,
            (UninferredImpl::ImplImpl(_), _) => std::cmp::Ordering::Less,
            (_, UninferredImpl::ImplImpl(_)) => std::cmp::Ordering::Greater,
        }
    }
}
impl<'db> PartialOrd for UninferredImplById<'db> {
    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
        Some(self.cmp(other))
    }
}
impl<'db> From<UninferredImpl<'db>> for UninferredImplById<'db> {
    fn from(uninferred_impl: UninferredImpl<'db>) -> Self {
        UninferredImplById(uninferred_impl)
    }
}

#[derive(Clone, Debug, Hash, PartialEq, Eq, DebugWithDb, salsa::Update, HeapSize)]
#[debug_db(dyn Database)]
pub struct ImplLookupContext<'db> {
    pub crate_id: CrateId<'db>,
    pub generic_params: Vec<GenericParamId<'db>>,
    pub inner_impls: BTreeSet<UninferredImplById<'db>>,
    pub negative_impls: Vec<GenericParamId<'db>>,
}

define_short_id!(ImplLookupContextId, ImplLookupContext<'db>);

impl<'db> ImplLookupContext<'db> {
    /// Creates a new [ImplLookupContext] from a [CrateId].
    pub fn new_from_crate(crate_id: CrateId<'db>) -> Self {
        Self {
            crate_id,
            generic_params: Default::default(),
            inner_impls: Default::default(),
            negative_impls: Default::default(),
        }
    }
    /// Creates a new [ImplLookupContext] from a [TypeId] with the crate being the crate of the
    /// type's module.
    pub fn new_from_type(ty: TypeId<'db>, db: &'db dyn Database) -> Self {
        Self::new_from_crate(
            ty.long(db)
                .module_id(db)
                .map(|m| m.owning_crate(db))
                .unwrap_or_else(|| db.core_crate()),
        )
    }
    /// Creates a new [ImplLookupContext] from a [ModuleId].
    pub fn new(
        module_id: ModuleId<'db>,
        generic_params: Vec<GenericParamId<'db>>,
        db: &'db dyn Database,
    ) -> ImplLookupContext<'db> {
        let crate_id = module_id.owning_crate(db);
        let negative_impls = generic_params
            .iter()
            .filter(|generic_param_id| matches!(generic_param_id.kind(db), GenericKind::NegImpl))
            .copied()
            .collect_vec();
        let generic_params = generic_params
            .iter()
            .filter(|generic_param_id| {
                if !matches!(generic_param_id.kind(db), GenericKind::Impl) {
                    return false;
                }

                let uninferred_impl = UninferredImpl::GenericParam(**generic_param_id);

                let Ok(trait_id) = uninferred_impl.trait_id(db) else {
                    return true;
                };
                let Some(set) = db.crate_global_impls(crate_id).get(&trait_id) else {
                    return true;
                };
                let uninferred_impl: UninferredImplById<'db> = uninferred_impl.into();
                if set.contains(&uninferred_impl) {
                    return false;
                };
                true
            })
            .copied()
            .collect_vec();
        let mut res = Self {
            crate_id,
            generic_params: generic_params
                .clone()
                .into_iter()
                .filter(|id| id.long(db).has_type_constraints_syntax(db))
                .collect_vec(),
            inner_impls: BTreeSet::from_iter(
                generic_params.into_iter().map(|id| UninferredImpl::GenericParam(id).into()),
            ),
            negative_impls,
        };
        res.insert_module(module_id, db);
        res
    }
    pub fn insert_lookup_scope(&mut self, db: &'db dyn Database, imp: &UninferredImpl<'db>) {
        match imp {
            UninferredImpl::Def(impl_def_id) => {
                self.insert_module(impl_def_id.parent_module(db), db)
            }
            UninferredImpl::ImplAlias(impl_alias_id) => {
                self.insert_module(impl_alias_id.parent_module(db), db)
            }
            UninferredImpl::GenericParam(param) => self.insert_module(param.parent_module(db), db),
            UninferredImpl::ImplImpl(impl_impl_id) => self.insert_impl(impl_impl_id.impl_id, db),
            UninferredImpl::GeneratedImpl(_) => {
                // GeneratedImpls do not extend the lookup context.
            }
        };
    }
    /// Inserts a module into the lookup context, extending the inner impls with the module's
    /// impls.
    pub fn insert_module(&mut self, module_id: ModuleId<'db>, db: &'db dyn Database) {
        // Make sure to use the module as perceived by the user, as it contains all the macros.
        let module_id = db.module_perceived_module(module_id);
        let crate_global_impls = db.crate_global_impls(self.crate_id);
        if let Ok(module_impls) = db.module_global_impls((), module_id) {
            module_impls.locals.iter().for_each(|imp| {
                if let Ok(trait_id) = imp.0.trait_id(db)
                    && let Some(set) = crate_global_impls.get(&trait_id)
                    && set.contains(imp)
                {
                    return;
                }

                self.inner_impls.insert(*imp);
            });
            // If the module is not in the lookup context's crate, we add its global impls
            if !crate_dependencies(db, self.crate_id).contains(&module_id.owning_crate(db)) {
                module_impls.globals_by_trait.iter().for_each(|(_, imps)| {
                    imps.iter().for_each(|imp| {
                        if let Ok(trait_id) = imp.0.trait_id(db)
                            && let Some(set) = crate_global_impls.get(&trait_id)
                            && set.contains(imp)
                        {
                            return;
                        }

                        self.inner_impls.insert(*imp);
                    });
                });
            }
        }
    }

    /// Inserts an impl into the lookup context, extending the inner impls with the impl's
    /// trait impls.
    pub fn insert_impl(&mut self, impl_id: ImplId<'db>, db: &'db dyn Database) {
        let mut uninferred_impls = Vec::new();
        let Ok(concrete_trait) = impl_id.concrete_trait(db) else {
            return;
        };
        let Ok(trait_impls) = db.trait_impls(concrete_trait.trait_id(db)) else {
            return;
        };
        for (_, trait_impl_id) in trait_impls.iter() {
            uninferred_impls.push(UninferredImpl::ImplImpl(ImplImplId::new(
                impl_id,
                *trait_impl_id,
                db,
            )));
        }
        for uninferred_impl in uninferred_impls {
            self.inner_impls.insert(uninferred_impl.into());
        }
    }

    /// Strips the lookup context of all impls that are not reachable in the dependency graph from
    /// the given trait.
    pub fn strip_for_trait_id(&mut self, db: &dyn Database, trait_id: TraitId<'db>) {
        let deps = db.reachable_trait_dependencies(trait_id, self.crate_id);
        let type_eq_trt = db.core_info().type_eq_trt;
        self.inner_impls.retain(|impl_by_id| {
            if let Ok(impl_trait_id) = impl_by_id.0.trait_id(db) {
                return trait_id == impl_trait_id
                    || trait_id == type_eq_trt
                    || deps.contains(&impl_trait_id);
            }

            false
        });
    }
}

/// A candidate impl for later inference.
#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, SemanticObject, HeapSize, salsa::Update)]
pub enum UninferredImpl<'db> {
    Def(ImplDefId<'db>),
    ImplAlias(ImplAliasId<'db>),
    GenericParam(GenericParamId<'db>),
    ImplImpl(ImplImplId<'db>),
    GeneratedImpl(UninferredGeneratedImplId<'db>),
}
impl<'db> UninferredImpl<'db> {
    pub fn concrete_trait(&self, db: &'db dyn Database) -> Maybe<ConcreteTraitId<'db>> {
        match self {
            UninferredImpl::Def(impl_def_id) => db.impl_def_concrete_trait(*impl_def_id),
            UninferredImpl::ImplAlias(impl_alias_id) => {
                let impl_id = db.impl_alias_resolved_impl(*impl_alias_id)?;
                impl_id.concrete_trait(db)
            }
            UninferredImpl::GenericParam(param) => {
                let param =
                    extract_matches!(db.generic_param_semantic(*param)?, GenericParam::Impl);
                param.concrete_trait
            }
            UninferredImpl::ImplImpl(impl_impl_id) => db.impl_impl_concrete_trait(*impl_impl_id),
            UninferredImpl::GeneratedImpl(generated_impl) => Ok(generated_impl.concrete_trait(db)),
        }
    }

    fn trait_id(&self, db: &'db dyn Database) -> Maybe<TraitId<'db>> {
        match self {
            UninferredImpl::Def(impl_def_id) => db.impl_def_trait(*impl_def_id),
            UninferredImpl::ImplAlias(impl_alias_id) => {
                let impl_def_id = db.impl_alias_impl_def(*impl_alias_id)?;
                db.impl_def_trait(impl_def_id)
            }
            UninferredImpl::GenericParam(param) => db.generic_impl_param_trait(*param),
            UninferredImpl::ImplImpl(impl_impl_id) => db
                .impl_impl_concrete_trait(*impl_impl_id)
                .map(|concrete_trait| concrete_trait.trait_id(db)),
            UninferredImpl::GeneratedImpl(generated_impl) => Ok(generated_impl.trait_id(db)),
        }
    }

    /// Returns the shallow generic arguments of the concrete trait of this impl.
    fn trait_shallow_generic_args(
        &self,
        db: &'db dyn Database,
    ) -> Maybe<&'db [(GenericParamId<'db>, ShallowGenericArg<'db>)]> {
        match self {
            UninferredImpl::Def(impl_def_id) => {
                db.impl_def_shallow_trait_generic_args(*impl_def_id)
            }

            UninferredImpl::ImplAlias(impl_alias_id) => {
                db.impl_alias_trait_generic_args(*impl_alias_id)
            }
            UninferredImpl::GenericParam(param) => {
                db.generic_impl_param_shallow_trait_generic_args(*param)
            }
            // Todo(TomerStarkware): Implement this for ImplImpl and GeneratedImpl.
            UninferredImpl::ImplImpl(_impl_impl_id) => Ok(&[]),
            UninferredImpl::GeneratedImpl(_generated_impl) => Ok(&[]),
        }
    }
}

impl<'db> DebugWithDb<'db> for UninferredImpl<'db> {
    type Db = dyn Database;

    fn fmt(&self, f: &mut std::fmt::Formatter<'_>, db: &'db dyn Database) -> std::fmt::Result {
        match self {
            UninferredImpl::Def(impl_def) => write!(f, "{:?}", impl_def.full_path(db)),
            UninferredImpl::ImplAlias(impl_alias) => {
                write!(f, "{:?}", impl_alias.full_path(db))
            }
            UninferredImpl::GenericParam(param) => {
                write!(
                    f,
                    "generic param {}",
                    param.name(db).map(|name| name.long(db).as_str()).unwrap_or("_")
                )
            }
            UninferredImpl::ImplImpl(impl_impl) => impl_impl.fmt(f, db),
            UninferredImpl::GeneratedImpl(generated_impl) => generated_impl.fmt(f, db),
        }
    }
}

define_short_id!(UninferredGeneratedImplId, UninferredGeneratedImplLongId<'db>);
impl<'db> UnstableSalsaId for UninferredGeneratedImplId<'db> {
    fn get_internal_id(&self) -> salsa::Id {
        self.0
    }
}
semantic_object_for_id!(UninferredGeneratedImplId, UninferredGeneratedImplLongId<'a>);

impl<'db> UninferredGeneratedImplId<'db> {
    pub fn concrete_trait(self, db: &'db dyn Database) -> ConcreteTraitId<'db> {
        self.long(db).concrete_trait
    }

    pub fn trait_id(&self, db: &'db dyn Database) -> TraitId<'db> {
        self.concrete_trait(db).trait_id(db)
    }
}

/// Generated impls before inference, see GeneratedImplLongId for more details.
#[derive(Clone, Debug, Hash, PartialEq, Eq, SemanticObject, salsa::Update, HeapSize)]
pub struct UninferredGeneratedImplLongId<'db> {
    pub concrete_trait: ConcreteTraitId<'db>,
    pub generic_params: Vec<GenericParam<'db>>,
    pub impl_items: GeneratedImplItems<'db>,
}

impl<'db> DebugWithDb<'db> for UninferredGeneratedImplLongId<'db> {
    type Db = dyn Database;

    fn fmt(&self, f: &mut std::fmt::Formatter<'_>, db: &'db dyn Database) -> std::fmt::Result {
        write!(f, "Generated {:?}", self.concrete_trait.debug(db))
    }
}

/// Query implementation of [ImplSemantic::trait_candidate_by_head].
#[salsa::tracked(returns(ref))]
fn trait_candidate_by_head<'db>(
    db: &'db dyn Database,
    crate_id: CrateId<'db>,
    trait_id: TraitId<'db>,
) -> OrderedHashMap<GenericsHeadFilter<'db>, OrderedHashSet<UninferredImplById<'db>>> {
    let mut res: OrderedHashMap<GenericsHeadFilter<'db>, OrderedHashSet<UninferredImplById<'db>>> =
        OrderedHashMap::default();

    if let Some(candidates) = db.crate_global_impls(crate_id).get(&trait_id) {
        for candidate in candidates.iter() {
            let Ok(shallow_generic_args) = candidate.0.trait_shallow_generic_args(db) else {
                continue;
            };
            let Ok(trait_params) = db.trait_generic_params(trait_id) else {
                continue;
            };
            let Some(first_param) = trait_params.first() else {
                res.entry(GenericsHeadFilter::NoGenerics).or_default().insert(*candidate);
                continue;
            };

            // look for the generic argument that matches the first generic parameter of the trait.
            let shallow_arg =
                shallow_generic_args.iter().find(|(param, _)| *param == first_param.id());
            if let Some(first_generic_head) = shallow_arg.map(|(_, arg)| arg.head()) {
                if !matches!(candidate.0, UninferredImpl::GenericParam(_)) {
                    let mut type_head = first_generic_head.clone();
                    while let TypeHead::Snapshot(inner) = type_head {
                        type_head = *inner;
                    }
                    if matches!(type_head, TypeHead::Generic(_)) {
                        res.entry(GenericsHeadFilter::NoFilter).or_default().insert(*candidate);
                        continue;
                    }
                }
                res.entry(GenericsHeadFilter::FirstGenericFilter(GenericArgumentHead::Type(
                    first_generic_head,
                )))
                .or_default()
                .insert(*candidate);
            } else {
                res.entry(GenericsHeadFilter::NoFilter).or_default().insert(*candidate);
            }
        }
    }
    res
}

/// Finds all the implementations of a concrete trait, in a specific lookup context.
pub fn find_candidates_at_context<'db>(
    db: &'db dyn Database,
    lookup_context: ImplLookupContextId<'db>,
    filter: TraitFilter<'db>,
) -> Maybe<OrderedHashSet<UninferredImplById<'db>>> {
    let mut res = OrderedHashSet::default();
    let lookup = lookup_context.long(db);
    let crate_id = lookup.crate_id;
    let locals = lookup
        .inner_impls
        .iter()
        .filter(|uninferred_impl| {
            let Ok(trait_id) = uninferred_impl.0.trait_id(db) else { return false };
            trait_id == filter.trait_id
        })
        .cloned();
    match filter.generics_filter {
        GenericsHeadFilter::NoFilter => {
            let globals = db.crate_global_impls(crate_id);
            let globals = globals.get(&filter.trait_id);
            res.extend(locals);
            res.extend(globals.into_iter().flat_map(|s| s.iter().cloned()))
        }
        _ => {
            let candidates_by_head = db.trait_candidate_by_head(crate_id, filter.trait_id);
            let filtered = candidates_by_head.get(&filter.generics_filter).cloned();
            let no_filtered = candidates_by_head.get(&GenericsHeadFilter::NoFilter).cloned();
            res.extend(filtered.into_iter().flat_map(|s| s.into_iter()));
            res.extend(no_filtered.into_iter().flat_map(|s| s.into_iter()));
            res.extend(locals.filter(|uninferred_impl| {
                let Ok(_) = uninferred_impl.0.concrete_trait(db) else {
                    return false;
                };
                // TODO(TomerStarkware): Check if the concrete trait fits the trait filter.
                // Currently, light inference will invalidate this.
                true
            }));
        }
    }
    Ok(res)
}

/// Finds the generated candidate for a concrete trait.
pub fn find_closure_generated_candidate<'db>(
    db: &'db dyn Database,
    concrete_trait_id: ConcreteTraitId<'db>,
) -> Option<UninferredImpl<'db>> {
    let GenericArgumentId::Type(closure_type) = *concrete_trait_id.generic_args(db).first()? else {
        return None;
    };
    let TypeLongId::Closure(closure_type_long) = closure_type.long(db) else {
        return None;
    };

    let info = db.core_info();

    // Handles the special cases of `Copy`, `Drop`, `Destruct` and `PanicDestruct`.
    let mem_trait_generic_params = |trait_id, neg_impl_trait: Option<_>| {
        let id = db.trait_generic_params(trait_id).unwrap().first().unwrap().id();
        chain!(
            closure_type_long.captured_types.iter().unique().map(|ty| {
                GenericParam::Impl(GenericParamImpl {
                    id,
                    concrete_trait: Maybe::Ok(ConcreteTraitId::new(
                        db,
                        ConcreteTraitLongId {
                            trait_id,
                            generic_args: vec![GenericArgumentId::Type(*ty)],
                        },
                    )),
                    type_constraints: Default::default(),
                })
            }),
            neg_impl_trait.map(|neg_impl_trait| {
                GenericParam::NegImpl(GenericParamImpl {
                    id,
                    concrete_trait: Maybe::Ok(neg_impl_trait),
                    type_constraints: Default::default(),
                })
            })
        )
        .collect()
    };
    let handle_mem_trait = |trait_id, neg_impl_trait: Option<_>| {
        (concrete_trait_id, mem_trait_generic_params(trait_id, neg_impl_trait), [].into())
    };
    let (concrete_trait, generic_params, impl_items) = match concrete_trait_id.trait_id(db) {
        trait_id if trait_id == info.fn_once_trt => {
            let concrete_trait = ConcreteTraitLongId {
                trait_id,
                generic_args: vec![
                    GenericArgumentId::Type(closure_type),
                    GenericArgumentId::Type(
                        TypeLongId::Tuple(closure_type_long.param_tys.clone()).intern(db),
                    ),
                ],
            }
            .intern(db);
            let ret_ty =
                db.trait_type_by_name(trait_id, SmolStrId::from(db, "Output")).unwrap().unwrap();

            let id = db.trait_generic_params(trait_id).unwrap().first().unwrap().id();
            // FnOnce is generated only if there is no fn trait.
            let param: GenericParam<'_> = GenericParam::NegImpl(GenericParamImpl {
                id,
                concrete_trait: Maybe::Ok(
                    ConcreteTraitLongId {
                        trait_id: info.fn_trt,
                        generic_args: vec![
                            GenericArgumentId::Type(closure_type),
                            GenericArgumentId::Type(
                                TypeLongId::Tuple(closure_type_long.param_tys.clone()).intern(db),
                            ),
                        ],
                    }
                    .intern(db),
                ),
                type_constraints: Default::default(),
            });
            (concrete_trait, vec![param], [(ret_ty, closure_type_long.ret_ty)].into())
        }
        trait_id if trait_id == info.fn_trt => {
            let concrete_trait = ConcreteTraitLongId {
                trait_id,
                generic_args: vec![
                    GenericArgumentId::Type(closure_type),
                    GenericArgumentId::Type(
                        TypeLongId::Tuple(closure_type_long.param_tys.clone()).intern(db),
                    ),
                ],
            }
            .intern(db);
            let ret_ty =
                db.trait_type_by_name(trait_id, SmolStrId::from(db, "Output")).unwrap().unwrap();

            (
                concrete_trait,
                // Makes the generated impl of fn_trait available only if the closure is copyable.
                mem_trait_generic_params(info.copy_trt, None),
                [(ret_ty, closure_type_long.ret_ty)].into(),
            )
        }
        trait_id if trait_id == info.drop_trt => handle_mem_trait(trait_id, None),
        trait_id if trait_id == info.destruct_trt => {
            handle_mem_trait(trait_id, Some(concrete_drop_trait(db, closure_type)))
        }
        trait_id if trait_id == info.panic_destruct_trt => {
            handle_mem_trait(trait_id, Some(concrete_destruct_trait(db, closure_type)))
        }
        trait_id if trait_id == info.copy_trt => handle_mem_trait(trait_id, None),
        _ => return None,
    };
    Some(UninferredImpl::GeneratedImpl(
        UninferredGeneratedImplLongId {
            concrete_trait,
            generic_params,
            impl_items: GeneratedImplItems(impl_items),
        }
        .intern(db),
    ))
}

/// Finds the synthetic generated candidate for a numeric-literal placeholder type
/// (`TypeLongId::NumericLiteral`). The placeholder always satisfies `Drop`, `Copy`, `Destruct`,
/// and `PanicDestruct` (these are the memory traits which the trait solver must be able to
/// discharge for the literal's containing expression to type-check while the literal's concrete
/// type is still being inferred). All other traits — including `NumericLiteral<T>` — are left to
/// the normal solver path once the placeholder is conformed to a concrete type.
pub fn find_integer_literal_generated_candidate<'db>(
    db: &'db dyn Database,
    concrete_trait_id: ConcreteTraitId<'db>,
) -> Option<UninferredImpl<'db>> {
    let GenericArgumentId::Type(ty) = *concrete_trait_id.generic_args(db).first()? else {
        return None;
    };
    if !matches!(ty.long(db), TypeLongId::NumericLiteral(_)) {
        return None;
    }
    let info = db.core_info();
    let trait_id = concrete_trait_id.trait_id(db);
    if ![info.drop_trt, info.copy_trt, info.destruct_trt, info.panic_destruct_trt]
        .contains(&trait_id)
    {
        return None;
    }
    Some(UninferredImpl::GeneratedImpl(
        UninferredGeneratedImplLongId {
            concrete_trait: concrete_trait_id,
            generic_params: vec![],
            impl_items: GeneratedImplItems(Default::default()),
        }
        .intern(db),
    ))
}

/// Checks if an impl of a trait function with a given self_ty exists.
/// This function does not change the state of the inference context.
///
/// `inference_errors` are aggregated here but are not reported here as diagnostics.
/// The caller has to make sure the diagnostics are reported appropriately.
pub fn can_infer_impl_by_self<'db>(
    ctx: &ComputationContext<'db, '_>,
    inference_errors: &mut Vec<(TraitFunctionId<'db>, InferenceError<'db>)>,
    trait_function_id: TraitFunctionId<'db>,
    self_ty: TypeId<'db>,
    stable_ptr: SyntaxStablePtrId<'db>,
) -> bool {
    let mut temp_inference_data = ctx.resolver.data.inference_data.temporary_clone();
    let mut temp_inference = temp_inference_data.inference(ctx.db);
    let lookup_context = ctx.resolver.impl_lookup_context();

    let Some((concrete_trait_id, _)) = temp_inference.infer_concrete_trait_by_self(
        trait_function_id,
        self_ty,
        lookup_context,
        Some(stable_ptr),
        inference_errors,
    ) else {
        return false;
    };
    // Find impls for it.
    if let Err(err_set) = temp_inference.solve() {
        // Error is propagated and will be reported later.
        if let Some(err) = temp_inference.consume_error_without_reporting(err_set) {
            inference_errors.push((trait_function_id, err));
        }
    }
    match temp_inference.trait_solution_set(
        concrete_trait_id,
        ImplVarTraitItemMappings::default(),
        lookup_context,
    ) {
        Ok(SolutionSet::Unique(_) | SolutionSet::Ambiguous(_)) => true,
        Ok(SolutionSet::None) => {
            inference_errors
                .push((trait_function_id, InferenceError::NoImplsFound(concrete_trait_id)));
            false
        }
        Err(err_set) => {
            // Error is propagated and will be reported later.
            if let Some(err) = temp_inference.consume_error_without_reporting(err_set) {
                inference_errors.push((trait_function_id, err));
            }
            false
        }
    }
}

/// Returns an impl of a given trait function with a given self_ty, as well as the number of
/// snapshots needed to be added to it.
pub fn infer_impl_by_self<'db>(
    ctx: &mut ComputationContext<'db, '_>,
    trait_function_id: TraitFunctionId<'db>,
    self_ty: TypeId<'db>,
    stable_ptr: SyntaxStablePtrId<'db>,
    generic_args_syntax: Option<Vec<GenericArg<'db>>>,
) -> Maybe<(FunctionId<'db>, usize)> {
    let lookup_context = ctx.resolver.impl_lookup_context();
    let (concrete_trait_id, n_snapshots) = ctx
        .resolver
        .inference()
        .infer_concrete_trait_by_self_without_errors(
            trait_function_id,
            self_ty,
            lookup_context,
            Some(stable_ptr),
        )
        .ok_or_else(skip_diagnostic)?;

    let concrete_trait_function_id =
        ConcreteTraitGenericFunctionLongId::new(ctx.db, concrete_trait_id, trait_function_id)
            .intern(ctx.db);
    let trait_func_generic_params =
        ctx.db.concrete_trait_function_generic_params(concrete_trait_function_id).unwrap();

    let impl_lookup_context = ctx.resolver.impl_lookup_context();
    let inference = &mut ctx.resolver.inference();
    let generic_function = inference.infer_trait_generic_function(
        concrete_trait_function_id,
        impl_lookup_context,
        Some(stable_ptr),
    );
    let generic_args = ctx.resolver.resolve_generic_args(
        ctx.diagnostics,
        GenericSubstitution::from_impl(generic_function.impl_id),
        trait_func_generic_params,
        &generic_args_syntax.unwrap_or_default(),
        stable_ptr,
    )?;

    Ok((
        FunctionLongId {
            function: ConcreteFunction {
                generic_function: GenericFunctionId::Impl(generic_function),
                generic_args,
            },
        }
        .intern(ctx.db),
        n_snapshots,
    ))
}

/// Returns all the trait functions that fit the given function name, can be called on the given
/// `self_ty`, and have at least one implementation in context.
///
/// `inference_errors` are aggregated here but are not reported here as diagnostics.
/// The caller has to make sure the diagnostics are reported appropriately.
pub fn filter_candidate_traits<'db>(
    ctx: &mut ComputationContext<'db, '_>,
    inference_errors: &mut Vec<(TraitFunctionId<'db>, InferenceError<'db>)>,
    self_ty: TypeId<'db>,
    candidate_traits: &[TraitId<'db>],
    function_name: SmolStrId<'db>,
    stable_ptr: SyntaxStablePtrId<'db>,
) -> Vec<TraitFunctionId<'db>> {
    let mut candidates = Vec::new();
    for trait_id in candidate_traits.iter().copied() {
        let Ok(trait_functions) = ctx.db.trait_functions(trait_id) else {
            continue;
        };
        for (&name, &trait_function) in trait_functions.iter() {
            if name == function_name
                && can_infer_impl_by_self(
                    ctx,
                    inference_errors,
                    trait_function,
                    self_ty,
                    stable_ptr,
                )
            {
                candidates.push(trait_function);
            }
        }
    }
    candidates
}

// === Impl Item Type definition ===

#[derive(Clone, Debug, PartialEq, Eq, DebugWithDb, salsa::Update)]
#[debug_db(dyn Database)]
struct ImplItemTypeData<'db> {
    type_alias_data: TypeAliasData<'db>,
    trait_type_id: Maybe<TraitTypeId<'db>>,
    /// The diagnostics of the module type alias, including the ones for the type alias itself.
    diagnostics: Diagnostics<'db, SemanticDiagnostic<'db>>,
}

// --- Selectors ---

// --- Computation ---

/// Returns data about an impl type definition.
#[salsa::tracked(cycle_result=impl_type_semantic_data_cycle, returns(ref))]
fn impl_type_semantic_data<'db>(
    db: &'db dyn Database,
    impl_type_def_id: ImplTypeDefId<'db>,
    in_cycle: bool,
) -> Maybe<ImplItemTypeData<'db>> {
    let mut diagnostics =
        SemanticDiagnostics::new(impl_type_def_id.impl_def_id(db).parent_module(db));
    let impl_type_def_ast = db.impl_type_by_id(impl_type_def_id)?;
    let generic_params_data =
        impl_type_def_generic_params_data(db, impl_type_def_id).maybe_as_ref()?.clone();
    let lookup_item_id = LookupItemId::ImplItem(ImplItemId::Type(impl_type_def_id));

    let trait_type_id =
        validate_impl_item_type(db, &mut diagnostics, impl_type_def_id, &impl_type_def_ast);

    if in_cycle {
        Ok(ImplItemTypeData {
            type_alias_data: type_alias_semantic_data_cycle_helper(
                db,
                &mut diagnostics,
                &impl_type_def_ast,
                lookup_item_id,
                generic_params_data,
            )?,
            trait_type_id,
            diagnostics: diagnostics.build(),
        })
    } else {
        // TODO(yuval): resolve type aliases later, like in module type aliases, to avoid cycles in
        // non-cyclic chains.
        Ok(ImplItemTypeData {
            type_alias_data: type_alias_semantic_data_helper(
                db,
                &mut diagnostics,
                &impl_type_def_ast,
                lookup_item_id,
                generic_params_data,
            )?,
            trait_type_id,
            diagnostics: diagnostics.build(),
        })
    }
}

fn impl_type_semantic_data_cycle<'db>(
    db: &'db dyn Database,
    _id: salsa::Id,
    impl_type_def_id: ImplTypeDefId<'db>,
    _in_cycle: bool,
) -> Maybe<ImplItemTypeData<'db>> {
    impl_type_semantic_data(db, impl_type_def_id, true).clone()
}

/// Returns the generic parameters data of an impl type definition.
#[salsa::tracked(returns(ref))]
fn impl_type_def_generic_params_data<'db>(
    db: &'db dyn Database,
    impl_type_def_id: ImplTypeDefId<'db>,
) -> Maybe<GenericParamsData<'db>> {
    let module_id = impl_type_def_id.parent_module(db);
    let impl_type_def_ast = db.impl_type_by_id(impl_type_def_id)?;
    let lookup_item_id = LookupItemId::ImplItem(ImplItemId::Type(impl_type_def_id));

    let impl_resolver_data = db.impl_def_resolver_data(impl_type_def_id.impl_def_id(db))?;
    type_alias_generic_params_data_helper(
        db,
        module_id,
        &impl_type_def_ast,
        lookup_item_id,
        Some(impl_resolver_data),
    )
}

/// Validates the impl item type, and returns the matching trait type id.
fn validate_impl_item_type<'db>(
    db: &'db dyn Database,
    diagnostics: &mut SemanticDiagnostics<'db>,
    impl_type_def_id: ImplTypeDefId<'db>,
    impl_type_ast: &ast::ItemTypeAlias<'db>,
) -> Maybe<TraitTypeId<'db>> {
    let impl_def_id = impl_type_def_id.impl_def_id(db);
    let concrete_trait_id = db.impl_def_concrete_trait(impl_def_id)?;
    let trait_id = concrete_trait_id.trait_id(db);
    let type_name = impl_type_def_id.name(db);
    let trait_type_id = db.trait_type_by_name(trait_id, type_name)?.ok_or_else(|| {
        diagnostics.report(
            impl_type_ast.stable_ptr(db),
            ImplItemNotInTrait {
                impl_def_id,
                impl_item_name: type_name,
                trait_id,
                item_kind: "type".into(),
            },
        )
    })?;

    // TODO(yuval): add validations for generic parameters, then remove this.
    // Generic parameters are not yet supported, make sure there are none.
    let generic_params_node = impl_type_ast.generic_params(db);
    if !generic_params_node.is_empty(db) {
        diagnostics.report(
            generic_params_node.stable_ptr(db),
            GenericsNotSupportedInItem { scope: "Impl".into(), item_kind: "type".into() },
        );
    }

    Ok(trait_type_id)
}

// === Impl Type ===

/// Implementation of [ImplSemantic::impl_type_concrete_implized].
fn impl_type_concrete_implized<'db>(
    db: &'db dyn Database,
    impl_type_id: ImplTypeId<'db>,
) -> Maybe<TypeId<'db>> {
    let concrete_impl = match impl_type_id.impl_id().long(db) {
        ImplLongId::Concrete(concrete_impl) => concrete_impl,
        ImplLongId::ImplImpl(imp_impl_id) => {
            let ImplLongId::Concrete(concrete_impl) =
                db.impl_impl_concrete_implized(*imp_impl_id)?.long(db)
            else {
                return Ok(TypeLongId::ImplType(impl_type_id).intern(db));
            };
            concrete_impl
        }
        ImplLongId::GenericParameter(_) | ImplLongId::SelfImpl(_) | ImplLongId::ImplVar(_) => {
            return Ok(TypeLongId::ImplType(impl_type_id).intern(db));
        }
        ImplLongId::GeneratedImpl(generated) => {
            return Ok(*generated.long(db).impl_items.0.get(&impl_type_id.ty()).unwrap());
        }
    };

    let impl_def_id = concrete_impl.impl_def_id(db);
    let ty = db.trait_type_implized_by_context(impl_type_id.ty(), impl_def_id)?;
    concrete_impl.substitution(db)?.substitute(db, ty)
}

#[salsa::tracked(cycle_result=impl_type_concrete_implized_cycle)]
fn impl_type_concrete_implized_helper<'db>(
    db: &'db dyn Database,
    _tracked: Tracked,
    impl_type_id: ImplTypeId<'db>,
) -> Maybe<TypeId<'db>> {
    impl_type_concrete_implized(db, impl_type_id)
}

/// Query implementation of [ImplSemantic::impl_type_concrete_implized].
fn impl_type_concrete_implized_tracked<'db>(
    db: &'db dyn Database,
    impl_type_id: ImplTypeId<'db>,
) -> Maybe<TypeId<'db>> {
    impl_type_concrete_implized_helper(db, (), impl_type_id)
}

/// Cycle handling for [ImplSemantic::impl_type_concrete_implized].
fn impl_type_concrete_implized_cycle<'db>(
    db: &'db dyn Database,
    _id: salsa::Id,
    _tracked: Tracked,
    impl_type_id: ImplTypeId<'db>,
) -> Maybe<TypeId<'db>> {
    // Forwarding cycle handling to `impl_type_semantic_data` handler.
    impl_type_concrete_implized(db, impl_type_id)
}

// === Impl Item Constant definition ===

#[derive(Clone, Debug, PartialEq, Eq, DebugWithDb, salsa::Update)]
#[debug_db(dyn Database)]
struct ImplItemConstantData<'db> {
    constant_data: ConstantData<'db>,
    trait_constant_id: Maybe<TraitConstantId<'db>>,
    /// The diagnostics of the impl constant, including the ones for the constant itself.
    diagnostics: Diagnostics<'db, SemanticDiagnostic<'db>>,
}

/// Returns data about an impl constant definition.
#[salsa::tracked(cycle_result=impl_constant_semantic_data_cycle, returns(ref))]
fn impl_constant_semantic_data<'db>(
    db: &'db dyn Database,
    impl_constant_def_id: ImplConstantDefId<'db>,
    in_cycle: bool,
) -> Maybe<ImplItemConstantData<'db>> {
    let impl_def_id = impl_constant_def_id.impl_def_id(db);
    let mut diagnostics = SemanticDiagnostics::new(impl_def_id.parent_module(db));
    let impl_constant_defs = db.impl_constants(impl_def_id)?;
    let impl_constant_def_ast = impl_constant_defs.get(&impl_constant_def_id).to_maybe()?;
    let lookup_item_id = LookupItemId::ImplItem(ImplItemId::Constant(impl_constant_def_id));

    let inference_id = InferenceId::LookupItemGenerics(LookupItemId::ImplItem(
        ImplItemId::Constant(impl_constant_def_id),
    ));
    let resolver_data = db.impl_def_resolver_data(impl_def_id)?;
    let mut resolver =
        Resolver::with_data(db, resolver_data.clone_with_inference_id(db, inference_id));

    let trait_constant_id = validate_impl_item_constant(
        db,
        &mut diagnostics,
        impl_constant_def_id,
        impl_constant_def_ast,
        &mut resolver,
    );
    let mut constant_data = if in_cycle {
        constant_semantic_data_cycle_helper(
            db,
            impl_constant_def_ast,
            lookup_item_id,
            Some(Arc::new(resolver.data)),
            &impl_def_id,
        )?
    } else {
        constant_semantic_data_helper(
            db,
            impl_constant_def_ast,
            lookup_item_id,
            Some(Arc::new(resolver.data)),
            &impl_def_id,
        )?
    };
    diagnostics.extend(mem::take(&mut constant_data.diagnostics));
    Ok(ImplItemConstantData { constant_data, trait_constant_id, diagnostics: diagnostics.build() })
}

fn impl_constant_semantic_data_cycle<'db>(
    db: &'db dyn Database,
    _id: salsa::Id,
    impl_constant_def_id: ImplConstantDefId<'db>,
    _in_cycle: bool,
) -> Maybe<ImplItemConstantData<'db>> {
    impl_constant_semantic_data(db, impl_constant_def_id, true).clone()
}

/// Validates the impl item constant, and returns the matching trait constant id.
fn validate_impl_item_constant<'db>(
    db: &'db dyn Database,
    diagnostics: &mut SemanticDiagnostics<'db>,
    impl_constant_def_id: ImplConstantDefId<'db>,
    impl_constant_ast: &ast::ItemConstant<'db>,
    resolver: &mut Resolver<'db>,
) -> Maybe<TraitConstantId<'db>> {
    let impl_def_id = impl_constant_def_id.impl_def_id(db);
    let concrete_trait_id = db.impl_def_concrete_trait(impl_def_id)?;
    let trait_id = concrete_trait_id.trait_id(db);
    let constant_name = impl_constant_def_id.name(db);

    let trait_constant_id =
        db.trait_constant_by_name(trait_id, constant_name)?.ok_or_else(|| {
            diagnostics.report(
                impl_constant_ast.stable_ptr(db),
                ImplItemNotInTrait {
                    impl_def_id,
                    impl_item_name: constant_name,
                    trait_id,
                    item_kind: "const".into(),
                },
            )
        })?;
    let concrete_trait_constant =
        ConcreteTraitConstantId::new_from_data(db, concrete_trait_id, trait_constant_id);
    let impl_def_substitution = db.impl_def_substitution(impl_def_id)?;
    let concrete_trait_constant_ty = impl_def_substitution
        .substitute(db, db.concrete_trait_constant_type(concrete_trait_constant)?)?;

    let impl_constant_type_clause_ast = impl_constant_ast.type_clause(db);

    let constant_ty =
        resolve_type(db, diagnostics, resolver, &impl_constant_type_clause_ast.ty(db));

    let inference = &mut resolver.inference();

    let expected_ty = inference.rewrite(concrete_trait_constant_ty).no_err();
    let actual_ty = inference.rewrite(constant_ty).no_err();
    if expected_ty != actual_ty && !expected_ty.is_missing(db) && !actual_ty.is_missing(db) {
        diagnostics.report(
            impl_constant_type_clause_ast.ty(db).stable_ptr(db),
            WrongType { expected_ty, actual_ty },
        );
    }
    Ok(trait_constant_id)
}

// === Impl Constant ===

/// Query implementation of [PrivImplSemantic::impl_constant_implized_by_context].
fn impl_constant_implized_by_context<'db>(
    db: &'db dyn Database,
    impl_constant_id: ImplConstantId<'db>,
    impl_def_id: ImplDefId<'db>,
) -> Maybe<ConstValueId<'db>> {
    let impl_constant_def_id: ImplConstantDefId<'_> =
        db.impl_constant_by_trait_constant(impl_def_id, impl_constant_id.trait_constant_id())?;

    db.impl_constant_def_value(impl_constant_def_id)
}

/// Query implementation of [ImplSemantic::impl_constant_implized_by_context].
#[salsa::tracked(cycle_result=impl_constant_implized_by_context_cycle)]
fn impl_constant_implized_by_context_tracked<'db>(
    db: &'db dyn Database,
    impl_constant_id: ImplConstantId<'db>,
    impl_def_id: ImplDefId<'db>,
) -> Maybe<ConstValueId<'db>> {
    impl_constant_implized_by_context(db, impl_constant_id, impl_def_id)
}

/// Cycle handling for [PrivImplSemantic::impl_constant_implized_by_context].
fn impl_constant_implized_by_context_cycle<'db>(
    db: &'db dyn Database,
    _id: salsa::Id,
    impl_constant_id: ImplConstantId<'db>,
    impl_def_id: ImplDefId<'db>,
) -> Maybe<ConstValueId<'db>> {
    // Forwarding cycle handling to `priv_impl_constant_semantic_data` handler.
    impl_constant_implized_by_context(db, impl_constant_id, impl_def_id)
}

/// Query implementation of [ImplSemantic::impl_constant_concrete_implized_value].
fn impl_constant_concrete_implized_value<'db>(
    db: &'db dyn Database,
    impl_constant_id: ImplConstantId<'db>,
) -> Maybe<ConstValueId<'db>> {
    if let ImplLongId::Concrete(concrete_impl) = impl_constant_id.impl_id().long(db) {
        let impl_def_id = concrete_impl.impl_def_id(db);
        let constant: ConstValueId<'db> =
            db.impl_constant_implized_by_context(impl_constant_id, impl_def_id)?;
        return concrete_impl.substitution(db)?.substitute(db, constant);
    }
    let substitution: GenericSubstitution<'db> =
        GenericSubstitution::from_impl(impl_constant_id.impl_id());
    let substitution_id = substitution.substitute(db, impl_constant_id)?;
    let const_val: ConstValue<'db> = ConstValue::ImplConstant(substitution_id);
    Ok(const_val.intern(db))
}

/// Query implementation of [ImplSemantic::impl_constant_concrete_implized_value].
fn impl_constant_concrete_implized_value_tracked<'db>(
    db: &'db dyn Database,
    impl_constant_id: ImplConstantId<'db>,
) -> Maybe<ConstValueId<'db>> {
    impl_constant_concrete_implized_value_helper(db, (), impl_constant_id)
}

/// Tracked implementation of [ImplSemantic::impl_constant_concrete_implized_value].
/// Receives a dummy id to support salsa tracking.
#[salsa::tracked(cycle_result=impl_constant_concrete_implized_value_cycle)]
fn impl_constant_concrete_implized_value_helper<'db>(
    db: &'db dyn Database,
    _tracked: Tracked,
    impl_constant_id: ImplConstantId<'db>,
) -> Maybe<ConstValueId<'db>> {
    impl_constant_concrete_implized_value(db, impl_constant_id)
}

/// Cycle handling for [ImplSemantic::impl_constant_concrete_implized_value].
fn impl_constant_concrete_implized_value_cycle<'db>(
    db: &'db dyn Database,
    _id: salsa::Id,
    _tracked: Tracked,
    impl_constant_id: ImplConstantId<'db>,
) -> Maybe<ConstValueId<'db>> {
    // Forwarding cycle handling to `priv_impl_const_semantic_data` handler.
    impl_constant_concrete_implized_value(db, impl_constant_id)
}

/// Query implementation of [ImplSemantic::impl_constant_concrete_implized_type].
fn impl_constant_concrete_implized_type<'db>(
    db: &'db dyn Database,
    impl_constant_id: ImplConstantId<'db>,
) -> Maybe<TypeId<'db>> {
    let concrete_trait_id = match impl_constant_id.impl_id().long(db) {
        ImplLongId::Concrete(concrete_impl) => {
            let impl_def_id = concrete_impl.impl_def_id(db);
            let ty = db.impl_constant_implized_by_context(impl_constant_id, impl_def_id)?.ty(db)?;
            return concrete_impl.substitution(db)?.substitute(db, ty);
        }
        ImplLongId::GenericParameter(param) => {
            let param_impl =
                extract_matches!(db.generic_param_semantic(*param)?, GenericParam::Impl);
            param_impl.concrete_trait?
        }
        ImplLongId::ImplVar(var) => var.long(db).concrete_trait_id,
        ImplLongId::ImplImpl(impl_impl) => db.impl_impl_concrete_trait(*impl_impl)?,
        ImplLongId::SelfImpl(concrete_trait_id) => *concrete_trait_id,
        ImplLongId::GeneratedImpl(generated_impl) => generated_impl.concrete_trait(db),
    };

    let ty = db.concrete_trait_constant_type(ConcreteTraitConstantId::new_from_data(
        db,
        concrete_trait_id,
        impl_constant_id.trait_constant_id(),
    ))?;
    GenericSubstitution::from_impl(impl_constant_id.impl_id()).substitute(db, ty)
}

/// Query implementation of [ImplSemantic::impl_constant_concrete_implized_type].
fn impl_constant_concrete_implized_type_tracked<'db>(
    db: &'db dyn Database,
    impl_constant_id: ImplConstantId<'db>,
) -> Maybe<TypeId<'db>> {
    impl_constant_concrete_implized_type_helper(db, (), impl_constant_id)
}

#[salsa::tracked(cycle_result=impl_constant_concrete_implized_type_cycle)]
fn impl_constant_concrete_implized_type_helper<'db>(
    db: &'db dyn Database,
    _tracked: Tracked,
    impl_constant_id: ImplConstantId<'db>,
) -> Maybe<TypeId<'db>> {
    impl_constant_concrete_implized_type(db, impl_constant_id)
}

/// Cycle handling for [ImplSemantic::impl_constant_concrete_implized_type].
fn impl_constant_concrete_implized_type_cycle<'db>(
    db: &'db dyn Database,
    _id: salsa::Id,
    _tracked: Tracked,
    impl_constant_id: ImplConstantId<'db>,
) -> Maybe<TypeId<'db>> {
    // Forwarding cycle handling to `priv_impl_const_semantic_data` handler.
    impl_constant_concrete_implized_type(db, impl_constant_id)
}

// === Impl Item Impl definition ===

#[derive(Clone, Debug, PartialEq, Eq, DebugWithDb, salsa::Update)]
#[debug_db(dyn Database)]
struct ImplItemImplData<'db> {
    impl_data: ImplAliasData<'db>,
    trait_impl_id: Maybe<TraitImplId<'db>>,
    /// The diagnostics of the impl impl, including the ones for the impl itself.
    diagnostics: Diagnostics<'db, SemanticDiagnostic<'db>>,
}

/// Returns data about an impl impl definition.
#[salsa::tracked(cycle_result=impl_impl_semantic_data_cycle, returns(ref))]
fn impl_impl_semantic_data<'db>(
    db: &'db dyn Database,
    impl_impl_def_id: ImplImplDefId<'db>,
    in_cycle: bool,
) -> Maybe<ImplItemImplData<'db>> {
    let impl_def_id = impl_impl_def_id.impl_def_id(db);
    let mut diagnostics = SemanticDiagnostics::new(impl_def_id.parent_module(db));
    let impl_impl_defs = db.impl_impls(impl_def_id)?;
    let impl_impl_def_ast = impl_impl_defs.get(&impl_impl_def_id).to_maybe()?;
    let generic_params_data =
        impl_impl_def_generic_params_data(db, impl_impl_def_id).maybe_as_ref()?.clone();
    let lookup_item_id = LookupItemId::ImplItem(ImplItemId::Impl(impl_impl_def_id));

    let inference_id = InferenceId::LookupItemGenerics(lookup_item_id);
    let resolver_data = db.impl_def_resolver_data(impl_def_id)?;
    let mut resolver =
        Resolver::with_data(db, resolver_data.clone_with_inference_id(db, inference_id));

    let mut impl_data = if in_cycle {
        impl_alias_semantic_data_cycle_helper(
            db,
            impl_impl_def_ast,
            lookup_item_id,
            generic_params_data,
        )?
    } else {
        impl_alias_semantic_data_helper(db, impl_impl_def_ast, lookup_item_id, generic_params_data)?
    };

    diagnostics.extend(mem::take(&mut impl_data.diagnostics));

    let trait_impl_id = validate_impl_item_impl(
        db,
        &mut diagnostics,
        impl_impl_def_id,
        impl_impl_def_ast,
        &impl_data,
        &mut resolver,
    );

    Ok(ImplItemImplData { impl_data, trait_impl_id, diagnostics: diagnostics.build() })
}

fn impl_impl_semantic_data_cycle<'db>(
    db: &'db dyn Database,
    _id: salsa::Id,
    impl_impl_def_id: ImplImplDefId<'db>,
    _in_cycle: bool,
) -> Maybe<ImplItemImplData<'db>> {
    impl_impl_semantic_data(db, impl_impl_def_id, true).clone()
}

/// Returns the generic parameters data of an impl impl definition.
#[salsa::tracked(returns(ref))]
fn impl_impl_def_generic_params_data<'db>(
    db: &'db dyn Database,
    impl_impl_def_id: ImplImplDefId<'db>,
) -> Maybe<GenericParamsData<'db>> {
    let module_id = impl_impl_def_id.parent_module(db);
    let impl_impl_def_ast = db.impl_impl_by_id(impl_impl_def_id)?;
    let lookup_item_id = LookupItemId::ImplItem(ImplItemId::Impl(impl_impl_def_id));

    let impl_resolver_data = db.impl_def_resolver_data(impl_impl_def_id.impl_def_id(db))?;
    impl_alias_generic_params_data_helper(
        db,
        module_id,
        &impl_impl_def_ast,
        lookup_item_id,
        Some(impl_resolver_data),
    )
}

/// Validates the impl item impl, and returns the matching trait impl id.
fn validate_impl_item_impl<'db>(
    db: &'db dyn Database,
    diagnostics: &mut SemanticDiagnostics<'db>,
    impl_impl_def_id: ImplImplDefId<'db>,
    impl_impl_ast: &ast::ItemImplAlias<'db>,
    impl_data: &ImplAliasData<'db>,
    resolver: &mut Resolver<'db>,
) -> Maybe<TraitImplId<'db>> {
    let impl_def_id = impl_impl_def_id.impl_def_id(db);
    let concrete_trait_id = db.impl_def_concrete_trait(impl_def_id)?;
    let trait_id = concrete_trait_id.trait_id(db);
    let impl_item_name = impl_impl_def_id.name(db);
    let trait_impl_id = db.trait_impl_by_name(trait_id, impl_item_name)?.ok_or_else(|| {
        diagnostics.report(
            impl_impl_ast.stable_ptr(db),
            ImplItemNotInTrait { impl_def_id, impl_item_name, trait_id, item_kind: "impl".into() },
        )
    })?;

    // TODO(TomerStarkware): add validations for generic parameters, then remove this.
    // Generic parameters are not yet supported, make sure there are none.
    let generic_params_node = impl_impl_ast.generic_params(db);
    if !generic_params_node.is_empty(db) {
        diagnostics.report(
            generic_params_node.stable_ptr(db),
            GenericsNotSupportedInItem { scope: "Impl".into(), item_kind: "impl".into() },
        );
    }

    let concrete_trait_impl =
        ConcreteTraitImplId::new_from_data(db, concrete_trait_id, trait_impl_id);
    let impl_def_substitution = db.impl_def_substitution(impl_def_id)?;

    let concrete_trait_impl_concrete_trait = db
        .concrete_trait_impl_concrete_trait(concrete_trait_impl)
        .and_then(|concrete_trait_id| impl_def_substitution.substitute(db, concrete_trait_id));

    let resolved_impl_concrete_trait =
        impl_data.resolved_impl.and_then(|imp| imp.concrete_trait(db));
    // used an IIFE to allow the use of the `?` operator.
    let _ = (|| -> Result<(), DiagnosticAdded> {
        if resolver
            .inference()
            .conform_traits(resolved_impl_concrete_trait?, concrete_trait_impl_concrete_trait?)
            .is_err()
        {
            diagnostics.report(
                impl_impl_ast.stable_ptr(db),
                TraitMismatch {
                    expected_trt: concrete_trait_impl_concrete_trait?,
                    actual_trt: resolved_impl_concrete_trait?,
                },
            );
        }
        Ok(())
    })();

    Ok(trait_impl_id)
}

#[derive(Clone, Debug, PartialEq, Eq, DebugWithDb, salsa::Update)]
#[debug_db(dyn Database)]
struct ImplicitImplImplData<'db> {
    resolved_impl: Maybe<ImplId<'db>>,
    trait_impl_id: TraitImplId<'db>,
    diagnostics: Diagnostics<'db, SemanticDiagnostic<'db>>,
}

/// Computes implicit impl semantic data with cycle handling.
fn implicit_impl_impl_semantic_data<'db>(
    db: &'db dyn Database,
    impl_def_id: ImplDefId<'db>,
    trait_impl_id: TraitImplId<'db>,
    in_cycle: bool,
) -> Maybe<ImplicitImplImplData<'db>> {
    let mut diagnostics = SemanticDiagnostics::new(impl_def_id.parent_module(db));
    if in_cycle {
        let err = Err(diagnostics.report(impl_def_id.stable_ptr(db).untyped(), ImplAliasCycle));
        return Ok(ImplicitImplImplData {
            resolved_impl: err,
            trait_impl_id,
            diagnostics: diagnostics.build(),
        });
    }
    let lookup_item_id = LookupItemId::ModuleItem(ModuleItemId::Impl(impl_def_id));

    let inference_id = InferenceId::LookupItemGenerics(lookup_item_id);
    let resolver_data = db.impl_def_resolver_data(impl_def_id)?;

    let mut resolver =
        Resolver::with_data(db, resolver_data.clone_with_inference_id(db, inference_id));
    // We cannot use `Self` as it will always find the implicit impl.
    resolver.trait_or_impl_ctx = TraitOrImplContext::None;

    let concrete_trait_impl_concrete_trait = db
        .impl_def_concrete_trait(impl_def_id)
        .and_then(|concrete_trait_id| {
            db.concrete_trait_impl_concrete_trait(ConcreteTraitImplId::new_from_data(
                db,
                concrete_trait_id,
                trait_impl_id,
            ))
        })
        .and_then(|concrete_trait_id| {
            let impl_def_substitution = db.impl_def_substitution(impl_def_id)?;
            impl_def_substitution.substitute(db, concrete_trait_id)
        });
    let impl_lookup_context = resolver.impl_lookup_context();
    let resolved_impl = concrete_trait_impl_concrete_trait.and_then(|concrete_trait_id| {
        let imp = resolver.inference().new_impl_var(concrete_trait_id, None, impl_lookup_context);
        resolver.inference().finalize_without_reporting().map_err(|err_set| {
            diagnostics.report(
                impl_def_id.stable_ptr(db).untyped(),
                ImplicitImplNotInferred { trait_impl_id, concrete_trait_id },
            );
            resolver.inference().report_on_pending_error(
                err_set,
                &mut diagnostics,
                impl_def_id.stable_ptr(db).untyped(),
            )
        })?;
        resolver.inference().rewrite(imp).map_err(|_| skip_diagnostic())
    });

    Ok(ImplicitImplImplData { resolved_impl, trait_impl_id, diagnostics: diagnostics.build() })
}

/// Computes implicit impl semantic data with cycle handling.
#[salsa::tracked(cycle_result=implicit_impl_impl_semantic_data_cycle, returns(ref))]
fn implicit_impl_impl_semantic_data_tracked<'db>(
    db: &'db dyn Database,
    impl_def_id: ImplDefId<'db>,
    trait_impl_id: TraitImplId<'db>,
    in_cycle: bool,
) -> Maybe<ImplicitImplImplData<'db>> {
    implicit_impl_impl_semantic_data(db, impl_def_id, trait_impl_id, in_cycle)
}

/// Cycle handling for implicit impl semantic data computation.
fn implicit_impl_impl_semantic_data_cycle<'db>(
    db: &'db dyn Database,
    _id: salsa::Id,
    impl_def_id: ImplDefId<'db>,
    trait_impl_id: TraitImplId<'db>,
    _in_cycle: bool,
) -> Maybe<ImplicitImplImplData<'db>> {
    // Forwarding cycle handling to `implicit_impl_impl_semantic_data` handler.
    implicit_impl_impl_semantic_data(db, impl_def_id, trait_impl_id, true)
}

// === Impl Impl ===

/// Query implementation of [PrivImplSemantic::impl_impl_implized_by_context].
fn impl_impl_implized_by_context<'db>(
    db: &'db dyn Database,
    impl_impl_id: ImplImplId<'db>,
    impl_def_id: ImplDefId<'db>,
    in_cycle: bool,
) -> Maybe<ImplId<'db>> {
    if db.is_implicit_impl_impl(impl_def_id, impl_impl_id.trait_impl_id())? {
        return db.implicit_impl_impl_impl(impl_def_id, impl_impl_id.trait_impl_id(), in_cycle);
    }

    let impl_impl_def_id = db.impl_impl_by_trait_impl(impl_def_id, impl_impl_id.trait_impl_id())?;

    db.impl_impl_def_impl(impl_impl_def_id, in_cycle)
}

/// Query implementation of [ImplSemantic::impl_impl_implized_by_context].
#[salsa::tracked(cycle_result=impl_impl_implized_by_context_cycle)]
fn impl_impl_implized_by_context_tracked<'db>(
    db: &'db dyn Database,
    impl_impl_id: ImplImplId<'db>,
    impl_def_id: ImplDefId<'db>,
    in_cycle: bool,
) -> Maybe<ImplId<'db>> {
    impl_impl_implized_by_context(db, impl_impl_id, impl_def_id, in_cycle)
}

/// Cycle handling for [PrivImplSemantic::impl_impl_implized_by_context].
fn impl_impl_implized_by_context_cycle<'db>(
    db: &'db dyn Database,
    _id: salsa::Id,
    impl_impl_id: ImplImplId<'db>,
    impl_def_id: ImplDefId<'db>,
    _in_cycle: bool,
) -> Maybe<ImplId<'db>> {
    // Forwarding cycle handling to `impl_impl_semantic_data` handler.
    impl_impl_implized_by_context(db, impl_impl_id, impl_def_id, true)
}

/// Implementation of [ImplSemantic::impl_impl_concrete_implized].
fn impl_impl_concrete_implized<'db>(
    db: &'db dyn Database,
    impl_impl_id: ImplImplId<'db>,
) -> Maybe<ImplId<'db>> {
    impl_impl_concrete_implized_ex(db, impl_impl_id, false)
}

/// Query implementation of [ImplSemantic::impl_impl_concrete_implized].
fn impl_impl_concrete_implized_tracked<'db>(
    db: &'db dyn Database,
    impl_impl_id: ImplImplId<'db>,
) -> Maybe<ImplId<'db>> {
    impl_impl_concrete_implized_helper(db, (), impl_impl_id)
}

#[salsa::tracked(cycle_result=impl_impl_concrete_implized_cycle)]
fn impl_impl_concrete_implized_helper<'db>(
    db: &'db dyn Database,
    _tracked: Tracked,
    impl_impl_id: ImplImplId<'db>,
) -> Maybe<ImplId<'db>> {
    impl_impl_concrete_implized(db, impl_impl_id)
}

/// Cycle handling for [ImplSemantic::impl_impl_concrete_implized].
fn impl_impl_concrete_implized_cycle<'db>(
    db: &'db dyn Database,
    _id: salsa::Id,
    _tracked: Tracked,
    impl_impl_id: ImplImplId<'db>,
) -> Maybe<ImplId<'db>> {
    impl_impl_concrete_implized_ex(db, impl_impl_id, true)
}

fn impl_impl_concrete_implized_ex<'db>(
    db: &'db dyn Database,
    impl_impl_id: ImplImplId<'db>,
    in_cycle: bool,
) -> Maybe<ImplId<'db>> {
    if let ImplLongId::Concrete(concrete_impl) = impl_impl_id.impl_id().long(db) {
        let impl_def_id = concrete_impl.impl_def_id(db);
        let imp = db.impl_impl_implized_by_context(impl_impl_id, impl_def_id, in_cycle)?;
        return concrete_impl.substitution(db)?.substitute(db, imp);
    }

    Ok(ImplLongId::ImplImpl(
        GenericSubstitution::from_impl(impl_impl_id.impl_id()).substitute(db, impl_impl_id)?,
    )
    .intern(db))
}

/// Implementation of [PrivImplSemantic::impl_impl_concrete_trait].
fn impl_impl_concrete_trait<'db>(
    db: &'db dyn Database,
    impl_impl_id: ImplImplId<'db>,
) -> Maybe<ConcreteTraitId<'db>> {
    let concrete_trait_impl = impl_impl_id.concrete_trait_impl_id(db)?;
    db.concrete_trait_impl_concrete_trait(concrete_trait_impl).and_then(|concrete_trait_id| {
        GenericSubstitution::from_impl(impl_impl_id.impl_id()).substitute(db, concrete_trait_id)
    })
}

/// Query implementation of [PrivImplSemantic::impl_impl_concrete_trait].
fn impl_impl_concrete_trait_tracked<'db>(
    db: &'db dyn Database,
    impl_impl_id: ImplImplId<'db>,
) -> Maybe<ConcreteTraitId<'db>> {
    impl_impl_concrete_trait_helper(db, (), impl_impl_id)
}

#[salsa::tracked]
fn impl_impl_concrete_trait_helper<'db>(
    db: &'db dyn Database,
    _tracked: Tracked,
    impl_impl_id: ImplImplId<'db>,
) -> Maybe<ConcreteTraitId<'db>> {
    impl_impl_concrete_trait(db, impl_impl_id)
}

// === Impl Function Declaration ===

#[derive(Clone, Debug, PartialEq, Eq, DebugWithDb, salsa::Update)]
#[debug_db(dyn Database)]
struct ImplFunctionDeclarationData<'db> {
    function_declaration_data: FunctionDeclarationData<'db>,
    trait_function_id: Maybe<TraitFunctionId<'db>>,
}

/// Returns the generic parameters data of an impl function.
#[salsa::tracked(returns(ref))]
fn impl_function_generic_params_data<'db>(
    db: &'db dyn Database,
    impl_function_id: ImplFunctionId<'db>,
) -> Maybe<GenericParamsData<'db>> {
    let module_id = impl_function_id.parent_module(db);
    let mut diagnostics = SemanticDiagnostics::new(module_id);
    let impl_def_id = impl_function_id.impl_def_id(db);
    let data = impl_definition_data(db, impl_def_id).maybe_as_ref()?;
    let function_syntax = &data.function_asts[&impl_function_id];
    let declaration = function_syntax.declaration(db);
    let inference_id = InferenceId::LookupItemGenerics(LookupItemId::ImplItem(
        ImplItemId::Function(impl_function_id),
    ));
    let resolver_data = db.impl_def_resolver_data(impl_def_id)?;
    let mut resolver =
        Resolver::with_data(db, resolver_data.clone_with_inference_id(db, inference_id));
    let generic_params = semantic_generic_params(
        db,
        &mut diagnostics,
        &mut resolver,
        module_id,
        &declaration.generic_params(db),
    );
    let inference = &mut resolver.inference();
    inference.finalize(&mut diagnostics, function_syntax.stable_ptr(db).untyped());

    let generic_params = inference.rewrite(generic_params).no_err();
    let resolver_data = Arc::new(resolver.data);
    Ok(GenericParamsData { generic_params, diagnostics: diagnostics.build(), resolver_data })
}

/// Returns data about an impl function declaration.
#[salsa::tracked(returns(ref))]
fn impl_function_declaration_data<'db>(
    db: &'db dyn Database,
    impl_function_id: ImplFunctionId<'db>,
) -> Maybe<ImplFunctionDeclarationData<'db>> {
    let impl_def_id = impl_function_id.impl_def_id(db);
    let mut diagnostics = SemanticDiagnostics::new(impl_def_id.parent_module(db));
    let data = impl_definition_data(db, impl_def_id).maybe_as_ref()?;
    let function_syntax = &data.function_asts[&impl_function_id];
    let declaration = function_syntax.declaration(db);

    let generic_params_data =
        impl_function_generic_params_data(db, impl_function_id).maybe_as_ref()?.clone();
    let generic_params = generic_params_data.generic_params;
    let lookup_item_id = LookupItemId::ImplItem(ImplItemId::Function(impl_function_id));
    let inference_id = InferenceId::LookupItemGenerics(lookup_item_id);
    let mut resolver = Resolver::with_data(
        db,
        (*generic_params_data.resolver_data).clone_with_inference_id(db, inference_id),
    );
    diagnostics.extend(generic_params_data.diagnostics);
    resolver.set_feature_config(&impl_function_id, function_syntax, &mut diagnostics);

    let mut environment = Environment::empty();
    let signature = semantic::Signature::from_ast(
        &mut diagnostics,
        db,
        &mut resolver,
        &declaration,
        FunctionTitleId::Impl(impl_function_id),
        &mut environment,
    );

    let attributes = function_syntax.attributes(db).structurize(db);
    let (implicit_precedence, _) =
        get_implicit_precedence(db, &mut diagnostics, &mut resolver, &attributes);

    let inference = &mut resolver.inference();
    // Check fully resolved.
    inference.finalize(&mut diagnostics, function_syntax.stable_ptr(db).untyped());
    let signature_syntax = declaration.signature(db);
    let trait_function_id = validate_impl_function_signature(
        db,
        &mut diagnostics,
        inference,
        ValidateImplFunctionSignatureParams {
            impl_function_id,
            signature_syntax: &signature_syntax,
            signature: &signature,
            impl_function_syntax: function_syntax,
            impl_func_generics: &generic_params,
        },
    );

    let inline_config = get_inline_config(db, &mut diagnostics, &attributes)?;

    forbid_inline_always_with_impl_generic_param(&mut diagnostics, &generic_params, &inline_config);

    let signature = inference.rewrite(signature).no_err();

    let resolver_data = Arc::new(resolver.data);
    Ok(ImplFunctionDeclarationData {
        function_declaration_data: FunctionDeclarationData {
            diagnostics: diagnostics.build(),
            signature,
            environment,
            attributes,
            resolver_data,
            inline_config,
            implicit_precedence,
        },
        trait_function_id,
    })
}

/// Struct for the parameters of [validate_impl_function_signature].
struct ValidateImplFunctionSignatureParams<'a, 'r> {
    /// The impl function to validate the signature of.
    impl_function_id: ImplFunctionId<'a>,
    /// The signature syntax.
    signature_syntax: &'r ast::FunctionSignature<'a>,
    // The semantic signature.
    signature: &'r semantic::Signature<'a>,
    /// The impl function syntax.
    impl_function_syntax: &'r ast::FunctionWithBody<'a>,
    /// The generic parameters of the impl function.
    impl_func_generics: &'r [GenericParam<'a>],
}

/// Validates the impl function, and returns the matching trait function id.
fn validate_impl_function_signature<'db>(
    db: &'db dyn Database,
    diagnostics: &mut SemanticDiagnostics<'db>,
    inference: &mut Inference<'db, '_>,
    ValidateImplFunctionSignatureParams {
        impl_function_id,
        signature_syntax,
        signature,
        impl_function_syntax,
        impl_func_generics,
    }: ValidateImplFunctionSignatureParams<'db, '_>,
) -> Maybe<TraitFunctionId<'db>> {
    let impl_def_id = impl_function_id.impl_def_id(db);
    let concrete_trait_id = db.impl_def_concrete_trait(impl_def_id)?;
    let trait_id = concrete_trait_id.trait_id(db);
    let function_name = impl_function_id.name(db);
    let trait_function_id =
        db.trait_function_by_name(trait_id, function_name)?.ok_or_else(|| {
            diagnostics.report(
                impl_function_syntax.stable_ptr(db),
                ImplItemNotInTrait {
                    impl_def_id,
                    impl_item_name: function_name,
                    trait_id,
                    item_kind: "function".into(),
                },
            )
        })?;
    let concrete_trait_function =
        ConcreteTraitGenericFunctionId::new_from_data(db, concrete_trait_id, trait_function_id);
    let concrete_trait_signature = db.concrete_trait_function_signature(concrete_trait_function)?;

    // Match generics of the function.
    // TODO(spapini): Compare the actual kinds and traits for the generic params.

    let func_generics = db.concrete_trait_function_generic_params(concrete_trait_function)?;
    if impl_func_generics.len() != func_generics.len() {
        diagnostics.report(
            impl_function_syntax.declaration(db).name(db).stable_ptr(db),
            WrongNumberOfGenericParamsForImplFunction {
                expected: func_generics.len(),
                actual: impl_func_generics.len(),
            },
        );
        return Ok(trait_function_id);
    }
    let impl_def_substitution = db.impl_def_substitution(impl_def_id)?;
    let func_generics: Vec<GenericParam<'_>> =
        impl_def_substitution.substitute(db, func_generics.to_vec())?;

    let function_substitution =
        GenericSubstitution::new(&func_generics, &generic_params_to_args(impl_func_generics, db));

    for (trait_generic_param, generic_param) in izip!(func_generics, impl_func_generics.iter()) {
        if let Some(name) = trait_generic_param.id().name(db)
            && Some(name) != generic_param.id().name(db)
        {
            diagnostics.report(
                generic_param.stable_ptr(db),
                WrongParameterName { impl_def_id, impl_function_id, trait_id, expected_name: name },
            );
        }
        match (generic_param, trait_generic_param) {
            (GenericParam::Type(_), GenericParam::Type(_)) => {}
            (GenericParam::Impl(generic_param), GenericParam::Impl(trait_generic_param))
            | (GenericParam::NegImpl(generic_param), GenericParam::NegImpl(trait_generic_param)) => {
                let rewritten_trait_param_trait =
                    function_substitution.substitute(db, trait_generic_param.concrete_trait)?;
                let rewritten_trait_param_type_constraints =
                    function_substitution.substitute(db, trait_generic_param.type_constraints)?;
                generic_param
                    .concrete_trait
                    .map(|actual_trait| {
                        rewritten_trait_param_trait
                            .map(|expected_trait| {
                                if actual_trait != expected_trait
                                    || generic_param.type_constraints
                                        != rewritten_trait_param_type_constraints
                                {
                                    diagnostics.report(
                                        generic_param.id.stable_ptr(db),
                                        WrongGenericParamTraitForImplFunction {
                                            impl_def_id,
                                            impl_function_id,
                                            trait_id,
                                            expected_trait,
                                            actual_trait,
                                        },
                                    );
                                }
                            })
                            .ok();
                    })
                    .ok();
            }
            (GenericParam::Const(generic_param), GenericParam::Const(trait_generic_param)) => {
                let expected_ty = function_substitution.substitute(db, trait_generic_param.ty)?;
                if generic_param.ty != expected_ty {
                    diagnostics.report(
                        generic_param.id.stable_ptr(db),
                        WrongParameterType {
                            impl_def_id,
                            impl_function_id,
                            trait_id,
                            expected_ty,
                            actual_ty: generic_param.ty,
                        },
                    );
                }
            }
            (generic_param, trait_generic_param) => {
                diagnostics.report(
                    generic_param.stable_ptr(db),
                    WrongGenericParamKindForImplFunction {
                        impl_def_id,
                        impl_function_id,
                        trait_id,
                        expected_kind: trait_generic_param.kind(),
                        actual_kind: generic_param.kind(),
                    },
                );
            }
        }
    }

    let concrete_trait_signature =
        function_substitution.substitute(db, concrete_trait_signature.clone())?;

    if signature.params.len() != concrete_trait_signature.params.len() {
        diagnostics.report(
            signature_syntax.parameters(db).stable_ptr(db),
            WrongNumberOfParameters {
                impl_def_id,
                impl_function_id,
                trait_id,
                expected: concrete_trait_signature.params.len(),
                actual: signature.params.len(),
            },
        );
    }
    let concrete_trait_signature =
        impl_def_substitution.substitute(db, concrete_trait_signature)?;
    for (param, trait_param) in
        izip!(signature.params.iter(), concrete_trait_signature.params.iter())
    {
        let expected_ty = inference.rewrite(trait_param.ty).no_err();
        let actual_ty = inference.rewrite(param.ty).no_err();

        if expected_ty != actual_ty && !expected_ty.is_missing(db) && !actual_ty.is_missing(db) {
            diagnostics.report(
                extract_matches!(
                    param.stable_ptr(db).lookup(db).type_clause(db),
                    OptionTypeClause::TypeClause
                )
                .ty(db)
                .stable_ptr(db),
                WrongParameterType {
                    impl_def_id,
                    impl_function_id,
                    trait_id,
                    expected_ty,
                    actual_ty,
                },
            );
        }

        if trait_param.mutability != param.mutability {
            if trait_param.mutability == Mutability::Reference {
                diagnostics.report(
                    param.stable_ptr(db).lookup(db).modifiers(db).stable_ptr(db),
                    ParameterShouldBeReference { impl_def_id, impl_function_id, trait_id },
                );
            }

            if param.mutability == Mutability::Reference {
                diagnostics.report(
                    param.stable_ptr(db).lookup(db).modifiers(db).stable_ptr(db),
                    ParameterShouldNotBeReference { impl_def_id, impl_function_id, trait_id },
                );
            }
        }

        if trait_param.name != param.name {
            diagnostics.report(
                param.stable_ptr(db).lookup(db).name(db).stable_ptr(db),
                WrongParameterName {
                    impl_def_id,
                    impl_function_id,
                    trait_id,
                    expected_name: trait_param.name,
                },
            );
        }
    }

    if !concrete_trait_signature.panicable && signature.panicable {
        diagnostics.report(
            signature_syntax.stable_ptr(db),
            PassPanicAsNopanic { impl_function_id, trait_id },
        );
    }

    if concrete_trait_signature.is_const && !signature.is_const {
        diagnostics.report(
            signature_syntax.stable_ptr(db),
            PassConstAsNonConst { impl_function_id, trait_id },
        );
    }

    let expected_ty = inference.rewrite(concrete_trait_signature.return_type).no_err();
    let actual_ty = inference.rewrite(signature.return_type).no_err();

    if expected_ty != actual_ty && !expected_ty.is_missing(db) && !actual_ty.is_missing(db) {
        let location_ptr = match signature_syntax.ret_ty(db) {
            OptionReturnTypeClause::ReturnTypeClause(ret_ty) => ret_ty.ty(db).as_syntax_node(),
            OptionReturnTypeClause::Empty(_) => {
                impl_function_syntax.body(db).lbrace(db).as_syntax_node()
            }
        }
        .stable_ptr(db);
        diagnostics.report(
            location_ptr,
            WrongReturnTypeForImpl {
                impl_def_id,
                impl_function_id,
                trait_id,
                expected_ty,
                actual_ty,
            },
        );
    }
    Ok(trait_function_id)
}

/// Computes impl function body data including diagnostics and resolver data.
fn priv_impl_function_body_data<'db>(
    db: &'db dyn Database,
    impl_function_id: ImplFunctionId<'db>,
) -> Maybe<FunctionBodyData<'db>> {
    let impl_def_id = impl_function_id.impl_def_id(db);
    let mut diagnostics = SemanticDiagnostics::new(impl_def_id.parent_module(db));
    let data = impl_definition_data(db, impl_def_id).maybe_as_ref()?;
    let function_syntax = &data.function_asts[&impl_function_id];
    // Compute declaration semantic.
    let declaration = impl_function_declaration_data(db, impl_function_id).maybe_as_ref()?;
    let parent_resolver_data = declaration.function_declaration_data.resolver_data.clone();
    let inference_id = InferenceId::LookupItemDefinition(LookupItemId::ImplItem(
        ImplItemId::Function(impl_function_id),
    ));
    let mut resolver =
        Resolver::with_data(db, (*parent_resolver_data).clone_with_inference_id(db, inference_id));
    let environment: Environment<'_> = declaration.function_declaration_data.environment.clone();

    let function_id = (|| {
        let trait_function_id = db.impl_function_trait_function(impl_function_id)?;
        let generic_parameters = db.impl_def_generic_params(impl_def_id)?;

        let generic_function = GenericFunctionId::Impl(ImplGenericFunctionId {
            impl_id: ImplLongId::Concrete(
                ConcreteImplLongId {
                    impl_def_id,
                    generic_args: generic_params_to_args(generic_parameters, db),
                }
                .intern(db),
            )
            .intern(db),
            function: trait_function_id,
        });

        Ok(FunctionLongId::from_generic(db, generic_function)?.intern(db))
    })();
    // Compute body semantic expr.
    let mut ctx = ComputationContext::new(
        db,
        &mut diagnostics,
        &mut resolver,
        Some(&declaration.function_declaration_data.signature),
        environment,
        ContextFunction::Function(function_id),
    );
    let function_body = function_syntax.body(db);
    let return_type = declaration.function_declaration_data.signature.return_type;
    let body_expr = compute_root_expr(&mut ctx, &function_body, return_type)?;
    let ComputationContext { arenas, .. } = ctx;

    let expr_lookup: UnorderedHashMap<_, _> =
        arenas.exprs.iter().map(|(id, expr)| (expr.stable_ptr(), id)).collect();
    let pattern_lookup: UnorderedHashMap<_, _> =
        arenas.patterns.iter().map(|(id, pattern)| (pattern.stable_ptr(), id)).collect();
    let resolver_data = Arc::new(resolver.data);
    Ok(FunctionBodyData {
        diagnostics: diagnostics.build(),
        expr_lookup,
        pattern_lookup,
        resolver_data,
        body: FunctionBody { arenas, body_expr },
    })
}

/// Computes impl function body data.
#[salsa::tracked(returns(ref))]
fn priv_impl_function_body_data_tracked<'db>(
    db: &'db dyn Database,
    impl_function_id: ImplFunctionId<'db>,
) -> Maybe<FunctionBodyData<'db>> {
    priv_impl_function_body_data(db, impl_function_id)
}

#[salsa::tracked]
fn impl_is_fully_concrete<'db>(db: &'db dyn Database, impl_id: ImplId<'db>) -> bool {
    impl_id.long(db).is_fully_concrete(db)
}

#[salsa::tracked]
fn impl_is_var_free<'db>(db: &'db dyn Database, impl_id: ImplId<'db>) -> bool {
    impl_id.long(db).is_var_free(db)
}

/// Returns crate dependencies.
#[salsa::tracked(returns(ref))]
fn crate_dependencies<'db>(
    db: &'db dyn Database,
    crate_id: CrateId<'db>,
) -> OrderedHashSet<CrateId<'db>> {
    let mut crates = [crate_id, db.core_crate()].into_iter().unique().collect_vec();
    let mut crates_set: OrderedHashSet<CrateId<'db>, _> = OrderedHashSet::<
        CrateId<'db>,
        std::collections::hash_map::RandomState,
    >::from_iter(crates.iter().copied());
    while let Some(crate_id) = crates.pop() {
        let default_settings = Default::default();
        let settings =
            db.crate_config(crate_id).as_ref().map(|c| &c.settings).unwrap_or(&default_settings);

        for (ident, dep) in &settings.dependencies {
            let dep_crate_id = CrateLongId::Real {
                name: SmolStrId::from(db, ident.clone()),
                discriminator: dep.discriminator.clone(),
            }
            .intern(db);
            if !crates_set.contains(&dep_crate_id) {
                crates.push(dep_crate_id);
                crates_set.insert(dep_crate_id);
            }
        }
    }
    crates_set
}

#[salsa::tracked(returns(ref))]
/// Query implementation of [PrivImplSemantic::crate_global_impls].
fn crate_global_impls<'db>(
    db: &'db dyn Database,
    crate_id: CrateId<'db>,
) -> UnorderedHashMap<TraitId<'db>, OrderedHashSet<UninferredImplById<'db>>> {
    let mut crate_global_impls: UnorderedHashMap<
        TraitId<'db>,
        OrderedHashSet<UninferredImplById<'db>>,
    > = UnorderedHashMap::default();
    for crate_id in crate_dependencies(db, crate_id).iter() {
        let mut modules = vec![ModuleId::CrateRoot(*crate_id)];
        while let Some(module_id) = modules.pop() {
            if let Ok(module_impls) = db.module_global_impls((), module_id) {
                for (trait_id, impls) in module_impls.globals_by_trait.iter() {
                    crate_global_impls.entry(*trait_id).or_default().extend(impls.clone());
                }
            }
            if let Ok(x) = db.module_submodules_ids(module_id) {
                modules.extend(x.iter().map(|sub_module| ModuleId::Submodule(*sub_module)));
            }
            if let Ok(macro_call_ids) = db.module_macro_calls_ids(module_id) {
                modules.extend(
                    macro_call_ids
                        .iter()
                        .map(|id| db.macro_call_module_id(*id))
                        .filter_map(|x| x.ok()),
                )
            }
        }
    }
    crate_global_impls
}

/// Query implementation of [PrivImplSemantic::crate_traits_dependencies].
#[salsa::tracked(returns(ref))]
fn crate_traits_dependencies<'db>(
    db: &'db dyn Database,
    crate_id: CrateId<'db>,
) -> UnorderedHashMap<TraitId<'db>, OrderedHashSet<TraitId<'db>>> {
    let mut dependencies: UnorderedHashMap<TraitId<'db>, OrderedHashSet<TraitId<'db>>> =
        UnorderedHashMap::default();
    for crate_id in crate_dependencies(db, crate_id).iter() {
        let mut modules = vec![ModuleId::CrateRoot(*crate_id)];
        while let Some(module_id) = modules.pop() {
            if let Ok(module_impls) = db.module_global_impls((), module_id) {
                for (trait_id, impls) in module_impls.trait_deps.iter() {
                    dependencies.entry(*trait_id).or_default().extend(impls.clone());
                }
            }
            if let Ok(x) = db.module_submodules_ids(module_id) {
                modules.extend(x.iter().map(|sub_module| ModuleId::Submodule(*sub_module)));
            }
        }
    }

    dependencies
}

/// Query implementation of [PrivImplSemantic::reachable_trait_dependencies].
#[salsa::tracked(returns(ref))]
fn reachable_trait_dependencies<'db>(
    db: &'db dyn Database,
    trait_id: TraitId<'db>,
    crate_id: CrateId<'db>,
) -> OrderedHashSet<TraitId<'db>> {
    let dependencies = db.crate_traits_dependencies(crate_id);
    let mut reachable_deps = OrderedHashSet::default();
    let mut to_visit = vec![trait_id];
    let mut visited: UnorderedHashSet<TraitId<'db>> = UnorderedHashSet::default();
    while let Some(current_trait) = to_visit.pop() {
        if visited.contains(&current_trait) {
            continue;
        }
        visited.insert(current_trait);
        if let Some(deps) = dependencies.get(&current_trait) {
            for dep in deps.iter() {
                reachable_deps.insert(*dep);
                if !visited.contains(dep) {
                    to_visit.push(*dep);
                }
            }
        }
    }
    reachable_deps
}

/// Adds the trait dependencies of an uninferred impl to the trait_deps map.
fn uninferred_impl_trait_dependency<'db>(
    db: &'db dyn Database,
    impl_id: UninferredImpl<'db>,
    trait_deps: &mut OrderedHashMap<TraitId<'db>, OrderedHashSet<TraitId<'db>>>,
) -> Maybe<()> {
    if let Ok(imp_trait_id) = impl_id.trait_id(db) {
        let (mut resolver, module_id, generic_params, mut diagnostics) = match impl_id {
            UninferredImpl::Def(impl_def_id) => {
                let module_id = impl_def_id.parent_module(db);
                let mut diagnostics = SemanticDiagnostics::new(module_id);

                let impl_ast = db.module_impl_by_id(impl_def_id)?;
                let inference_id = InferenceId::ImplDefTrait(impl_def_id);

                let mut resolver = Resolver::new(db, module_id, inference_id);
                resolver.set_feature_config(&impl_def_id, &impl_ast, &mut diagnostics);
                (resolver, module_id, impl_ast.generic_params(db), diagnostics)
            }
            UninferredImpl::ImplAlias(impl_alias_id) => {
                let module_id = impl_alias_id.parent_module(db);
                let mut diagnostics = SemanticDiagnostics::new(module_id);

                let impl_ast = db.module_impl_alias_by_id(impl_alias_id)?;
                let inference_id = InferenceId::ImplAliasImplDef(impl_alias_id);

                let mut resolver = Resolver::new(db, module_id, inference_id);
                resolver.set_feature_config(&impl_alias_id, &impl_ast, &mut diagnostics);
                (resolver, module_id, impl_ast.generic_params(db), diagnostics)
            }
            _ => {
                return Ok(());
            }
        };
        if let OptionWrappedGenericParamList::WrappedGenericParamList(params_list) = generic_params
        {
            params_list.generic_params(db).elements(db).for_each(|param_syntax| {
                let generic_param_id =
                    GenericParamLongId(module_id, param_syntax.stable_ptr(db)).intern(db);
                resolver.add_generic_param(generic_param_id);
                let trait_path = match param_syntax {
                    ast::GenericParam::ImplNamed(param) => param.trait_path(db),
                    ast::GenericParam::ImplAnonymous(param) => param.trait_path(db),
                    ast::GenericParam::NegativeImpl(param) => param.trait_path(db),

                    _ => return,
                };
                let dependant_trait_id =
                    resolve_trait_path(db, &mut diagnostics, &mut resolver, &trait_path);

                let Ok(dependant_trait_id) = dependant_trait_id else {
                    return;
                };
                trait_deps.entry(imp_trait_id).or_default().insert(dependant_trait_id);
            })
        };
    };
    Ok(())
}

#[derive(Default, Debug, Eq, PartialEq, salsa::Update)]
struct ModuleImpls<'db> {
    globals_by_trait: OrderedHashMap<TraitId<'db>, OrderedHashSet<UninferredImplById<'db>>>,
    trait_deps: OrderedHashMap<TraitId<'db>, OrderedHashSet<TraitId<'db>>>,
    globals_by_type: OrderedHashMap<TypeId<'db>, Vec<UninferredImpl<'db>>>,

    locals: BTreeSet<UninferredImplById<'db>>,
}

#[salsa::tracked(returns(ref))]
fn module_global_impls<'db>(
    db: &'db dyn Database,
    _tracked: Tracked,
    module_id: ModuleId<'db>,
) -> Maybe<ModuleImpls<'db>> {
    let mut module_impls = ModuleImpls::default();
    for (containing_module, info) in db.module_imported_modules((), module_id).iter() {
        for defined_module in module_macro_modules(db, true, *containing_module) {
            let Ok(module_semantic_data) = db.priv_module_semantic_data(*defined_module) else {
                continue;
            };
            for item in module_semantic_data.items.values().filter(|item| {
                info.user_modules.iter().any(|user_module| {
                    peek_visible_in(db, item.visibility, *containing_module, *user_module)
                })
            }) {
                let imp = match item.item_id {
                    ModuleItemId::Use(use_id) => match db.use_resolved_item(use_id) {
                        Ok(ResolvedGenericItem::Impl(impl_def_id)) => {
                            UninferredImpl::Def(impl_def_id)
                        }
                        Ok(ResolvedGenericItem::GenericImplAlias(impl_alias_id)) => {
                            UninferredImpl::ImplAlias(impl_alias_id)
                        }
                        _ => continue,
                    },
                    ModuleItemId::Impl(impl_def_id) => {
                        if let Ok(impl_ast) = db.module_impl_by_id(impl_def_id) {
                            global_impls_insert_generic_impls(
                                db,
                                &impl_ast.generic_params(db),
                                impl_def_id.parent_module(db),
                                &mut module_impls.globals_by_trait,
                            );
                        }

                        // TODO(TomerStarkware): Add the generic impls of the functions in the impl.

                        UninferredImpl::Def(impl_def_id)
                    }
                    // TODO(TomerStarkware): Add the generic impls of the ImplAlias.
                    ModuleItemId::ImplAlias(impl_alias_id) => {
                        UninferredImpl::ImplAlias(impl_alias_id)
                    }
                    ModuleItemId::FreeFunction(free_function_id) => {
                        if let Ok(function_ast) = db.module_free_function_by_id(free_function_id) {
                            let declaration = function_ast.declaration(db);
                            global_impls_insert_generic_impls(
                                db,
                                &declaration.generic_params(db),
                                free_function_id.parent_module(db),
                                &mut module_impls.globals_by_trait,
                            );
                        }
                        continue;
                    }
                    _ => continue,
                };

                uninferred_impl_trait_dependency(db, imp, &mut module_impls.trait_deps)?;

                if let Ok(true) = is_global_impl(db, imp, module_id) {
                    let trait_id = imp.trait_id(db)?;
                    module_impls.globals_by_trait.entry(trait_id).or_default().insert(imp.into());
                } else {
                    module_impls.locals.insert(imp.into());
                }
            }
        }
    }

    Ok(module_impls)
}

/// Checks if an impl is global.
/// An impl is global if it is defined in the same module as the trait it implements or in the same
/// module as one of its concrete traits' types.
fn is_global_impl<'db>(
    db: &'db dyn Database,
    impl_id: UninferredImpl<'db>,
    impl_module: ModuleId<'db>,
) -> Maybe<bool> {
    let trait_id = impl_id.trait_id(db)?;
    if trait_id.parent_module(db) == impl_module {
        return Ok(true);
    }

    Ok(impl_id
        .trait_shallow_generic_args(db)?
        .iter()
        .any(|(_, arg)| arg.module_id(db) == Some(impl_module)))
}

/// Inserts the generic impls of a function or impl into the globals_by_trait map.
/// A generic impl is global if one of its generic arguments is a generic type which is defined in
/// the same parameter list as the impl.
fn global_impls_insert_generic_impls<'db>(
    db: &'db dyn Database,
    generic_params: &ast::OptionWrappedGenericParamList<'db>,
    module_id: ModuleId<'db>,
    globals_by_trait: &mut OrderedHashMap<TraitId<'db>, OrderedHashSet<UninferredImplById<'db>>>,
) {
    let ast::OptionWrappedGenericParamList::WrappedGenericParamList(generic_params) =
        generic_params
    else {
        return;
    };
    let mut generic_types = OrderedHashMap::<_, GenericParamId<'db>, _>::default();
    for param in generic_params.generic_params(db).elements(db) {
        let (trait_path, type_constraints) = match &param {
            ast::GenericParam::Type(_) => {
                let param_id = GenericParamLongId(module_id, param.stable_ptr(db)).intern(db);
                if let Some(name) = param_id.name(db) {
                    generic_types.insert(name, param_id);
                }
                continue;
            }
            ast::GenericParam::ImplNamed(impl_param) => {
                (impl_param.trait_path(db), impl_param.type_constrains(db))
            }
            ast::GenericParam::ImplAnonymous(impl_param) => {
                (impl_param.trait_path(db), impl_param.type_constrains(db))
            }
            _ => continue,
        };
        if is_global_impl_generic_param(db, &generic_types, &trait_path) {
            let uninferred_impl = UninferredImpl::GenericParam(
                GenericParamLongId(module_id, param.stable_ptr(db)).intern(db),
            );
            if let Ok(trait_id) = uninferred_impl.trait_id(db) {
                if trait_id == db.core_info().type_eq_trt {
                    continue;
                }
                if matches!(
                    type_constraints,
                    ast::OptionAssociatedItemConstraints::AssociatedItemConstraints(_)
                ) {
                    continue;
                }
                globals_by_trait.entry(trait_id).or_default().insert(uninferred_impl.into());
            }
        }
    }
}

/// Returns true if a generic parameter impl is global.
fn is_global_impl_generic_param<'db>(
    db: &'db dyn Database,
    generic_types: &OrderedHashMap<SmolStrId<'db>, GenericParamId<'db>>,
    trait_syntax: &ast::ExprPath<'db>,
) -> bool {
    let trait_segments = trait_syntax.to_segments(db);
    let ast::PathSegment::WithGenericArgs(trait_segment) = trait_segments.last().unwrap() else {
        return false;
    };

    let generic_args = trait_segment.generic_args(db);

    for arg in generic_args.generic_args(db).elements(db) {
        let mut expr = match arg {
            ast::GenericArg::Unnamed(arg) => arg.value(db),
            ast::GenericArg::Named(arg) => arg.value(db),
        };

        while let ast::Expr::Unary(unary_expr) = &expr {
            if !matches!(unary_expr.op(db), UnaryOperator::At(_)) {
                break;
            }

            expr = unary_expr.expr(db);
        }

        let ast::Expr::Path(path) = expr else {
            continue;
        };
        let path_segments = path.to_segments(db);
        let [segment] = path_segments.as_slice() else {
            continue;
        };

        let ast::PathSegment::Simple(simple_segment) = segment else {
            continue;
        };
        if generic_types.contains_key(&simple_segment.identifier(db)) {
            return true;
        }
    }

    false
}

/// Trait for impl-related semantic queries.
pub trait ImplSemantic<'db>: Database {
    /// Returns the semantic declaration diagnostics of an impl.
    fn impl_semantic_declaration_diagnostics(
        &'db self,
        impl_def_id: ImplDefId<'db>,
    ) -> Diagnostics<'db, SemanticDiagnostic<'db>> {
        impl_declaration_data(self.as_dyn_database(), impl_def_id)
            .as_ref()
            .map(|data| data.diagnostics.clone())
            .unwrap_or_default()
    }
    /// Returns the generic parameters of an impl.
    fn impl_def_generic_params(
        &'db self,
        impl_def_id: ImplDefId<'db>,
    ) -> Maybe<&'db [GenericParam<'db>]> {
        Ok(&impl_def_generic_params_data(self.as_dyn_database(), impl_def_id)
            .maybe_as_ref()?
            .generic_params)
    }
    /// Returns the resolution resolved_items of an impl.
    fn impl_def_resolver_data(
        &'db self,
        impl_def_id: ImplDefId<'db>,
    ) -> Maybe<Arc<ResolverData<'db>>> {
        Ok(impl_declaration_data(self.as_dyn_database(), impl_def_id)
            .maybe_as_ref()?
            .resolver_data
            .clone())
    }
    /// Returns the concrete trait that is implemented by the impl.
    fn impl_def_concrete_trait(
        &'db self,
        impl_def_id: ImplDefId<'db>,
    ) -> Maybe<ConcreteTraitId<'db>> {
        impl_declaration_data(self.as_dyn_database(), impl_def_id).maybe_as_ref()?.concrete_trait
    }
    /// Returns the attributes attached to the impl.
    fn impl_def_attributes(&'db self, impl_def_id: ImplDefId<'db>) -> Maybe<&'db [Attribute<'db>]> {
        Ok(&impl_declaration_data(self.as_dyn_database(), impl_def_id).maybe_as_ref()?.attributes)
    }
    /// Returns the concrete trait that is implemented by the concrete impl.
    fn impl_concrete_trait(&'db self, impl_id: ImplId<'db>) -> Maybe<ConcreteTraitId<'db>> {
        impl_concrete_trait_tracked(self.as_dyn_database(), impl_id)
    }
    /// Returns the trait that is implemented by the impl, or an error if the RHS of the `of` is not
    /// a trait.
    fn impl_def_trait(&'db self, impl_def_id: ImplDefId<'db>) -> Maybe<TraitId<'db>> {
        impl_def_trait(self.as_dyn_database(), impl_def_id)
    }
    /// Returns the semantic definition diagnostics of an impl.
    fn impl_semantic_definition_diagnostics(
        &'db self,
        impl_def_id: ImplDefId<'db>,
    ) -> Diagnostics<'db, SemanticDiagnostic<'db>> {
        impl_semantic_definition_diagnostics_tracked(self.as_dyn_database(), impl_def_id)
    }
    /// Returns the metadata for an impl item, by the given `name`, if exists.
    fn impl_item_info_by_name(
        &'db self,
        impl_def_id: ImplDefId<'db>,
        name: SmolStrId<'db>,
    ) -> Maybe<Option<ImplItemInfo<'db>>> {
        impl_item_info_by_name_tracked(self.as_dyn_database(), impl_def_id, name)
    }
    /// Returns all the items used within the impl.
    fn impl_all_used_uses(
        &'db self,
        impl_def_id: ImplDefId<'db>,
    ) -> Maybe<&'db OrderedHashSet<UseId<'db>>> {
        impl_all_used_uses(self.as_dyn_database(), impl_def_id).maybe_as_ref()
    }
    /// Returns the type items in the impl.
    fn impl_types(
        &'db self,
        impl_def_id: ImplDefId<'db>,
    ) -> Maybe<&'db OrderedHashMap<ImplTypeDefId<'db>, ast::ItemTypeAlias<'db>>> {
        Ok(&impl_definition_data(self.as_dyn_database(), impl_def_id)
            .maybe_as_ref()?
            .item_type_asts)
    }
    /// Returns the impl type item that matches the given trait type item, if exists.
    fn impl_type_by_trait_type(
        &'db self,
        impl_def_id: ImplDefId<'db>,
        trait_type_id: TraitTypeId<'db>,
    ) -> Maybe<ImplTypeDefId<'db>> {
        impl_type_by_trait_type_tracked(self.as_dyn_database(), impl_def_id, trait_type_id)
    }
    /// Returns the constant items in the impl.
    fn impl_constants(
        &'db self,
        impl_def_id: ImplDefId<'db>,
    ) -> Maybe<&'db OrderedHashMap<ImplConstantDefId<'db>, ast::ItemConstant<'db>>> {
        Ok(&impl_definition_data(self.as_dyn_database(), impl_def_id)
            .maybe_as_ref()?
            .item_constant_asts)
    }
    /// Returns the functions in the impl.
    fn impl_functions(
        &'db self,
        impl_def_id: ImplDefId<'db>,
    ) -> Maybe<&'db OrderedHashMap<SmolStrId<'db>, ImplFunctionId<'db>>> {
        impl_functions(self.as_dyn_database(), impl_def_id).maybe_as_ref()
    }

    // Impl type def.
    // ================
    /// Returns the resolved type of an impl item type.
    fn impl_type_def_resolved_type(&'db self, id: ImplTypeDefId<'db>) -> Maybe<TypeId<'db>> {
        impl_type_semantic_data(self.as_dyn_database(), id, false)
            .maybe_as_ref()?
            .type_alias_data
            .resolved_type
    }
    /// Returns the generic parameters of an impl item type.
    fn impl_type_def_generic_params(
        &'db self,
        id: ImplTypeDefId<'db>,
    ) -> Maybe<Vec<GenericParam<'db>>> {
        Ok(impl_type_def_generic_params_data(self.as_dyn_database(), id)
            .maybe_as_ref()?
            .generic_params
            .clone())
    }
    /// Returns the attributes of an impl type.
    fn impl_type_def_attributes(&'db self, id: ImplTypeDefId<'db>) -> Maybe<&'db [Attribute<'db>]> {
        Ok(&impl_type_semantic_data(self.as_dyn_database(), id, false)
            .maybe_as_ref()?
            .type_alias_data
            .attributes)
    }
    /// Returns the resolution resolved_items of an impl item type.
    fn impl_type_def_resolver_data(
        &'db self,
        id: ImplTypeDefId<'db>,
    ) -> Maybe<Arc<ResolverData<'db>>> {
        Ok(impl_type_semantic_data(self.as_dyn_database(), id, false)
            .maybe_as_ref()?
            .type_alias_data
            .resolver_data
            .clone())
    }
    /// Returns the deref chain and diagnostics for a given type.
    fn deref_chain(
        &'db self,
        ty: TypeId<'db>,
        crate_id: CrateId<'db>,
        try_deref_mut: bool,
    ) -> Maybe<&'db DerefChain<'db>> {
        deref_chain(self.as_dyn_database(), ty, crate_id, try_deref_mut).maybe_as_ref()
    }

    // Impl type.
    // ================
    /// Returns the implized impl type if the impl is concrete. Returns a TypeId that's not an impl
    /// type with a concrete impl.
    // TODO(Gil): Consider removing the cycle handling here if we will upgrade the salsa version.
    fn impl_type_concrete_implized(
        &'db self,
        impl_type_def_id: ImplTypeId<'db>,
    ) -> Maybe<TypeId<'db>> {
        impl_type_concrete_implized_tracked(self.as_dyn_database(), impl_type_def_id)
    }

    // Impl constant def.
    // ================
    /// Returns the resolved constant value of an impl item constant.
    fn impl_constant_def_value(&'db self, id: ImplConstantDefId<'db>) -> Maybe<ConstValueId<'db>> {
        Ok(impl_constant_semantic_data(self.as_dyn_database(), id, false)
            .maybe_as_ref()?
            .constant_data
            .const_value)
    }
    /// Returns the resolution resolved_items of an impl item constant.
    fn impl_constant_def_resolver_data(
        &'db self,
        id: ImplConstantDefId<'db>,
    ) -> Maybe<Arc<ResolverData<'db>>> {
        Ok(impl_constant_semantic_data(self.as_dyn_database(), id, false)
            .maybe_as_ref()?
            .constant_data
            .resolver_data
            .clone())
    }

    // Impl constant.
    // ================
    /// Returns the implized impl constant value if the impl is concrete.
    // TODO(Gil): Consider removing the cycle handling here if we will upgrade the salsa version.
    fn impl_constant_concrete_implized_value(
        &'db self,
        impl_constant_id: ImplConstantId<'db>,
    ) -> Maybe<ConstValueId<'db>> {
        impl_constant_concrete_implized_value_tracked(self.as_dyn_database(), impl_constant_id)
    }
    /// Returns the implized impl constant type if the impl is concrete.
    // TODO(Gil): Consider removing the cycle handling here if we will upgrade the salsa version.
    fn impl_constant_concrete_implized_type(
        &'db self,
        impl_constant_id: ImplConstantId<'db>,
    ) -> Maybe<TypeId<'db>> {
        impl_constant_concrete_implized_type_tracked(self.as_dyn_database(), impl_constant_id)
    }

    // Impl impl def.
    // ================
    /// Returns the resolution resolved_items of an impl item impl.
    fn impl_impl_def_resolver_data(
        &'db self,
        id: ImplImplDefId<'db>,
    ) -> Maybe<Arc<ResolverData<'db>>> {
        Ok(impl_impl_semantic_data(self.as_dyn_database(), id, false)
            .maybe_as_ref()?
            .impl_data
            .resolver_data
            .clone())
    }

    // Impl impl.
    // ================
    /// Returns the implized impl impl value if the impl is concrete.
    fn impl_impl_concrete_implized(&'db self, impl_impl_id: ImplImplId<'db>) -> Maybe<ImplId<'db>> {
        impl_impl_concrete_implized_tracked(self.as_dyn_database(), impl_impl_id)
    }

    // Impl function.
    // ================
    /// Returns the semantic diagnostics of an impl function's declaration (signature).
    fn impl_function_declaration_diagnostics(
        &'db self,
        id: ImplFunctionId<'db>,
    ) -> Diagnostics<'db, SemanticDiagnostic<'db>> {
        impl_function_declaration_data(self.as_dyn_database(), id)
            .as_ref()
            .map(|data| data.function_declaration_data.diagnostics.clone())
            .unwrap_or_default()
    }
    /// Returns the signature of an impl function.
    fn impl_function_signature(
        &'db self,
        id: ImplFunctionId<'db>,
    ) -> Maybe<&'db semantic::Signature<'db>> {
        Ok(&impl_function_declaration_data(self.as_dyn_database(), id)
            .maybe_as_ref()?
            .function_declaration_data
            .signature)
    }
    /// Returns the generic params of an impl function.
    fn impl_function_generic_params(
        &'db self,
        id: ImplFunctionId<'db>,
    ) -> Maybe<&'db [GenericParam<'db>]> {
        Ok(&impl_function_generic_params_data(self.as_dyn_database(), id)
            .maybe_as_ref()?
            .generic_params)
    }
    /// Returns the attributes of an impl function.
    fn impl_function_attributes(
        &'db self,
        id: ImplFunctionId<'db>,
    ) -> Maybe<&'db [Attribute<'db>]> {
        Ok(&impl_function_declaration_data(self.as_dyn_database(), id)
            .maybe_as_ref()?
            .function_declaration_data
            .attributes)
    }
    /// Returns the resolution resolved_items of an impl function's declaration.
    fn impl_function_resolver_data(
        &'db self,
        id: ImplFunctionId<'db>,
    ) -> Maybe<Arc<ResolverData<'db>>> {
        Ok(impl_function_declaration_data(self.as_dyn_database(), id)
            .maybe_as_ref()?
            .function_declaration_data
            .resolver_data
            .clone())
    }
    /// Returns the inline configuration of an impl function's declaration.
    fn impl_function_declaration_inline_config(
        &'db self,
        id: ImplFunctionId<'db>,
    ) -> Maybe<InlineConfiguration<'db>> {
        Ok(impl_function_declaration_data(self.as_dyn_database(), id)
            .maybe_as_ref()?
            .function_declaration_data
            .inline_config
            .clone())
    }
    /// Returns the implicits precedence of an impl function.
    fn impl_function_declaration_implicit_precedence(
        &'db self,
        id: ImplFunctionId<'db>,
    ) -> Maybe<&'db ImplicitPrecedence<'db>> {
        Ok(&impl_function_declaration_data(self.as_dyn_database(), id)
            .maybe_as_ref()?
            .function_declaration_data
            .implicit_precedence)
    }
    /// Returns the trait function of an impl function.
    fn impl_function_trait_function(
        &'db self,
        id: ImplFunctionId<'db>,
    ) -> Maybe<TraitFunctionId<'db>> {
        impl_function_declaration_data(self.as_dyn_database(), id).maybe_as_ref()?.trait_function_id
    }
    /// Returns the semantic diagnostics of an impl function definition (declaration + body).
    fn impl_function_body_diagnostics(
        &'db self,
        impl_function_id: ImplFunctionId<'db>,
    ) -> Diagnostics<'db, SemanticDiagnostic<'db>> {
        self.priv_impl_function_body_data(impl_function_id)
            .map(|data| data.diagnostics.clone())
            .unwrap_or_default()
    }
    /// Returns the definition of an impl function.
    fn impl_function_body(
        &'db self,
        impl_function_id: ImplFunctionId<'db>,
    ) -> Maybe<&'db FunctionBody<'db>> {
        Ok(&self.priv_impl_function_body_data(impl_function_id)?.body)
    }
    /// Returns the resolution resolved_items of an impl function's definition.
    fn impl_function_body_resolver_data(
        &'db self,
        impl_function_id: ImplFunctionId<'db>,
    ) -> Maybe<Arc<ResolverData<'db>>> {
        Ok(self.priv_impl_function_body_data(impl_function_id)?.resolver_data.clone())
    }
    /// Private query to compute data about an impl function definition (declaration + body).
    fn priv_impl_function_body_data(
        &'db self,
        impl_function_id: ImplFunctionId<'db>,
    ) -> Maybe<&'db FunctionBodyData<'db>> {
        priv_impl_function_body_data_tracked(self.as_dyn_database(), impl_function_id)
            .maybe_as_ref()
    }
}
impl<'db, T: Database + ?Sized> ImplSemantic<'db> for T {}

/// Trait for private impl-related semantic queries.
trait PrivImplSemantic<'db>: Database {
    /// Returns the substitution for generics for the impl.
    fn impl_def_substitution(
        &'db self,
        impl_def_id: ImplDefId<'db>,
    ) -> Maybe<&'db GenericSubstitution<'db>> {
        impl_def_substitution(self.as_dyn_database(), impl_def_id).maybe_as_ref()
    }
    /// Returns the shallow trait generic arguments of an impl.
    fn impl_def_shallow_trait_generic_args(
        &'db self,
        impl_def_id: ImplDefId<'db>,
    ) -> Maybe<&'db [(GenericParamId<'db>, ShallowGenericArg<'db>)]> {
        impl_def_shallow_trait_generic_args(self.as_dyn_database(), impl_def_id)
    }
    /// Returns the shallow trait generic arguments of an impl alias.
    fn impl_alias_trait_generic_args(
        &'db self,
        impl_def_id: ImplAliasId<'db>,
    ) -> Maybe<&'db [(GenericParamId<'db>, ShallowGenericArg<'db>)]> {
        impl_alias_trait_generic_args(self.as_dyn_database(), impl_def_id)
    }
    /// Returns the item of the impl, by the given `name`, if exists.
    fn impl_item_by_name(
        &'db self,
        impl_def_id: ImplDefId<'db>,
        name: SmolStrId<'db>,
    ) -> Maybe<Option<ImplItemId<'db>>> {
        Ok(impl_definition_data(self.as_dyn_database(), impl_def_id)
            .maybe_as_ref()?
            .item_id_by_name
            .get(&name)
            .map(|info| info.id))
    }
    /// Returns the trait impl of an implicit impl if `name` exists in trait and not in the impl.
    fn impl_implicit_impl_by_name(
        &'db self,
        impl_def_id: ImplDefId<'db>,
        name: SmolStrId<'db>,
    ) -> Maybe<Option<TraitImplId<'db>>> {
        Ok(impl_definition_data(self.as_dyn_database(), impl_def_id)
            .maybe_as_ref()?
            .implicit_impls_id_by_name
            .get(&name)
            .copied())
    }
    /// Returns the impl AST of the impl type that matches the given id, if exists.
    fn impl_type_by_id(
        &'db self,
        impl_type_id: ImplTypeDefId<'db>,
    ) -> Maybe<ast::ItemTypeAlias<'db>> {
        impl_type_by_id(self.as_dyn_database(), impl_type_id)
    }
    /// Returns the impls items in the impl.
    fn impl_impls(
        &'db self,
        impl_def_id: ImplDefId<'db>,
    ) -> Maybe<&'db OrderedHashMap<ImplImplDefId<'db>, ast::ItemImplAlias<'db>>> {
        Ok(&impl_definition_data(self.as_dyn_database(), impl_def_id)
            .maybe_as_ref()?
            .item_impl_asts)
    }
    /// Returns the impl AST of the impl impl that matches the given id, if exists.
    fn impl_impl_by_id(
        &'db self,
        impl_impl_id: ImplImplDefId<'db>,
    ) -> Maybe<ast::ItemImplAlias<'db>> {
        impl_impl_by_id(self.as_dyn_database(), impl_impl_id)
    }
    /// Returns the impl impl item that matches the given trait impl item, if exists.
    fn impl_impl_by_trait_impl(
        &'db self,
        impl_def_id: ImplDefId<'db>,
        trait_impl_id: TraitImplId<'db>,
    ) -> Maybe<ImplImplDefId<'db>> {
        impl_impl_by_trait_impl(self.as_dyn_database(), impl_def_id, trait_impl_id)
    }
    /// Returns whether `trait_impl_id` is an implicit impl in `impl_def_id`.
    fn is_implicit_impl_impl(
        &self,
        impl_def_id: ImplDefId<'db>,
        trait_impl_id: TraitImplId<'db>,
    ) -> Maybe<bool> {
        is_implicit_impl_impl(self.as_dyn_database(), impl_def_id, trait_impl_id)
    }
    /// Returns the impl constant item that matches the given trait constant item, if exists.
    fn impl_constant_by_trait_constant(
        &'db self,
        impl_def_id: ImplDefId<'db>,
        trait_constant_id: TraitConstantId<'db>,
    ) -> Maybe<ImplConstantDefId<'db>> {
        impl_constant_by_trait_constant(self.as_dyn_database(), impl_def_id, trait_constant_id)
    }
    /// Returns the impl function that matches the given trait function, if exists.
    /// Note that a function that doesn't exist in the impl doesn't necessarily indicate an error,
    /// as, e.g., a trait function that has a default implementation doesn't have to be
    /// implemented in the impl.
    fn impl_function_by_trait_function(
        &'db self,
        impl_def_id: ImplDefId<'db>,
        trait_function_id: TraitFunctionId<'db>,
    ) -> Maybe<Option<ImplFunctionId<'db>>> {
        impl_function_by_trait_function(self.as_dyn_database(), impl_def_id, trait_function_id)
    }
    /// Returns the semantic diagnostics of an impl item type.
    fn impl_type_def_semantic_diagnostics(
        &'db self,
        id: ImplTypeDefId<'db>,
    ) -> Diagnostics<'db, SemanticDiagnostic<'db>> {
        impl_type_semantic_data(self.as_dyn_database(), id, false)
            .as_ref()
            .map(|data| data.diagnostics.clone())
            .unwrap_or_default()
    }
    /// Returns the semantic diagnostics of an impl item constant.
    fn impl_constant_def_semantic_diagnostics(
        &'db self,
        id: ImplConstantDefId<'db>,
    ) -> Diagnostics<'db, SemanticDiagnostic<'db>> {
        impl_constant_semantic_data(self.as_dyn_database(), id, false)
            .as_ref()
            .map(|data| data.diagnostics.clone())
            .unwrap_or_default()
    }
    /// Returns the given impl constant, implized by the given impl context.
    fn impl_constant_implized_by_context(
        &'db self,
        impl_constant_id: ImplConstantId<'db>,
        impl_def_id: ImplDefId<'db>,
    ) -> Maybe<ConstValueId<'db>> {
        impl_constant_implized_by_context_tracked(
            self.as_dyn_database(),
            impl_constant_id,
            impl_def_id,
        )
    }
    /// Returns the semantic diagnostics of an impl item impl.
    fn impl_impl_def_semantic_diagnostics(
        &'db self,
        id: ImplImplDefId<'db>,
    ) -> Diagnostics<'db, SemanticDiagnostic<'db>> {
        impl_impl_semantic_data(self.as_dyn_database(), id, false)
            .as_ref()
            .map(|data| data.diagnostics.clone())
            .unwrap_or_default()
    }
    /// Returns the resolved impl of an impl item impl.
    fn impl_impl_def_impl(
        &'db self,
        impl_impl_def_id: ImplImplDefId<'db>,
        in_cycle: bool,
    ) -> Maybe<ImplId<'db>> {
        impl_impl_semantic_data(self.as_dyn_database(), impl_impl_def_id, in_cycle)
            .maybe_as_ref()?
            .impl_data
            .resolved_impl
    }
    /// Returns the semantic diagnostics of an implicit impl.
    fn implicit_impl_impl_semantic_diagnostics(
        &'db self,
        impl_def_id: ImplDefId<'db>,
        trait_impl_id: TraitImplId<'db>,
    ) -> Diagnostics<'db, SemanticDiagnostic<'db>> {
        implicit_impl_impl_semantic_data_tracked(
            self.as_dyn_database(),
            impl_def_id,
            trait_impl_id,
            false,
        )
        .as_ref()
        .map(|data| data.diagnostics.clone())
        .unwrap_or_default()
    }
    /// Returns the resolved impl of an implicit impl.
    fn implicit_impl_impl_impl(
        &'db self,
        impl_def_id: ImplDefId<'db>,
        trait_impl_id: TraitImplId<'db>,
        in_cycle: bool,
    ) -> Maybe<ImplId<'db>> {
        implicit_impl_impl_semantic_data_tracked(
            self.as_dyn_database(),
            impl_def_id,
            trait_impl_id,
            in_cycle,
        )
        .maybe_as_ref()?
        .resolved_impl
    }
    /// Returns the implized impl impl if the impl is concrete.
    fn impl_impl_implized_by_context(
        &'db self,
        impl_impl_id: ImplImplId<'db>,
        impl_def_id: ImplDefId<'db>,
        in_cycle: bool,
    ) -> Maybe<ImplId<'db>> {
        impl_impl_implized_by_context_tracked(
            self.as_dyn_database(),
            impl_impl_id,
            impl_def_id,
            in_cycle,
        )
    }
    /// Returns the concrete trait of an impl impl.
    fn impl_impl_concrete_trait(
        &'db self,
        impl_impl_id: ImplImplId<'db>,
    ) -> Maybe<ConcreteTraitId<'db>> {
        impl_impl_concrete_trait_tracked(self.as_dyn_database(), impl_impl_id)
    }
    /// Returns the uninferred impls of a crate which are global.
    /// An impl is global if it is defined in the same module as the trait it implements or in the
    /// same module as one of its concrete traits' types.
    fn crate_global_impls(
        &'db self,
        crate_id: CrateId<'db>,
    ) -> &'db UnorderedHashMap<TraitId<'db>, OrderedHashSet<UninferredImplById<'db>>> {
        crate_global_impls(self.as_dyn_database(), crate_id)
    }
    /// Returns the traits which impls of a trait directly depend on.
    fn crate_traits_dependencies(
        &'db self,
        crate_id: CrateId<'db>,
    ) -> &'db UnorderedHashMap<TraitId<'db>, OrderedHashSet<TraitId<'db>>> {
        crate_traits_dependencies(self.as_dyn_database(), crate_id)
    }
    /// Returns the traits which are reachable from a trait.
    fn reachable_trait_dependencies(
        &'db self,
        trait_id: TraitId<'db>,
        crate_id: CrateId<'db>,
    ) -> &'db OrderedHashSet<TraitId<'db>> {
        reachable_trait_dependencies(self.as_dyn_database(), trait_id, crate_id)
    }
    /// Returns the global and local impls of a module.
    fn module_global_impls(
        &'db self,
        _tracked: Tracked,
        module_id: ModuleId<'db>,
    ) -> &'db Maybe<ModuleImpls<'db>> {
        module_global_impls(self.as_dyn_database(), _tracked, module_id)
    }
    /// Returns the candidates for a trait by its head.
    fn trait_candidate_by_head(
        &'db self,
        crate_id: CrateId<'db>,
        trait_id: TraitId<'db>,
    ) -> &'db OrderedHashMap<GenericsHeadFilter<'db>, OrderedHashSet<UninferredImplById<'db>>> {
        trait_candidate_by_head(self.as_dyn_database(), crate_id, trait_id)
    }
}
impl<'db, T: Database + ?Sized> PrivImplSemantic<'db> for T {}