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Rollup merge of #127146 - compiler-errors:fast-reject, r=lcnr

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Uplift fast rejection to new solver

Self explanatory.

r? lcnr
This commit is contained in:
Matthias Krüger 2024-07-02 17:47:47 +02:00 committed by GitHub
commit 36da46ab98
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GPG Key ID: B5690EEEBB952194
13 changed files with 419 additions and 402 deletions
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2
compiler/rustc_hir_typeck/src/method/suggest.rs
View File

@ -2129,7 +2129,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
let target_ty = self
.autoderef(sugg_span, rcvr_ty)
.find(|(rcvr_ty, _)| {
DeepRejectCtxt { treat_obligation_params: TreatParams::AsCandidateKey }
DeepRejectCtxt::new(self.tcx, TreatParams::ForLookup)
.types_may_unify(*rcvr_ty, impl_ty)
})
.map_or(impl_ty, |(ty, _)| ty)

11
compiler/rustc_middle/src/ty/context.rs
View File

@ -373,17 +373,6 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
.map(|assoc_item| assoc_item.def_id)
}
fn args_may_unify_deep(
self,
obligation_args: ty::GenericArgsRef<'tcx>,
impl_args: ty::GenericArgsRef<'tcx>,
) -> bool {
ty::fast_reject::DeepRejectCtxt {
treat_obligation_params: ty::fast_reject::TreatParams::ForLookup,
}
.args_may_unify(obligation_args, impl_args)
}
// This implementation is a bit different from `TyCtxt::for_each_relevant_impl`,
// since we want to skip over blanket impls for non-rigid aliases, and also we
// only want to consider types that *actually* unify with float/int vars.

368
compiler/rustc_middle/src/ty/fast_reject.rs
View File

@ -1,369 +1,9 @@
use crate::mir::Mutability;
use crate::ty::GenericArgKind;
use crate::ty::{self, GenericArgsRef, Ty, TyCtxt, TypeVisitableExt};
use rustc_hir::def_id::DefId;
use rustc_macros::{HashStable, TyDecodable, TyEncodable};
use std::fmt::Debug;
use std::hash::Hash;
use std::iter;
/// See `simplify_type`.
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable, HashStable)]
pub enum SimplifiedType {
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,
}
use super::TyCtxt;
/// 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.
AsCandidateKey,
/// 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.
ForLookup,
}
pub use rustc_type_ir::fast_reject::*;
/// 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<'tcx>(
tcx: TyCtxt<'tcx>,
ty: Ty<'tcx>,
treat_params: TreatParams,
) -> Option<SimplifiedType> {
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.did())),
ty::Str => Some(SimplifiedType::Str),
ty::Array(..) => Some(SimplifiedType::Array),
ty::Slice(..) => Some(SimplifiedType::Slice),
ty::Pat(ty, ..) => simplify_type(tcx, 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 !tcx.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(f) => Some(SimplifiedType::Function(f.skip_binder().inputs().len())),
ty::Placeholder(..) => Some(SimplifiedType::Placeholder),
ty::Param(_) => match treat_params {
TreatParams::ForLookup => Some(SimplifiedType::Placeholder),
TreatParams::AsCandidateKey => 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::ForLookup if !ty.has_non_region_infer() => {
Some(SimplifiedType::Placeholder)
}
TreatParams::ForLookup | TreatParams::AsCandidateKey => None,
},
ty::Foreign(def_id) => Some(SimplifiedType::Foreign(def_id)),
ty::Error(_) => Some(SimplifiedType::Error),
ty::Bound(..) | ty::Infer(_) => None,
}
}
pub type DeepRejectCtxt<'tcx> = rustc_type_ir::fast_reject::DeepRejectCtxt<TyCtxt<'tcx>>;
impl SimplifiedType {
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 from an obligation and an impl,
/// could these two be unified after replacing parameters in the
/// the impl with inference variables.
///
/// For obligations, parameters won't be replaced by inference
/// variables and only unify with themselves. We treat them
/// the same way we treat placeholders.
///
/// 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. This behavior is toggled
/// using the `treat_obligation_params` field.
#[derive(Debug, Clone, Copy)]
pub struct DeepRejectCtxt {
pub treat_obligation_params: TreatParams,
}
impl DeepRejectCtxt {
pub fn args_may_unify<'tcx>(
self,
obligation_args: GenericArgsRef<'tcx>,
impl_args: GenericArgsRef<'tcx>,
) -> bool {
iter::zip(obligation_args, impl_args).all(|(obl, imp)| {
match (obl.unpack(), imp.unpack()) {
// We don't fast reject based on regions.
(GenericArgKind::Lifetime(_), GenericArgKind::Lifetime(_)) => true,
(GenericArgKind::Type(obl), GenericArgKind::Type(imp)) => {
self.types_may_unify(obl, imp)
}
(GenericArgKind::Const(obl), GenericArgKind::Const(imp)) => {
self.consts_may_unify(obl, imp)
}
_ => bug!("kind mismatch: {obl} {imp}"),
}
})
}
pub fn types_may_unify<'tcx>(self, obligation_ty: Ty<'tcx>, impl_ty: Ty<'tcx>) -> bool {
match impl_ty.kind() {
// Start by checking whether the type in the impl may unify with
// pretty much everything. Just return `true` in that case.
ty::Param(_) | ty::Error(_) | ty::Alias(..) => return true,
// 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::FnPtr(..)
| ty::Foreign(..) => debug_assert!(impl_ty.is_known_rigid()),
ty::FnDef(..)
| ty::Closure(..)
| ty::CoroutineClosure(..)
| ty::Coroutine(..)
| ty::CoroutineWitness(..)
| ty::Placeholder(..)
| ty::Bound(..)
| ty::Infer(_) => bug!("unexpected impl_ty: {impl_ty}"),
}
let k = impl_ty.kind();
match *obligation_ty.kind() {
// Purely rigid types, use structural equivalence.
ty::Bool
| ty::Char
| ty::Int(_)
| ty::Uint(_)
| ty::Float(_)
| ty::Str
| ty::Never
| ty::Foreign(_) => obligation_ty == impl_ty,
ty::Ref(_, obl_ty, obl_mutbl) => match k {
&ty::Ref(_, impl_ty, impl_mutbl) => {
obl_mutbl == impl_mutbl && self.types_may_unify(obl_ty, impl_ty)
}
_ => false,
},
ty::Adt(obl_def, obl_args) => match k {
&ty::Adt(impl_def, impl_args) => {
obl_def == impl_def && self.args_may_unify(obl_args, impl_args)
}
_ => false,
},
ty::Pat(obl_ty, _) => {
// FIXME(pattern_types): take pattern into account
matches!(k, &ty::Pat(impl_ty, _) if self.types_may_unify(obl_ty, impl_ty))
}
ty::Slice(obl_ty) => {
matches!(k, &ty::Slice(impl_ty) if self.types_may_unify(obl_ty, impl_ty))
}
ty::Array(obl_ty, obl_len) => match k {
&ty::Array(impl_ty, impl_len) => {
self.types_may_unify(obl_ty, impl_ty)
&& self.consts_may_unify(obl_len, impl_len)
}
_ => false,
},
ty::Tuple(obl) => match k {
&ty::Tuple(imp) => {
obl.len() == imp.len()
&& iter::zip(obl, imp).all(|(obl, imp)| self.types_may_unify(obl, imp))
}
_ => false,
},
ty::RawPtr(obl_ty, obl_mutbl) => match *k {
ty::RawPtr(imp_ty, imp_mutbl) => {
obl_mutbl == imp_mutbl && self.types_may_unify(obl_ty, imp_ty)
}
_ => false,
},
ty::Dynamic(obl_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!(k, ty::Dynamic(impl_preds, ..) if
obl_preds.principal_def_id() == impl_preds.principal_def_id()
)
}
ty::FnPtr(obl_sig) => match k {
ty::FnPtr(impl_sig) => {
let ty::FnSig { inputs_and_output, c_variadic, safety, abi } =
obl_sig.skip_binder();
let impl_sig = impl_sig.skip_binder();
abi == impl_sig.abi
&& c_variadic == impl_sig.c_variadic
&& safety == impl_sig.safety
&& inputs_and_output.len() == impl_sig.inputs_and_output.len()
&& iter::zip(inputs_and_output, impl_sig.inputs_and_output)
.all(|(obl, imp)| self.types_may_unify(obl, imp))
}
_ => false,
},
// Impls cannot contain these types as these cannot be named directly.
ty::FnDef(..) | ty::Closure(..) | ty::CoroutineClosure(..) | ty::Coroutine(..) => false,
// Placeholder types don't unify with anything on their own
ty::Placeholder(..) | ty::Bound(..) => false,
// Depending on the value of `treat_obligation_params`, we either
// treat generic parameters like placeholders or like inference variables.
ty::Param(_) => match self.treat_obligation_params {
TreatParams::ForLookup => false,
TreatParams::AsCandidateKey => true,
},
ty::Infer(ty::IntVar(_)) => impl_ty.is_integral(),
ty::Infer(ty::FloatVar(_)) => impl_ty.is_floating_point(),
ty::Infer(_) => true,
// 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::Error(_) => true,
ty::CoroutineWitness(..) => {
bug!("unexpected obligation type: {:?}", obligation_ty)
}
}
}
pub fn consts_may_unify(self, obligation_ct: ty::Const<'_>, impl_ct: ty::Const<'_>) -> bool {
let impl_val = match impl_ct.kind() {
ty::ConstKind::Expr(_)
| ty::ConstKind::Param(_)
| ty::ConstKind::Unevaluated(_)
| ty::ConstKind::Error(_) => {
return true;
}
ty::ConstKind::Value(_, impl_val) => impl_val,
ty::ConstKind::Infer(_) | ty::ConstKind::Bound(..) | ty::ConstKind::Placeholder(_) => {
bug!("unexpected impl arg: {:?}", impl_ct)
}
};
match obligation_ct.kind() {
ty::ConstKind::Param(_) => match self.treat_obligation_params {
TreatParams::ForLookup => false,
TreatParams::AsCandidateKey => true,
},
// Placeholder consts don't unify with anything on their own
ty::ConstKind::Placeholder(_) => false,
// 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::Value(_, obl_val) => obl_val == impl_val,
ty::ConstKind::Infer(_) => true,
ty::ConstKind::Bound(..) => {
bug!("unexpected obl const: {:?}", obligation_ct)
}
}
}
}
pub type SimplifiedType = rustc_type_ir::fast_reject::SimplifiedType<DefId>;

13
compiler/rustc_middle/src/ty/impls_ty.rs
View File

@ -4,7 +4,6 @@
use crate::middle::region;
use crate::mir;
use crate::ty;
use crate::ty::fast_reject::SimplifiedType;
use rustc_data_structures::fingerprint::Fingerprint;
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::stable_hasher::HashingControls;
@ -57,18 +56,6 @@ where
}
}
impl<'a> ToStableHashKey<StableHashingContext<'a>> for SimplifiedType {
type KeyType = Fingerprint;
#[inline]
fn to_stable_hash_key(&self, hcx: &StableHashingContext<'a>) -> Fingerprint {
let mut hasher = StableHasher::new();
let mut hcx: StableHashingContext<'a> = hcx.clone();
self.hash_stable(&mut hcx, &mut hasher);
hasher.finish()
}
}
impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for ty::GenericArg<'tcx> {
fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
self.unpack().hash_stable(hcx, hasher);

3
compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs
View File

@ -3,6 +3,7 @@ mod inherent;
mod opaque_types;
mod weak_types;
use rustc_type_ir::fast_reject::{DeepRejectCtxt, TreatParams};
use rustc_type_ir::inherent::*;
use rustc_type_ir::lang_items::TraitSolverLangItem;
use rustc_type_ir::Upcast as _;
@ -144,7 +145,7 @@ where
let goal_trait_ref = goal.predicate.alias.trait_ref(cx);
let impl_trait_ref = cx.impl_trait_ref(impl_def_id);
if !ecx.cx().args_may_unify_deep(
if !DeepRejectCtxt::new(ecx.cx(), TreatParams::ForLookup).args_may_unify(
goal.predicate.alias.trait_ref(cx).args,
impl_trait_ref.skip_binder().args,
) {

4
compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
View File

@ -2,6 +2,7 @@
use rustc_ast_ir::Movability;
use rustc_type_ir::data_structures::IndexSet;
use rustc_type_ir::fast_reject::{DeepRejectCtxt, TreatParams};
use rustc_type_ir::inherent::*;
use rustc_type_ir::lang_items::TraitSolverLangItem;
use rustc_type_ir::visit::TypeVisitableExt as _;
@ -46,7 +47,8 @@ where
let cx = ecx.cx();
let impl_trait_ref = cx.impl_trait_ref(impl_def_id);
if !cx.args_may_unify_deep(goal.predicate.trait_ref.args, impl_trait_ref.skip_binder().args)
if !DeepRejectCtxt::new(ecx.cx(), TreatParams::ForLookup)
.args_may_unify(goal.predicate.trait_ref.args, impl_trait_ref.skip_binder().args)
{
return Err(NoSolution);
}

2
compiler/rustc_trait_selection/src/traits/coherence.rs
View File

@ -121,7 +121,7 @@ pub fn overlapping_impls(
// Before doing expensive operations like entering an inference context, do
// a quick check via fast_reject to tell if the impl headers could possibly
// unify.
let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::AsCandidateKey };
let drcx = DeepRejectCtxt::new(tcx, TreatParams::AsCandidateKey);
let impl1_ref = tcx.impl_trait_ref(impl1_def_id);
let impl2_ref = tcx.impl_trait_ref(impl2_def_id);
let may_overlap = match (impl1_ref, impl2_ref) {

2
compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
View File

@ -571,7 +571,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
return;
}
let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::ForLookup };
let drcx = DeepRejectCtxt::new(self.tcx(), TreatParams::ForLookup);
let obligation_args = obligation.predicate.skip_binder().trait_ref.args;
self.tcx().for_each_relevant_impl(
obligation.predicate.def_id(),

397
compiler/rustc_type_ir/src/fast_reject.rs Normal file
View File

@ -0,0 +1,397 @@
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.
AsCandidateKey,
/// 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.
ForLookup,
}
/// 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>(
tcx: 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(tcx, 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 !tcx.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(f) => Some(SimplifiedType::Function(f.skip_binder().inputs().len())),
ty::Placeholder(..) => Some(SimplifiedType::Placeholder),
ty::Param(_) => match treat_params {
TreatParams::ForLookup => Some(SimplifiedType::Placeholder),
TreatParams::AsCandidateKey => 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::ForLookup if !ty.has_non_region_infer() => {
Some(SimplifiedType::Placeholder)
}
TreatParams::ForLookup | TreatParams::AsCandidateKey => 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 from an obligation and an impl,
/// could these two be unified after replacing parameters in the
/// the impl with inference variables.
///
/// For obligations, parameters won't be replaced by inference
/// variables and only unify with themselves. We treat them
/// the same way we treat placeholders.
///
/// 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. This behavior is toggled
/// using the `treat_obligation_params` field.
#[derive(Debug, Clone, Copy)]
pub struct DeepRejectCtxt<I: Interner> {
treat_obligation_params: TreatParams,
_interner: PhantomData<I>,
}
impl<I: Interner> DeepRejectCtxt<I> {
pub fn new(_interner: I, treat_obligation_params: TreatParams) -> Self {
DeepRejectCtxt { treat_obligation_params, _interner: PhantomData }
}
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, obligation_ty: I::Ty, impl_ty: I::Ty) -> bool {
match impl_ty.kind() {
// Start by checking whether the type in the impl may unify with
// pretty much everything. Just return `true` in that case.
ty::Param(_) | ty::Error(_) | ty::Alias(..) => return true,
// 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::FnPtr(..)
| ty::Foreign(..) => debug_assert!(impl_ty.is_known_rigid()),
ty::FnDef(..)
| ty::Closure(..)
| ty::CoroutineClosure(..)
| ty::Coroutine(..)
| ty::CoroutineWitness(..)
| ty::Placeholder(..)
| ty::Bound(..)
| ty::Infer(_) => panic!("unexpected impl_ty: {impl_ty:?}"),
}
let k = impl_ty.kind();
match obligation_ty.kind() {
// Purely rigid types, use structural equivalence.
ty::Bool
| ty::Char
| ty::Int(_)
| ty::Uint(_)
| ty::Float(_)
| ty::Str
| ty::Never
| ty::Foreign(_) => obligation_ty == impl_ty,
ty::Ref(_, obl_ty, obl_mutbl) => match k {
ty::Ref(_, impl_ty, impl_mutbl) => {
obl_mutbl == impl_mutbl && self.types_may_unify(obl_ty, impl_ty)
}
_ => false,
},
ty::Adt(obl_def, obl_args) => match k {
ty::Adt(impl_def, impl_args) => {
obl_def == impl_def && self.args_may_unify(obl_args, impl_args)
}
_ => false,
},
ty::Pat(obl_ty, _) => {
// FIXME(pattern_types): take pattern into account
matches!(k, ty::Pat(impl_ty, _) if self.types_may_unify(obl_ty, impl_ty))
}
ty::Slice(obl_ty) => {
matches!(k, ty::Slice(impl_ty) if self.types_may_unify(obl_ty, impl_ty))
}
ty::Array(obl_ty, obl_len) => match k {
ty::Array(impl_ty, impl_len) => {
self.types_may_unify(obl_ty, impl_ty)
&& self.consts_may_unify(obl_len, impl_len)
}
_ => false,
},
ty::Tuple(obl) => match k {
ty::Tuple(imp) => {
obl.len() == imp.len()
&& iter::zip(obl.iter(), imp.iter())
.all(|(obl, imp)| self.types_may_unify(obl, imp))
}
_ => false,
},
ty::RawPtr(obl_ty, obl_mutbl) => match k {
ty::RawPtr(imp_ty, imp_mutbl) => {
obl_mutbl == imp_mutbl && self.types_may_unify(obl_ty, imp_ty)
}
_ => false,
},
ty::Dynamic(obl_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!(k, ty::Dynamic(impl_preds, ..) if
obl_preds.principal_def_id() == impl_preds.principal_def_id()
)
}
ty::FnPtr(obl_sig) => match k {
ty::FnPtr(impl_sig) => {
let ty::FnSig { inputs_and_output, c_variadic, safety, abi } =
obl_sig.skip_binder();
let impl_sig = impl_sig.skip_binder();
abi == impl_sig.abi
&& c_variadic == impl_sig.c_variadic
&& safety == impl_sig.safety
&& inputs_and_output.len() == impl_sig.inputs_and_output.len()
&& iter::zip(inputs_and_output.iter(), impl_sig.inputs_and_output.iter())
.all(|(obl, imp)| self.types_may_unify(obl, imp))
}
_ => false,
},
// Impls cannot contain these types as these cannot be named directly.
ty::FnDef(..) | ty::Closure(..) | ty::CoroutineClosure(..) | ty::Coroutine(..) => false,
// Placeholder types don't unify with anything on their own
ty::Placeholder(..) | ty::Bound(..) => false,
// Depending on the value of `treat_obligation_params`, we either
// treat generic parameters like placeholders or like inference variables.
ty::Param(_) => match self.treat_obligation_params {
TreatParams::ForLookup => false,
TreatParams::AsCandidateKey => true,
},
ty::Infer(ty::IntVar(_)) => impl_ty.is_integral(),
ty::Infer(ty::FloatVar(_)) => impl_ty.is_floating_point(),
ty::Infer(_) => true,
// 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::Error(_) => true,
ty::CoroutineWitness(..) => {
panic!("unexpected obligation type: {:?}", obligation_ty)
}
}
}
pub fn consts_may_unify(self, obligation_ct: I::Const, impl_ct: I::Const) -> bool {
let impl_val = match impl_ct.kind() {
ty::ConstKind::Expr(_)
| ty::ConstKind::Param(_)
| ty::ConstKind::Unevaluated(_)
| ty::ConstKind::Error(_) => {
return true;
}
ty::ConstKind::Value(_, impl_val) => impl_val,
ty::ConstKind::Infer(_) | ty::ConstKind::Bound(..) | ty::ConstKind::Placeholder(_) => {
panic!("unexpected impl arg: {:?}", impl_ct)
}
};
match obligation_ct.kind() {
ty::ConstKind::Param(_) => match self.treat_obligation_params {
TreatParams::ForLookup => false,
TreatParams::AsCandidateKey => true,
},
// Placeholder consts don't unify with anything on their own
ty::ConstKind::Placeholder(_) => false,
// 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::Value(_, obl_val) => obl_val == impl_val,
ty::ConstKind::Infer(_) => true,
ty::ConstKind::Bound(..) => {
panic!("unexpected obl const: {:?}", obligation_ct)
}
}
}
}

8
compiler/rustc_type_ir/src/inherent.rs
View File

@ -120,6 +120,14 @@ pub trait Ty<I: Interner<Ty = Self>>:
matches!(self.kind(), ty::Infer(ty::TyVar(_)))
}
fn is_floating_point(self) -> bool {
matches!(self.kind(), ty::Float(_) | ty::Infer(ty::FloatVar(_)))
}
fn is_integral(self) -> bool {
matches!(self.kind(), ty::Infer(ty::IntVar(_)) | ty::Int(_) | ty::Uint(_))
}
fn is_fn_ptr(self) -> bool {
matches!(self.kind(), ty::FnPtr(_))
}

7
compiler/rustc_type_ir/src/interner.rs
View File

@ -222,13 +222,6 @@ pub trait Interner:
fn associated_type_def_ids(self, def_id: Self::DefId) -> impl IntoIterator<Item = Self::DefId>;
// FIXME: move `fast_reject` into `rustc_type_ir`.
fn args_may_unify_deep(
self,
obligation_args: Self::GenericArgs,
impl_args: Self::GenericArgs,
) -> bool;
fn for_each_relevant_impl(
self,
trait_def_id: Self::DefId,

1
compiler/rustc_type_ir/src/lib.rs
View File

@ -21,6 +21,7 @@ pub mod visit;
pub mod codec;
pub mod data_structures;
pub mod error;
pub mod fast_reject;
pub mod fold;
pub mod inherent;
pub mod ir_print;

3
src/librustdoc/html/render/write_shared.rs
View File

@ -507,8 +507,7 @@ else if (window.initSearch) window.initSearch(searchIndex);
// Be aware of `tests/rustdoc/type-alias/deeply-nested-112515.rs` which might regress.
let Some(impl_did) = impl_item_id.as_def_id() else { continue };
let for_ty = self.cx.tcx().type_of(impl_did).skip_binder();
let reject_cx =
DeepRejectCtxt { treat_obligation_params: TreatParams::AsCandidateKey };
let reject_cx = DeepRejectCtxt::new(self.cx.tcx(), TreatParams::AsCandidateKey);
if !reject_cx.types_may_unify(aliased_ty, for_ty) {
continue;
}