//! This module is concerned with finding methods that a given type provides. //! For details about how this works in rustc, see the method lookup page in the //! [rustc guide](https://rust-lang.github.io/rustc-guide/method-lookup.html) //! and the corresponding code mostly in librustc_typeck/check/method/probe.rs. use std::sync::Arc; use arrayvec::ArrayVec; use hir_def::{ lang_item::LangItemTarget, type_ref::Mutability, AssocContainerId, AssocItemId, FunctionId, HasModule, ImplId, Lookup, TraitId, }; use hir_expand::name::Name; use ra_db::CrateId; use ra_prof::profile; use rustc_hash::{FxHashMap, FxHashSet}; use super::Substs; use crate::{ autoderef, db::HirDatabase, primitive::{FloatBitness, Uncertain}, utils::all_super_traits, ApplicationTy, Canonical, DebruijnIndex, InEnvironment, TraitEnvironment, TraitRef, Ty, TypeCtor, TypeWalk, }; /// This is used as a key for indexing impls. #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)] pub enum TyFingerprint { Apply(TypeCtor), } impl TyFingerprint { /// Creates a TyFingerprint for looking up an impl. Only certain types can /// have impls: if we have some `struct S`, we can have an `impl S`, but not /// `impl &S`. Hence, this will return `None` for reference types and such. pub(crate) fn for_impl(ty: &Ty) -> Option<TyFingerprint> { match ty { Ty::Apply(a_ty) => Some(TyFingerprint::Apply(a_ty.ctor)), _ => None, } } } #[derive(Debug, PartialEq, Eq)] pub struct CrateImplDefs { impls: FxHashMap<TyFingerprint, Vec<ImplId>>, impls_by_trait: FxHashMap<TraitId, FxHashMap<Option<TyFingerprint>, Vec<ImplId>>>, } impl CrateImplDefs { pub(crate) fn impls_in_crate_query(db: &dyn HirDatabase, krate: CrateId) -> Arc<CrateImplDefs> { let _p = profile("impls_in_crate_query"); let mut res = CrateImplDefs { impls: FxHashMap::default(), impls_by_trait: FxHashMap::default() }; let crate_def_map = db.crate_def_map(krate); for (_module_id, module_data) in crate_def_map.modules.iter() { for impl_id in module_data.scope.impls() { match db.impl_trait(impl_id) { Some(tr) => { let self_ty = db.impl_self_ty(impl_id); let self_ty_fp = TyFingerprint::for_impl(&self_ty.value); res.impls_by_trait .entry(tr.value.trait_) .or_default() .entry(self_ty_fp) .or_default() .push(impl_id); } None => { let self_ty = db.impl_self_ty(impl_id); if let Some(self_ty_fp) = TyFingerprint::for_impl(&self_ty.value) { res.impls.entry(self_ty_fp).or_default().push(impl_id); } } } } } Arc::new(res) } pub fn lookup_impl_defs(&self, ty: &Ty) -> impl Iterator<Item = ImplId> + '_ { let fingerprint = TyFingerprint::for_impl(ty); fingerprint.and_then(|f| self.impls.get(&f)).into_iter().flatten().copied() } pub fn lookup_impl_defs_for_trait(&self, tr: TraitId) -> impl Iterator<Item = ImplId> + '_ { self.impls_by_trait .get(&tr) .into_iter() .flat_map(|m| m.values().flat_map(|v| v.iter().copied())) } pub fn lookup_impl_defs_for_trait_and_ty( &self, tr: TraitId, fp: TyFingerprint, ) -> impl Iterator<Item = ImplId> + '_ { self.impls_by_trait .get(&tr) .and_then(|m| m.get(&Some(fp))) .into_iter() .flatten() .copied() .chain( self.impls_by_trait .get(&tr) .and_then(|m| m.get(&None)) .into_iter() .flatten() .copied(), ) } pub fn all_impls<'a>(&'a self) -> impl Iterator<Item = ImplId> + 'a { self.impls .values() .chain(self.impls_by_trait.values().flat_map(|m| m.values())) .flatten() .copied() } } impl Ty { pub fn def_crates( &self, db: &dyn HirDatabase, cur_crate: CrateId, ) -> Option<ArrayVec<[CrateId; 2]>> { // Types like slice can have inherent impls in several crates, (core and alloc). // The corresponding impls are marked with lang items, so we can use them to find the required crates. macro_rules! lang_item_crate { ($($name:expr),+ $(,)?) => {{ let mut v = ArrayVec::<[LangItemTarget; 2]>::new(); $( v.extend(db.lang_item(cur_crate, $name.into())); )+ v }}; } let lang_item_targets = match self { Ty::Apply(a_ty) => match a_ty.ctor { TypeCtor::Adt(def_id) => { return Some(std::iter::once(def_id.module(db.upcast()).krate).collect()) } TypeCtor::Bool => lang_item_crate!("bool"), TypeCtor::Char => lang_item_crate!("char"), TypeCtor::Float(Uncertain::Known(f)) => match f.bitness { // There are two lang items: one in libcore (fXX) and one in libstd (fXX_runtime) FloatBitness::X32 => lang_item_crate!("f32", "f32_runtime"), FloatBitness::X64 => lang_item_crate!("f64", "f64_runtime"), }, TypeCtor::Int(Uncertain::Known(i)) => lang_item_crate!(i.ty_to_string()), TypeCtor::Str => lang_item_crate!("str_alloc", "str"), TypeCtor::Slice => lang_item_crate!("slice_alloc", "slice"), TypeCtor::RawPtr(Mutability::Shared) => lang_item_crate!("const_ptr"), TypeCtor::RawPtr(Mutability::Mut) => lang_item_crate!("mut_ptr"), _ => return None, }, _ => return None, }; let res = lang_item_targets .into_iter() .filter_map(|it| match it { LangItemTarget::ImplDefId(it) => Some(it), _ => None, }) .map(|it| it.lookup(db.upcast()).container.module(db.upcast()).krate) .collect(); Some(res) } } /// Look up the method with the given name, returning the actual autoderefed /// receiver type (but without autoref applied yet). pub(crate) fn lookup_method( ty: &Canonical<Ty>, db: &dyn HirDatabase, env: Arc<TraitEnvironment>, krate: CrateId, traits_in_scope: &FxHashSet<TraitId>, name: &Name, ) -> Option<(Ty, FunctionId)> { iterate_method_candidates( ty, db, env, krate, &traits_in_scope, Some(name), LookupMode::MethodCall, |ty, f| match f { AssocItemId::FunctionId(f) => Some((ty.clone(), f)), _ => None, }, ) } /// Whether we're looking up a dotted method call (like `v.len()`) or a path /// (like `Vec::new`). #[derive(Copy, Clone, Debug, PartialEq, Eq)] pub enum LookupMode { /// Looking up a method call like `v.len()`: We only consider candidates /// that have a `self` parameter, and do autoderef. MethodCall, /// Looking up a path like `Vec::new` or `Vec::default`: We consider all /// candidates including associated constants, but don't do autoderef. Path, } // This would be nicer if it just returned an iterator, but that runs into // lifetime problems, because we need to borrow temp `CrateImplDefs`. // FIXME add a context type here? pub fn iterate_method_candidates<T>( ty: &Canonical<Ty>, db: &dyn HirDatabase, env: Arc<TraitEnvironment>, krate: CrateId, traits_in_scope: &FxHashSet<TraitId>, name: Option<&Name>, mode: LookupMode, mut callback: impl FnMut(&Ty, AssocItemId) -> Option<T>, ) -> Option<T> { match mode { LookupMode::MethodCall => { // For method calls, rust first does any number of autoderef, and then one // autoref (i.e. when the method takes &self or &mut self). We just ignore // the autoref currently -- when we find a method matching the given name, // we assume it fits. // Also note that when we've got a receiver like &S, even if the method we // find in the end takes &self, we still do the autoderef step (just as // rustc does an autoderef and then autoref again). let ty = InEnvironment { value: ty.clone(), environment: env.clone() }; // We have to be careful about the order we're looking at candidates // in here. Consider the case where we're resolving `x.clone()` // where `x: &Vec<_>`. This resolves to the clone method with self // type `Vec<_>`, *not* `&_`. I.e. we need to consider methods where // the receiver type exactly matches before cases where we have to // do autoref. But in the autoderef steps, the `&_` self type comes // up *before* the `Vec<_>` self type. // // On the other hand, we don't want to just pick any by-value method // before any by-autoref method; it's just that we need to consider // the methods by autoderef order of *receiver types*, not *self // types*. let deref_chain = autoderef_method_receiver(db, krate, ty); for i in 0..deref_chain.len() { if let Some(result) = iterate_method_candidates_with_autoref( &deref_chain[i..], db, env.clone(), krate, traits_in_scope, name, &mut callback, ) { return Some(result); } } None } LookupMode::Path => { // No autoderef for path lookups iterate_method_candidates_for_self_ty( &ty, db, env, krate, traits_in_scope, name, &mut callback, ) } } } fn iterate_method_candidates_with_autoref<T>( deref_chain: &[Canonical<Ty>], db: &dyn HirDatabase, env: Arc<TraitEnvironment>, krate: CrateId, traits_in_scope: &FxHashSet<TraitId>, name: Option<&Name>, mut callback: impl FnMut(&Ty, AssocItemId) -> Option<T>, ) -> Option<T> { if let Some(result) = iterate_method_candidates_by_receiver( &deref_chain[0], &deref_chain[1..], db, env.clone(), krate, &traits_in_scope, name, &mut callback, ) { return Some(result); } let refed = Canonical { num_vars: deref_chain[0].num_vars, value: Ty::apply_one(TypeCtor::Ref(Mutability::Shared), deref_chain[0].value.clone()), }; if let Some(result) = iterate_method_candidates_by_receiver( &refed, deref_chain, db, env.clone(), krate, &traits_in_scope, name, &mut callback, ) { return Some(result); } let ref_muted = Canonical { num_vars: deref_chain[0].num_vars, value: Ty::apply_one(TypeCtor::Ref(Mutability::Mut), deref_chain[0].value.clone()), }; if let Some(result) = iterate_method_candidates_by_receiver( &ref_muted, deref_chain, db, env, krate, &traits_in_scope, name, &mut callback, ) { return Some(result); } None } fn iterate_method_candidates_by_receiver<T>( receiver_ty: &Canonical<Ty>, rest_of_deref_chain: &[Canonical<Ty>], db: &dyn HirDatabase, env: Arc<TraitEnvironment>, krate: CrateId, traits_in_scope: &FxHashSet<TraitId>, name: Option<&Name>, mut callback: impl FnMut(&Ty, AssocItemId) -> Option<T>, ) -> Option<T> { // We're looking for methods with *receiver* type receiver_ty. These could // be found in any of the derefs of receiver_ty, so we have to go through // that. for self_ty in std::iter::once(receiver_ty).chain(rest_of_deref_chain) { if let Some(result) = iterate_inherent_methods(self_ty, db, name, Some(receiver_ty), krate, &mut callback) { return Some(result); } } for self_ty in std::iter::once(receiver_ty).chain(rest_of_deref_chain) { if let Some(result) = iterate_trait_method_candidates( self_ty, db, env.clone(), krate, &traits_in_scope, name, Some(receiver_ty), &mut callback, ) { return Some(result); } } None } fn iterate_method_candidates_for_self_ty<T>( self_ty: &Canonical<Ty>, db: &dyn HirDatabase, env: Arc<TraitEnvironment>, krate: CrateId, traits_in_scope: &FxHashSet<TraitId>, name: Option<&Name>, mut callback: impl FnMut(&Ty, AssocItemId) -> Option<T>, ) -> Option<T> { if let Some(result) = iterate_inherent_methods(self_ty, db, name, None, krate, &mut callback) { return Some(result); } if let Some(result) = iterate_trait_method_candidates( self_ty, db, env, krate, traits_in_scope, name, None, &mut callback, ) { return Some(result); } None } fn iterate_trait_method_candidates<T>( self_ty: &Canonical<Ty>, db: &dyn HirDatabase, env: Arc<TraitEnvironment>, krate: CrateId, traits_in_scope: &FxHashSet<TraitId>, name: Option<&Name>, receiver_ty: Option<&Canonical<Ty>>, mut callback: impl FnMut(&Ty, AssocItemId) -> Option<T>, ) -> Option<T> { // if ty is `dyn Trait`, the trait doesn't need to be in scope let inherent_trait = self_ty.value.dyn_trait().into_iter().flat_map(|t| all_super_traits(db.upcast(), t)); let env_traits = if let Ty::Placeholder(_) = self_ty.value { // if we have `T: Trait` in the param env, the trait doesn't need to be in scope env.trait_predicates_for_self_ty(&self_ty.value) .map(|tr| tr.trait_) .flat_map(|t| all_super_traits(db.upcast(), t)) .collect() } else { Vec::new() }; let traits = inherent_trait.chain(env_traits.into_iter()).chain(traits_in_scope.iter().copied()); 'traits: for t in traits { let data = db.trait_data(t); // we'll be lazy about checking whether the type implements the // trait, but if we find out it doesn't, we'll skip the rest of the // iteration let mut known_implemented = false; for (_name, item) in data.items.iter() { if !is_valid_candidate(db, name, receiver_ty, *item, self_ty) { continue; } if !known_implemented { let goal = generic_implements_goal(db, env.clone(), t, self_ty.clone()); if db.trait_solve(krate, goal).is_none() { continue 'traits; } } known_implemented = true; if let Some(result) = callback(&self_ty.value, *item) { return Some(result); } } } None } fn iterate_inherent_methods<T>( self_ty: &Canonical<Ty>, db: &dyn HirDatabase, name: Option<&Name>, receiver_ty: Option<&Canonical<Ty>>, krate: CrateId, mut callback: impl FnMut(&Ty, AssocItemId) -> Option<T>, ) -> Option<T> { for krate in self_ty.value.def_crates(db, krate)? { let impls = db.impls_in_crate(krate); for impl_def in impls.lookup_impl_defs(&self_ty.value) { for &item in db.impl_data(impl_def).items.iter() { if !is_valid_candidate(db, name, receiver_ty, item, self_ty) { continue; } // we have to check whether the self type unifies with the type // that the impl is for. If we have a receiver type, this // already happens in `is_valid_candidate` above; if not, we // check it here if receiver_ty.is_none() && inherent_impl_substs(db, impl_def, self_ty).is_none() { test_utils::mark::hit!(impl_self_type_match_without_receiver); continue; } if let Some(result) = callback(&self_ty.value, item) { return Some(result); } } } } None } /// Returns the self type for the index trait call. pub fn resolve_indexing_op( db: &dyn HirDatabase, ty: &Canonical<Ty>, env: Arc<TraitEnvironment>, krate: CrateId, index_trait: TraitId, ) -> Option<Canonical<Ty>> { let ty = InEnvironment { value: ty.clone(), environment: env.clone() }; let deref_chain = autoderef_method_receiver(db, krate, ty); for ty in deref_chain { let goal = generic_implements_goal(db, env.clone(), index_trait, ty.clone()); if db.trait_solve(krate, goal).is_some() { return Some(ty); } } None } fn is_valid_candidate( db: &dyn HirDatabase, name: Option<&Name>, receiver_ty: Option<&Canonical<Ty>>, item: AssocItemId, self_ty: &Canonical<Ty>, ) -> bool { match item { AssocItemId::FunctionId(m) => { let data = db.function_data(m); if let Some(name) = name { if &data.name != name { return false; } } if let Some(receiver_ty) = receiver_ty { if !data.has_self_param { return false; } let transformed_receiver_ty = match transform_receiver_ty(db, m, self_ty) { Some(ty) => ty, None => return false, }; if transformed_receiver_ty != receiver_ty.value { return false; } } true } AssocItemId::ConstId(c) => { let data = db.const_data(c); name.map_or(true, |name| data.name.as_ref() == Some(name)) && receiver_ty.is_none() } _ => false, } } pub(crate) fn inherent_impl_substs( db: &dyn HirDatabase, impl_id: ImplId, self_ty: &Canonical<Ty>, ) -> Option<Substs> { // we create a var for each type parameter of the impl; we need to keep in // mind here that `self_ty` might have vars of its own let vars = Substs::build_for_def(db, impl_id) .fill_with_bound_vars(DebruijnIndex::INNERMOST, self_ty.num_vars) .build(); let self_ty_with_vars = db.impl_self_ty(impl_id).subst(&vars); let self_ty_with_vars = Canonical { num_vars: vars.len() + self_ty.num_vars, value: self_ty_with_vars }; let substs = super::infer::unify(&self_ty_with_vars, self_ty); // We only want the substs for the vars we added, not the ones from self_ty. // Also, if any of the vars we added are still in there, we replace them by // Unknown. I think this can only really happen if self_ty contained // Unknown, and in that case we want the result to contain Unknown in those // places again. substs.map(|s| fallback_bound_vars(s.suffix(vars.len()), self_ty.num_vars)) } /// This replaces any 'free' Bound vars in `s` (i.e. those with indices past /// num_vars_to_keep) by `Ty::Unknown`. fn fallback_bound_vars(s: Substs, num_vars_to_keep: usize) -> Substs { s.fold_binders( &mut |ty, binders| { if let Ty::Bound(bound) = &ty { if bound.index >= num_vars_to_keep && bound.debruijn >= binders { Ty::Unknown } else { ty } } else { ty } }, DebruijnIndex::INNERMOST, ) } fn transform_receiver_ty( db: &dyn HirDatabase, function_id: FunctionId, self_ty: &Canonical<Ty>, ) -> Option<Ty> { let substs = match function_id.lookup(db.upcast()).container { AssocContainerId::TraitId(_) => Substs::build_for_def(db, function_id) .push(self_ty.value.clone()) .fill_with_unknown() .build(), AssocContainerId::ImplId(impl_id) => inherent_impl_substs(db, impl_id, &self_ty)?, AssocContainerId::ContainerId(_) => unreachable!(), }; let sig = db.callable_item_signature(function_id.into()); Some(sig.value.params()[0].clone().subst_bound_vars(&substs)) } pub fn implements_trait( ty: &Canonical<Ty>, db: &dyn HirDatabase, env: Arc<TraitEnvironment>, krate: CrateId, trait_: TraitId, ) -> bool { let goal = generic_implements_goal(db, env, trait_, ty.clone()); let solution = db.trait_solve(krate, goal); solution.is_some() } /// This creates Substs for a trait with the given Self type and type variables /// for all other parameters, to query Chalk with it. fn generic_implements_goal( db: &dyn HirDatabase, env: Arc<TraitEnvironment>, trait_: TraitId, self_ty: Canonical<Ty>, ) -> Canonical<InEnvironment<super::Obligation>> { let num_vars = self_ty.num_vars; let substs = super::Substs::build_for_def(db, trait_) .push(self_ty.value) .fill_with_bound_vars(DebruijnIndex::INNERMOST, num_vars) .build(); let num_vars = substs.len() - 1 + self_ty.num_vars; let trait_ref = TraitRef { trait_, substs }; let obligation = super::Obligation::Trait(trait_ref); Canonical { num_vars, value: InEnvironment::new(env, obligation) } } fn autoderef_method_receiver( db: &dyn HirDatabase, krate: CrateId, ty: InEnvironment<Canonical<Ty>>, ) -> Vec<Canonical<Ty>> { let mut deref_chain: Vec<_> = autoderef::autoderef(db, Some(krate), ty).collect(); // As a last step, we can do array unsizing (that's the only unsizing that rustc does for method receivers!) if let Some(Ty::Apply(ApplicationTy { ctor: TypeCtor::Array, parameters })) = deref_chain.last().map(|ty| &ty.value) { let num_vars = deref_chain.last().unwrap().num_vars; let unsized_ty = Ty::apply(TypeCtor::Slice, parameters.clone()); deref_chain.push(Canonical { value: unsized_ty, num_vars }) } deref_chain }