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// `#![no_std]`: these arrive with the standard prelude and name no path, so a `std::`
// search cannot see them - and a `#[derive]` can use them without the name appearing
// in this file at all, which is why they are not trimmed by inspection.
use alloc::borrow::ToOwned;
use alloc::boxed::Box;
use alloc::format;
use alloc::string::{String, ToString};
use alloc::vec;
use alloc::vec::Vec;
use core::iter;
use crate::rustc_data_structures::fx::FxIndexMap;
use crate::rustc_errors::ErrorGuaranteed;
use crate::rustc_hir::def::DefKind;
use crate::rustc_hir::def_id::{DefId, LOCAL_CRATE};
use crate::rustc_hir::{self as hir, find_attr};
use rustc_macros::{Decodable, Encodable, StableHash};
use crate::rustc_span::Span;
use tracing::debug;
use crate::rustc_middle::query::LocalCrate;
use crate::rustc_middle::traits::specialization_graph;
use crate::rustc_middle::ty::fast_reject::{self, SimplifiedType, TreatParams};
use crate::rustc_middle::ty::{self, Ident, Interner, RestrictionKind, Ty, TyCtxt, VisitorResult, try_visit};
/// A trait's definition with type information.
#[derive(StableHash, Encodable, Decodable)]
pub struct TraitDef {
pub def_id: DefId,
/// Restrictions on trait implementations.
pub impl_restriction: RestrictionKind,
pub safety: hir::Safety,
/// Whether this trait is `const`.
pub constness: hir::Constness,
/// 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 the `#[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 `#[fundamental]` attribute. This
/// affects how conherence computes whether a trait may have trait implementations
/// added in the future.
pub is_fundamental: bool,
/// If `true`, then this trait has the `#[rustc_skip_during_method_dispatch(array)]`
/// 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,
/// If `true`, then this trait has the `#[rustc_skip_during_method_dispatch(boxed_slice)]`
/// attribute, indicating that editions before 2024 should not consider this trait
/// during method dispatch if the receiver is a boxed slice.
pub skip_boxed_slice_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 the trait should be considered dyn-incompatible, even if it otherwise
/// satisfies the requirements to be dyn-compatible.
pub force_dyn_incompatible: Option<Span>,
/// 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]`.
pub deny_explicit_impl: bool,
}
/// Whether this trait is treated specially by the standard library
/// specialization lint.
#[derive(StableHash, 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_allow_lifetime_dependent_specialization`
/// 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, StableHash)]
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> {
/// 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<R: VisitorResult>(
self,
trait_def_id: DefId,
self_ty: Ty<'tcx>,
mut f: impl FnMut(DefId) -> R,
) -> R {
let tcx = self;
let trait_impls = tcx.trait_impls_of(trait_def_id);
let mut consider_impls_for_simplified_type = |simp| {
if let Some(impls_for_type) = trait_impls.non_blanket_impls().get(&simp) {
for &impl_def_id in impls_for_type {
try_visit!(f(impl_def_id))
}
}
R::output()
};
match self_ty.kind() {
ty::Bool
| ty::Char
| ty::Int(_)
| ty::Uint(_)
| ty::Float(_)
| ty::Adt(_, _)
| ty::Foreign(_)
| ty::Str
| ty::Array(_, _)
| ty::Slice(_)
| ty::RawPtr(_, _)
| ty::Ref(_, _, _)
| ty::FnDef(_, _)
| ty::FnPtr(..)
| ty::Dynamic(_, _)
| ty::Closure(..)
| ty::CoroutineClosure(..)
| ty::Coroutine(_, _)
| ty::Never
| ty::Tuple(_)
| ty::UnsafeBinder(_) => {
let simp = ty::fast_reject::simplify_type(
tcx,
self_ty,
ty::fast_reject::TreatParams::AsRigid,
)
.unwrap();
try_visit!(consider_impls_for_simplified_type(simp));
}
// HACK: For integer and float variables we have to manually look at all impls
// which have some integer or float as a self type.
ty::Infer(ty::IntVar(_)) => {
use ty::IntTy::*;
use ty::UintTy::*;
// This causes a compiler error if any new integer kinds are added.
let (I8 | I16 | I32 | I64 | I128 | Isize): ty::IntTy;
let (U8 | U16 | U32 | U64 | U128 | Usize): ty::UintTy;
let possible_integers = [
// signed integers
ty::SimplifiedType::Int(I8),
ty::SimplifiedType::Int(I16),
ty::SimplifiedType::Int(I32),
ty::SimplifiedType::Int(I64),
ty::SimplifiedType::Int(I128),
ty::SimplifiedType::Int(Isize),
// unsigned integers
ty::SimplifiedType::Uint(U8),
ty::SimplifiedType::Uint(U16),
ty::SimplifiedType::Uint(U32),
ty::SimplifiedType::Uint(U64),
ty::SimplifiedType::Uint(U128),
ty::SimplifiedType::Uint(Usize),
];
for simp in possible_integers {
try_visit!(consider_impls_for_simplified_type(simp));
}
}
ty::Infer(ty::FloatVar(_)) => {
// This causes a compiler error if any new float kinds are added.
let (ty::FloatTy::F16 | ty::FloatTy::F32 | ty::FloatTy::F64 | ty::FloatTy::F128);
let possible_floats = [
ty::SimplifiedType::Float(ty::FloatTy::F16),
ty::SimplifiedType::Float(ty::FloatTy::F32),
ty::SimplifiedType::Float(ty::FloatTy::F64),
ty::SimplifiedType::Float(ty::FloatTy::F128),
];
for simp in possible_floats {
try_visit!(consider_impls_for_simplified_type(simp));
}
}
// Pattern type might not have a simplified type.
ty::Pat(_, _) => {
if let Some(simp) = ty::fast_reject::simplify_type(
tcx,
self_ty,
ty::fast_reject::TreatParams::AsRigid,
) {
try_visit!(consider_impls_for_simplified_type(simp));
}
}
// This is only for diagnostics and normally ty vars should be handled by the callers.
ty::Infer(ty::TyVar(_)) => {
for &impl_def_id in trait_impls.non_blanket_impls().values().flatten() {
try_visit!(f(impl_def_id));
}
}
// The only traits applying to aliases and placeholders are blanket impls.
//
// Impls which apply to an alias after normalization are handled by
// `assemble_candidates_after_normalizing_self_ty`.
ty::Alias(ty::IsRigid::Yes, _) | ty::Placeholder(..) | ty::Error(_) => (),
// FIXME(-Znext-solver=no): Need to support aliases not marked as
// rigid for the old solver.
ty::Alias(ty::IsRigid::No, _) => (),
// FIXME: These should ideally not exist as a self type. It would be nice for
// the builtin auto trait impls of coroutines to instead directly recurse
// into the witness.
ty::CoroutineWitness(..) => (),
// These are used in diagnostics or in the old solver.
ty::Param(_) | ty::Bound(_, _) => (),
// These variants should not exist as a self type.
ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
bug!("unexpected self type: {self_ty:?}");
}
}
self.for_each_blanket_impl(trait_def_id, f)
}
/// `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> {
let impls = self.trait_impls_of(trait_def_id);
if let Some(simp) =
fast_reject::simplify_type(self, self_ty, TreatParams::InstantiateWithInfer)
{
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> {
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.local_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().skip_norm_wip();
if let Some(simplified_self_ty) =
fast_reject::simplify_type(tcx, impl_self_ty, TreatParams::InstantiateWithInfer)
{
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] {
if let Some(def_id) = simp.def()
&& !find_attr!(tcx, def_id, RustcHasIncoherentInherentImpls)
{
return &[];
}
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)
}
pub(super) fn traits_provider(tcx: TyCtxt<'_>, _: LocalCrate) -> &[DefId] {
let mut traits = Vec::new();
for id in tcx.hir_free_items() {
if matches!(tcx.def_kind(id.owner_id), DefKind::Trait | DefKind::TraitAlias) {
traits.push(id.owner_id.to_def_id())
}
}
tcx.arena.alloc_slice(&traits)
}
pub(super) fn trait_impls_in_crate_provider(tcx: TyCtxt<'_>, _: LocalCrate) -> &[DefId] {
let mut trait_impls = Vec::new();
for id in tcx.hir_free_items() {
if tcx.def_kind(id.owner_id) == (DefKind::Impl { of_trait: true }) {
trait_impls.push(id.owner_id.to_def_id())
}
}
tcx.arena.alloc_slice(&trait_impls)
}