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use std::fmt::Debug;
use std::hash::Hash;
use std::iter;
use std::marker::PhantomData;
use rustc_ast_ir::Mutability;
#[cfg(feature = "nightly")]
use rustc_data_structures::fingerprint::Fingerprint;
#[cfg(feature = "nightly")]
use rustc_data_structures::stable_hasher::{HashStable, StableHasher, ToStableHashKey};
#[cfg(feature = "nightly")]
use rustc_macros::{HashStable_NoContext, TyDecodable, TyEncodable};
use crate::inherent::*;
use crate::visit::TypeVisitableExt as _;
use crate::{self as ty, Interner};
/// See `simplify_type`.
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "nightly", derive(TyEncodable, TyDecodable, HashStable_NoContext))]
pub enum SimplifiedType<DefId> {
Bool,
Char,
Int(ty::IntTy),
Uint(ty::UintTy),
Float(ty::FloatTy),
Adt(DefId),
Foreign(DefId),
Str,
Array,
Slice,
Ref(Mutability),
Ptr(Mutability),
Never,
Tuple(usize),
/// A trait object, all of whose components are markers
/// (e.g., `dyn Send + Sync`).
MarkerTraitObject,
Trait(DefId),
Closure(DefId),
Coroutine(DefId),
CoroutineWitness(DefId),
Function(usize),
Placeholder,
Error,
}
#[cfg(feature = "nightly")]
impl<HCX: Clone, DefId: HashStable<HCX>> ToStableHashKey<HCX> for SimplifiedType<DefId> {
type KeyType = Fingerprint;
#[inline]
fn to_stable_hash_key(&self, hcx: &HCX) -> Fingerprint {
let mut hasher = StableHasher::new();
let mut hcx: HCX = hcx.clone();
self.hash_stable(&mut hcx, &mut hasher);
hasher.finish()
}
}
/// Generic parameters are pretty much just bound variables, e.g.
/// the type of `fn foo<'a, T>(x: &'a T) -> u32 { ... }` can be thought of as
/// `for<'a, T> fn(&'a T) -> u32`.
///
/// Typecheck of `foo` has to succeed for all possible generic arguments, so
/// during typeck, we have to treat its generic parameters as if they
/// were placeholders.
///
/// But when calling `foo` we only have to provide a specific generic argument.
/// In that case the generic parameters are instantiated with inference variables.
/// As we use `simplify_type` before that instantiation happens, we just treat
/// generic parameters as if they were inference variables in that case.
#[derive(PartialEq, Eq, Debug, Clone, Copy)]
pub enum TreatParams {
/// Treat parameters as infer vars. This is the correct mode for caching
/// an impl's type for lookup.
InstantiateWithInfer,
/// Treat parameters as placeholders in the given environment. This is the
/// correct mode for *lookup*, as during candidate selection.
///
/// This also treats projections with inference variables as infer vars
/// since they could be further normalized.
AsRigid,
}
/// Tries to simplify a type by only returning the outermost injective¹ layer, if one exists.
///
/// **This function should only be used if you need to store or retrieve the type from some
/// hashmap. If you want to quickly decide whether two types may unify, use the [DeepRejectCtxt]
/// instead.**
///
/// The idea is to get something simple that we can use to quickly decide if two types could unify,
/// for example during method lookup. If this function returns `Some(x)` it can only unify with
/// types for which this method returns either `Some(x)` as well or `None`.
///
/// A special case here are parameters and projections, which are only injective
/// if they are treated as placeholders.
///
/// For example when storing impls based on their simplified self type, we treat
/// generic parameters as if they were inference variables. We must not simplify them here,
/// as they can unify with any other type.
///
/// With projections we have to be even more careful, as treating them as placeholders
/// is only correct if they are fully normalized.
///
/// ¹ meaning that if the outermost layers are different, then the whole types are also different.
pub fn simplify_type<I: Interner>(
cx: I,
ty: I::Ty,
treat_params: TreatParams,
) -> Option<SimplifiedType<I::DefId>> {
match ty.kind() {
ty::Bool => Some(SimplifiedType::Bool),
ty::Char => Some(SimplifiedType::Char),
ty::Int(int_type) => Some(SimplifiedType::Int(int_type)),
ty::Uint(uint_type) => Some(SimplifiedType::Uint(uint_type)),
ty::Float(float_type) => Some(SimplifiedType::Float(float_type)),
ty::Adt(def, _) => Some(SimplifiedType::Adt(def.def_id())),
ty::Str => Some(SimplifiedType::Str),
ty::Array(..) => Some(SimplifiedType::Array),
ty::Slice(..) => Some(SimplifiedType::Slice),
ty::Pat(ty, ..) => simplify_type(cx, ty, treat_params),
ty::RawPtr(_, mutbl) => Some(SimplifiedType::Ptr(mutbl)),
ty::Dynamic(trait_info, ..) => match trait_info.principal_def_id() {
Some(principal_def_id) if !cx.trait_is_auto(principal_def_id) => {
Some(SimplifiedType::Trait(principal_def_id))
}
_ => Some(SimplifiedType::MarkerTraitObject),
},
ty::Ref(_, _, mutbl) => Some(SimplifiedType::Ref(mutbl)),
ty::FnDef(def_id, _) | ty::Closure(def_id, _) | ty::CoroutineClosure(def_id, _) => {
Some(SimplifiedType::Closure(def_id))
}
ty::Coroutine(def_id, _) => Some(SimplifiedType::Coroutine(def_id)),
ty::CoroutineWitness(def_id, _) => Some(SimplifiedType::CoroutineWitness(def_id)),
ty::Never => Some(SimplifiedType::Never),
ty::Tuple(tys) => Some(SimplifiedType::Tuple(tys.len())),
ty::FnPtr(sig_tys, _hdr) => {
Some(SimplifiedType::Function(sig_tys.skip_binder().inputs().len()))
}
ty::Placeholder(..) => Some(SimplifiedType::Placeholder),
ty::Param(_) => match treat_params {
TreatParams::AsRigid => Some(SimplifiedType::Placeholder),
TreatParams::InstantiateWithInfer => None,
},
ty::Alias(..) => match treat_params {
// When treating `ty::Param` as a placeholder, projections also
// don't unify with anything else as long as they are fully normalized.
// FIXME(-Znext-solver): Can remove this `if` and always simplify to `Placeholder`
// when the new solver is enabled by default.
TreatParams::AsRigid if !ty.has_non_region_infer() => Some(SimplifiedType::Placeholder),
TreatParams::AsRigid | TreatParams::InstantiateWithInfer => None,
},
ty::Foreign(def_id) => Some(SimplifiedType::Foreign(def_id)),
ty::Error(_) => Some(SimplifiedType::Error),
ty::Bound(..) | ty::Infer(_) => None,
}
}
impl<DefId> SimplifiedType<DefId> {
pub fn def(self) -> Option<DefId> {
match self {
SimplifiedType::Adt(d)
| SimplifiedType::Foreign(d)
| SimplifiedType::Trait(d)
| SimplifiedType::Closure(d)
| SimplifiedType::Coroutine(d)
| SimplifiedType::CoroutineWitness(d) => Some(d),
_ => None,
}
}
}
/// Given generic arguments, could they be unified after
/// replacing parameters with inference variables or placeholders.
/// This behavior is toggled using the const generics.
///
/// We use this to quickly reject impl/wc candidates without needing
/// to instantiate generic arguments/having to enter a probe.
///
/// We also use this function during coherence. For coherence the
/// impls only have to overlap for some value, so we treat parameters
/// on both sides like inference variables.
#[derive(Debug, Clone, Copy)]
pub struct DeepRejectCtxt<
I: Interner,
const INSTANTIATE_LHS_WITH_INFER: bool,
const INSTANTIATE_RHS_WITH_INFER: bool,
> {
_interner: PhantomData<I>,
}
impl<I: Interner> DeepRejectCtxt<I, false, false> {
/// Treat parameters in both the lhs and the rhs as rigid.
pub fn relate_rigid_rigid(_interner: I) -> DeepRejectCtxt<I, false, false> {
DeepRejectCtxt { _interner: PhantomData }
}
}
impl<I: Interner> DeepRejectCtxt<I, true, true> {
/// Treat parameters in both the lhs and the rhs as infer vars.
pub fn relate_infer_infer(_interner: I) -> DeepRejectCtxt<I, true, true> {
DeepRejectCtxt { _interner: PhantomData }
}
}
impl<I: Interner> DeepRejectCtxt<I, false, true> {
/// Treat parameters in the lhs as rigid, and in rhs as infer vars.
pub fn relate_rigid_infer(_interner: I) -> DeepRejectCtxt<I, false, true> {
DeepRejectCtxt { _interner: PhantomData }
}
}
impl<I: Interner, const INSTANTIATE_LHS_WITH_INFER: bool, const INSTANTIATE_RHS_WITH_INFER: bool>
DeepRejectCtxt<I, INSTANTIATE_LHS_WITH_INFER, INSTANTIATE_RHS_WITH_INFER>
{
pub fn args_may_unify(
self,
obligation_args: I::GenericArgs,
impl_args: I::GenericArgs,
) -> bool {
iter::zip(obligation_args.iter(), impl_args.iter()).all(|(obl, imp)| {
match (obl.kind(), imp.kind()) {
// We don't fast reject based on regions.
(ty::GenericArgKind::Lifetime(_), ty::GenericArgKind::Lifetime(_)) => true,
(ty::GenericArgKind::Type(obl), ty::GenericArgKind::Type(imp)) => {
self.types_may_unify(obl, imp)
}
(ty::GenericArgKind::Const(obl), ty::GenericArgKind::Const(imp)) => {
self.consts_may_unify(obl, imp)
}
_ => panic!("kind mismatch: {obl:?} {imp:?}"),
}
})
}
pub fn types_may_unify(self, lhs: I::Ty, rhs: I::Ty) -> bool {
match rhs.kind() {
// Start by checking whether the `rhs` type may unify with
// pretty much everything. Just return `true` in that case.
ty::Param(_) => {
if INSTANTIATE_RHS_WITH_INFER {
return true;
}
}
ty::Error(_) | ty::Alias(..) | ty::Bound(..) => return true,
ty::Infer(var) => return self.var_and_ty_may_unify(var, lhs),
// These types only unify with inference variables or their own
// variant.
ty::Bool
| ty::Char
| ty::Int(_)
| ty::Uint(_)
| ty::Float(_)
| ty::Adt(..)
| ty::Str
| ty::Array(..)
| ty::Slice(..)
| ty::RawPtr(..)
| ty::Dynamic(..)
| ty::Pat(..)
| ty::Ref(..)
| ty::Never
| ty::Tuple(..)
| ty::FnDef(..)
| ty::FnPtr(..)
| ty::Closure(..)
| ty::CoroutineClosure(..)
| ty::Coroutine(..)
| ty::CoroutineWitness(..)
| ty::Foreign(_)
| ty::Placeholder(_) => {}
};
// For purely rigid types, use structural equivalence.
match lhs.kind() {
ty::Ref(_, lhs_ty, lhs_mutbl) => match rhs.kind() {
ty::Ref(_, rhs_ty, rhs_mutbl) => {
lhs_mutbl == rhs_mutbl && self.types_may_unify(lhs_ty, rhs_ty)
}
_ => false,
},
ty::Adt(lhs_def, lhs_args) => match rhs.kind() {
ty::Adt(rhs_def, rhs_args) => {
lhs_def == rhs_def && self.args_may_unify(lhs_args, rhs_args)
}
_ => false,
},
// Depending on the value of const generics, we either treat generic parameters
// like placeholders or like inference variables.
ty::Param(lhs) => {
INSTANTIATE_LHS_WITH_INFER
|| match rhs.kind() {
ty::Param(rhs) => lhs == rhs,
_ => false,
}
}
// Placeholder types don't unify with anything on their own.
ty::Placeholder(lhs) => {
matches!(rhs.kind(), ty::Placeholder(rhs) if lhs == rhs)
}
ty::Infer(var) => self.var_and_ty_may_unify(var, rhs),
// As we're walking the whole type, it may encounter projections
// inside of binders and what not, so we're just going to assume that
// projections can unify with other stuff.
//
// Looking forward to lazy normalization this is the safer strategy anyways.
ty::Alias(..) => true,
ty::Int(_)
| ty::Uint(_)
| ty::Float(_)
| ty::Str
| ty::Bool
| ty::Char
| ty::Never
| ty::Foreign(_) => lhs == rhs,
ty::Tuple(lhs) => match rhs.kind() {
ty::Tuple(rhs) => {
lhs.len() == rhs.len()
&& iter::zip(lhs.iter(), rhs.iter())
.all(|(lhs, rhs)| self.types_may_unify(lhs, rhs))
}
_ => false,
},
ty::Array(lhs_ty, lhs_len) => match rhs.kind() {
ty::Array(rhs_ty, rhs_len) => {
self.types_may_unify(lhs_ty, rhs_ty) && self.consts_may_unify(lhs_len, rhs_len)
}
_ => false,
},
ty::RawPtr(lhs_ty, lhs_mutbl) => match rhs.kind() {
ty::RawPtr(rhs_ty, rhs_mutbl) => {
lhs_mutbl == rhs_mutbl && self.types_may_unify(lhs_ty, rhs_ty)
}
_ => false,
},
ty::Slice(lhs_ty) => {
matches!(rhs.kind(), ty::Slice(rhs_ty) if self.types_may_unify(lhs_ty, rhs_ty))
}
ty::Dynamic(lhs_preds, ..) => {
// Ideally we would walk the existential predicates here or at least
// compare their length. But considering that the relevant `Relate` impl
// actually sorts and deduplicates these, that doesn't work.
matches!(rhs.kind(), ty::Dynamic(rhs_preds, ..) if
lhs_preds.principal_def_id() == rhs_preds.principal_def_id()
)
}
ty::FnPtr(lhs_sig_tys, lhs_hdr) => match rhs.kind() {
ty::FnPtr(rhs_sig_tys, rhs_hdr) => {
let lhs_sig_tys = lhs_sig_tys.skip_binder().inputs_and_output;
let rhs_sig_tys = rhs_sig_tys.skip_binder().inputs_and_output;
lhs_hdr == rhs_hdr
&& lhs_sig_tys.len() == rhs_sig_tys.len()
&& iter::zip(lhs_sig_tys.iter(), rhs_sig_tys.iter())
.all(|(lhs, rhs)| self.types_may_unify(lhs, rhs))
}
_ => false,
},
ty::Bound(..) => true,
ty::FnDef(lhs_def_id, lhs_args) => match rhs.kind() {
ty::FnDef(rhs_def_id, rhs_args) => {
lhs_def_id == rhs_def_id && self.args_may_unify(lhs_args, rhs_args)
}
_ => false,
},
ty::Closure(lhs_def_id, lhs_args) => match rhs.kind() {
ty::Closure(rhs_def_id, rhs_args) => {
lhs_def_id == rhs_def_id && self.args_may_unify(lhs_args, rhs_args)
}
_ => false,
},
ty::CoroutineClosure(lhs_def_id, lhs_args) => match rhs.kind() {
ty::CoroutineClosure(rhs_def_id, rhs_args) => {
lhs_def_id == rhs_def_id && self.args_may_unify(lhs_args, rhs_args)
}
_ => false,
},
ty::Coroutine(lhs_def_id, lhs_args) => match rhs.kind() {
ty::Coroutine(rhs_def_id, rhs_args) => {
lhs_def_id == rhs_def_id && self.args_may_unify(lhs_args, rhs_args)
}
_ => false,
},
ty::CoroutineWitness(lhs_def_id, lhs_args) => match rhs.kind() {
ty::CoroutineWitness(rhs_def_id, rhs_args) => {
lhs_def_id == rhs_def_id && self.args_may_unify(lhs_args, rhs_args)
}
_ => false,
},
ty::Pat(lhs_ty, _) => {
// FIXME(pattern_types): take pattern into account
matches!(rhs.kind(), ty::Pat(rhs_ty, _) if self.types_may_unify(lhs_ty, rhs_ty))
}
ty::Error(..) => true,
}
}
pub fn consts_may_unify(self, lhs: I::Const, rhs: I::Const) -> bool {
match rhs.kind() {
ty::ConstKind::Param(_) => {
if INSTANTIATE_RHS_WITH_INFER {
return true;
}
}
ty::ConstKind::Expr(_)
| ty::ConstKind::Unevaluated(_)
| ty::ConstKind::Error(_)
| ty::ConstKind::Infer(_)
| ty::ConstKind::Bound(..) => {
return true;
}
ty::ConstKind::Value(..) | ty::ConstKind::Placeholder(_) => {}
};
match lhs.kind() {
ty::ConstKind::Value(_, lhs_val) => match rhs.kind() {
ty::ConstKind::Value(_, rhs_val) => lhs_val == rhs_val,
_ => false,
},
ty::ConstKind::Param(lhs) => {
INSTANTIATE_LHS_WITH_INFER
|| match rhs.kind() {
ty::ConstKind::Param(rhs) => lhs == rhs,
_ => false,
}
}
// Placeholder consts don't unify with anything on their own
ty::ConstKind::Placeholder(lhs) => {
matches!(rhs.kind(), ty::ConstKind::Placeholder(rhs) if lhs == rhs)
}
// As we don't necessarily eagerly evaluate constants,
// they might unify with any value.
ty::ConstKind::Expr(_) | ty::ConstKind::Unevaluated(_) | ty::ConstKind::Error(_) => {
true
}
ty::ConstKind::Infer(_) | ty::ConstKind::Bound(..) => true,
}
}
fn var_and_ty_may_unify(self, var: ty::InferTy, ty: I::Ty) -> bool {
if !ty.is_known_rigid() {
return true;
}
match var {
ty::IntVar(_) => ty.is_integral(),
ty::FloatVar(_) => ty.is_floating_point(),
_ => true,
}
}
}