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use crate::traits::specialization_graph;
use crate::ty::fast_reject::{self, SimplifiedType, TreatParams, TreatProjections};
use crate::ty::visit::TypeVisitableExt;
use crate::ty::{Ident, Ty, TyCtxt};
use hir::def_id::LOCAL_CRATE;
use rustc_hir as hir;
use rustc_hir::def_id::DefId;
use std::iter;
use rustc_data_structures::fx::FxIndexMap;
use rustc_errors::ErrorGuaranteed;
use rustc_macros::HashStable;
/// A trait's definition with type information.
#[derive(HashStable, Encodable, Decodable)]
pub struct TraitDef {
pub def_id: DefId,
pub unsafety: hir::Unsafety,
/// If `true`, then this trait had the `#[rustc_paren_sugar]`
/// attribute, indicating that it should be used with `Foo()`
/// sugar. This is a temporary thing -- eventually any trait will
/// be usable with the sugar (or without it).
pub paren_sugar: bool,
pub has_auto_impl: bool,
/// If `true`, then this trait has the `#[marker]` attribute, indicating
/// that all its associated items have defaults that cannot be overridden,
/// and thus `impl`s of it are allowed to overlap.
pub is_marker: bool,
/// If `true`, then this trait has to `#[rustc_coinductive]` attribute or
/// is an auto trait. This indicates that trait solver cycles involving an
/// `X: ThisTrait` goal are accepted.
///
/// In the future all traits should be coinductive, but we need a better
/// formal understanding of what exactly that means and should probably
/// also have already switched to the new trait solver.
pub is_coinductive: bool,
/// If `true`, then this trait has the `#[rustc_skip_array_during_method_dispatch]`
/// attribute, indicating that editions before 2021 should not consider this trait
/// during method dispatch if the receiver is an array.
pub skip_array_during_method_dispatch: bool,
/// Used to determine whether the standard library is allowed to specialize
/// on this trait.
pub specialization_kind: TraitSpecializationKind,
/// List of functions from `#[rustc_must_implement_one_of]` attribute one of which
/// must be implemented.
pub must_implement_one_of: Option<Box<[Ident]>>,
/// Whether to add a builtin `dyn Trait: Trait` implementation.
/// This is enabled for all traits except ones marked with
/// `#[rustc_deny_explicit_impl(implement_via_object = false)]`.
pub implement_via_object: bool,
/// Whether a trait is fully built-in, and any implementation is disallowed.
/// This only applies to built-in traits, and is marked via
/// `#[rustc_deny_explicit_impl(implement_via_object = ...)]`.
pub deny_explicit_impl: bool,
}
/// Whether this trait is treated specially by the standard library
/// specialization lint.
#[derive(HashStable, PartialEq, Clone, Copy, Encodable, Decodable)]
pub enum TraitSpecializationKind {
/// The default. Specializing on this trait is not allowed.
None,
/// Specializing on this trait is allowed because it doesn't have any
/// methods. For example `Sized` or `FusedIterator`.
/// Applies to traits with the `rustc_unsafe_specialization_marker`
/// attribute.
Marker,
/// Specializing on this trait is allowed because all of the impls of this
/// trait are "always applicable". Always applicable means that if
/// `X<'x>: T<'y>` for any lifetimes, then `for<'a, 'b> X<'a>: T<'b>`.
/// Applies to traits with the `rustc_specialization_trait` attribute.
AlwaysApplicable,
}
#[derive(Default, Debug, HashStable)]
pub struct TraitImpls {
blanket_impls: Vec<DefId>,
/// Impls indexed by their simplified self type, for fast lookup.
non_blanket_impls: FxIndexMap<SimplifiedType, Vec<DefId>>,
}
impl TraitImpls {
pub fn is_empty(&self) -> bool {
self.blanket_impls.is_empty() && self.non_blanket_impls.is_empty()
}
pub fn blanket_impls(&self) -> &[DefId] {
self.blanket_impls.as_slice()
}
pub fn non_blanket_impls(&self) -> &FxIndexMap<SimplifiedType, Vec<DefId>> {
&self.non_blanket_impls
}
}
impl<'tcx> TraitDef {
pub fn ancestors(
&self,
tcx: TyCtxt<'tcx>,
of_impl: DefId,
) -> Result<specialization_graph::Ancestors<'tcx>, ErrorGuaranteed> {
specialization_graph::ancestors(tcx, self.def_id, of_impl)
}
}
impl<'tcx> TyCtxt<'tcx> {
/// `trait_def_id` MUST BE the `DefId` of a trait.
pub fn for_each_impl<F: FnMut(DefId)>(self, trait_def_id: DefId, mut f: F) {
let impls = self.trait_impls_of(trait_def_id);
for &impl_def_id in impls.blanket_impls.iter() {
f(impl_def_id);
}
for v in impls.non_blanket_impls.values() {
for &impl_def_id in v {
f(impl_def_id);
}
}
}
/// Iterate over every impl that could possibly match the self type `self_ty`.
///
/// `trait_def_id` MUST BE the `DefId` of a trait.
pub fn for_each_relevant_impl(
self,
trait_def_id: DefId,
self_ty: Ty<'tcx>,
f: impl FnMut(DefId),
) {
self.for_each_relevant_impl_treating_projections(
trait_def_id,
self_ty,
TreatProjections::ForLookup,
f,
)
}
pub fn for_each_relevant_impl_treating_projections(
self,
trait_def_id: DefId,
self_ty: Ty<'tcx>,
treat_projections: TreatProjections,
mut f: impl FnMut(DefId),
) {
// FIXME: This depends on the set of all impls for the trait. That is
// unfortunate wrt. incremental compilation.
//
// If we want to be faster, we could have separate queries for
// blanket and non-blanket impls, and compare them separately.
let impls = self.trait_impls_of(trait_def_id);
for &impl_def_id in impls.blanket_impls.iter() {
f(impl_def_id);
}
// Note that we're using `TreatParams::ForLookup` to query `non_blanket_impls` while using
// `TreatParams::AsCandidateKey` while actually adding them.
let treat_params = match treat_projections {
TreatProjections::NextSolverLookup => TreatParams::NextSolverLookup,
TreatProjections::ForLookup => TreatParams::ForLookup,
};
// This way, when searching for some impl for `T: Trait`, we do not look at any impls
// whose outer level is not a parameter or projection. Especially for things like
// `T: Clone` this is incredibly useful as we would otherwise look at all the impls
// of `Clone` for `Option<T>`, `Vec<T>`, `ConcreteType` and so on.
if let Some(simp) = fast_reject::simplify_type(self, self_ty, treat_params) {
if let Some(impls) = impls.non_blanket_impls.get(&simp) {
for &impl_def_id in impls {
f(impl_def_id);
}
}
} else {
for &impl_def_id in impls.non_blanket_impls.values().flatten() {
f(impl_def_id);
}
}
}
/// `trait_def_id` MUST BE the `DefId` of a trait.
pub fn non_blanket_impls_for_ty(
self,
trait_def_id: DefId,
self_ty: Ty<'tcx>,
) -> impl Iterator<Item = DefId> + 'tcx {
let impls = self.trait_impls_of(trait_def_id);
if let Some(simp) = fast_reject::simplify_type(self, self_ty, TreatParams::AsCandidateKey) {
if let Some(impls) = impls.non_blanket_impls.get(&simp) {
return impls.iter().copied();
}
}
[].iter().copied()
}
/// Returns an iterator containing all impls for `trait_def_id`.
///
/// `trait_def_id` MUST BE the `DefId` of a trait.
pub fn all_impls(self, trait_def_id: DefId) -> impl Iterator<Item = DefId> + 'tcx {
let TraitImpls { blanket_impls, non_blanket_impls } = self.trait_impls_of(trait_def_id);
blanket_impls.iter().chain(non_blanket_impls.iter().flat_map(|(_, v)| v)).cloned()
}
}
/// Query provider for `trait_impls_of`.
pub(super) fn trait_impls_of_provider(tcx: TyCtxt<'_>, trait_id: DefId) -> TraitImpls {
let mut impls = TraitImpls::default();
// Traits defined in the current crate can't have impls in upstream
// crates, so we don't bother querying the cstore.
if !trait_id.is_local() {
for &cnum in tcx.crates(()).iter() {
for &(impl_def_id, simplified_self_ty) in
tcx.implementations_of_trait((cnum, trait_id)).iter()
{
if let Some(simplified_self_ty) = simplified_self_ty {
impls
.non_blanket_impls
.entry(simplified_self_ty)
.or_default()
.push(impl_def_id);
} else {
impls.blanket_impls.push(impl_def_id);
}
}
}
}
for &impl_def_id in tcx.hir().trait_impls(trait_id) {
let impl_def_id = impl_def_id.to_def_id();
let impl_self_ty = tcx.type_of(impl_def_id).instantiate_identity();
if impl_self_ty.references_error() {
continue;
}
if let Some(simplified_self_ty) =
fast_reject::simplify_type(tcx, impl_self_ty, TreatParams::AsCandidateKey)
{
impls.non_blanket_impls.entry(simplified_self_ty).or_default().push(impl_def_id);
} else {
impls.blanket_impls.push(impl_def_id);
}
}
impls
}
/// Query provider for `incoherent_impls`.
pub(super) fn incoherent_impls_provider(tcx: TyCtxt<'_>, simp: SimplifiedType) -> &[DefId] {
let mut impls = Vec::new();
for cnum in iter::once(LOCAL_CRATE).chain(tcx.crates(()).iter().copied()) {
for &impl_def_id in tcx.crate_incoherent_impls((cnum, simp)) {
impls.push(impl_def_id)
}
}
debug!(?impls);
tcx.arena.alloc_slice(&impls)
}