rustc_middle/ty/

context.rs

//! Type context book-keeping.

#![allow(rustc::usage_of_ty_tykind)]

mod impl_interner;
pub mod tls;

use std::borrow::{Borrow, Cow};
use std::cmp::Ordering;
use std::env::VarError;
use std::ffi::OsStr;
use std::hash::{Hash, Hasher};
use std::marker::PointeeSized;
use std::ops::Deref;
use std::sync::{Arc, OnceLock};
use std::{fmt, iter, mem};

use rustc_abi::{ExternAbi, FieldIdx, Layout, LayoutData, TargetDataLayout, VariantIdx};
use rustc_ast as ast;
use rustc_data_structures::defer;
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::intern::Interned;
use rustc_data_structures::jobserver::Proxy;
use rustc_data_structures::profiling::SelfProfilerRef;
use rustc_data_structures::sharded::{IntoPointer, ShardedHashMap};
use rustc_data_structures::stable_hash::StableHash;
use rustc_data_structures::steal::Steal;
use rustc_data_structures::sync::{
    self, DynSend, DynSync, FreezeReadGuard, Lock, RwLock, WorkerLocal,
};
use rustc_errors::{Applicability, Diag, DiagCtxtHandle, Diagnostic, MultiSpan};
use rustc_hir::def::DefKind;
use rustc_hir::def_id::{CrateNum, DefId, LOCAL_CRATE, LocalDefId};
use rustc_hir::definitions::{DefPathData, Definitions, PerParentDisambiguatorState};
use rustc_hir::intravisit::VisitorExt;
use rustc_hir::lang_items::LangItem;
use rustc_hir::limit::Limit;
use rustc_hir::{self as hir, CRATE_HIR_ID, HirId, Node, TraitCandidate, find_attr};
use rustc_index::IndexVec;
use rustc_macros::Diagnostic;
use rustc_session::Session;
use rustc_session::config::CrateType;
use rustc_session::cstore::{CrateStoreDyn, Untracked};
use rustc_session::lint::Lint;
use rustc_span::def_id::{CRATE_DEF_ID, DefPathHash, StableCrateId};
use rustc_span::{DUMMY_SP, Ident, Span, Symbol, kw, sym};
use rustc_type_ir::TyKind::*;
pub use rustc_type_ir::lift::Lift;
use rustc_type_ir::{CollectAndApply, WithCachedTypeInfo, elaborate, search_graph};
use tracing::{debug, instrument};

use crate::arena::Arena;
use crate::dep_graph::dep_node::make_metadata;
use crate::dep_graph::{DepGraph, DepKindVTable, DepNodeIndex};
use crate::hir::{ProjectedMaybeOwner, ProjectedOwnerInfo};
use crate::ich::StableHashState;
use crate::infer::canonical::{CanonicalParamEnvCache, CanonicalVarKind};
use crate::lint::emit_lint_base;
use crate::metadata::ModChild;
use crate::middle::codegen_fn_attrs::{CodegenFnAttrs, TargetFeature};
use crate::middle::resolve_bound_vars;
use crate::mir::interpret::{self, Allocation, ConstAllocation};
use crate::mir::{Body, Local, Place, PlaceElem, ProjectionKind, Promoted};
use crate::query::{IntoQueryKey, LocalCrate, Providers, QuerySystem, TyCtxtAt};
use crate::thir::Thir;
use crate::traits;
use crate::traits::solve::{ExternalConstraints, ExternalConstraintsData, PredefinedOpaques};
use crate::ty::predicate::ExistentialPredicateStableCmpExt as _;
use crate::ty::{
    self, AdtDef, AdtDefData, AdtKind, Binder, Clause, Clauses, Const, FnSigKind, GenericArg,
    GenericArgs, GenericArgsRef, GenericParamDefKind, List, ListWithCachedTypeInfo, ParamConst,
    Pattern, PatternKind, PolyExistentialPredicate, PolyFnSig, Predicate, PredicateKind,
    PredicatePolarity, Region, RegionKind, ReprOptions, TraitObjectVisitor, Ty, TyKind, TyVid,
    ValTree, ValTreeKind, Visibility,
};

impl<'tcx> rustc_type_ir::inherent::DefId<TyCtxt<'tcx>> for DefId {
    fn is_local(self) -> bool {
        self.is_local()
    }

    fn as_local(self) -> Option<LocalDefId> {
        self.as_local()
    }
}

impl<'tcx> rustc_type_ir::inherent::Safety<TyCtxt<'tcx>> for hir::Safety {
    fn safe() -> Self {
        hir::Safety::Safe
    }

    fn unsafe_mode() -> Self {
        hir::Safety::Unsafe
    }

    fn is_safe(self) -> bool {
        self.is_safe()
    }

    fn prefix_str(self) -> &'static str {
        self.prefix_str()
    }
}

impl<'tcx> rustc_type_ir::inherent::Features<TyCtxt<'tcx>> for &'tcx rustc_feature::Features {
    fn generic_const_exprs(self) -> bool {
        self.generic_const_exprs()
    }

    fn generic_const_args(self) -> bool {
        self.generic_const_args()
    }

    fn coroutine_clone(self) -> bool {
        self.coroutine_clone()
    }

    fn feature_bound_holds_in_crate(self, symbol: Symbol) -> bool {
        // We don't consider feature bounds to hold in the crate when `staged_api` feature is
        // enabled, even if it is enabled through `#[feature]`.
        // This is to prevent accidentally leaking unstable APIs to stable.
        !self.staged_api() && self.enabled(symbol)
    }
}

impl<'tcx> rustc_type_ir::inherent::Span<TyCtxt<'tcx>> for Span {
    fn dummy() -> Self {
        DUMMY_SP
    }
}

type InternedSet<'tcx, T> = ShardedHashMap<InternedInSet<'tcx, T>, ()>;

pub struct CtxtInterners<'tcx> {
    /// The arena that types, regions, etc. are allocated from.
    arena: &'tcx WorkerLocal<Arena<'tcx>>,

    // Specifically use a speedy hash algorithm for these hash sets, since
    // they're accessed quite often.
    type_: InternedSet<'tcx, WithCachedTypeInfo<TyKind<'tcx>>>,
    const_lists: InternedSet<'tcx, List<ty::Const<'tcx>>>,
    args: InternedSet<'tcx, GenericArgs<'tcx>>,
    type_lists: InternedSet<'tcx, List<Ty<'tcx>>>,
    canonical_var_kinds: InternedSet<'tcx, List<CanonicalVarKind<'tcx>>>,
    region: InternedSet<'tcx, RegionKind<'tcx>>,
    poly_existential_predicates: InternedSet<'tcx, List<PolyExistentialPredicate<'tcx>>>,
    predicate: InternedSet<'tcx, WithCachedTypeInfo<ty::Binder<'tcx, PredicateKind<'tcx>>>>,
    clauses: InternedSet<'tcx, ListWithCachedTypeInfo<Clause<'tcx>>>,
    projs: InternedSet<'tcx, List<ProjectionKind>>,
    place_elems: InternedSet<'tcx, List<PlaceElem<'tcx>>>,
    const_: InternedSet<'tcx, WithCachedTypeInfo<ty::ConstKind<'tcx>>>,
    pat: InternedSet<'tcx, PatternKind<'tcx>>,
    const_allocation: InternedSet<'tcx, Allocation>,
    bound_variable_kinds: InternedSet<'tcx, List<ty::BoundVariableKind<'tcx>>>,
    layout: InternedSet<'tcx, LayoutData<FieldIdx, VariantIdx>>,
    adt_def: InternedSet<'tcx, AdtDefData>,
    external_constraints: InternedSet<'tcx, ExternalConstraintsData<TyCtxt<'tcx>>>,
    predefined_opaques_in_body: InternedSet<'tcx, List<(ty::OpaqueTypeKey<'tcx>, Ty<'tcx>)>>,
    fields: InternedSet<'tcx, List<FieldIdx>>,
    local_def_ids: InternedSet<'tcx, List<LocalDefId>>,
    captures: InternedSet<'tcx, List<&'tcx ty::CapturedPlace<'tcx>>>,
    valtree: InternedSet<'tcx, ty::ValTreeKind<TyCtxt<'tcx>>>,
    patterns: InternedSet<'tcx, List<ty::Pattern<'tcx>>>,
    outlives: InternedSet<'tcx, List<ty::ArgOutlivesPredicate<'tcx>>>,
}

impl<'tcx> CtxtInterners<'tcx> {
    fn new(arena: &'tcx WorkerLocal<Arena<'tcx>>) -> CtxtInterners<'tcx> {
        // Default interner size - this value has been chosen empirically, and may need to be
        // adjusted as the compiler evolves.
        const N: usize = 2048;
        CtxtInterners {
            arena,
            // The factors have been chosen by @FractalFir based on observed interner sizes, and
            // local perf runs. To get the interner sizes, insert `eprintln` printing the size of
            // the interner in functions like `intern_ty`. Bigger benchmarks tend to give more
            // accurate ratios, so use something like `x perf eprintln --includes cargo`.
            type_: InternedSet::with_capacity(N * 16),
            const_lists: InternedSet::with_capacity(N * 4),
            args: InternedSet::with_capacity(N * 4),
            type_lists: InternedSet::with_capacity(N * 4),
            region: InternedSet::with_capacity(N * 4),
            poly_existential_predicates: InternedSet::with_capacity(N / 4),
            canonical_var_kinds: InternedSet::with_capacity(N / 2),
            predicate: InternedSet::with_capacity(N),
            clauses: InternedSet::with_capacity(N),
            projs: InternedSet::with_capacity(N * 4),
            place_elems: InternedSet::with_capacity(N * 2),
            const_: InternedSet::with_capacity(N * 2),
            pat: InternedSet::with_capacity(N),
            const_allocation: InternedSet::with_capacity(N),
            bound_variable_kinds: InternedSet::with_capacity(N * 2),
            layout: InternedSet::with_capacity(N),
            adt_def: InternedSet::with_capacity(N),
            external_constraints: InternedSet::with_capacity(N),
            predefined_opaques_in_body: InternedSet::with_capacity(N),
            fields: InternedSet::with_capacity(N * 4),
            local_def_ids: InternedSet::with_capacity(N),
            captures: InternedSet::with_capacity(N),
            valtree: InternedSet::with_capacity(N),
            patterns: InternedSet::with_capacity(N),
            outlives: InternedSet::with_capacity(N),
        }
    }

    /// Interns a type. (Use `mk_*` functions instead, where possible.)
    #[allow(rustc::usage_of_ty_tykind)]
    #[inline(never)]
    fn intern_ty(&self, kind: TyKind<'tcx>) -> Ty<'tcx> {
        Ty(Interned::new_unchecked(
            self.type_
                .intern(kind, |kind| {
                    let flags = ty::FlagComputation::<TyCtxt<'tcx>>::for_kind(&kind);
                    InternedInSet(self.arena.alloc(WithCachedTypeInfo {
                        internee: kind,
                        flags: flags.flags,
                        outer_exclusive_binder: flags.outer_exclusive_binder,
                    }))
                })
                .0,
        ))
    }

    /// Interns a const. (Use `mk_*` functions instead, where possible.)
    #[allow(rustc::usage_of_ty_tykind)]
    #[inline(never)]
    fn intern_const(&self, kind: ty::ConstKind<'tcx>) -> Const<'tcx> {
        Const(Interned::new_unchecked(
            self.const_
                .intern(kind, |kind: ty::ConstKind<'_>| {
                    let flags = ty::FlagComputation::<TyCtxt<'tcx>>::for_const_kind(&kind);
                    InternedInSet(self.arena.alloc(WithCachedTypeInfo {
                        internee: kind,
                        flags: flags.flags,
                        outer_exclusive_binder: flags.outer_exclusive_binder,
                    }))
                })
                .0,
        ))
    }

    /// Interns a predicate. (Use `mk_predicate` instead, where possible.)
    #[inline(never)]
    fn intern_predicate(&self, kind: Binder<'tcx, PredicateKind<'tcx>>) -> Predicate<'tcx> {
        Predicate(Interned::new_unchecked(
            self.predicate
                .intern(kind, |kind| {
                    let flags = ty::FlagComputation::<TyCtxt<'tcx>>::for_predicate(kind);
                    InternedInSet(self.arena.alloc(WithCachedTypeInfo {
                        internee: kind,
                        flags: flags.flags,
                        outer_exclusive_binder: flags.outer_exclusive_binder,
                    }))
                })
                .0,
        ))
    }

    fn intern_clauses(&self, clauses: &[Clause<'tcx>]) -> Clauses<'tcx> {
        if clauses.is_empty() {
            ListWithCachedTypeInfo::empty()
        } else {
            self.clauses
                .intern_ref(clauses, || {
                    let flags = ty::FlagComputation::<TyCtxt<'tcx>>::for_clauses(clauses);

                    InternedInSet(ListWithCachedTypeInfo::from_arena(
                        &*self.arena,
                        flags.into(),
                        clauses,
                    ))
                })
                .0
        }
    }
}

// For these preinterned values, an alternative would be to have
// variable-length vectors that grow as needed. But that turned out to be
// slightly more complex and no faster.

const NUM_PREINTERNED_TY_VARS: u32 = 100;
const NUM_PREINTERNED_FRESH_TYS: u32 = 20;
const NUM_PREINTERNED_FRESH_INT_TYS: u32 = 3;
const NUM_PREINTERNED_FRESH_FLOAT_TYS: u32 = 3;
const NUM_PREINTERNED_ANON_BOUND_TYS_I: u32 = 3;

// From general profiling of the *max vars during canonicalization* of a value:
// - about 90% of the time, there are no canonical vars
// - about 9% of the time, there is only one canonical var
// - there are rarely more than 3-5 canonical vars (with exceptions in particularly pathological
//   cases)
// This may not match the number of bound vars found in `for`s.
// Given that this is all heap interned, it seems likely that interning fewer
// vars here won't make an appreciable difference. Though, if we were to inline the data (in an
// array), we may want to consider reducing the number for canonicalized vars down to 4 or so.
const NUM_PREINTERNED_ANON_BOUND_TYS_V: u32 = 20;

// This number may seem high, but it is reached in all but the smallest crates.
const NUM_PREINTERNED_RE_VARS: u32 = 500;
const NUM_PREINTERNED_ANON_RE_BOUNDS_I: u32 = 3;
const NUM_PREINTERNED_ANON_RE_BOUNDS_V: u32 = 20;

pub struct CommonTypes<'tcx> {
    pub unit: Ty<'tcx>,
    pub bool: Ty<'tcx>,
    pub char: Ty<'tcx>,
    pub isize: Ty<'tcx>,
    pub i8: Ty<'tcx>,
    pub i16: Ty<'tcx>,
    pub i32: Ty<'tcx>,
    pub i64: Ty<'tcx>,
    pub i128: Ty<'tcx>,
    pub usize: Ty<'tcx>,
    pub u8: Ty<'tcx>,
    pub u16: Ty<'tcx>,
    pub u32: Ty<'tcx>,
    pub u64: Ty<'tcx>,
    pub u128: Ty<'tcx>,
    pub f16: Ty<'tcx>,
    pub f32: Ty<'tcx>,
    pub f64: Ty<'tcx>,
    pub f128: Ty<'tcx>,
    pub str_: Ty<'tcx>,
    pub never: Ty<'tcx>,
    pub self_param: Ty<'tcx>,

    /// A dummy type that can be used as the self type of trait object types outside of
    /// [`ty::ExistentialTraitRef`], [`ty::ExistentialProjection`], etc.
    ///
    /// This is most useful or even necessary when you want to manipulate existential predicates
    /// together with normal predicates or if you want to pass them to an API that only expects
    /// normal predicates.
    ///
    /// Indeed, you can sometimes use the trait object type itself as the self type instead of this
    /// dummy type. However, that's not always correct: For example, if said trait object type can
    /// also appear "naturally" in whatever type system entity you're working with (like predicates)
    /// but you still need to be able to identify the erased self type later on.
    /// That's when this dummy type comes in handy.
    ///
    /// HIR ty lowering guarantees / has to guarantee that this dummy type doesn't appear in the
    /// lowered types, so you can "freely" use it (see warning below).
    ///
    /// <div class="warning">
    ///
    /// Under the hood, this type is just `ty::Infer(ty::FreshTy(0))`. Consequently, you must be
    /// sure that fresh types cannot appear by other means in whatever type system entity you're
    /// working with.
    ///
    /// Keep uses of this dummy type as local as possible and try not to leak it to subsequent
    /// passes!
    ///
    /// </div>
    pub trait_object_dummy_self: Ty<'tcx>,

    /// Pre-interned `Infer(ty::TyVar(n))` for small values of `n`.
    pub ty_vars: Vec<Ty<'tcx>>,

    /// Pre-interned `Infer(ty::FreshTy(n))` for small values of `n`.
    pub fresh_tys: Vec<Ty<'tcx>>,

    /// Pre-interned `Infer(ty::FreshIntTy(n))` for small values of `n`.
    pub fresh_int_tys: Vec<Ty<'tcx>>,

    /// Pre-interned `Infer(ty::FreshFloatTy(n))` for small values of `n`.
    pub fresh_float_tys: Vec<Ty<'tcx>>,

    /// Pre-interned values of the form:
    /// `Bound(BoundVarIndexKind::Bound(DebruijnIndex(i)), BoundTy { var: v, kind:
    /// BoundTyKind::Anon})` for small values of `i` and `v`.
    pub anon_bound_tys: Vec<Vec<Ty<'tcx>>>,

    // Pre-interned values of the form:
    // `Bound(BoundVarIndexKind::Canonical, BoundTy { var: v, kind: BoundTyKind::Anon })`
    // for small values of `v`.
    pub anon_canonical_bound_tys: Vec<Ty<'tcx>>,
}

pub struct CommonLifetimes<'tcx> {
    /// `ReStatic`
    pub re_static: Region<'tcx>,

    /// Erased region, used outside of type inference.
    pub re_erased: Region<'tcx>,

    /// Pre-interned `ReVar(ty::RegionVar(n))` for small values of `n`.
    pub re_vars: Vec<Region<'tcx>>,

    /// Pre-interned values of the form:
    /// `ReBound(BoundVarIndexKind::Bound(DebruijnIndex(i)), BoundRegion { var: v, kind: BoundRegionKind::Anon })`
    /// for small values of `i` and `v`.
    pub anon_re_bounds: Vec<Vec<Region<'tcx>>>,

    // Pre-interned values of the form:
    // `ReBound(BoundVarIndexKind::Canonical, BoundRegion { var: v, kind: BoundRegionKind::Anon })`
    // for small values of `v`.
    pub anon_re_canonical_bounds: Vec<Region<'tcx>>,
}

pub struct CommonConsts<'tcx> {
    pub unit: Const<'tcx>,
    pub true_: Const<'tcx>,
    pub false_: Const<'tcx>,
    /// Use [`ty::ValTree::zst`] instead.
    pub(crate) valtree_zst: ValTree<'tcx>,
}

impl<'tcx> CommonTypes<'tcx> {
    fn new(interners: &CtxtInterners<'tcx>) -> CommonTypes<'tcx> {
        let mk = |ty| interners.intern_ty(ty);

        let ty_vars =
            (0..NUM_PREINTERNED_TY_VARS).map(|n| mk(Infer(ty::TyVar(TyVid::from(n))))).collect();
        let fresh_tys: Vec<_> =
            (0..NUM_PREINTERNED_FRESH_TYS).map(|n| mk(Infer(ty::FreshTy(n)))).collect();
        let fresh_int_tys: Vec<_> =
            (0..NUM_PREINTERNED_FRESH_INT_TYS).map(|n| mk(Infer(ty::FreshIntTy(n)))).collect();
        let fresh_float_tys: Vec<_> =
            (0..NUM_PREINTERNED_FRESH_FLOAT_TYS).map(|n| mk(Infer(ty::FreshFloatTy(n)))).collect();

        let anon_bound_tys = (0..NUM_PREINTERNED_ANON_BOUND_TYS_I)
            .map(|i| {
                (0..NUM_PREINTERNED_ANON_BOUND_TYS_V)
                    .map(|v| {
                        mk(ty::Bound(
                            ty::BoundVarIndexKind::Bound(ty::DebruijnIndex::from(i)),
                            ty::BoundTy { var: ty::BoundVar::from(v), kind: ty::BoundTyKind::Anon },
                        ))
                    })
                    .collect()
            })
            .collect();

        let anon_canonical_bound_tys = (0..NUM_PREINTERNED_ANON_BOUND_TYS_V)
            .map(|v| {
                mk(ty::Bound(
                    ty::BoundVarIndexKind::Canonical,
                    ty::BoundTy { var: ty::BoundVar::from(v), kind: ty::BoundTyKind::Anon },
                ))
            })
            .collect();

        CommonTypes {
            unit: mk(Tuple(List::empty())),
            bool: mk(Bool),
            char: mk(Char),
            never: mk(Never),
            isize: mk(Int(ty::IntTy::Isize)),
            i8: mk(Int(ty::IntTy::I8)),
            i16: mk(Int(ty::IntTy::I16)),
            i32: mk(Int(ty::IntTy::I32)),
            i64: mk(Int(ty::IntTy::I64)),
            i128: mk(Int(ty::IntTy::I128)),
            usize: mk(Uint(ty::UintTy::Usize)),
            u8: mk(Uint(ty::UintTy::U8)),
            u16: mk(Uint(ty::UintTy::U16)),
            u32: mk(Uint(ty::UintTy::U32)),
            u64: mk(Uint(ty::UintTy::U64)),
            u128: mk(Uint(ty::UintTy::U128)),
            f16: mk(Float(ty::FloatTy::F16)),
            f32: mk(Float(ty::FloatTy::F32)),
            f64: mk(Float(ty::FloatTy::F64)),
            f128: mk(Float(ty::FloatTy::F128)),
            str_: mk(Str),
            self_param: mk(ty::Param(ty::ParamTy { index: 0, name: kw::SelfUpper })),

            trait_object_dummy_self: fresh_tys[0],

            ty_vars,
            fresh_tys,
            fresh_int_tys,
            fresh_float_tys,
            anon_bound_tys,
            anon_canonical_bound_tys,
        }
    }
}

impl<'tcx> CommonLifetimes<'tcx> {
    fn new(interners: &CtxtInterners<'tcx>) -> CommonLifetimes<'tcx> {
        let mk = |r| {
            Region(Interned::new_unchecked(
                interners.region.intern(r, |r| InternedInSet(interners.arena.alloc(r))).0,
            ))
        };

        let re_vars =
            (0..NUM_PREINTERNED_RE_VARS).map(|n| mk(ty::ReVar(ty::RegionVid::from(n)))).collect();

        let anon_re_bounds = (0..NUM_PREINTERNED_ANON_RE_BOUNDS_I)
            .map(|i| {
                (0..NUM_PREINTERNED_ANON_RE_BOUNDS_V)
                    .map(|v| {
                        mk(ty::ReBound(
                            ty::BoundVarIndexKind::Bound(ty::DebruijnIndex::from(i)),
                            ty::BoundRegion {
                                var: ty::BoundVar::from(v),
                                kind: ty::BoundRegionKind::Anon,
                            },
                        ))
                    })
                    .collect()
            })
            .collect();

        let anon_re_canonical_bounds = (0..NUM_PREINTERNED_ANON_RE_BOUNDS_V)
            .map(|v| {
                mk(ty::ReBound(
                    ty::BoundVarIndexKind::Canonical,
                    ty::BoundRegion { var: ty::BoundVar::from(v), kind: ty::BoundRegionKind::Anon },
                ))
            })
            .collect();

        CommonLifetimes {
            re_static: mk(ty::ReStatic),
            re_erased: mk(ty::ReErased),
            re_vars,
            anon_re_bounds,
            anon_re_canonical_bounds,
        }
    }
}

impl<'tcx> CommonConsts<'tcx> {
    fn new(interners: &CtxtInterners<'tcx>, types: &CommonTypes<'tcx>) -> CommonConsts<'tcx> {
        let mk_const = |c| interners.intern_const(c);

        let mk_valtree = |v| {
            ty::ValTree(Interned::new_unchecked(
                interners.valtree.intern(v, |v| InternedInSet(interners.arena.alloc(v))).0,
            ))
        };

        let valtree_zst = mk_valtree(ty::ValTreeKind::Branch(List::empty()));
        let valtree_true = mk_valtree(ty::ValTreeKind::Leaf(ty::ScalarInt::TRUE));
        let valtree_false = mk_valtree(ty::ValTreeKind::Leaf(ty::ScalarInt::FALSE));

        CommonConsts {
            unit: mk_const(ty::ConstKind::Value(ty::Value {
                ty: types.unit,
                valtree: valtree_zst,
            })),
            true_: mk_const(ty::ConstKind::Value(ty::Value {
                ty: types.bool,
                valtree: valtree_true,
            })),
            false_: mk_const(ty::ConstKind::Value(ty::Value {
                ty: types.bool,
                valtree: valtree_false,
            })),
            valtree_zst,
        }
    }
}

/// This struct contains information regarding a free parameter region,
/// either a `ReEarlyParam` or `ReLateParam`.
#[derive(Debug)]
pub struct FreeRegionInfo {
    /// `LocalDefId` of the scope.
    pub scope: LocalDefId,
    /// the `DefId` of the free region.
    pub region_def_id: DefId,
    /// checks if bound region is in Impl Item
    pub is_impl_item: bool,
}

/// This struct should only be created by `create_def`.
#[derive(Copy, Clone)]
pub struct TyCtxtFeed<'tcx, K: Copy> {
    pub tcx: TyCtxt<'tcx>,
    // Do not allow direct access, as downstream code must not mutate this field.
    key: K,
}

/// Only queries that create a `DefId` are allowed to feed queries for that `DefId`.
impl<K: Copy> !StableHash for TyCtxtFeed<'_, K> {}

/// Some workarounds to use cases that cannot use `create_def`.
/// Do not add new ways to create `TyCtxtFeed` without consulting
/// with T-compiler and making an analysis about why your addition
/// does not cause incremental compilation issues.
impl<'tcx> TyCtxt<'tcx> {
    /// Can only be fed before queries are run, and is thus exempt from any
    /// incremental issues. Do not use except for the initial query feeding.
    pub fn feed_unit_query(self) -> TyCtxtFeed<'tcx, ()> {
        self.dep_graph.assert_ignored();
        TyCtxtFeed { tcx: self, key: () }
    }

    /// Only used in the resolver to register the `CRATE_DEF_ID` `DefId` and feed
    /// some queries for it. It will panic if used twice.
    pub fn create_local_crate_def_id(self, span: Span) -> TyCtxtFeed<'tcx, LocalDefId> {
        let key = self.untracked().source_span.push(span);
        assert_eq!(key, CRATE_DEF_ID);
        TyCtxtFeed { tcx: self, key }
    }

    /// In order to break cycles involving `AnonConst`, we need to set the expected type by side
    /// effect. However, we do not want this as a general capability, so this interface restricts
    /// to the only allowed case.
    pub fn feed_anon_const_type(self, key: LocalDefId, value: ty::EarlyBinder<'tcx, Ty<'tcx>>) {
        debug_assert_eq!(self.def_kind(key), DefKind::AnonConst);
        debug_assert!(self.anon_const_kind(key) != ty::AnonConstKind::NonTypeSystemInline);
        TyCtxtFeed { tcx: self, key }.type_of(value)
    }

    // Trait impl item visibility is inherited from its trait when not specified
    // explicitly. In that case we cannot determine it in early resolve,
    // but instead are feeding it in late resolve, where we don't have access to the
    // `TyCtxtFeed` anymore.
    // To avoid having to hash the `LocalDefId` multiple times for inserting and removing the
    // `TyCtxtFeed` from a hash table, we add this hack to feed the visibility.
    // Do not use outside of the resolver query.
    pub fn feed_visibility_for_trait_impl_item(self, key: LocalDefId, vis: ty::Visibility) {
        if cfg!(debug_assertions) {
            match self.def_kind(self.local_parent(key)) {
                DefKind::Impl { of_trait: true } => {}
                other => bug!("{key:?} is not an assoc item of a trait impl: {other:?}"),
            }
        }
        TyCtxtFeed { tcx: self, key }.visibility(vis.to_def_id())
    }
}

impl<'tcx, K: Copy> TyCtxtFeed<'tcx, K> {
    #[inline(always)]
    pub fn key(&self) -> K {
        self.key
    }
}

impl<'tcx> TyCtxtFeed<'tcx, LocalDefId> {
    #[inline(always)]
    pub fn def_id(&self) -> LocalDefId {
        self.key
    }

    // Caller must ensure that `self.key` ID is indeed an owner.
    pub fn feed_owner_id(&self) -> TyCtxtFeed<'tcx, hir::OwnerId> {
        TyCtxtFeed { tcx: self.tcx, key: hir::OwnerId { def_id: self.key } }
    }

    // Fills in all the important parts needed by HIR queries
    pub fn feed_hir(&self) {
        self.hir_owner(ProjectedMaybeOwner::Owner(ProjectedOwnerInfo::new(
            self.tcx.arena.alloc(hir::OwnerNodes::synthetic()),
            self.tcx.arena.alloc(Default::default()),
            self.tcx.arena.alloc(Default::default()),
            self.tcx.arena.alloc(Steal::new(Default::default())),
        )));

        self.feed_owner_id().hir_attr_map(hir::AttributeMap::EMPTY);
    }
}

/// The central data structure of the compiler. It stores references
/// to the various **arenas** and also houses the results of the
/// various **compiler queries** that have been performed. See the
/// [rustc dev guide] for more details.
///
/// [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/ty.html
///
/// An implementation detail: `TyCtxt` is a wrapper type for [GlobalCtxt],
/// which is the struct that actually holds all the data. `TyCtxt` derefs to
/// `GlobalCtxt`, and in practice `TyCtxt` is passed around everywhere, and all
/// operations are done via `TyCtxt`. A `TyCtxt` is obtained for a `GlobalCtxt`
/// by calling `enter` with a closure `f`. That function creates both the
/// `TyCtxt`, and an `ImplicitCtxt` around it that is put into TLS. Within `f`:
/// - The `ImplicitCtxt` is available implicitly via TLS.
/// - The `TyCtxt` is available explicitly via the `tcx` parameter, and also
///   implicitly within the `ImplicitCtxt`. Explicit access is preferred when
///   possible.
#[derive(Copy, Clone)]
#[rustc_diagnostic_item = "TyCtxt"]
#[rustc_pass_by_value]
pub struct TyCtxt<'tcx> {
    gcx: &'tcx GlobalCtxt<'tcx>,
}

// Explicitly implement `DynSync` and `DynSend` for `TyCtxt` to short circuit trait resolution. Its
// field are asserted to implement these traits below, so this is trivially safe, and it greatly
// speeds-up compilation of this crate and its dependents.
unsafe impl DynSend for TyCtxt<'_> {}
unsafe impl DynSync for TyCtxt<'_> {}
fn _assert_tcx_fields() {
    sync::assert_dyn_sync::<&'_ GlobalCtxt<'_>>();
    sync::assert_dyn_send::<&'_ GlobalCtxt<'_>>();
}

impl<'tcx> Deref for TyCtxt<'tcx> {
    type Target = &'tcx GlobalCtxt<'tcx>;
    #[inline(always)]
    fn deref(&self) -> &Self::Target {
        &self.gcx
    }
}

/// See [TyCtxt] for details about this type.
pub struct GlobalCtxt<'tcx> {
    pub arena: &'tcx WorkerLocal<Arena<'tcx>>,
    pub hir_arena: &'tcx WorkerLocal<hir::Arena<'tcx>>,

    interners: CtxtInterners<'tcx>,

    pub sess: &'tcx Session,
    crate_types: Vec<CrateType>,
    /// The `stable_crate_id` is constructed out of the crate name and all the
    /// `-C metadata` arguments passed to the compiler. Its value forms a unique
    /// global identifier for the crate. It is used to allow multiple crates
    /// with the same name to coexist. See the
    /// `rustc_symbol_mangling` crate for more information.
    stable_crate_id: StableCrateId,

    pub dep_graph: DepGraph,

    pub prof: SelfProfilerRef,

    /// Common types, pre-interned for your convenience.
    pub types: CommonTypes<'tcx>,

    /// Common lifetimes, pre-interned for your convenience.
    pub lifetimes: CommonLifetimes<'tcx>,

    /// Common consts, pre-interned for your convenience.
    pub consts: CommonConsts<'tcx>,

    /// Hooks to be able to register functions in other crates that can then still
    /// be called from rustc_middle.
    pub(crate) hooks: crate::hooks::Providers,

    untracked: Untracked,

    pub query_system: QuerySystem<'tcx>,
    pub(crate) dep_kind_vtables: &'tcx [DepKindVTable<'tcx>],

    // Internal caches for metadata decoding. No need to track deps on this.
    pub ty_rcache: Lock<FxHashMap<ty::CReaderCacheKey, Ty<'tcx>>>,

    /// Caches the results of trait selection. This cache is used
    /// for things that do not have to do with the parameters in scope.
    pub selection_cache: traits::SelectionCache<'tcx, ty::TypingEnv<'tcx>>,

    /// Caches the results of trait evaluation. This cache is used
    /// for things that do not have to do with the parameters in scope.
    /// Merge this with `selection_cache`?
    pub evaluation_cache: traits::EvaluationCache<'tcx, ty::TypingEnv<'tcx>>,

    /// Caches the results of goal evaluation in the new solver.
    pub new_solver_evaluation_cache: Lock<search_graph::GlobalCache<TyCtxt<'tcx>>>,
    pub new_solver_canonical_param_env_cache:
        Lock<FxHashMap<ty::ParamEnv<'tcx>, ty::CanonicalParamEnvCacheEntry<TyCtxt<'tcx>>>>,

    pub canonical_param_env_cache: CanonicalParamEnvCache<'tcx>,

    /// Caches the index of the highest bound var in clauses in a canonical binder.
    pub highest_var_in_clauses_cache: Lock<FxHashMap<ty::Clauses<'tcx>, usize>>,
    /// Caches the instantiation of a canonical binder given a set of args.
    pub clauses_cache:
        Lock<FxHashMap<(ty::Clauses<'tcx>, &'tcx [ty::GenericArg<'tcx>]), ty::Clauses<'tcx>>>,

    /// Data layout specification for the current target.
    pub data_layout: TargetDataLayout,

    /// Stores memory for globals (statics/consts).
    pub(crate) alloc_map: interpret::AllocMap<'tcx>,

    current_gcx: CurrentGcx,

    /// A jobserver reference used to release then acquire a token while waiting on a query.
    pub jobserver_proxy: Arc<Proxy>,
}

impl<'tcx> GlobalCtxt<'tcx> {
    /// Installs `self` in a `TyCtxt` and `ImplicitCtxt` for the duration of
    /// `f`.
    pub fn enter<F, R>(&'tcx self, f: F) -> R
    where
        F: FnOnce(TyCtxt<'tcx>) -> R,
    {
        let icx = tls::ImplicitCtxt::new(self);

        // Reset `current_gcx` to `None` when we exit.
        let _on_drop = defer(move || {
            *self.current_gcx.value.write() = None;
        });

        // Set this `GlobalCtxt` as the current one.
        {
            let mut guard = self.current_gcx.value.write();
            assert!(guard.is_none(), "no `GlobalCtxt` is currently set");
            *guard = Some(self as *const _ as *const ());
        }

        tls::enter_context(&icx, || f(icx.tcx))
    }
}

/// This is used to get a reference to a `GlobalCtxt` if one is available.
///
/// This is needed to allow the deadlock handler access to `GlobalCtxt` to look for query cycles.
/// It cannot use the `TLV` global because that's only guaranteed to be defined on the thread
/// creating the `GlobalCtxt`. Other threads have access to the `TLV` only inside Rayon jobs, but
/// the deadlock handler is not called inside such a job.
#[derive(Clone)]
pub struct CurrentGcx {
    /// This stores a pointer to a `GlobalCtxt`. This is set to `Some` inside `GlobalCtxt::enter`
    /// and reset to `None` when that function returns or unwinds.
    value: Arc<RwLock<Option<*const ()>>>,
}

unsafe impl DynSend for CurrentGcx {}
unsafe impl DynSync for CurrentGcx {}

impl CurrentGcx {
    pub fn new() -> Self {
        Self { value: Arc::new(RwLock::new(None)) }
    }

    pub fn access<R>(&self, f: impl for<'tcx> FnOnce(&'tcx GlobalCtxt<'tcx>) -> R) -> R {
        let read_guard = self.value.read();
        let gcx: *const GlobalCtxt<'_> = read_guard.unwrap() as *const _;
        // SAFETY: We hold the read lock for the `GlobalCtxt` pointer. That prevents
        // `GlobalCtxt::enter` from returning as it would first acquire the write lock.
        // This ensures the `GlobalCtxt` is live during `f`.
        f(unsafe { &*gcx })
    }
}

impl<'tcx> TyCtxt<'tcx> {
    pub fn has_typeck_results(self, def_id: LocalDefId) -> bool {
        // Closures' typeck results come from their outermost function,
        // as they are part of the same "inference environment".
        let root = self.typeck_root_def_id_local(def_id);
        self.hir_node_by_def_id(root).body_id().is_some()
    }

    /// Expects a body and returns its codegen attributes.
    ///
    /// Unlike `codegen_fn_attrs`, this returns `CodegenFnAttrs::EMPTY` for
    /// constants.
    pub fn body_codegen_attrs(self, def_id: DefId) -> &'tcx CodegenFnAttrs {
        let def_kind = self.def_kind(def_id);
        if def_kind.has_codegen_attrs() {
            self.codegen_fn_attrs(def_id)
        } else if matches!(
            def_kind,
            DefKind::AnonConst
                | DefKind::AssocConst { .. }
                | DefKind::Const { .. }
                | DefKind::GlobalAsm
        ) {
            CodegenFnAttrs::EMPTY
        } else {
            bug!(
                "body_codegen_fn_attrs called on unexpected definition: {:?} {:?}",
                def_id,
                def_kind
            )
        }
    }

    pub fn alloc_steal_thir(self, thir: Thir<'tcx>) -> &'tcx Steal<Thir<'tcx>> {
        self.arena.alloc(Steal::new(thir))
    }

    pub fn alloc_steal_mir(self, mir: Body<'tcx>) -> &'tcx Steal<Body<'tcx>> {
        self.arena.alloc(Steal::new(mir))
    }

    pub fn alloc_steal_promoted(
        self,
        promoted: IndexVec<Promoted, Body<'tcx>>,
    ) -> &'tcx Steal<IndexVec<Promoted, Body<'tcx>>> {
        self.arena.alloc(Steal::new(promoted))
    }

    pub fn mk_adt_def(
        self,
        did: DefId,
        kind: AdtKind,
        variants: IndexVec<VariantIdx, ty::VariantDef>,
        repr: ReprOptions,
    ) -> ty::AdtDef<'tcx> {
        self.mk_adt_def_from_data(ty::AdtDefData::new(self, did, kind, variants, repr))
    }

    /// Allocates a read-only byte or string literal for `mir::interpret` with alignment 1.
    /// Returns the same `AllocId` if called again with the same bytes.
    pub fn allocate_bytes_dedup<'a>(
        self,
        bytes: impl Into<Cow<'a, [u8]>>,
        salt: usize,
    ) -> interpret::AllocId {
        // Create an allocation that just contains these bytes.
        let alloc = interpret::Allocation::from_bytes_byte_aligned_immutable(bytes, ());
        let alloc = self.mk_const_alloc(alloc);
        self.reserve_and_set_memory_dedup(alloc, salt)
    }

    /// Traits added on all bounds by default, excluding `Sized` which is treated separately.
    pub fn default_traits(self) -> &'static [rustc_hir::LangItem] {
        if self.sess.opts.unstable_opts.experimental_default_bounds {
            &[
                LangItem::DefaultTrait1,
                LangItem::DefaultTrait2,
                LangItem::DefaultTrait3,
                LangItem::DefaultTrait4,
            ]
        } else {
            &[]
        }
    }

    pub fn is_default_trait(self, def_id: DefId) -> bool {
        self.default_traits().iter().any(|&default_trait| self.is_lang_item(def_id, default_trait))
    }

    pub fn is_sizedness_trait(self, def_id: DefId) -> bool {
        matches!(self.as_lang_item(def_id), Some(LangItem::Sized | LangItem::MetaSized))
    }

    pub fn lift<T: Lift<TyCtxt<'tcx>>>(self, value: T) -> T::Lifted {
        value.lift_to_interner(self)
    }

    /// Creates a type context. To use the context call `fn enter` which
    /// provides a `TyCtxt`.
    ///
    /// By only providing the `TyCtxt` inside of the closure we enforce that the type
    /// context and any interned value (types, args, etc.) can only be used while `ty::tls`
    /// has a valid reference to the context, to allow formatting values that need it.
    pub fn create_global_ctxt<T>(
        gcx_cell: &'tcx OnceLock<GlobalCtxt<'tcx>>,
        sess: &'tcx Session,
        crate_types: Vec<CrateType>,
        stable_crate_id: StableCrateId,
        arena: &'tcx WorkerLocal<Arena<'tcx>>,
        hir_arena: &'tcx WorkerLocal<hir::Arena<'tcx>>,
        untracked: Untracked,
        dep_graph: DepGraph,
        dep_kind_vtables: &'tcx [DepKindVTable<'tcx>],
        query_system: QuerySystem<'tcx>,
        hooks: crate::hooks::Providers,
        current_gcx: CurrentGcx,
        jobserver_proxy: Arc<Proxy>,
        f: impl FnOnce(TyCtxt<'tcx>) -> T,
    ) -> T {
        let data_layout = sess.target.parse_data_layout().unwrap_or_else(|err| {
            sess.dcx().emit_fatal(err);
        });
        let interners = CtxtInterners::new(arena);
        let common_types = CommonTypes::new(&interners);
        let common_lifetimes = CommonLifetimes::new(&interners);
        let common_consts = CommonConsts::new(&interners, &common_types);

        let gcx = gcx_cell.get_or_init(|| GlobalCtxt {
            sess,
            crate_types,
            stable_crate_id,
            arena,
            hir_arena,
            interners,
            dep_graph,
            hooks,
            prof: sess.prof.clone(),
            types: common_types,
            lifetimes: common_lifetimes,
            consts: common_consts,
            untracked,
            query_system,
            dep_kind_vtables,
            ty_rcache: Default::default(),
            selection_cache: Default::default(),
            evaluation_cache: Default::default(),
            new_solver_evaluation_cache: Default::default(),
            new_solver_canonical_param_env_cache: Default::default(),
            canonical_param_env_cache: Default::default(),
            highest_var_in_clauses_cache: Default::default(),
            clauses_cache: Default::default(),
            data_layout,
            alloc_map: interpret::AllocMap::new(),
            current_gcx,
            jobserver_proxy,
        });

        // This is a separate function to work around a crash with parallel rustc (#135870)
        gcx.enter(f)
    }

    /// Obtain all lang items of this crate and all dependencies (recursively)
    pub fn lang_items(self) -> &'tcx rustc_hir::lang_items::LanguageItems {
        self.get_lang_items(())
    }

    /// Gets a `Ty` representing the [`LangItem::OrderingEnum`]
    #[track_caller]
    pub fn ty_ordering_enum(self, span: Span) -> Ty<'tcx> {
        let ordering_enum = self.require_lang_item(hir::LangItem::OrderingEnum, span);
        self.type_of(ordering_enum).no_bound_vars().unwrap()
    }

    /// Obtain the given diagnostic item's `DefId`. Use `is_diagnostic_item` if you just want to
    /// compare against another `DefId`, since `is_diagnostic_item` is cheaper.
    pub fn get_diagnostic_item(self, name: Symbol) -> Option<DefId> {
        self.all_diagnostic_items(()).name_to_id.get(&name).copied()
    }

    /// Obtain the diagnostic item's name
    pub fn get_diagnostic_name(self, id: DefId) -> Option<Symbol> {
        self.diagnostic_items(id.krate).id_to_name.get(&id).copied()
    }

    /// Check whether the diagnostic item with the given `name` has the given `DefId`.
    pub fn is_diagnostic_item(self, name: Symbol, did: DefId) -> bool {
        self.diagnostic_items(did.krate).name_to_id.get(&name) == Some(&did)
    }

    pub fn is_coroutine(self, def_id: DefId) -> bool {
        self.coroutine_kind(def_id).is_some()
    }

    pub fn is_async_drop_in_place_coroutine(self, def_id: DefId) -> bool {
        self.is_lang_item(self.parent(def_id), LangItem::AsyncDropInPlace)
    }

    pub fn type_const_span(self, def_id: DefId) -> Option<Span> {
        if !self.is_type_const(def_id) {
            return None;
        }
        Some(self.def_span(def_id))
    }

    /// Check if the given `def_id` is a `type const` (mgca)
    pub fn is_type_const(self, def_id: impl IntoQueryKey<DefId>) -> bool {
        let def_id = def_id.into_query_key();
        match self.def_kind(def_id) {
            DefKind::Const { is_type_const } | DefKind::AssocConst { is_type_const } => {
                is_type_const
            }
            _ => false,
        }
    }

    /// Returns the movability of the coroutine of `def_id`, or panics
    /// if given a `def_id` that is not a coroutine.
    pub fn coroutine_movability(self, def_id: DefId) -> hir::Movability {
        self.coroutine_kind(def_id).expect("expected a coroutine").movability()
    }

    /// Returns `true` if the node pointed to by `def_id` is a coroutine for an async construct.
    pub fn coroutine_is_async(self, def_id: DefId) -> bool {
        matches!(
            self.coroutine_kind(def_id),
            Some(hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Async, _))
        )
    }

    // Whether the body owner is synthetic, which in this case means it does not correspond to
    // meaningful HIR. This is currently used to skip over MIR borrowck.
    pub fn is_synthetic_mir(self, def_id: impl Into<DefId>) -> bool {
        matches!(self.def_kind(def_id.into()), DefKind::SyntheticCoroutineBody)
    }

    /// Returns `true` if the node pointed to by `def_id` is a general coroutine that implements `Coroutine`.
    /// This means it is neither an `async` or `gen` construct.
    pub fn is_general_coroutine(self, def_id: DefId) -> bool {
        matches!(self.coroutine_kind(def_id), Some(hir::CoroutineKind::Coroutine(_)))
    }

    /// Returns `true` if the node pointed to by `def_id` is a coroutine for a `gen` construct.
    pub fn coroutine_is_gen(self, def_id: DefId) -> bool {
        matches!(
            self.coroutine_kind(def_id),
            Some(hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Gen, _))
        )
    }

    /// Returns `true` if the node pointed to by `def_id` is a coroutine for a `async gen` construct.
    pub fn coroutine_is_async_gen(self, def_id: DefId) -> bool {
        matches!(
            self.coroutine_kind(def_id),
            Some(hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::AsyncGen, _))
        )
    }

    pub fn features(self) -> &'tcx rustc_feature::Features {
        self.features_query(())
    }

    pub fn def_key(self, id: impl IntoQueryKey<DefId>) -> rustc_hir::definitions::DefKey {
        let id = id.into_query_key();
        // Accessing the DefKey is ok, since it is part of DefPathHash.
        if let Some(id) = id.as_local() {
            self.definitions_untracked().def_key(id)
        } else {
            self.cstore_untracked().def_key(id)
        }
    }

    /// Converts a `DefId` into its fully expanded `DefPath` (every
    /// `DefId` is really just an interned `DefPath`).
    ///
    /// Note that if `id` is not local to this crate, the result will
    ///  be a non-local `DefPath`.
    pub fn def_path(self, id: DefId) -> rustc_hir::definitions::DefPath {
        // Accessing the DefPath is ok, since it is part of DefPathHash.
        if let Some(id) = id.as_local() {
            self.definitions_untracked().def_path(id)
        } else {
            self.cstore_untracked().def_path(id)
        }
    }

    #[inline]
    pub fn def_path_hash(self, def_id: DefId) -> rustc_hir::definitions::DefPathHash {
        // Accessing the DefPathHash is ok, it is incr. comp. stable.
        if let Some(def_id) = def_id.as_local() {
            self.definitions_untracked().def_path_hash(def_id)
        } else {
            self.cstore_untracked().def_path_hash(def_id)
        }
    }

    #[inline]
    pub fn crate_types(self) -> &'tcx [CrateType] {
        &self.crate_types
    }

    pub fn needs_metadata(self) -> bool {
        self.crate_types().iter().any(|ty| match *ty {
            CrateType::Executable
            | CrateType::StaticLib
            | CrateType::Cdylib
            | CrateType::Sdylib => false,
            CrateType::Rlib | CrateType::Dylib | CrateType::ProcMacro => true,
        })
    }

    pub fn needs_hir_hash(self) -> bool {
        // Why is the hir hash needed for these configurations?
        // - debug_assertions: for the "fingerprint the result" check in
        //   `rustc_query_impl::execution::execute_job`.
        // - incremental: for query lookups.
        // - needs_metadata: it is included in the crate metadata through the crate_hash query
        // - instrument_coverage: for putting into coverage data (see
        //   `hash_mir_source`).
        // - metrics_dir: metrics use the strict version hash in the filenames
        //   for dumped metrics files to prevent overwriting distinct metrics
        //   for similar source builds (may change in the future, this is part
        //   of the proof of concept impl for the metrics initiative project goal)
        cfg!(debug_assertions)
            || self.sess.opts.incremental.is_some()
            || self.needs_metadata()
            || self.sess.instrument_coverage()
            || self.sess.opts.unstable_opts.metrics_dir.is_some()
    }

    #[inline]
    pub fn stable_crate_id(self, crate_num: CrateNum) -> StableCrateId {
        if crate_num == LOCAL_CRATE {
            self.stable_crate_id
        } else {
            self.cstore_untracked().stable_crate_id(crate_num)
        }
    }

    /// Maps a StableCrateId to the corresponding CrateNum. This method assumes
    /// that the crate in question has already been loaded by the CrateStore.
    #[inline]
    pub fn stable_crate_id_to_crate_num(self, stable_crate_id: StableCrateId) -> CrateNum {
        if stable_crate_id == self.stable_crate_id(LOCAL_CRATE) {
            LOCAL_CRATE
        } else {
            *self
                .untracked()
                .stable_crate_ids
                .read()
                .get(&stable_crate_id)
                .unwrap_or_else(|| bug!("uninterned StableCrateId: {stable_crate_id:?}"))
        }
    }

    /// Converts a `DefPathHash` to its corresponding `DefId` in the current compilation
    /// session, if it still exists. This is used during incremental compilation to
    /// turn a deserialized `DefPathHash` into its current `DefId`.
    pub fn def_path_hash_to_def_id(self, hash: DefPathHash) -> Option<DefId> {
        debug!("def_path_hash_to_def_id({:?})", hash);

        let stable_crate_id = hash.stable_crate_id();

        // If this is a DefPathHash from the local crate, we can look up the
        // DefId in the tcx's `Definitions`.
        if stable_crate_id == self.stable_crate_id(LOCAL_CRATE) {
            Some(self.untracked.definitions.read().local_def_path_hash_to_def_id(hash)?.to_def_id())
        } else {
            self.def_path_hash_to_def_id_extern(hash, stable_crate_id)
        }
    }

    pub fn def_path_debug_str(self, def_id: DefId) -> String {
        // We are explicitly not going through queries here in order to get
        // crate name and stable crate id since this code is called from debug!()
        // statements within the query system and we'd run into endless
        // recursion otherwise.
        let (crate_name, stable_crate_id) = if def_id.is_local() {
            (self.crate_name(LOCAL_CRATE), self.stable_crate_id(LOCAL_CRATE))
        } else {
            let cstore = &*self.cstore_untracked();
            (cstore.crate_name(def_id.krate), cstore.stable_crate_id(def_id.krate))
        };

        format!(
            "{}[{:04x}]{}",
            crate_name,
            // Don't print the whole stable crate id. That's just
            // annoying in debug output.
            stable_crate_id.as_u64() >> (8 * 6),
            self.def_path(def_id).to_string_no_crate_verbose()
        )
    }

    pub fn dcx(self) -> DiagCtxtHandle<'tcx> {
        self.sess.dcx()
    }

    /// Checks to see if the caller (`body_features`) has all the features required by the callee
    /// (`callee_features`).
    pub fn is_target_feature_call_safe(
        self,
        callee_features: &[TargetFeature],
        body_features: &[TargetFeature],
    ) -> bool {
        // If the called function has target features the calling function hasn't,
        // the call requires `unsafe`. Don't check this on wasm
        // targets, though. For more information on wasm see the
        // is_like_wasm check in hir_analysis/src/collect.rs
        self.sess.target.options.is_like_wasm
            || callee_features
                .iter()
                .all(|feature| body_features.iter().any(|f| f.name == feature.name))
    }

    /// Returns the safe version of the signature of the given function, if calling it
    /// would be safe in the context of the given caller.
    pub fn adjust_target_feature_sig(
        self,
        fun_def: DefId,
        fun_sig: ty::Binder<'tcx, ty::FnSig<'tcx>>,
        caller: DefId,
    ) -> Option<ty::Binder<'tcx, ty::FnSig<'tcx>>> {
        let fun_features = &self.codegen_fn_attrs(fun_def).target_features;
        let caller_features = &self.body_codegen_attrs(caller).target_features;
        if self.is_target_feature_call_safe(&fun_features, &caller_features) {
            return Some(fun_sig.map_bound(|sig| ty::FnSig {
                fn_sig_kind: fun_sig.fn_sig_kind().set_safety(hir::Safety::Safe),
                ..sig
            }));
        }
        None
    }

    /// Helper to get a tracked environment variable via. [`TyCtxt::env_var_os`] and converting to
    /// UTF-8 like [`std::env::var`].
    pub fn env_var<K: ?Sized + AsRef<OsStr>>(self, key: &'tcx K) -> Result<&'tcx str, VarError> {
        match self.env_var_os(key.as_ref()) {
            Some(value) => value.to_str().ok_or_else(|| VarError::NotUnicode(value.to_os_string())),
            None => Err(VarError::NotPresent),
        }
    }
}

impl<'tcx> TyCtxtAt<'tcx> {
    /// Create a new definition within the incr. comp. engine.
    pub fn create_def(
        self,
        parent: LocalDefId,
        name: Option<Symbol>,
        def_kind: DefKind,
        override_def_path_data: Option<DefPathData>,
        disambiguator: &mut PerParentDisambiguatorState,
    ) -> TyCtxtFeed<'tcx, LocalDefId> {
        let feed =
            self.tcx.create_def(parent, name, def_kind, override_def_path_data, disambiguator);

        feed.def_span(self.span);
        feed
    }
}

impl<'tcx> TyCtxt<'tcx> {
    /// `tcx`-dependent operations performed for every created definition.
    pub fn create_def(
        self,
        parent: LocalDefId,
        name: Option<Symbol>,
        def_kind: DefKind,
        override_def_path_data: Option<DefPathData>,
        disambiguator: &mut PerParentDisambiguatorState,
    ) -> TyCtxtFeed<'tcx, LocalDefId> {
        let data = override_def_path_data.unwrap_or_else(|| def_kind.def_path_data(name));
        // The following call has the side effect of modifying the tables inside `definitions`.
        // These very tables are relied on by the incr. comp. engine to decode DepNodes and to
        // decode the on-disk cache.
        //
        // Any LocalDefId which is used within queries, either as key or result, either:
        // - has been created before the construction of the TyCtxt;
        // - has been created by this call to `create_def`.
        // As a consequence, this LocalDefId is always re-created before it is needed by the incr.
        // comp. engine itself.
        let def_id = self.untracked.definitions.write().create_def(parent, data, disambiguator);

        // This function modifies `self.definitions` using a side-effect.
        // We need to ensure that these side effects are re-run by the incr. comp. engine.
        // Depending on the forever-red node will tell the graph that the calling query
        // needs to be re-evaluated.
        self.dep_graph.read_index(DepNodeIndex::FOREVER_RED_NODE);

        let feed = TyCtxtFeed { tcx: self, key: def_id };
        feed.def_kind(def_kind);
        // Unique types created for closures participate in type privacy checking.
        // They have visibilities inherited from the module they are defined in.
        // Visibilities for opaque types are meaningless, but still provided
        // so that all items have visibilities.
        if matches!(def_kind, DefKind::Closure | DefKind::OpaqueTy) {
            let parent_mod = self.parent_module_from_def_id(def_id).to_def_id();
            feed.visibility(ty::Visibility::Restricted(parent_mod));
        }

        feed
    }

    pub fn create_crate_num(
        self,
        stable_crate_id: StableCrateId,
    ) -> Result<TyCtxtFeed<'tcx, CrateNum>, CrateNum> {
        let mut lock = self.untracked().stable_crate_ids.write();
        if let Some(&existing) = lock.get(&stable_crate_id) {
            return Err(existing);
        }
        let num = CrateNum::new(lock.len());
        lock.insert(stable_crate_id, num);
        Ok(TyCtxtFeed { key: num, tcx: self })
    }

    pub fn iter_local_def_id(self) -> impl Iterator<Item = LocalDefId> {
        // Depend on the `analysis` query to ensure compilation if finished.
        self.ensure_ok().analysis(());

        let definitions = &self.untracked.definitions;
        gen {
            let mut i = 0;

            // Recompute the number of definitions each time, because our caller may be creating
            // new ones.
            while i < { definitions.read().num_definitions() } {
                let local_def_index = rustc_span::def_id::DefIndex::from_usize(i);
                yield LocalDefId { local_def_index };
                i += 1;
            }

            // Freeze definitions once we finish iterating on them, to prevent adding new ones.
            definitions.freeze();
        }
    }

    pub fn definitions(self) -> &'tcx rustc_hir::definitions::Definitions {
        // Depend on the `analysis` query to ensure compilation if finished.
        self.ensure_ok().analysis(());

        // Freeze definitions once we start iterating on them, to prevent adding new ones
        // while iterating. If some query needs to add definitions, it should be `ensure`d above.
        self.untracked.definitions.freeze()
    }

    pub fn def_path_hash_to_def_index_map(
        self,
    ) -> &'tcx rustc_hir::def_path_hash_map::DefPathHashMap {
        // Create a dependency to the crate to be sure we re-execute this when the amount of
        // definitions change.
        self.ensure_ok().hir_crate_items(());
        // Freeze definitions once we start iterating on them, to prevent adding new ones
        // while iterating. If some query needs to add definitions, it should be `ensure`d above.
        self.untracked.definitions.freeze().def_path_hash_to_def_index_map()
    }

    /// Note that this is *untracked* and should only be used within the query
    /// system if the result is otherwise tracked through queries
    #[inline]
    pub fn cstore_untracked(self) -> FreezeReadGuard<'tcx, CrateStoreDyn> {
        FreezeReadGuard::map(self.untracked.cstore.read(), |c| &**c)
    }

    /// Give out access to the untracked data without any sanity checks.
    pub fn untracked(self) -> &'tcx Untracked {
        &self.untracked
    }
    /// Note that this is *untracked* and should only be used within the query
    /// system if the result is otherwise tracked through queries
    #[inline]
    pub fn definitions_untracked(self) -> FreezeReadGuard<'tcx, Definitions> {
        self.untracked.definitions.read()
    }

    /// Note that this is *untracked* and should only be used within the query
    /// system if the result is otherwise tracked through queries
    #[inline]
    pub fn source_span_untracked(self, def_id: LocalDefId) -> Span {
        self.untracked.source_span.get(def_id).unwrap_or(DUMMY_SP)
    }

    #[inline(always)]
    pub fn with_stable_hashing_context<R>(self, f: impl FnOnce(StableHashState<'_>) -> R) -> R {
        f(StableHashState::new(self.sess, &self.untracked))
    }

    #[inline]
    pub fn local_crate_exports_generics(self) -> bool {
        // compiler-builtins has some special treatment in codegen, which can result in confusing
        // behavior if another crate ends up calling into its monomorphizations.
        // https://github.com/rust-lang/rust/issues/150173
        if self.is_compiler_builtins(LOCAL_CRATE) {
            return false;
        }
        self.crate_types().iter().any(|crate_type| {
            match crate_type {
                CrateType::Executable
                | CrateType::StaticLib
                | CrateType::ProcMacro
                | CrateType::Cdylib
                | CrateType::Sdylib => false,

                // FIXME rust-lang/rust#64319, rust-lang/rust#64872:
                // We want to block export of generics from dylibs,
                // but we must fix rust-lang/rust#65890 before we can
                // do that robustly.
                CrateType::Dylib => true,

                CrateType::Rlib => true,
            }
        })
    }

    /// Returns the `DefId` and the `BoundRegionKind` corresponding to the given region.
    pub fn is_suitable_region(
        self,
        generic_param_scope: LocalDefId,
        mut region: Region<'tcx>,
    ) -> Option<FreeRegionInfo> {
        let (suitable_region_binding_scope, region_def_id) = loop {
            let def_id =
                region.opt_param_def_id(self, generic_param_scope.to_def_id())?.as_local()?;
            let scope = self.local_parent(def_id);
            if self.def_kind(scope) == DefKind::OpaqueTy {
                // Lifetime params of opaque types are synthetic and thus irrelevant to
                // diagnostics. Map them back to their origin!
                region = self.map_opaque_lifetime_to_parent_lifetime(def_id);
                continue;
            }
            break (scope, def_id.into());
        };

        let is_impl_item = match self.hir_node_by_def_id(suitable_region_binding_scope) {
            Node::Item(..) | Node::TraitItem(..) => false,
            Node::ImplItem(impl_item) => match impl_item.impl_kind {
                // For now, we do not try to target impls of traits. This is
                // because this message is going to suggest that the user
                // change the fn signature, but they may not be free to do so,
                // since the signature must match the trait.
                //
                // FIXME(#42706) -- in some cases, we could do better here.
                hir::ImplItemImplKind::Trait { .. } => true,
                _ => false,
            },
            _ => false,
        };

        Some(FreeRegionInfo { scope: suitable_region_binding_scope, region_def_id, is_impl_item })
    }

    /// Given a `DefId` for an `fn`, return all the `dyn` and `impl` traits in its return type.
    pub fn return_type_impl_or_dyn_traits(
        self,
        scope_def_id: LocalDefId,
    ) -> Vec<&'tcx hir::Ty<'tcx>> {
        let hir_id = self.local_def_id_to_hir_id(scope_def_id);
        let Some(hir::FnDecl { output: hir::FnRetTy::Return(hir_output), .. }) =
            self.hir_fn_decl_by_hir_id(hir_id)
        else {
            return vec![];
        };

        let mut v = TraitObjectVisitor(vec![]);
        v.visit_ty_unambig(hir_output);
        v.0
    }

    /// Given a `DefId` for an `fn`, return all the `dyn` and `impl` traits in
    /// its return type, and the associated alias span when type alias is used,
    /// along with a span for lifetime suggestion (if there are existing generics).
    pub fn return_type_impl_or_dyn_traits_with_type_alias(
        self,
        scope_def_id: LocalDefId,
    ) -> Option<(Vec<&'tcx hir::Ty<'tcx>>, Span, Option<Span>)> {
        let hir_id = self.local_def_id_to_hir_id(scope_def_id);
        let mut v = TraitObjectVisitor(vec![]);
        // when the return type is a type alias
        if let Some(hir::FnDecl { output: hir::FnRetTy::Return(hir_output), .. }) = self.hir_fn_decl_by_hir_id(hir_id)
            && let hir::TyKind::Path(hir::QPath::Resolved(
                None,
                hir::Path { res: hir::def::Res::Def(DefKind::TyAlias, def_id), .. }, )) = hir_output.kind
            && let Some(local_id) = def_id.as_local()
            && let Some(alias_ty) = self.hir_node_by_def_id(local_id).alias_ty() // it is type alias
            && let Some(alias_generics) = self.hir_node_by_def_id(local_id).generics()
        {
            v.visit_ty_unambig(alias_ty);
            if !v.0.is_empty() {
                return Some((
                    v.0,
                    alias_generics.span,
                    alias_generics.span_for_lifetime_suggestion(),
                ));
            }
        }
        None
    }

    /// Determines whether identifiers in the assembly have strict naming rules.
    /// Currently, only NVPTX* targets need it.
    pub fn has_strict_asm_symbol_naming(self) -> bool {
        self.sess.target.llvm_target.starts_with("nvptx")
    }

    /// Returns `&'static core::panic::Location<'static>`.
    pub fn caller_location_ty(self) -> Ty<'tcx> {
        Ty::new_imm_ref(
            self,
            self.lifetimes.re_static,
            self.type_of(self.require_lang_item(LangItem::PanicLocation, DUMMY_SP))
                .instantiate(self, self.mk_args(&[self.lifetimes.re_static.into()]))
                .skip_norm_wip(),
        )
    }

    /// Returns a displayable description and article for the given `def_id` (e.g. `("a", "struct")`).
    pub fn article_and_description(self, def_id: DefId) -> (&'static str, &'static str) {
        let kind = self.def_kind(def_id);
        (self.def_kind_descr_article(kind, def_id), self.def_kind_descr(kind, def_id))
    }

    pub fn type_length_limit(self) -> Limit {
        self.limits(()).type_length_limit
    }

    pub fn recursion_limit(self) -> Limit {
        self.limits(()).recursion_limit
    }

    pub fn move_size_limit(self) -> Limit {
        self.limits(()).move_size_limit
    }

    pub fn pattern_complexity_limit(self) -> Limit {
        self.limits(()).pattern_complexity_limit
    }

    /// All traits in the crate graph, including those not visible to the user.
    pub fn all_traits_including_private(self) -> impl Iterator<Item = DefId> {
        iter::once(LOCAL_CRATE)
            .chain(self.crates(()).iter().copied())
            .flat_map(move |cnum| self.traits(cnum).iter().copied())
    }

    /// All traits that are visible within the crate graph (i.e. excluding private dependencies).
    pub fn visible_traits(self) -> impl Iterator<Item = DefId> {
        let visible_crates =
            self.crates(()).iter().copied().filter(move |cnum| self.is_user_visible_dep(*cnum));

        iter::once(LOCAL_CRATE)
            .chain(visible_crates)
            .flat_map(move |cnum| self.traits(cnum).iter().copied())
    }

    #[inline]
    pub fn local_visibility(self, def_id: LocalDefId) -> Visibility {
        self.visibility(def_id).expect_local()
    }

    /// Returns the origin of the opaque type `def_id`.
    #[instrument(skip(self), level = "trace", ret)]
    pub fn local_opaque_ty_origin(self, def_id: LocalDefId) -> hir::OpaqueTyOrigin<LocalDefId> {
        self.hir_expect_opaque_ty(def_id).origin
    }

    pub fn finish(self) {
        // We assume that no queries are run past here. If there are new queries
        // after this point, they'll show up as "<unknown>" in self-profiling data.
        self.alloc_self_profile_query_strings();

        self.save_dep_graph();
        self.verify_query_key_hashes();

        if let Err((path, error)) = self.dep_graph.finish_encoding() {
            self.sess.dcx().emit_fatal(crate::error::FailedWritingFile { path: &path, error });
        }
    }

    pub fn report_unused_features(self) {
        #[derive(Diagnostic)]
        #[diag("feature `{$feature}` is declared but not used")]
        struct UnusedFeature {
            feature: Symbol,
        }

        // Collect first to avoid holding the lock while linting.
        let used_features = self.sess.used_features.lock();
        let unused_features = self
            .features()
            .enabled_features_iter_stable_order()
            .filter(|(f, _)| {
                !used_features.contains_key(f)
                // FIXME: `restricted_std` is used to tell a standard library built
                // for a platform that it doesn't know how to support. But it
                // could only gate a private mod (see `__restricted_std_workaround`)
                // with `cfg(not(restricted_std))`, so it cannot be recorded as used
                // in downstream crates. It should never be linted, but should we
                // hack this in the linter to ignore it?
                && f.as_str() != "restricted_std"
                // `doc_cfg` affects rustdoc behavior: rustdoc checks it via
                // `tcx.features().doc_cfg()`, but a normal rustc compilation may
                // never observe that use. Do not lint it as unused here.
                && *f != sym::doc_cfg
            })
            .collect::<Vec<_>>();

        for (feature, span) in unused_features {
            self.emit_node_span_lint(
                rustc_session::lint::builtin::UNUSED_FEATURES,
                CRATE_HIR_ID,
                span,
                UnusedFeature { feature },
            );
        }
    }
}

macro_rules! nop_lift {
    ($set:ident; $ty:ty => $lifted:ty) => {
        impl<'a, 'tcx> Lift<TyCtxt<'tcx>> for $ty {
            type Lifted = $lifted;
            #[track_caller]
            fn lift_to_interner(self, tcx: TyCtxt<'tcx>) -> Self::Lifted {
                // Assert that the set has the right type.
                // Given an argument that has an interned type, the return type has the type of
                // the corresponding interner set. This won't actually return anything, we're
                // just doing this to compute said type!
                fn _intern_set_ty_from_interned_ty<'tcx, Inner>(
                    _x: Interned<'tcx, Inner>,
                ) -> InternedSet<'tcx, Inner> {
                    unreachable!()
                }
                fn _type_eq<T>(_x: &T, _y: &T) {}
                fn _test<'tcx>(x: $lifted, tcx: TyCtxt<'tcx>) {
                    // If `x` is a newtype around an `Interned<T>`, then `interner` is an
                    // interner of appropriate type. (Ideally we'd also check that `x` is a
                    // newtype with just that one field. Not sure how to do that.)
                    let interner = _intern_set_ty_from_interned_ty(x.0);
                    // Now check that this is the same type as `interners.$set`.
                    _type_eq(&interner, &tcx.interners.$set);
                }

                assert!(tcx.interners.$set.contains_pointer_to(&InternedInSet(&*self.0.0)));
                // SAFETY: we just checked that `self` is interned and therefore is valid for the
                // entire lifetime of the `TyCtxt`.
                unsafe { mem::transmute(self) }
            }
        }
    };
}

macro_rules! nop_list_lift {
    ($set:ident; $ty:ty => $lifted:ty) => {
        nop_list_lift! { $set: List; $ty => $lifted }
    };
    // Allows defining own list type
    ($set:ident: $list:ident; $ty:ty => $lifted:ty) => {
        impl<'a, 'tcx> Lift<TyCtxt<'tcx>> for &'a $list<$ty> {
            type Lifted = &'tcx $list<$lifted>;
            fn lift_to_interner(self, tcx: TyCtxt<'tcx>) -> Self::Lifted {
                // Assert that the set has the right type.
                if false {
                    let _x: &InternedSet<'tcx, $list<$lifted>> = &tcx.interners.$set;
                }

                if self.is_empty() {
                    return $list::empty();
                }
                assert!(tcx.interners.$set.contains_pointer_to(&InternedInSet(self)));
                // SAFETY: we just checked that `self` is interned and therefore is valid for the
                // entire lifetime of the `TyCtxt`.
                unsafe { mem::transmute(self) }
            }
        }
    };
}

nop_lift! { type_; Ty<'a> => Ty<'tcx> }
nop_lift! { region; Region<'a> => Region<'tcx> }
nop_lift! { const_; Const<'a> => Const<'tcx> }
nop_lift! { pat; Pattern<'a> => Pattern<'tcx> }
nop_lift! { const_allocation; ConstAllocation<'a> => ConstAllocation<'tcx> }
nop_lift! { predicate; Predicate<'a> => Predicate<'tcx> }
nop_lift! { predicate; Clause<'a> => Clause<'tcx> }
nop_lift! { layout; Layout<'a> => Layout<'tcx> }
nop_lift! { valtree; ValTree<'a> => ValTree<'tcx> }

nop_list_lift! { type_lists; Ty<'a> => Ty<'tcx> }
nop_list_lift! { clauses: ListWithCachedTypeInfo; Clause<'a> => Clause<'tcx> }
nop_list_lift! {
    poly_existential_predicates; PolyExistentialPredicate<'a> => PolyExistentialPredicate<'tcx>
}
nop_list_lift! { bound_variable_kinds; ty::BoundVariableKind<'a> => ty::BoundVariableKind<'tcx> }
nop_list_lift! { patterns; Pattern<'a> => Pattern<'tcx> }
nop_list_lift! {
    outlives; ty::ArgOutlivesPredicate<'a> => ty::ArgOutlivesPredicate<'tcx>
}

// This is the impl for `&'a GenericArgs<'a>`.
nop_list_lift! { args; GenericArg<'a> => GenericArg<'tcx> }

macro_rules! sty_debug_print {
    ($fmt: expr, $ctxt: expr, $($variant: ident),*) => {{
        // Curious inner module to allow variant names to be used as
        // variable names.
        #[allow(non_snake_case)]
        mod inner {
            use crate::ty::{self, TyCtxt};
            use crate::ty::context::InternedInSet;

            #[derive(Copy, Clone)]
            struct DebugStat {
                total: usize,
                lt_infer: usize,
                ty_infer: usize,
                ct_infer: usize,
                all_infer: usize,
            }

            pub(crate) fn go(fmt: &mut std::fmt::Formatter<'_>, tcx: TyCtxt<'_>) -> std::fmt::Result {
                let mut total = DebugStat {
                    total: 0,
                    lt_infer: 0,
                    ty_infer: 0,
                    ct_infer: 0,
                    all_infer: 0,
                };
                $(let mut $variant = total;)*

                for shard in tcx.interners.type_.lock_shards() {
                    // It seems that ordering doesn't affect anything here.
                    #[allow(rustc::potential_query_instability)]
                    let types = shard.iter();
                    for &(InternedInSet(t), ()) in types {
                        let variant = match t.internee {
                            ty::Bool | ty::Char | ty::Int(..) | ty::Uint(..) |
                                ty::Float(..) | ty::Str | ty::Never => continue,
                            ty::Error(_) => /* unimportant */ continue,
                            $(ty::$variant(..) => &mut $variant,)*
                        };
                        let lt = t.flags.intersects(ty::TypeFlags::HAS_RE_INFER);
                        let ty = t.flags.intersects(ty::TypeFlags::HAS_TY_INFER);
                        let ct = t.flags.intersects(ty::TypeFlags::HAS_CT_INFER);

                        variant.total += 1;
                        total.total += 1;
                        if lt { total.lt_infer += 1; variant.lt_infer += 1 }
                        if ty { total.ty_infer += 1; variant.ty_infer += 1 }
                        if ct { total.ct_infer += 1; variant.ct_infer += 1 }
                        if lt && ty && ct { total.all_infer += 1; variant.all_infer += 1 }
                    }
                }
                writeln!(fmt, "Ty interner             total           ty lt ct all")?;
                $(writeln!(fmt, "    {:18}: {uses:6} {usespc:4.1}%, \
                            {ty:4.1}% {lt:5.1}% {ct:4.1}% {all:4.1}%",
                    stringify!($variant),
                    uses = $variant.total,
                    usespc = $variant.total as f64 * 100.0 / total.total as f64,
                    ty = $variant.ty_infer as f64 * 100.0  / total.total as f64,
                    lt = $variant.lt_infer as f64 * 100.0  / total.total as f64,
                    ct = $variant.ct_infer as f64 * 100.0  / total.total as f64,
                    all = $variant.all_infer as f64 * 100.0  / total.total as f64)?;
                )*
                writeln!(fmt, "                  total {uses:6}        \
                          {ty:4.1}% {lt:5.1}% {ct:4.1}% {all:4.1}%",
                    uses = total.total,
                    ty = total.ty_infer as f64 * 100.0  / total.total as f64,
                    lt = total.lt_infer as f64 * 100.0  / total.total as f64,
                    ct = total.ct_infer as f64 * 100.0  / total.total as f64,
                    all = total.all_infer as f64 * 100.0  / total.total as f64)
            }
        }

        inner::go($fmt, $ctxt)
    }}
}

impl<'tcx> TyCtxt<'tcx> {
    pub fn debug_stats(self) -> impl fmt::Debug {
        fmt::from_fn(move |fmt| {
            sty_debug_print!(
                fmt,
                self,
                Adt,
                Array,
                Slice,
                RawPtr,
                Ref,
                FnDef,
                FnPtr,
                UnsafeBinder,
                Placeholder,
                Coroutine,
                CoroutineWitness,
                Dynamic,
                Closure,
                CoroutineClosure,
                Tuple,
                Bound,
                Param,
                Infer,
                Alias,
                Pat,
                Foreign
            )?;

            writeln!(fmt, "GenericArgs interner: #{}", self.interners.args.len())?;
            writeln!(fmt, "Region interner: #{}", self.interners.region.len())?;
            writeln!(fmt, "Const Allocation interner: #{}", self.interners.const_allocation.len())?;
            writeln!(fmt, "Layout interner: #{}", self.interners.layout.len())?;

            Ok(())
        })
    }
}

// This type holds a `T` in the interner. The `T` is stored in the arena and
// this type just holds a pointer to it, but it still effectively owns it. It
// impls `Borrow` so that it can be looked up using the original
// (non-arena-memory-owning) types.
struct InternedInSet<'tcx, T: ?Sized + PointeeSized>(&'tcx T);

impl<'tcx, T: 'tcx + ?Sized + PointeeSized> Clone for InternedInSet<'tcx, T> {
    fn clone(&self) -> Self {
        *self
    }
}

impl<'tcx, T: 'tcx + ?Sized + PointeeSized> Copy for InternedInSet<'tcx, T> {}

impl<'tcx, T: 'tcx + ?Sized + PointeeSized> IntoPointer for InternedInSet<'tcx, T> {
    fn into_pointer(&self) -> *const () {
        self.0 as *const _ as *const ()
    }
}

#[allow(rustc::usage_of_ty_tykind)]
impl<'tcx, T> Borrow<T> for InternedInSet<'tcx, WithCachedTypeInfo<T>> {
    fn borrow(&self) -> &T {
        &self.0.internee
    }
}

impl<'tcx, T: PartialEq> PartialEq for InternedInSet<'tcx, WithCachedTypeInfo<T>> {
    fn eq(&self, other: &InternedInSet<'tcx, WithCachedTypeInfo<T>>) -> bool {
        // The `Borrow` trait requires that `x.borrow() == y.borrow()` equals
        // `x == y`.
        self.0.internee == other.0.internee
    }
}

impl<'tcx, T: Eq> Eq for InternedInSet<'tcx, WithCachedTypeInfo<T>> {}

impl<'tcx, T: Hash> Hash for InternedInSet<'tcx, WithCachedTypeInfo<T>> {
    fn hash<H: Hasher>(&self, s: &mut H) {
        // The `Borrow` trait requires that `x.borrow().hash(s) == x.hash(s)`.
        self.0.internee.hash(s)
    }
}

impl<'tcx, T> Borrow<[T]> for InternedInSet<'tcx, List<T>> {
    fn borrow(&self) -> &[T] {
        &self.0[..]
    }
}

impl<'tcx, T: PartialEq> PartialEq for InternedInSet<'tcx, List<T>> {
    fn eq(&self, other: &InternedInSet<'tcx, List<T>>) -> bool {
        // The `Borrow` trait requires that `x.borrow() == y.borrow()` equals
        // `x == y`.
        self.0[..] == other.0[..]
    }
}

impl<'tcx, T: Eq> Eq for InternedInSet<'tcx, List<T>> {}

impl<'tcx, T: Hash> Hash for InternedInSet<'tcx, List<T>> {
    fn hash<H: Hasher>(&self, s: &mut H) {
        // The `Borrow` trait requires that `x.borrow().hash(s) == x.hash(s)`.
        self.0[..].hash(s)
    }
}

impl<'tcx, T> Borrow<[T]> for InternedInSet<'tcx, ListWithCachedTypeInfo<T>> {
    fn borrow(&self) -> &[T] {
        &self.0[..]
    }
}

impl<'tcx, T: PartialEq> PartialEq for InternedInSet<'tcx, ListWithCachedTypeInfo<T>> {
    fn eq(&self, other: &InternedInSet<'tcx, ListWithCachedTypeInfo<T>>) -> bool {
        // The `Borrow` trait requires that `x.borrow() == y.borrow()` equals
        // `x == y`.
        self.0[..] == other.0[..]
    }
}

impl<'tcx, T: Eq> Eq for InternedInSet<'tcx, ListWithCachedTypeInfo<T>> {}

impl<'tcx, T: Hash> Hash for InternedInSet<'tcx, ListWithCachedTypeInfo<T>> {
    fn hash<H: Hasher>(&self, s: &mut H) {
        // The `Borrow` trait requires that `x.borrow().hash(s) == x.hash(s)`.
        self.0[..].hash(s)
    }
}

macro_rules! direct_interners {
    ($($name:ident: $vis:vis $method:ident($ty:ty): $ret_ctor:ident -> $ret_ty:ty,)+) => {
        $(impl<'tcx> Borrow<$ty> for InternedInSet<'tcx, $ty> {
            fn borrow<'a>(&'a self) -> &'a $ty {
                &self.0
            }
        }

        impl<'tcx> PartialEq for InternedInSet<'tcx, $ty> {
            fn eq(&self, other: &Self) -> bool {
                // The `Borrow` trait requires that `x.borrow() == y.borrow()`
                // equals `x == y`.
                self.0 == other.0
            }
        }

        impl<'tcx> Eq for InternedInSet<'tcx, $ty> {}

        impl<'tcx> Hash for InternedInSet<'tcx, $ty> {
            fn hash<H: Hasher>(&self, s: &mut H) {
                // The `Borrow` trait requires that `x.borrow().hash(s) ==
                // x.hash(s)`.
                self.0.hash(s)
            }
        }

        impl<'tcx> TyCtxt<'tcx> {
            $vis fn $method(self, v: $ty) -> $ret_ty {
                $ret_ctor(Interned::new_unchecked(self.interners.$name.intern(v, |v| {
                    InternedInSet(self.interners.arena.alloc(v))
                }).0))
            }
        })+
    }
}

// Functions with a `mk_` prefix are intended for use outside this file and
// crate. Functions with an `intern_` prefix are intended for use within this
// crate only, and have a corresponding `mk_` function.
direct_interners! {
    region: pub(crate) intern_region(RegionKind<'tcx>): Region -> Region<'tcx>,
    valtree: pub(crate) intern_valtree(ValTreeKind<TyCtxt<'tcx>>): ValTree -> ValTree<'tcx>,
    pat: pub mk_pat(PatternKind<'tcx>): Pattern -> Pattern<'tcx>,
    const_allocation: pub mk_const_alloc(Allocation): ConstAllocation -> ConstAllocation<'tcx>,
    layout: pub mk_layout(LayoutData<FieldIdx, VariantIdx>): Layout -> Layout<'tcx>,
    adt_def: pub mk_adt_def_from_data(AdtDefData): AdtDef -> AdtDef<'tcx>,
    external_constraints: pub mk_external_constraints(ExternalConstraintsData<TyCtxt<'tcx>>):
        ExternalConstraints -> ExternalConstraints<'tcx>,
}

macro_rules! slice_interners {
    ($($field:ident: $vis:vis $method:ident($ty:ty)),+ $(,)?) => (
        impl<'tcx> TyCtxt<'tcx> {
            $($vis fn $method(self, v: &[$ty]) -> &'tcx List<$ty> {
                if v.is_empty() {
                    List::empty()
                } else {
                    self.interners.$field.intern_ref(v, || {
                        InternedInSet(List::from_arena(&*self.arena, (), v))
                    }).0
                }
            })+
        }
    );
}

// These functions intern slices. They all have a corresponding
// `mk_foo_from_iter` function that interns an iterator. The slice version
// should be used when possible, because it's faster.
slice_interners!(
    const_lists: pub mk_const_list(Const<'tcx>),
    args: pub mk_args(GenericArg<'tcx>),
    type_lists: pub mk_type_list(Ty<'tcx>),
    canonical_var_kinds: pub mk_canonical_var_kinds(CanonicalVarKind<'tcx>),
    poly_existential_predicates: intern_poly_existential_predicates(PolyExistentialPredicate<'tcx>),
    projs: pub mk_projs(ProjectionKind),
    place_elems: pub mk_place_elems(PlaceElem<'tcx>),
    bound_variable_kinds: pub mk_bound_variable_kinds(ty::BoundVariableKind<'tcx>),
    fields: pub mk_fields(FieldIdx),
    local_def_ids: intern_local_def_ids(LocalDefId),
    captures: intern_captures(&'tcx ty::CapturedPlace<'tcx>),
    patterns: pub mk_patterns(Pattern<'tcx>),
    outlives: pub mk_outlives(ty::ArgOutlivesPredicate<'tcx>),
    predefined_opaques_in_body: pub mk_predefined_opaques_in_body((ty::OpaqueTypeKey<'tcx>, Ty<'tcx>)),
);

impl<'tcx> TyCtxt<'tcx> {
    /// Given a `fn` sig, returns an equivalent `unsafe fn` type;
    /// that is, a `fn` type that is equivalent in every way for being
    /// unsafe.
    pub fn safe_to_unsafe_fn_ty(self, sig: PolyFnSig<'tcx>) -> Ty<'tcx> {
        assert!(sig.safety().is_safe());
        Ty::new_fn_ptr(
            self,
            sig.map_bound(|sig| ty::FnSig {
                fn_sig_kind: sig.fn_sig_kind.set_safety(hir::Safety::Unsafe),
                ..sig
            }),
        )
    }

    /// Given a `fn` sig, returns an equivalent `unsafe fn` sig;
    /// that is, a `fn` sig that is equivalent in every way for being
    /// unsafe.
    pub fn safe_to_unsafe_sig(self, sig: PolyFnSig<'tcx>) -> PolyFnSig<'tcx> {
        assert!(sig.safety().is_safe());
        sig.map_bound(|sig| ty::FnSig {
            fn_sig_kind: sig.fn_sig_kind.set_safety(hir::Safety::Unsafe),
            ..sig
        })
    }

    /// Given the def_id of a Trait `trait_def_id` and the name of an associated item `assoc_name`
    /// returns true if the `trait_def_id` defines an associated item of name `assoc_name`.
    pub fn trait_may_define_assoc_item(self, trait_def_id: DefId, assoc_name: Ident) -> bool {
        elaborate::supertrait_def_ids(self, trait_def_id).any(|trait_did| {
            self.associated_items(trait_did)
                .filter_by_name_unhygienic(assoc_name.name)
                .any(|item| self.hygienic_eq(assoc_name, item.ident(self), trait_did))
        })
    }

    /// Given a `ty`, return whether it's an `impl Future<...>`.
    pub fn ty_is_opaque_future(self, ty: Ty<'_>) -> bool {
        let ty::Alias(_, ty::AliasTy { kind: ty::Opaque { def_id }, .. }) = *ty.kind() else {
            return false;
        };
        let future_trait = self.require_lang_item(LangItem::Future, DUMMY_SP);

        self.explicit_item_self_bounds(def_id).skip_binder().iter().any(|&(predicate, _)| {
            let ty::ClauseKind::Trait(trait_predicate) = predicate.kind().skip_binder() else {
                return false;
            };
            trait_predicate.trait_ref.def_id == future_trait
                && trait_predicate.polarity == PredicatePolarity::Positive
        })
    }

    /// Given a closure signature, returns an equivalent fn signature. Detuples
    /// and so forth -- so e.g., if we have a sig with `Fn<(u32, i32)>` then
    /// you would get a `fn(u32, i32)`.
    /// `unsafety` determines the unsafety of the fn signature. If you pass
    /// `hir::Safety::Unsafe` in the previous example, then you would get
    /// an `unsafe fn (u32, i32)`.
    /// It cannot convert a closure that requires unsafe.
    pub fn signature_unclosure(self, sig: PolyFnSig<'tcx>, safety: hir::Safety) -> PolyFnSig<'tcx> {
        sig.map_bound(|s| {
            let params = match s.inputs()[0].kind() {
                ty::Tuple(params) => *params,
                _ => bug!(),
            };
            // Ignore splatting, it is unsupported on closures.
            assert!(s.splatted().is_none());
            self.mk_fn_sig(
                params,
                s.output(),
                s.fn_sig_kind.set_safety(safety).set_abi(ExternAbi::Rust),
            )
        })
    }

    #[inline]
    pub fn mk_predicate(self, binder: Binder<'tcx, PredicateKind<'tcx>>) -> Predicate<'tcx> {
        self.interners.intern_predicate(binder)
    }

    #[inline]
    pub fn reuse_or_mk_predicate(
        self,
        pred: Predicate<'tcx>,
        binder: Binder<'tcx, PredicateKind<'tcx>>,
    ) -> Predicate<'tcx> {
        if pred.kind() != binder { self.mk_predicate(binder) } else { pred }
    }

    pub fn check_args_compatible(self, def_id: DefId, args: &'tcx [ty::GenericArg<'tcx>]) -> bool {
        self.check_args_compatible_inner(def_id, args, false)
    }

    fn check_args_compatible_inner(
        self,
        def_id: DefId,
        args: &'tcx [ty::GenericArg<'tcx>],
        nested: bool,
    ) -> bool {
        let generics = self.generics_of(def_id);

        // IATs and IACs (inherent associated types/consts with `type const`) themselves have a
        // weird arg setup (self + own args), but nested items *in* IATs (namely: opaques, i.e.
        // ATPITs) do not.
        let is_inherent_assoc_ty = matches!(self.def_kind(def_id), DefKind::AssocTy)
            && matches!(self.def_kind(self.parent(def_id)), DefKind::Impl { of_trait: false });
        let is_inherent_assoc_type_const =
            matches!(self.def_kind(def_id), DefKind::AssocConst { is_type_const: true })
                && matches!(self.def_kind(self.parent(def_id)), DefKind::Impl { of_trait: false });
        let own_args = if !nested && (is_inherent_assoc_ty || is_inherent_assoc_type_const) {
            if generics.own_params.len() + 1 != args.len() {
                return false;
            }

            if !matches!(args[0].kind(), ty::GenericArgKind::Type(_)) {
                return false;
            }

            &args[1..]
        } else {
            if generics.count() != args.len() {
                return false;
            }

            let (parent_args, own_args) = args.split_at(generics.parent_count);

            if let Some(parent) = generics.parent
                && !self.check_args_compatible_inner(parent, parent_args, true)
            {
                return false;
            }

            own_args
        };

        for (param, arg) in std::iter::zip(&generics.own_params, own_args) {
            match (&param.kind, arg.kind()) {
                (ty::GenericParamDefKind::Type { .. }, ty::GenericArgKind::Type(_))
                | (ty::GenericParamDefKind::Lifetime, ty::GenericArgKind::Lifetime(_))
                | (ty::GenericParamDefKind::Const { .. }, ty::GenericArgKind::Const(_)) => {}
                _ => return false,
            }
        }

        true
    }

    /// With `cfg(debug_assertions)`, assert that args are compatible with their generics,
    /// and print out the args if not.
    pub fn debug_assert_args_compatible(self, def_id: DefId, args: &'tcx [ty::GenericArg<'tcx>]) {
        if cfg!(debug_assertions) && !self.check_args_compatible(def_id, args) {
            let is_inherent_assoc_ty = matches!(self.def_kind(def_id), DefKind::AssocTy)
                && matches!(self.def_kind(self.parent(def_id)), DefKind::Impl { of_trait: false });
            let is_inherent_assoc_type_const =
                matches!(self.def_kind(def_id), DefKind::AssocConst { is_type_const: true })
                    && matches!(
                        self.def_kind(self.parent(def_id)),
                        DefKind::Impl { of_trait: false }
                    );
            if is_inherent_assoc_ty || is_inherent_assoc_type_const {
                bug!(
                    "args not compatible with generics for {}: args={:#?}, generics={:#?}",
                    self.def_path_str(def_id),
                    args,
                    // Make `[Self, GAT_ARGS...]` (this could be simplified)
                    self.mk_args_from_iter(
                        [self.types.self_param.into()].into_iter().chain(
                            self.generics_of(def_id)
                                .own_args(ty::GenericArgs::identity_for_item(self, def_id))
                                .iter()
                                .copied()
                        )
                    )
                );
            } else {
                bug!(
                    "args not compatible with generics for {}: args={:#?}, generics={:#?}",
                    self.def_path_str(def_id),
                    args,
                    ty::GenericArgs::identity_for_item(self, def_id)
                );
            }
        }
    }

    #[inline(always)]
    pub(crate) fn check_and_mk_args(
        self,
        def_id: DefId,
        args: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
    ) -> GenericArgsRef<'tcx> {
        let args = self.mk_args_from_iter(args.into_iter().map(Into::into));
        self.debug_assert_args_compatible(def_id, args);
        args
    }

    #[inline]
    pub fn mk_ct_from_kind(self, kind: ty::ConstKind<'tcx>) -> Const<'tcx> {
        self.interners.intern_const(kind)
    }

    // Avoid this in favour of more specific `Ty::new_*` methods, where possible.
    #[allow(rustc::usage_of_ty_tykind)]
    #[inline]
    pub fn mk_ty_from_kind(self, st: TyKind<'tcx>) -> Ty<'tcx> {
        self.interners.intern_ty(st)
    }

    pub fn mk_param_from_def(self, param: &ty::GenericParamDef) -> GenericArg<'tcx> {
        match param.kind {
            GenericParamDefKind::Lifetime => {
                ty::Region::new_early_param(self, param.to_early_bound_region_data()).into()
            }
            GenericParamDefKind::Type { .. } => Ty::new_param(self, param.index, param.name).into(),
            GenericParamDefKind::Const { .. } => {
                ty::Const::new_param(self, ParamConst { index: param.index, name: param.name })
                    .into()
            }
        }
    }

    pub fn mk_place_field(self, place: Place<'tcx>, f: FieldIdx, ty: Ty<'tcx>) -> Place<'tcx> {
        self.mk_place_elem(place, PlaceElem::Field(f, ty))
    }

    pub fn mk_place_deref(self, place: Place<'tcx>) -> Place<'tcx> {
        self.mk_place_elem(place, PlaceElem::Deref)
    }

    pub fn mk_place_downcast(
        self,
        place: Place<'tcx>,
        adt_def: AdtDef<'tcx>,
        variant_index: VariantIdx,
    ) -> Place<'tcx> {
        self.mk_place_elem(
            place,
            PlaceElem::Downcast(Some(adt_def.variant(variant_index).name), variant_index),
        )
    }

    pub fn mk_place_downcast_unnamed(
        self,
        place: Place<'tcx>,
        variant_index: VariantIdx,
    ) -> Place<'tcx> {
        self.mk_place_elem(place, PlaceElem::Downcast(None, variant_index))
    }

    pub fn mk_place_index(self, place: Place<'tcx>, index: Local) -> Place<'tcx> {
        self.mk_place_elem(place, PlaceElem::Index(index))
    }

    /// This method copies `Place`'s projection, add an element and reintern it. Should not be used
    /// to build a full `Place` it's just a convenient way to grab a projection and modify it in
    /// flight.
    pub fn mk_place_elem(self, place: Place<'tcx>, elem: PlaceElem<'tcx>) -> Place<'tcx> {
        Place {
            local: place.local,
            projection: self.mk_place_elems_from_iter(place.projection.iter().chain([elem])),
        }
    }

    pub fn mk_poly_existential_predicates(
        self,
        eps: &[PolyExistentialPredicate<'tcx>],
    ) -> &'tcx List<PolyExistentialPredicate<'tcx>> {
        assert!(!eps.is_empty());
        assert!(
            eps.array_windows()
                .all(|[a, b]| a.skip_binder().stable_cmp(self, &b.skip_binder())
                    != Ordering::Greater)
        );
        self.intern_poly_existential_predicates(eps)
    }

    pub fn mk_clauses(self, clauses: &[Clause<'tcx>]) -> Clauses<'tcx> {
        // FIXME consider asking the input slice to be sorted to avoid
        // re-interning permutations, in which case that would be asserted
        // here.
        self.interners.intern_clauses(clauses)
    }

    pub fn mk_local_def_ids(self, def_ids: &[LocalDefId]) -> &'tcx List<LocalDefId> {
        // FIXME consider asking the input slice to be sorted to avoid
        // re-interning permutations, in which case that would be asserted
        // here.
        self.intern_local_def_ids(def_ids)
    }

    pub fn mk_patterns_from_iter<I, T>(self, iter: I) -> T::Output
    where
        I: Iterator<Item = T>,
        T: CollectAndApply<ty::Pattern<'tcx>, &'tcx List<ty::Pattern<'tcx>>>,
    {
        T::collect_and_apply(iter, |xs| self.mk_patterns(xs))
    }

    pub fn mk_local_def_ids_from_iter<I, T>(self, iter: I) -> T::Output
    where
        I: Iterator<Item = T>,
        T: CollectAndApply<LocalDefId, &'tcx List<LocalDefId>>,
    {
        T::collect_and_apply(iter, |xs| self.mk_local_def_ids(xs))
    }

    pub fn mk_captures_from_iter<I, T>(self, iter: I) -> T::Output
    where
        I: Iterator<Item = T>,
        T: CollectAndApply<
                &'tcx ty::CapturedPlace<'tcx>,
                &'tcx List<&'tcx ty::CapturedPlace<'tcx>>,
            >,
    {
        T::collect_and_apply(iter, |xs| self.intern_captures(xs))
    }

    pub fn mk_const_list_from_iter<I, T>(self, iter: I) -> T::Output
    where
        I: Iterator<Item = T>,
        T: CollectAndApply<ty::Const<'tcx>, &'tcx List<ty::Const<'tcx>>>,
    {
        T::collect_and_apply(iter, |xs| self.mk_const_list(xs))
    }

    // Unlike various other `mk_*_from_iter` functions, this one uses `I:
    // IntoIterator` instead of `I: Iterator`, and it doesn't have a slice
    // variant, because of the need to combine `inputs` and `output`. This
    // explains the lack of `_from_iter` suffix.
    pub fn mk_fn_sig<I, T>(
        self,
        inputs: I,
        output: I::Item,
        fn_sig_kind: FnSigKind<'tcx>,
    ) -> T::Output
    where
        I: IntoIterator<Item = T>,
        T: CollectAndApply<Ty<'tcx>, ty::FnSig<'tcx>>,
    {
        T::collect_and_apply(inputs.into_iter().chain(iter::once(output)), |xs| ty::FnSig {
            inputs_and_output: self.mk_type_list(xs),
            fn_sig_kind,
        })
    }

    /// `mk_fn_sig`, but with a Rust ABI, and no C-variadic argument.
    pub fn mk_fn_sig_rust_abi<I, T>(
        self,
        inputs: I,
        output: I::Item,
        safety: hir::Safety,
    ) -> T::Output
    where
        I: IntoIterator<Item = T>,
        T: CollectAndApply<Ty<'tcx>, ty::FnSig<'tcx>>,
    {
        self.mk_fn_sig(inputs, output, FnSigKind::default().set_safety(safety))
    }

    /// `mk_fn_sig`, but with a safe Rust ABI, and no C-variadic argument.
    pub fn mk_fn_sig_safe_rust_abi<I, T>(self, inputs: I, output: I::Item) -> T::Output
    where
        I: IntoIterator<Item = T>,
        T: CollectAndApply<Ty<'tcx>, ty::FnSig<'tcx>>,
    {
        self.mk_fn_sig(inputs, output, FnSigKind::default().set_safety(hir::Safety::Safe))
    }

    /// `mk_fn_sig`, but with an **un**safe Rust ABI, and no C-variadic argument.
    pub fn mk_fn_sig_unsafe_rust_abi<I, T>(self, inputs: I, output: I::Item) -> T::Output
    where
        I: IntoIterator<Item = T>,
        T: CollectAndApply<Ty<'tcx>, ty::FnSig<'tcx>>,
    {
        self.mk_fn_sig(inputs, output, FnSigKind::default().set_safety(hir::Safety::Unsafe))
    }

    pub fn mk_poly_existential_predicates_from_iter<I, T>(self, iter: I) -> T::Output
    where
        I: Iterator<Item = T>,
        T: CollectAndApply<
                PolyExistentialPredicate<'tcx>,
                &'tcx List<PolyExistentialPredicate<'tcx>>,
            >,
    {
        T::collect_and_apply(iter, |xs| self.mk_poly_existential_predicates(xs))
    }

    pub fn mk_predefined_opaques_in_body_from_iter<I, T>(self, iter: I) -> T::Output
    where
        I: Iterator<Item = T>,
        T: CollectAndApply<(ty::OpaqueTypeKey<'tcx>, Ty<'tcx>), PredefinedOpaques<'tcx>>,
    {
        T::collect_and_apply(iter, |xs| self.mk_predefined_opaques_in_body(xs))
    }

    pub fn mk_clauses_from_iter<I, T>(self, iter: I) -> T::Output
    where
        I: Iterator<Item = T>,
        T: CollectAndApply<Clause<'tcx>, Clauses<'tcx>>,
    {
        T::collect_and_apply(iter, |xs| self.mk_clauses(xs))
    }

    pub fn mk_type_list_from_iter<I, T>(self, iter: I) -> T::Output
    where
        I: Iterator<Item = T>,
        T: CollectAndApply<Ty<'tcx>, &'tcx List<Ty<'tcx>>>,
    {
        T::collect_and_apply(iter, |xs| self.mk_type_list(xs))
    }

    pub fn mk_args_from_iter<I, T>(self, iter: I) -> T::Output
    where
        I: Iterator<Item = T>,
        T: CollectAndApply<GenericArg<'tcx>, ty::GenericArgsRef<'tcx>>,
    {
        T::collect_and_apply(iter, |xs| self.mk_args(xs))
    }

    pub fn mk_canonical_var_infos_from_iter<I, T>(self, iter: I) -> T::Output
    where
        I: Iterator<Item = T>,
        T: CollectAndApply<CanonicalVarKind<'tcx>, &'tcx List<CanonicalVarKind<'tcx>>>,
    {
        T::collect_and_apply(iter, |xs| self.mk_canonical_var_kinds(xs))
    }

    pub fn mk_place_elems_from_iter<I, T>(self, iter: I) -> T::Output
    where
        I: Iterator<Item = T>,
        T: CollectAndApply<PlaceElem<'tcx>, &'tcx List<PlaceElem<'tcx>>>,
    {
        T::collect_and_apply(iter, |xs| self.mk_place_elems(xs))
    }

    pub fn mk_fields_from_iter<I, T>(self, iter: I) -> T::Output
    where
        I: Iterator<Item = T>,
        T: CollectAndApply<FieldIdx, &'tcx List<FieldIdx>>,
    {
        T::collect_and_apply(iter, |xs| self.mk_fields(xs))
    }

    pub fn mk_args_trait(
        self,
        self_ty: Ty<'tcx>,
        rest: impl IntoIterator<Item = GenericArg<'tcx>>,
    ) -> GenericArgsRef<'tcx> {
        self.mk_args_from_iter(iter::once(self_ty.into()).chain(rest))
    }

    pub fn mk_bound_variable_kinds_from_iter<I, T>(self, iter: I) -> T::Output
    where
        I: Iterator<Item = T>,
        T: CollectAndApply<ty::BoundVariableKind<'tcx>, &'tcx List<ty::BoundVariableKind<'tcx>>>,
    {
        T::collect_and_apply(iter, |xs| self.mk_bound_variable_kinds(xs))
    }

    pub fn mk_outlives_from_iter<I, T>(self, iter: I) -> T::Output
    where
        I: Iterator<Item = T>,
        T: CollectAndApply<
                ty::ArgOutlivesPredicate<'tcx>,
                &'tcx ty::List<ty::ArgOutlivesPredicate<'tcx>>,
            >,
    {
        T::collect_and_apply(iter, |xs| self.mk_outlives(xs))
    }

    /// Emit a lint at `span` from a lint struct (some type that implements `Diagnostic`,
    /// typically generated by `#[derive(Diagnostic)]`).
    #[track_caller]
    pub fn emit_node_span_lint(
        self,
        lint: &'static Lint,
        hir_id: HirId,
        span: impl Into<MultiSpan>,
        decorator: impl for<'a> Diagnostic<'a, ()>,
    ) {
        let level_spec = self.lint_level_spec_at_node(lint, hir_id);
        emit_lint_base(self.sess, lint, level_spec, Some(span.into()), decorator)
    }

    /// Find the appropriate span where `use` and outer attributes can be inserted at.
    pub fn crate_level_attribute_injection_span(self) -> Span {
        let node = self.hir_node(hir::CRATE_HIR_ID);
        let hir::Node::Crate(m) = node else { bug!() };
        m.spans.inject_use_span.shrink_to_lo()
    }

    pub fn disabled_nightly_features<E: rustc_errors::EmissionGuarantee>(
        self,
        diag: &mut Diag<'_, E>,
        features: impl IntoIterator<Item = (String, Symbol)>,
    ) {
        if !self.sess.is_nightly_build() {
            return;
        }

        let span = self.crate_level_attribute_injection_span();
        for (desc, feature) in features {
            // FIXME: make this string translatable
            let msg =
                format!("add `#![feature({feature})]` to the crate attributes to enable{desc}");
            diag.span_suggestion_verbose(
                span,
                msg,
                format!("#![feature({feature})]\n"),
                Applicability::MaybeIncorrect,
            );
        }
    }

    /// Emit a lint from a lint struct (some type that implements `Diagnostic`, typically generated
    /// by `#[derive(Diagnostic)]`).
    #[track_caller]
    pub fn emit_node_lint(
        self,
        lint: &'static Lint,
        id: HirId,
        decorator: impl for<'a> Diagnostic<'a, ()>,
    ) {
        let level_spec = self.lint_level_spec_at_node(lint, id);
        emit_lint_base(self.sess, lint, level_spec, None, decorator);
    }

    pub fn in_scope_traits(self, id: HirId) -> Option<&'tcx [TraitCandidate<'tcx>]> {
        let map = self.in_scope_traits_map(id.owner)?;
        let candidates = map.get(&id.local_id)?;
        Some(candidates)
    }

    pub fn named_bound_var(self, id: HirId) -> Option<resolve_bound_vars::ResolvedArg> {
        debug!(?id, "named_region");
        self.named_variable_map(id.owner).get(&id.local_id).cloned()
    }

    pub fn is_late_bound(self, id: HirId) -> bool {
        self.is_late_bound_map(id.owner).is_some_and(|set| set.contains(&id.local_id))
    }

    pub fn late_bound_vars(self, id: HirId) -> &'tcx List<ty::BoundVariableKind<'tcx>> {
        self.mk_bound_variable_kinds(
            &self
                .late_bound_vars_map(id.owner)
                .get(&id.local_id)
                .cloned()
                .unwrap_or_else(|| bug!("No bound vars found for {}", self.hir_id_to_string(id))),
        )
    }

    /// Given the def-id of an early-bound lifetime on an opaque corresponding to
    /// a duplicated captured lifetime, map it back to the early- or late-bound
    /// lifetime of the function from which it originally as captured. If it is
    /// a late-bound lifetime, this will represent the liberated (`ReLateParam`) lifetime
    /// of the signature.
    // FIXME(RPITIT): if we ever synthesize new lifetimes for RPITITs and not just
    // re-use the generics of the opaque, this function will need to be tweaked slightly.
    pub fn map_opaque_lifetime_to_parent_lifetime(
        self,
        mut opaque_lifetime_param_def_id: LocalDefId,
    ) -> ty::Region<'tcx> {
        debug_assert!(
            matches!(self.def_kind(opaque_lifetime_param_def_id), DefKind::LifetimeParam),
            "{opaque_lifetime_param_def_id:?} is a {}",
            self.def_descr(opaque_lifetime_param_def_id.to_def_id())
        );

        loop {
            let parent = self.local_parent(opaque_lifetime_param_def_id);
            let lifetime_mapping = self.opaque_captured_lifetimes(parent);

            let Some((lifetime, _)) = lifetime_mapping
                .iter()
                .find(|(_, duplicated_param)| *duplicated_param == opaque_lifetime_param_def_id)
            else {
                bug!("duplicated lifetime param should be present");
            };

            match *lifetime {
                resolve_bound_vars::ResolvedArg::EarlyBound(ebv) => {
                    let new_parent = self.local_parent(ebv);

                    // If we map to another opaque, then it should be a parent
                    // of the opaque we mapped from. Continue mapping.
                    if matches!(self.def_kind(new_parent), DefKind::OpaqueTy) {
                        debug_assert_eq!(self.local_parent(parent), new_parent);
                        opaque_lifetime_param_def_id = ebv;
                        continue;
                    }

                    let generics = self.generics_of(new_parent);
                    return ty::Region::new_early_param(
                        self,
                        ty::EarlyParamRegion {
                            index: generics
                                .param_def_id_to_index(self, ebv.to_def_id())
                                .expect("early-bound var should be present in fn generics"),
                            name: self.item_name(ebv.to_def_id()),
                        },
                    );
                }
                resolve_bound_vars::ResolvedArg::LateBound(_, _, lbv) => {
                    let new_parent = self.local_parent(lbv);
                    return ty::Region::new_late_param(
                        self,
                        new_parent.to_def_id(),
                        ty::LateParamRegionKind::Named(lbv.to_def_id()),
                    );
                }
                resolve_bound_vars::ResolvedArg::Error(guar) => {
                    return ty::Region::new_error(self, guar);
                }
                _ => {
                    return ty::Region::new_error_with_message(
                        self,
                        self.def_span(opaque_lifetime_param_def_id),
                        "cannot resolve lifetime",
                    );
                }
            }
        }
    }

    /// Whether `def_id` is a stable const fn (i.e., doesn't need any feature gates to be called).
    ///
    /// When this is `false`, the function may still be callable as a `const fn` due to features
    /// being enabled!
    pub fn is_stable_const_fn(self, def_id: DefId) -> bool {
        self.is_const_fn(def_id)
            && match self.lookup_const_stability(def_id) {
                None => true, // a fn in a non-staged_api crate
                Some(stability) if stability.is_const_stable() => true,
                _ => false,
            }
    }

    /// Whether the trait impl is marked const. This does not consider stability or feature gates.
    pub fn is_const_trait_impl(self, def_id: DefId) -> bool {
        self.def_kind(def_id) == DefKind::Impl { of_trait: true }
            && matches!(
                self.impl_trait_header(def_id).constness,
                hir::Constness::Const { always: false }
            )
    }

    pub fn is_sdylib_interface_build(self) -> bool {
        self.sess.opts.unstable_opts.build_sdylib_interface
    }

    pub fn intrinsic(self, def_id: impl IntoQueryKey<DefId>) -> Option<ty::IntrinsicDef> {
        let def_id = def_id.into_query_key();
        match self.def_kind(def_id) {
            DefKind::Fn | DefKind::AssocFn => self.intrinsic_raw(def_id),
            _ => None,
        }
    }

    pub fn next_trait_solver_globally(self) -> bool {
        self.sess.opts.unstable_opts.next_solver.globally
    }

    pub fn next_trait_solver_in_coherence(self) -> bool {
        self.sess.opts.unstable_opts.next_solver.coherence
    }

    pub fn disable_trait_solver_fast_paths(self) -> bool {
        self.sess.opts.unstable_opts.disable_fast_paths
    }

    pub fn disable_param_env_normalization_hack(self) -> bool {
        self.sess.opts.unstable_opts.disable_param_env_normalization_hack
    }

    pub fn renormalize_rigid_aliases(self) -> bool {
        self.sess.opts.unstable_opts.renormalize_rigid_aliases
    }

    #[allow(rustc::bad_opt_access)]
    pub fn use_typing_mode_post_typeck_until_borrowck(self) -> bool {
        self.next_trait_solver_globally()
            || self.sess.opts.unstable_opts.typing_mode_post_typeck_until_borrowck
    }

    pub fn assumptions_on_binders(self) -> bool {
        self.sess.opts.unstable_opts.assumptions_on_binders
    }

    pub fn is_impl_trait_in_trait(self, def_id: DefId) -> bool {
        self.opt_rpitit_info(def_id).is_some()
    }

    pub fn get_impl_future_output_ty(self, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
        let (def_id, args) = match *ty.kind() {
            ty::Alias(_, ty::AliasTy { kind: ty::Opaque { def_id }, args, .. }) => (def_id, args),
            ty::Alias(_, ty::AliasTy { kind: ty::Projection { def_id }, args, .. })
                if self.is_impl_trait_in_trait(def_id) =>
            {
                (def_id, args)
            }
            _ => return None,
        };

        let future_trait = self.require_lang_item(LangItem::Future, DUMMY_SP);
        let item_def_id = self.associated_item_def_ids(future_trait)[0];

        self.explicit_item_self_bounds(def_id)
            .iter_instantiated_copied(self, args)
            .map(ty::Unnormalized::skip_norm_wip)
            .find_map(|(predicate, _)| {
                predicate
                    .kind()
                    .map_bound(|kind| match kind {
                        ty::ClauseKind::Projection(projection_predicate)
                            if projection_predicate.def_id() == item_def_id =>
                        {
                            projection_predicate.term.as_type()
                        }
                        _ => None,
                    })
                    .no_bound_vars()
                    .flatten()
            })
    }

    /// Named module children from all kinds of items, including imports.
    /// In addition to regular items this list also includes struct and variant constructors, and
    /// items inside `extern {}` blocks because all of them introduce names into parent module.
    ///
    /// Module here is understood in name resolution sense - it can be a `mod` item,
    /// or a crate root, or an enum, or a trait.
    ///
    /// This is not a query, making it a query causes perf regressions
    /// (probably due to hashing spans in `ModChild`ren).
    pub fn module_children_local(self, def_id: LocalDefId) -> &'tcx [ModChild] {
        self.resolutions(()).module_children.get(&def_id).map_or(&[], |v| &v[..])
    }

    /// Return the crate imported by given use item.
    pub fn extern_mod_stmt_cnum(self, def_id: LocalDefId) -> Option<CrateNum> {
        self.resolutions(()).extern_crate_map.get(&def_id).copied()
    }

    pub fn resolver_for_lowering(
        self,
    ) -> (&'tcx Steal<ty::ResolverAstLowering<'tcx>>, &'tcx Steal<ast::Crate>) {
        let (resolver, krate, _) = self.resolver_for_lowering_raw(());
        (resolver, krate)
    }

    pub fn metadata_dep_node(self) -> crate::dep_graph::DepNode {
        make_metadata(self)
    }

    pub fn needs_coroutine_by_move_body_def_id(self, def_id: DefId) -> bool {
        if let Some(hir::CoroutineKind::Desugared(_, hir::CoroutineSource::Closure)) =
            self.coroutine_kind(def_id)
            && let ty::Coroutine(_, args) =
                self.type_of(def_id).instantiate_identity().skip_norm_wip().kind()
            && args.as_coroutine().kind_ty().to_opt_closure_kind() != Some(ty::ClosureKind::FnOnce)
        {
            true
        } else {
            false
        }
    }

    /// Whether this is a trait implementation that has `#[diagnostic::do_not_recommend]`
    pub fn do_not_recommend_impl(self, def_id: DefId) -> bool {
        find_attr!(self, def_id, DoNotRecommend)
    }

    pub fn is_trivial_const(self, def_id: impl IntoQueryKey<DefId>) -> bool {
        let def_id = def_id.into_query_key();
        self.trivial_const(def_id).is_some()
    }

    /// Whether this def is one of the special bin crate entrypoint functions that must have a
    /// monomorphization and also not be internalized in the bin crate.
    pub fn is_entrypoint(self, def_id: DefId) -> bool {
        if self.is_lang_item(def_id, LangItem::Start) {
            return true;
        }
        if let Some((entry_def_id, _)) = self.entry_fn(())
            && entry_def_id == def_id
        {
            return true;
        }
        false
    }
}

pub fn provide(providers: &mut Providers) {
    providers.is_panic_runtime = |tcx, LocalCrate| find_attr!(tcx, crate, PanicRuntime);
    providers.is_compiler_builtins = |tcx, LocalCrate| find_attr!(tcx, crate, CompilerBuiltins);
    providers.has_panic_handler = |tcx, LocalCrate| {
        // We want to check if the panic handler was defined in this crate
        tcx.lang_items().panic_impl().is_some_and(|did| did.is_local())
    };
    providers.source_span = |tcx, def_id| tcx.untracked.source_span.get(def_id).unwrap_or(DUMMY_SP);
}