Merge commit '0cce3f643bfcbb92d5a1bb71858c9cbaff749d6b' into clippyup

[rust.git] / compiler / rustc_middle / src / query / mod.rs

// Each of these queries corresponds to a function pointer field in the
// `Providers` struct for requesting a value of that type, and a method
// on `tcx: TyCtxt` (and `tcx.at(span)`) for doing that request in a way
// which memoizes and does dep-graph tracking, wrapping around the actual
// `Providers` that the driver creates (using several `rustc_*` crates).
//
// The result type of each query must implement `Clone`, and additionally
// `ty::query::values::Value`, which produces an appropriate placeholder
// (error) value if the query resulted in a query cycle.
// Queries marked with `fatal_cycle` do not need the latter implementation,
// as they will raise an fatal error on query cycles instead.
rustc_queries! {
    query trigger_delay_span_bug(key: DefId) -> () {
        desc { "trigger a delay span bug" }
    }

    query resolutions(_: ()) -> &'tcx ty::ResolverOutputs {
        eval_always
        no_hash
        desc { "get the resolver outputs" }
    }

    /// Represents crate as a whole (as distinct from the top-level crate module).
    /// If you call `hir_crate` (e.g., indirectly by calling `tcx.hir().krate()`),
    /// we will have to assume that any change means that you need to be recompiled.
    /// This is because the `hir_crate` query gives you access to all other items.
    /// To avoid this fate, do not call `tcx.hir().krate()`; instead,
    /// prefer wrappers like `tcx.visit_all_items_in_krate()`.
    query hir_crate(key: ()) -> &'tcx Crate<'tcx> {
        eval_always
        no_hash
        desc { "get the crate HIR" }
    }

    /// The indexed HIR. This can be conveniently accessed by `tcx.hir()`.
    /// Avoid calling this query directly.
    query index_hir(_: ()) -> &'tcx crate::hir::IndexedHir<'tcx> {
        eval_always
        no_hash
        desc { "index HIR" }
    }

    /// The items in a module.
    ///
    /// This can be conveniently accessed by `tcx.hir().visit_item_likes_in_module`.
    /// Avoid calling this query directly.
    query hir_module_items(key: LocalDefId) -> &'tcx hir::ModuleItems {
        eval_always
        desc { |tcx| "HIR module items in `{}`", tcx.def_path_str(key.to_def_id()) }
    }

    /// Gives access to the HIR node for the HIR owner `key`.
    ///
    /// This can be conveniently accessed by methods on `tcx.hir()`.
    /// Avoid calling this query directly.
    query hir_owner(key: LocalDefId) -> Option<crate::hir::Owner<'tcx>> {
        eval_always
        desc { |tcx| "HIR owner of `{}`", tcx.def_path_str(key.to_def_id()) }
    }

    /// Gives access to the HIR node's parent for the HIR owner `key`.
    ///
    /// This can be conveniently accessed by methods on `tcx.hir()`.
    /// Avoid calling this query directly.
    query hir_owner_parent(key: LocalDefId) -> hir::HirId {
        eval_always
        desc { |tcx| "HIR parent of `{}`", tcx.def_path_str(key.to_def_id()) }
    }

    /// Gives access to the HIR nodes and bodies inside the HIR owner `key`.
    ///
    /// This can be conveniently accessed by methods on `tcx.hir()`.
    /// Avoid calling this query directly.
    query hir_owner_nodes(key: LocalDefId) -> Option<&'tcx crate::hir::OwnerNodes<'tcx>> {
        eval_always
        desc { |tcx| "HIR owner items in `{}`", tcx.def_path_str(key.to_def_id()) }
    }

    /// Gives access to the HIR attributes inside the HIR owner `key`.
    ///
    /// This can be conveniently accessed by methods on `tcx.hir()`.
    /// Avoid calling this query directly.
    query hir_attrs(key: LocalDefId) -> rustc_middle::hir::AttributeMap<'tcx> {
        eval_always
        desc { |tcx| "HIR owner attributes in `{}`", tcx.def_path_str(key.to_def_id()) }
    }

    /// Computes the `DefId` of the corresponding const parameter in case the `key` is a
    /// const argument and returns `None` otherwise.
    ///
    /// ```ignore (incomplete)
    /// let a = foo::<7>();
    /// //            ^ Calling `opt_const_param_of` for this argument,
    ///
    /// fn foo<const N: usize>()
    /// //           ^ returns this `DefId`.
    ///
    /// fn bar() {
    /// // ^ While calling `opt_const_param_of` for other bodies returns `None`.
    /// }
    /// ```
    // It looks like caching this query on disk actually slightly
    // worsened performance in #74376.
    //
    // Once const generics are more prevalently used, we might want to
    // consider only caching calls returning `Some`.
    query opt_const_param_of(key: LocalDefId) -> Option<DefId> {
        desc { |tcx| "computing the optional const parameter of `{}`", tcx.def_path_str(key.to_def_id()) }
    }

    /// Given the def_id of a const-generic parameter, computes the associated default const
    /// parameter. e.g. `fn example<const N: usize=3>` called on `N` would return `3`.
    query const_param_default(param: DefId) -> &'tcx ty::Const<'tcx> {
        desc { |tcx| "compute const default for a given parameter `{}`", tcx.def_path_str(param)  }
    }

    /// Records the type of every item.
    query type_of(key: DefId) -> Ty<'tcx> {
        desc { |tcx| "computing type of `{}`", tcx.def_path_str(key) }
        cache_on_disk_if { key.is_local() }
    }

    query analysis(key: ()) -> Result<(), ErrorReported> {
        eval_always
        desc { "running analysis passes on this crate" }
    }

    /// Maps from the `DefId` of an item (trait/struct/enum/fn) to its
    /// associated generics.
    query generics_of(key: DefId) -> ty::Generics {
        desc { |tcx| "computing generics of `{}`", tcx.def_path_str(key) }
        storage(ArenaCacheSelector<'tcx>)
        cache_on_disk_if { key.is_local() }
    }

    /// Maps from the `DefId` of an item (trait/struct/enum/fn) to the
    /// predicates (where-clauses) that must be proven true in order
    /// to reference it. This is almost always the "predicates query"
    /// that you want.
    ///
    /// `predicates_of` builds on `predicates_defined_on` -- in fact,
    /// it is almost always the same as that query, except for the
    /// case of traits. For traits, `predicates_of` contains
    /// an additional `Self: Trait<...>` predicate that users don't
    /// actually write. This reflects the fact that to invoke the
    /// trait (e.g., via `Default::default`) you must supply types
    /// that actually implement the trait. (However, this extra
    /// predicate gets in the way of some checks, which are intended
    /// to operate over only the actual where-clauses written by the
    /// user.)
    query predicates_of(key: DefId) -> ty::GenericPredicates<'tcx> {
        desc { |tcx| "computing predicates of `{}`", tcx.def_path_str(key) }
        cache_on_disk_if { key.is_local() }
    }

    /// Returns the list of bounds that can be used for
    /// `SelectionCandidate::ProjectionCandidate(_)` and
    /// `ProjectionTyCandidate::TraitDef`.
    /// Specifically this is the bounds written on the trait's type
    /// definition, or those after the `impl` keyword
    ///
    /// ```ignore (incomplete)
    /// type X: Bound + 'lt
    /// //      ^^^^^^^^^^^
    /// impl Debug + Display
    /// //   ^^^^^^^^^^^^^^^
    /// ```
    ///
    /// `key` is the `DefId` of the associated type or opaque type.
    ///
    /// Bounds from the parent (e.g. with nested impl trait) are not included.
    query explicit_item_bounds(key: DefId) -> &'tcx [(ty::Predicate<'tcx>, Span)] {
        desc { |tcx| "finding item bounds for `{}`", tcx.def_path_str(key) }
    }

    /// Elaborated version of the predicates from `explicit_item_bounds`.
    ///
    /// For example:
    ///
    /// ```
    /// trait MyTrait {
    ///     type MyAType: Eq + ?Sized;
    /// }
    /// ```
    ///
    /// `explicit_item_bounds` returns `[<Self as MyTrait>::MyAType: Eq]`,
    /// and `item_bounds` returns
    /// ```text
    /// [
    ///     <Self as Trait>::MyAType: Eq,
    ///     <Self as Trait>::MyAType: PartialEq<<Self as Trait>::MyAType>
    /// ]
    /// ```
    ///
    /// Bounds from the parent (e.g. with nested impl trait) are not included.
    query item_bounds(key: DefId) -> &'tcx ty::List<ty::Predicate<'tcx>> {
        desc { |tcx| "elaborating item bounds for `{}`", tcx.def_path_str(key) }
    }

    query native_libraries(_: CrateNum) -> Lrc<Vec<NativeLib>> {
        desc { "looking up the native libraries of a linked crate" }
    }

    query lint_levels(_: ()) -> LintLevelMap {
        storage(ArenaCacheSelector<'tcx>)
        eval_always
        desc { "computing the lint levels for items in this crate" }
    }

    query parent_module_from_def_id(key: LocalDefId) -> LocalDefId {
        eval_always
        desc { |tcx| "parent module of `{}`", tcx.def_path_str(key.to_def_id()) }
    }

    query expn_that_defined(key: DefId) -> rustc_span::ExpnId {
        // This query reads from untracked data in definitions.
        eval_always
        desc { |tcx| "expansion that defined `{}`", tcx.def_path_str(key) }
    }

    query is_panic_runtime(_: CrateNum) -> bool {
        fatal_cycle
        desc { "checking if the crate is_panic_runtime" }
    }

    /// Fetch the THIR for a given body. If typeck for that body failed, returns an empty `Thir`.
    query thir_body(key: ty::WithOptConstParam<LocalDefId>) -> (&'tcx Steal<thir::Thir<'tcx>>, thir::ExprId) {
        // Perf tests revealed that hashing THIR is inefficient (see #85729).
        no_hash
        desc { |tcx| "building THIR for `{}`", tcx.def_path_str(key.did.to_def_id()) }
    }

    /// Create a THIR tree for debugging.
    query thir_tree(key: ty::WithOptConstParam<LocalDefId>) -> String {
        no_hash
        desc { |tcx| "constructing THIR tree for `{}`", tcx.def_path_str(key.did.to_def_id()) }
    }

    /// Set of all the `DefId`s in this crate that have MIR associated with
    /// them. This includes all the body owners, but also things like struct
    /// constructors.
    query mir_keys(_: ()) -> FxHashSet<LocalDefId> {
        storage(ArenaCacheSelector<'tcx>)
        desc { "getting a list of all mir_keys" }
    }

    /// Maps DefId's that have an associated `mir::Body` to the result
    /// of the MIR const-checking pass. This is the set of qualifs in
    /// the final value of a `const`.
    query mir_const_qualif(key: DefId) -> mir::ConstQualifs {
        desc { |tcx| "const checking `{}`", tcx.def_path_str(key) }
        cache_on_disk_if { key.is_local() }
    }
    query mir_const_qualif_const_arg(
        key: (LocalDefId, DefId)
    ) -> mir::ConstQualifs {
        desc {
            |tcx| "const checking the const argument `{}`",
            tcx.def_path_str(key.0.to_def_id())
        }
    }

    /// Fetch the MIR for a given `DefId` right after it's built - this includes
    /// unreachable code.
    query mir_built(key: ty::WithOptConstParam<LocalDefId>) -> &'tcx Steal<mir::Body<'tcx>> {
        desc { |tcx| "building MIR for `{}`", tcx.def_path_str(key.did.to_def_id()) }
    }

    /// Fetch the MIR for a given `DefId` up till the point where it is
    /// ready for const qualification.
    ///
    /// See the README for the `mir` module for details.
    query mir_const(key: ty::WithOptConstParam<LocalDefId>) -> &'tcx Steal<mir::Body<'tcx>> {
        desc {
            |tcx| "processing MIR for {}`{}`",
            if key.const_param_did.is_some() { "the const argument " } else { "" },
            tcx.def_path_str(key.did.to_def_id()),
        }
        no_hash
    }

    /// Try to build an abstract representation of the given constant.
    query mir_abstract_const(
        key: DefId
    ) -> Result<Option<&'tcx [mir::abstract_const::Node<'tcx>]>, ErrorReported> {
        desc {
            |tcx| "building an abstract representation for {}", tcx.def_path_str(key),
        }
    }
    /// Try to build an abstract representation of the given constant.
    query mir_abstract_const_of_const_arg(
        key: (LocalDefId, DefId)
    ) -> Result<Option<&'tcx [mir::abstract_const::Node<'tcx>]>, ErrorReported> {
        desc {
            |tcx|
            "building an abstract representation for the const argument {}",
            tcx.def_path_str(key.0.to_def_id()),
        }
    }

    query try_unify_abstract_consts(key: (
        (ty::WithOptConstParam<DefId>, SubstsRef<'tcx>),
        (ty::WithOptConstParam<DefId>, SubstsRef<'tcx>)
    )) -> bool {
        desc {
            |tcx| "trying to unify the generic constants {} and {}",
            tcx.def_path_str(key.0.0.did), tcx.def_path_str(key.1.0.did)
        }
    }

    query mir_drops_elaborated_and_const_checked(
        key: ty::WithOptConstParam<LocalDefId>
    ) -> &'tcx Steal<mir::Body<'tcx>> {
        no_hash
        desc { |tcx| "elaborating drops for `{}`", tcx.def_path_str(key.did.to_def_id()) }
    }

    query mir_for_ctfe(
        key: DefId
    ) -> &'tcx mir::Body<'tcx> {
        desc { |tcx| "caching mir of `{}` for CTFE", tcx.def_path_str(key) }
        cache_on_disk_if { key.is_local() }
    }

    query mir_for_ctfe_of_const_arg(key: (LocalDefId, DefId)) -> &'tcx mir::Body<'tcx> {
        desc {
            |tcx| "MIR for CTFE of the const argument `{}`",
            tcx.def_path_str(key.0.to_def_id())
        }
    }

    query mir_promoted(key: ty::WithOptConstParam<LocalDefId>) ->
        (
            &'tcx Steal<mir::Body<'tcx>>,
            &'tcx Steal<IndexVec<mir::Promoted, mir::Body<'tcx>>>
        ) {
        no_hash
        desc {
            |tcx| "processing {}`{}`",
            if key.const_param_did.is_some() { "the const argument " } else { "" },
            tcx.def_path_str(key.did.to_def_id()),
        }
    }

    /// MIR after our optimization passes have run. This is MIR that is ready
    /// for codegen. This is also the only query that can fetch non-local MIR, at present.
    query optimized_mir(key: DefId) -> &'tcx mir::Body<'tcx> {
        desc { |tcx| "optimizing MIR for `{}`", tcx.def_path_str(key) }
        cache_on_disk_if { key.is_local() }
    }

    /// Returns coverage summary info for a function, after executing the `InstrumentCoverage`
    /// MIR pass (assuming the -Zinstrument-coverage option is enabled).
    query coverageinfo(key: ty::InstanceDef<'tcx>) -> mir::CoverageInfo {
        desc { |tcx| "retrieving coverage info from MIR for `{}`", tcx.def_path_str(key.def_id()) }
        storage(ArenaCacheSelector<'tcx>)
    }

    /// Returns the name of the file that contains the function body, if instrumented for coverage.
    query covered_file_name(key: DefId) -> Option<Symbol> {
        desc {
            |tcx| "retrieving the covered file name, if instrumented, for `{}`",
            tcx.def_path_str(key)
        }
        storage(ArenaCacheSelector<'tcx>)
        cache_on_disk_if { key.is_local() }
    }

    /// Returns the `CodeRegions` for a function that has instrumented coverage, in case the
    /// function was optimized out before codegen, and before being added to the Coverage Map.
    query covered_code_regions(key: DefId) -> Vec<&'tcx mir::coverage::CodeRegion> {
        desc {
            |tcx| "retrieving the covered `CodeRegion`s, if instrumented, for `{}`",
            tcx.def_path_str(key)
        }
        storage(ArenaCacheSelector<'tcx>)
        cache_on_disk_if { key.is_local() }
    }

    /// The `DefId` is the `DefId` of the containing MIR body. Promoteds do not have their own
    /// `DefId`. This function returns all promoteds in the specified body. The body references
    /// promoteds by the `DefId` and the `mir::Promoted` index. This is necessary, because
    /// after inlining a body may refer to promoteds from other bodies. In that case you still
    /// need to use the `DefId` of the original body.
    query promoted_mir(key: DefId) -> &'tcx IndexVec<mir::Promoted, mir::Body<'tcx>> {
        desc { |tcx| "optimizing promoted MIR for `{}`", tcx.def_path_str(key) }
        cache_on_disk_if { key.is_local() }
    }
    query promoted_mir_of_const_arg(
        key: (LocalDefId, DefId)
    ) -> &'tcx IndexVec<mir::Promoted, mir::Body<'tcx>> {
        desc {
            |tcx| "optimizing promoted MIR for the const argument `{}`",
            tcx.def_path_str(key.0.to_def_id()),
        }
    }

    /// Erases regions from `ty` to yield a new type.
    /// Normally you would just use `tcx.erase_regions(value)`,
    /// however, which uses this query as a kind of cache.
    query erase_regions_ty(ty: Ty<'tcx>) -> Ty<'tcx> {
        // This query is not expected to have input -- as a result, it
        // is not a good candidates for "replay" because it is essentially a
        // pure function of its input (and hence the expectation is that
        // no caller would be green **apart** from just these
        // queries). Making it anonymous avoids hashing the result, which
        // may save a bit of time.
        anon
        desc { "erasing regions from `{:?}`", ty }
    }

    query wasm_import_module_map(_: CrateNum) -> FxHashMap<DefId, String> {
        storage(ArenaCacheSelector<'tcx>)
        desc { "wasm import module map" }
    }

    /// Maps from the `DefId` of an item (trait/struct/enum/fn) to the
    /// predicates (where-clauses) directly defined on it. This is
    /// equal to the `explicit_predicates_of` predicates plus the
    /// `inferred_outlives_of` predicates.
    query predicates_defined_on(key: DefId) -> ty::GenericPredicates<'tcx> {
        desc { |tcx| "computing predicates of `{}`", tcx.def_path_str(key) }
    }

    /// Returns everything that looks like a predicate written explicitly
    /// by the user on a trait item.
    ///
    /// Traits are unusual, because predicates on associated types are
    /// converted into bounds on that type for backwards compatibility:
    ///
    /// trait X where Self::U: Copy { type U; }
    ///
    /// becomes
    ///
    /// trait X { type U: Copy; }
    ///
    /// `explicit_predicates_of` and `explicit_item_bounds` will then take
    /// the appropriate subsets of the predicates here.
    query trait_explicit_predicates_and_bounds(key: LocalDefId) -> ty::GenericPredicates<'tcx> {
        desc { |tcx| "computing explicit predicates of trait `{}`", tcx.def_path_str(key.to_def_id()) }
    }

    /// Returns the predicates written explicitly by the user.
    query explicit_predicates_of(key: DefId) -> ty::GenericPredicates<'tcx> {
        desc { |tcx| "computing explicit predicates of `{}`", tcx.def_path_str(key) }
    }

    /// Returns the inferred outlives predicates (e.g., for `struct
    /// Foo<'a, T> { x: &'a T }`, this would return `T: 'a`).
    query inferred_outlives_of(key: DefId) -> &'tcx [(ty::Predicate<'tcx>, Span)] {
        desc { |tcx| "computing inferred outlives predicates of `{}`", tcx.def_path_str(key) }
    }

    /// Maps from the `DefId` of a trait to the list of
    /// super-predicates. This is a subset of the full list of
    /// predicates. We store these in a separate map because we must
    /// evaluate them even during type conversion, often before the
    /// full predicates are available (note that supertraits have
    /// additional acyclicity requirements).
    query super_predicates_of(key: DefId) -> ty::GenericPredicates<'tcx> {
        desc { |tcx| "computing the super predicates of `{}`", tcx.def_path_str(key) }
    }

    /// The `Option<Ident>` is the name of an associated type. If it is `None`, then this query
    /// returns the full set of predicates. If `Some<Ident>`, then the query returns only the
    /// subset of super-predicates that reference traits that define the given associated type.
    /// This is used to avoid cycles in resolving types like `T::Item`.
    query super_predicates_that_define_assoc_type(key: (DefId, Option<rustc_span::symbol::Ident>)) -> ty::GenericPredicates<'tcx> {
        desc { |tcx| "computing the super traits of `{}`{}",
            tcx.def_path_str(key.0),
            if let Some(assoc_name) = key.1 { format!(" with associated type name `{}`", assoc_name) } else { "".to_string() },
        }
    }

    /// To avoid cycles within the predicates of a single item we compute
    /// per-type-parameter predicates for resolving `T::AssocTy`.
    query type_param_predicates(key: (DefId, LocalDefId, rustc_span::symbol::Ident)) -> ty::GenericPredicates<'tcx> {
        desc { |tcx| "computing the bounds for type parameter `{}`", {
            let id = tcx.hir().local_def_id_to_hir_id(key.1);
            tcx.hir().ty_param_name(id)
        }}
    }

    query trait_def(key: DefId) -> ty::TraitDef {
        desc { |tcx| "computing trait definition for `{}`", tcx.def_path_str(key) }
        storage(ArenaCacheSelector<'tcx>)
    }
    query adt_def(key: DefId) -> &'tcx ty::AdtDef {
        desc { |tcx| "computing ADT definition for `{}`", tcx.def_path_str(key) }
    }
    query adt_destructor(key: DefId) -> Option<ty::Destructor> {
        desc { |tcx| "computing `Drop` impl for `{}`", tcx.def_path_str(key) }
    }

    // The cycle error here should be reported as an error by `check_representable`.
    // We consider the type as Sized in the meanwhile to avoid
    // further errors (done in impl Value for AdtSizedConstraint).
    // Use `cycle_delay_bug` to delay the cycle error here to be emitted later
    // in case we accidentally otherwise don't emit an error.
    query adt_sized_constraint(
        key: DefId
    ) -> AdtSizedConstraint<'tcx> {
        desc { |tcx| "computing `Sized` constraints for `{}`", tcx.def_path_str(key) }
        cycle_delay_bug
    }

    query adt_dtorck_constraint(
        key: DefId
    ) -> Result<DtorckConstraint<'tcx>, NoSolution> {
        desc { |tcx| "computing drop-check constraints for `{}`", tcx.def_path_str(key) }
    }

    /// Returns `true` if this is a const fn, use the `is_const_fn` to know whether your crate
    /// actually sees it as const fn (e.g., the const-fn-ness might be unstable and you might
    /// not have the feature gate active).
    ///
    /// **Do not call this function manually.** It is only meant to cache the base data for the
    /// `is_const_fn` function.
    query is_const_fn_raw(key: DefId) -> bool {
        desc { |tcx| "checking if item is const fn: `{}`", tcx.def_path_str(key) }
    }

    /// Returns `true` if this is a const `impl`. **Do not call this function manually.**
    ///
    /// This query caches the base data for the `is_const_impl` helper function, which also
    /// takes into account stability attributes (e.g., `#[rustc_const_unstable]`).
    query is_const_impl_raw(key: DefId) -> bool {
        desc { |tcx| "checking if item is const impl: `{}`", tcx.def_path_str(key) }
    }

    query asyncness(key: DefId) -> hir::IsAsync {
        desc { |tcx| "checking if the function is async: `{}`", tcx.def_path_str(key) }
    }

    /// Returns `true` if calls to the function may be promoted.
    ///
    /// This is either because the function is e.g., a tuple-struct or tuple-variant
    /// constructor, or because it has the `#[rustc_promotable]` attribute. The attribute should
    /// be removed in the future in favour of some form of check which figures out whether the
    /// function does not inspect the bits of any of its arguments (so is essentially just a
    /// constructor function).
    query is_promotable_const_fn(key: DefId) -> bool {
        desc { |tcx| "checking if item is promotable: `{}`", tcx.def_path_str(key) }
    }

    /// Returns `true` if this is a foreign item (i.e., linked via `extern { ... }`).
    query is_foreign_item(key: DefId) -> bool {
        desc { |tcx| "checking if `{}` is a foreign item", tcx.def_path_str(key) }
    }

    /// Returns `Some(mutability)` if the node pointed to by `def_id` is a static item.
    query static_mutability(def_id: DefId) -> Option<hir::Mutability> {
        desc { |tcx| "looking up static mutability of `{}`", tcx.def_path_str(def_id) }
    }

    /// Returns `Some(generator_kind)` if the node pointed to by `def_id` is a generator.
    query generator_kind(def_id: DefId) -> Option<hir::GeneratorKind> {
        desc { |tcx| "looking up generator kind of `{}`", tcx.def_path_str(def_id) }
    }

    /// Gets a map with the variance of every item; use `item_variance` instead.
    query crate_variances(_: ()) -> ty::CrateVariancesMap<'tcx> {
        storage(ArenaCacheSelector<'tcx>)
        desc { "computing the variances for items in this crate" }
    }

    /// Maps from the `DefId` of a type or region parameter to its (inferred) variance.
    query variances_of(def_id: DefId) -> &'tcx [ty::Variance] {
        desc { |tcx| "computing the variances of `{}`", tcx.def_path_str(def_id) }
    }

    /// Maps from thee `DefId` of a type to its (inferred) outlives.
    query inferred_outlives_crate(_: ()) -> ty::CratePredicatesMap<'tcx> {
        storage(ArenaCacheSelector<'tcx>)
        desc { "computing the inferred outlives predicates for items in this crate" }
    }

    /// Maps from an impl/trait `DefId to a list of the `DefId`s of its items.
    query associated_item_def_ids(key: DefId) -> &'tcx [DefId] {
        desc { |tcx| "collecting associated items of `{}`", tcx.def_path_str(key) }
    }

    /// Maps from a trait item to the trait item "descriptor".
    query associated_item(key: DefId) -> ty::AssocItem {
        desc { |tcx| "computing associated item data for `{}`", tcx.def_path_str(key) }
        storage(ArenaCacheSelector<'tcx>)
    }

    /// Collects the associated items defined on a trait or impl.
    query associated_items(key: DefId) -> ty::AssocItems<'tcx> {
        storage(ArenaCacheSelector<'tcx>)
        desc { |tcx| "collecting associated items of {}", tcx.def_path_str(key) }
    }

    /// Given an `impl_id`, return the trait it implements.
    /// Return `None` if this is an inherent impl.
    query impl_trait_ref(impl_id: DefId) -> Option<ty::TraitRef<'tcx>> {
        desc { |tcx| "computing trait implemented by `{}`", tcx.def_path_str(impl_id) }
    }
    query impl_polarity(impl_id: DefId) -> ty::ImplPolarity {
        desc { |tcx| "computing implementation polarity of `{}`", tcx.def_path_str(impl_id) }
    }

    query issue33140_self_ty(key: DefId) -> Option<ty::Ty<'tcx>> {
        desc { |tcx| "computing Self type wrt issue #33140 `{}`", tcx.def_path_str(key) }
    }

    /// Maps a `DefId` of a type to a list of its inherent impls.
    /// Contains implementations of methods that are inherent to a type.
    /// Methods in these implementations don't need to be exported.
    query inherent_impls(key: DefId) -> &'tcx [DefId] {
        desc { |tcx| "collecting inherent impls for `{}`", tcx.def_path_str(key) }
        eval_always
    }

    /// The result of unsafety-checking this `LocalDefId`.
    query unsafety_check_result(key: LocalDefId) -> &'tcx mir::UnsafetyCheckResult {
        desc { |tcx| "unsafety-checking `{}`", tcx.def_path_str(key.to_def_id()) }
        cache_on_disk_if { true }
    }
    query unsafety_check_result_for_const_arg(key: (LocalDefId, DefId)) -> &'tcx mir::UnsafetyCheckResult {
        desc {
            |tcx| "unsafety-checking the const argument `{}`",
            tcx.def_path_str(key.0.to_def_id())
        }
    }

    /// Unsafety-check this `LocalDefId` with THIR unsafeck. This should be
    /// used with `-Zthir-unsafeck`.
    query thir_check_unsafety(key: LocalDefId) {
        desc { |tcx| "unsafety-checking `{}`", tcx.def_path_str(key.to_def_id()) }
        cache_on_disk_if { true }
    }
    query thir_check_unsafety_for_const_arg(key: (LocalDefId, DefId)) {
        desc {
            |tcx| "unsafety-checking the const argument `{}`",
            tcx.def_path_str(key.0.to_def_id())
        }
    }

    /// HACK: when evaluated, this reports a "unsafe derive on repr(packed)" error.
    ///
    /// Unsafety checking is executed for each method separately, but we only want
    /// to emit this error once per derive. As there are some impls with multiple
    /// methods, we use a query for deduplication.
    query unsafe_derive_on_repr_packed(key: LocalDefId) -> () {
        desc { |tcx| "processing `{}`", tcx.def_path_str(key.to_def_id()) }
    }

    /// The signature of functions.
    query fn_sig(key: DefId) -> ty::PolyFnSig<'tcx> {
        desc { |tcx| "computing function signature of `{}`", tcx.def_path_str(key) }
    }

    query lint_mod(key: LocalDefId) -> () {
        desc { |tcx| "linting {}", describe_as_module(key, tcx) }
    }

    /// Checks the attributes in the module.
    query check_mod_attrs(key: LocalDefId) -> () {
        desc { |tcx| "checking attributes in {}", describe_as_module(key, tcx) }
    }

    query check_mod_unstable_api_usage(key: LocalDefId) -> () {
        desc { |tcx| "checking for unstable API usage in {}", describe_as_module(key, tcx) }
    }

    /// Checks the const bodies in the module for illegal operations (e.g. `if` or `loop`).
    query check_mod_const_bodies(key: LocalDefId) -> () {
        desc { |tcx| "checking consts in {}", describe_as_module(key, tcx) }
    }

    /// Checks the loops in the module.
    query check_mod_loops(key: LocalDefId) -> () {
        desc { |tcx| "checking loops in {}", describe_as_module(key, tcx) }
    }

    query check_mod_naked_functions(key: LocalDefId) -> () {
        desc { |tcx| "checking naked functions in {}", describe_as_module(key, tcx) }
    }

    query check_mod_item_types(key: LocalDefId) -> () {
        desc { |tcx| "checking item types in {}", describe_as_module(key, tcx) }
    }

    query check_mod_privacy(key: LocalDefId) -> () {
        desc { |tcx| "checking privacy in {}", describe_as_module(key, tcx) }
    }

    query check_mod_intrinsics(key: LocalDefId) -> () {
        desc { |tcx| "checking intrinsics in {}", describe_as_module(key, tcx) }
    }

    query check_mod_liveness(key: LocalDefId) -> () {
        desc { |tcx| "checking liveness of variables in {}", describe_as_module(key, tcx) }
    }

    query check_mod_impl_wf(key: LocalDefId) -> () {
        desc { |tcx| "checking that impls are well-formed in {}", describe_as_module(key, tcx) }
    }

    query collect_mod_item_types(key: LocalDefId) -> () {
        desc { |tcx| "collecting item types in {}", describe_as_module(key, tcx) }
    }

    /// Caches `CoerceUnsized` kinds for impls on custom types.
    query coerce_unsized_info(key: DefId)
        -> ty::adjustment::CoerceUnsizedInfo {
            desc { |tcx| "computing CoerceUnsized info for `{}`", tcx.def_path_str(key) }
        }

    query typeck_item_bodies(_: ()) -> () {
        desc { "type-checking all item bodies" }
    }

    query typeck(key: LocalDefId) -> &'tcx ty::TypeckResults<'tcx> {
        desc { |tcx| "type-checking `{}`", tcx.def_path_str(key.to_def_id()) }
        cache_on_disk_if { true }
    }
    query typeck_const_arg(
        key: (LocalDefId, DefId)
    ) -> &'tcx ty::TypeckResults<'tcx> {
        desc {
            |tcx| "type-checking the const argument `{}`",
            tcx.def_path_str(key.0.to_def_id()),
        }
    }
    query diagnostic_only_typeck(key: LocalDefId) -> &'tcx ty::TypeckResults<'tcx> {
        desc { |tcx| "type-checking `{}`", tcx.def_path_str(key.to_def_id()) }
        cache_on_disk_if { true }
        load_cached(tcx, id) {
            let typeck_results: Option<ty::TypeckResults<'tcx>> = tcx
                .on_disk_cache().as_ref()
                .and_then(|c| c.try_load_query_result(*tcx, id));

            typeck_results.map(|x| &*tcx.arena.alloc(x))
        }
    }

    query used_trait_imports(key: LocalDefId) -> &'tcx FxHashSet<LocalDefId> {
        desc { |tcx| "used_trait_imports `{}`", tcx.def_path_str(key.to_def_id()) }
        cache_on_disk_if { true }
    }

    query has_typeck_results(def_id: DefId) -> bool {
        desc { |tcx| "checking whether `{}` has a body", tcx.def_path_str(def_id) }
    }

    query coherent_trait(def_id: DefId) -> () {
        desc { |tcx| "coherence checking all impls of trait `{}`", tcx.def_path_str(def_id) }
    }

    /// Borrow-checks the function body. If this is a closure, returns
    /// additional requirements that the closure's creator must verify.
    query mir_borrowck(key: LocalDefId) -> &'tcx mir::BorrowCheckResult<'tcx> {
        desc { |tcx| "borrow-checking `{}`", tcx.def_path_str(key.to_def_id()) }
        cache_on_disk_if(tcx, opt_result) {
            tcx.is_closure(key.to_def_id())
                || opt_result.map_or(false, |r| !r.concrete_opaque_types.is_empty())
        }
    }
    query mir_borrowck_const_arg(key: (LocalDefId, DefId)) -> &'tcx mir::BorrowCheckResult<'tcx> {
        desc {
            |tcx| "borrow-checking the const argument`{}`",
            tcx.def_path_str(key.0.to_def_id())
        }
    }

    /// Gets a complete map from all types to their inherent impls.
    /// Not meant to be used directly outside of coherence.
    query crate_inherent_impls(k: ()) -> CrateInherentImpls {
        storage(ArenaCacheSelector<'tcx>)
        eval_always
        desc { "all inherent impls defined in crate" }
    }

    /// Checks all types in the crate for overlap in their inherent impls. Reports errors.
    /// Not meant to be used directly outside of coherence.
    query crate_inherent_impls_overlap_check(_: ())
        -> () {
        eval_always
        desc { "check for overlap between inherent impls defined in this crate" }
    }

    /// Check whether the function has any recursion that could cause the inliner to trigger
    /// a cycle. Returns the call stack causing the cycle. The call stack does not contain the
    /// current function, just all intermediate functions.
    query mir_callgraph_reachable(key: (ty::Instance<'tcx>, LocalDefId)) -> bool {
        fatal_cycle
        desc { |tcx|
            "computing if `{}` (transitively) calls `{}`",
            key.0,
            tcx.def_path_str(key.1.to_def_id()),
        }
    }

    /// Obtain all the calls into other local functions
    query mir_inliner_callees(key: ty::InstanceDef<'tcx>) -> &'tcx [(DefId, SubstsRef<'tcx>)] {
        fatal_cycle
        desc { |tcx|
            "computing all local function calls in `{}`",
            tcx.def_path_str(key.def_id()),
        }
    }

    /// Evaluates a constant and returns the computed allocation.
    ///
    /// **Do not use this** directly, use the `tcx.eval_static_initializer` wrapper.
    query eval_to_allocation_raw(key: ty::ParamEnvAnd<'tcx, GlobalId<'tcx>>)
        -> EvalToAllocationRawResult<'tcx> {
        desc { |tcx|
            "const-evaluating + checking `{}`",
            key.value.display(tcx)
        }
        cache_on_disk_if { true }
    }

    /// Evaluates const items or anonymous constants
    /// (such as enum variant explicit discriminants or array lengths)
    /// into a representation suitable for the type system and const generics.
    ///
    /// **Do not use this** directly, use one of the following wrappers: `tcx.const_eval_poly`,
    /// `tcx.const_eval_resolve`, `tcx.const_eval_instance`, or `tcx.const_eval_global_id`.
    query eval_to_const_value_raw(key: ty::ParamEnvAnd<'tcx, GlobalId<'tcx>>)
        -> EvalToConstValueResult<'tcx> {
        desc { |tcx|
            "simplifying constant for the type system `{}`",
            key.value.display(tcx)
        }
        cache_on_disk_if { true }
    }

    /// Convert an evaluated constant to a type level constant or
    /// return `None` if that is not possible.
    query const_to_valtree(
        key: ty::ParamEnvAnd<'tcx, ConstAlloc<'tcx>>
    ) -> Option<ty::ValTree<'tcx>> {
        desc { "destructure constant" }
    }

    /// Destructure a constant ADT or array into its variant index and its
    /// field values.
    query destructure_const(
        key: ty::ParamEnvAnd<'tcx, &'tcx ty::Const<'tcx>>
    ) -> mir::DestructuredConst<'tcx> {
        desc { "destructure constant" }
    }

    /// Dereference a constant reference or raw pointer and turn the result into a constant
    /// again.
    query deref_const(
        key: ty::ParamEnvAnd<'tcx, &'tcx ty::Const<'tcx>>
    ) -> &'tcx ty::Const<'tcx> {
        desc { "deref constant" }
    }

    query const_caller_location(key: (rustc_span::Symbol, u32, u32)) -> ConstValue<'tcx> {
        desc { "get a &core::panic::Location referring to a span" }
    }

    query lit_to_const(
        key: LitToConstInput<'tcx>
    ) -> Result<&'tcx ty::Const<'tcx>, LitToConstError> {
        desc { "converting literal to const" }
    }

    query check_match(key: DefId) {
        desc { |tcx| "match-checking `{}`", tcx.def_path_str(key) }
        cache_on_disk_if { key.is_local() }
    }

    /// Performs part of the privacy check and computes "access levels".
    query privacy_access_levels(_: ()) -> &'tcx AccessLevels {
        eval_always
        desc { "privacy access levels" }
    }
    query check_private_in_public(_: ()) -> () {
        eval_always
        desc { "checking for private elements in public interfaces" }
    }

    query reachable_set(_: ()) -> FxHashSet<LocalDefId> {
        storage(ArenaCacheSelector<'tcx>)
        desc { "reachability" }
    }

    /// Per-body `region::ScopeTree`. The `DefId` should be the owner `DefId` for the body;
    /// in the case of closures, this will be redirected to the enclosing function.
    query region_scope_tree(def_id: DefId) -> &'tcx region::ScopeTree {
        desc { |tcx| "computing drop scopes for `{}`", tcx.def_path_str(def_id) }
    }

    query mir_shims(key: ty::InstanceDef<'tcx>) -> mir::Body<'tcx> {
        storage(ArenaCacheSelector<'tcx>)
        desc { |tcx| "generating MIR shim for `{}`", tcx.def_path_str(key.def_id()) }
    }

    /// The `symbol_name` query provides the symbol name for calling a
    /// given instance from the local crate. In particular, it will also
    /// look up the correct symbol name of instances from upstream crates.
    query symbol_name(key: ty::Instance<'tcx>) -> ty::SymbolName<'tcx> {
        desc { "computing the symbol for `{}`", key }
        cache_on_disk_if { true }
    }

    query opt_def_kind(def_id: DefId) -> Option<DefKind> {
        desc { |tcx| "looking up definition kind of `{}`", tcx.def_path_str(def_id) }
    }

    query def_span(def_id: DefId) -> Span {
        desc { |tcx| "looking up span for `{}`", tcx.def_path_str(def_id) }
        // FIXME(mw): DefSpans are not really inputs since they are derived from
        // HIR. But at the moment HIR hashing still contains some hacks that allow
        // to make type debuginfo to be source location independent. Declaring
        // DefSpan an input makes sure that changes to these are always detected
        // regardless of HIR hashing.
        eval_always
    }

    query def_ident_span(def_id: DefId) -> Option<Span> {
        desc { |tcx| "looking up span for `{}`'s identifier", tcx.def_path_str(def_id) }
    }

    query lookup_stability(def_id: DefId) -> Option<&'tcx attr::Stability> {
        desc { |tcx| "looking up stability of `{}`", tcx.def_path_str(def_id) }
    }

    query lookup_const_stability(def_id: DefId) -> Option<&'tcx attr::ConstStability> {
        desc { |tcx| "looking up const stability of `{}`", tcx.def_path_str(def_id) }
    }

    query should_inherit_track_caller(def_id: DefId) -> bool {
        desc { |tcx| "computing should_inherit_track_caller of `{}`", tcx.def_path_str(def_id) }
    }

    query lookup_deprecation_entry(def_id: DefId) -> Option<DeprecationEntry> {
        desc { |tcx| "checking whether `{}` is deprecated", tcx.def_path_str(def_id) }
    }

    query item_attrs(def_id: DefId) -> &'tcx [ast::Attribute] {
        desc { |tcx| "collecting attributes of `{}`", tcx.def_path_str(def_id) }
    }

    query codegen_fn_attrs(def_id: DefId) -> CodegenFnAttrs {
        desc { |tcx| "computing codegen attributes of `{}`", tcx.def_path_str(def_id) }
        storage(ArenaCacheSelector<'tcx>)
        cache_on_disk_if { true }
    }

    query fn_arg_names(def_id: DefId) -> &'tcx [rustc_span::symbol::Ident] {
        desc { |tcx| "looking up function parameter names for `{}`", tcx.def_path_str(def_id) }
    }
    /// Gets the rendered value of the specified constant or associated constant.
    /// Used by rustdoc.
    query rendered_const(def_id: DefId) -> String {
        desc { |tcx| "rendering constant intializer of `{}`", tcx.def_path_str(def_id) }
    }
    query impl_parent(def_id: DefId) -> Option<DefId> {
        desc { |tcx| "computing specialization parent impl of `{}`", tcx.def_path_str(def_id) }
    }

    /// Given an `associated_item`, find the trait it belongs to.
    /// Return `None` if the `DefId` is not an associated item.
    query trait_of_item(associated_item: DefId) -> Option<DefId> {
        desc { |tcx| "finding trait defining `{}`", tcx.def_path_str(associated_item) }
    }

    query is_ctfe_mir_available(key: DefId) -> bool {
        desc { |tcx| "checking if item has ctfe mir available: `{}`", tcx.def_path_str(key) }
    }
    query is_mir_available(key: DefId) -> bool {
        desc { |tcx| "checking if item has mir available: `{}`", tcx.def_path_str(key) }
    }

    query vtable_entries(key: ty::PolyTraitRef<'tcx>)
                        -> &'tcx [ty::VtblEntry<'tcx>] {
        desc { |tcx| "finding all vtable entries for trait {}", tcx.def_path_str(key.def_id()) }
    }

    query codegen_fulfill_obligation(
        key: (ty::ParamEnv<'tcx>, ty::PolyTraitRef<'tcx>)
    ) -> Result<ImplSource<'tcx, ()>, ErrorReported> {
        cache_on_disk_if { true }
        desc { |tcx|
            "checking if `{}` fulfills its obligations",
            tcx.def_path_str(key.1.def_id())
        }
    }

    /// Return all `impl` blocks in the current crate.
    ///
    /// To allow caching this between crates, you must pass in [`LOCAL_CRATE`] as the crate number.
    /// Passing in any other crate will cause an ICE.
    ///
    /// [`LOCAL_CRATE`]: rustc_hir::def_id::LOCAL_CRATE
    query all_local_trait_impls(_: ()) -> &'tcx BTreeMap<DefId, Vec<LocalDefId>> {
        desc { "local trait impls" }
    }

    /// Given a trait `trait_id`, return all known `impl` blocks.
    query trait_impls_of(trait_id: DefId) -> ty::trait_def::TraitImpls {
        storage(ArenaCacheSelector<'tcx>)
        desc { |tcx| "trait impls of `{}`", tcx.def_path_str(trait_id) }
    }

    query specialization_graph_of(trait_id: DefId) -> specialization_graph::Graph {
        storage(ArenaCacheSelector<'tcx>)
        desc { |tcx| "building specialization graph of trait `{}`", tcx.def_path_str(trait_id) }
        cache_on_disk_if { true }
    }
    query object_safety_violations(trait_id: DefId) -> &'tcx [traits::ObjectSafetyViolation] {
        desc { |tcx| "determine object safety of trait `{}`", tcx.def_path_str(trait_id) }
    }

    /// Gets the ParameterEnvironment for a given item; this environment
    /// will be in "user-facing" mode, meaning that it is suitable for
    /// type-checking etc, and it does not normalize specializable
    /// associated types. This is almost always what you want,
    /// unless you are doing MIR optimizations, in which case you
    /// might want to use `reveal_all()` method to change modes.
    query param_env(def_id: DefId) -> ty::ParamEnv<'tcx> {
        desc { |tcx| "computing normalized predicates of `{}`", tcx.def_path_str(def_id) }
    }

    /// Like `param_env`, but returns the `ParamEnv` in `Reveal::All` mode.
    /// Prefer this over `tcx.param_env(def_id).with_reveal_all_normalized(tcx)`,
    /// as this method is more efficient.
    query param_env_reveal_all_normalized(def_id: DefId) -> ty::ParamEnv<'tcx> {
        desc { |tcx| "computing revealed normalized predicates of `{}`", tcx.def_path_str(def_id) }
    }

    /// Trait selection queries. These are best used by invoking `ty.is_copy_modulo_regions()`,
    /// `ty.is_copy()`, etc, since that will prune the environment where possible.
    query is_copy_raw(env: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
        desc { "computing whether `{}` is `Copy`", env.value }
    }
    /// Query backing `TyS::is_sized`.
    query is_sized_raw(env: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
        desc { "computing whether `{}` is `Sized`", env.value }
    }
    /// Query backing `TyS::is_freeze`.
    query is_freeze_raw(env: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
        desc { "computing whether `{}` is freeze", env.value }
    }
    /// Query backing `TyS::is_unpin`.
    query is_unpin_raw(env: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
        desc { "computing whether `{}` is `Unpin`", env.value }
    }
    /// Query backing `TyS::needs_drop`.
    query needs_drop_raw(env: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
        desc { "computing whether `{}` needs drop", env.value }
    }
    /// Query backing `TyS::has_significant_drop_raw`.
    query has_significant_drop_raw(env: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
        desc { "computing whether `{}` has a significant drop", env.value }
    }

    /// Query backing `TyS::is_structural_eq_shallow`.
    ///
    /// This is only correct for ADTs. Call `is_structural_eq_shallow` to handle all types
    /// correctly.
    query has_structural_eq_impls(ty: Ty<'tcx>) -> bool {
        desc {
            "computing whether `{:?}` implements `PartialStructuralEq` and `StructuralEq`",
            ty
        }
    }

    /// A list of types where the ADT requires drop if and only if any of
    /// those types require drop. If the ADT is known to always need drop
    /// then `Err(AlwaysRequiresDrop)` is returned.
    query adt_drop_tys(def_id: DefId) -> Result<&'tcx ty::List<Ty<'tcx>>, AlwaysRequiresDrop> {
        desc { |tcx| "computing when `{}` needs drop", tcx.def_path_str(def_id) }
        cache_on_disk_if { true }
    }

    /// A list of types where the ADT requires drop if and only if any of those types
    /// has significant drop. A type marked with the attribute `rustc_insignificant_dtor`
    /// is considered to not be significant. A drop is significant if it is implemented
    /// by the user or does anything that will have any observable behavior (other than
    /// freeing up memory). If the ADT is known to have a significant destructor then
    /// `Err(AlwaysRequiresDrop)` is returned.
    query adt_significant_drop_tys(def_id: DefId) -> Result<&'tcx ty::List<Ty<'tcx>>, AlwaysRequiresDrop> {
        desc { |tcx| "computing when `{}` has a significant destructor", tcx.def_path_str(def_id) }
        cache_on_disk_if { false }
    }

    query layout_raw(
        env: ty::ParamEnvAnd<'tcx, Ty<'tcx>>
    ) -> Result<&'tcx rustc_target::abi::Layout, ty::layout::LayoutError<'tcx>> {
        desc { "computing layout of `{}`", env.value }
    }

    query dylib_dependency_formats(_: CrateNum)
                                    -> &'tcx [(CrateNum, LinkagePreference)] {
        desc { "dylib dependency formats of crate" }
    }

    query dependency_formats(_: ()) -> Lrc<crate::middle::dependency_format::Dependencies> {
        desc { "get the linkage format of all dependencies" }
    }

    query is_compiler_builtins(_: CrateNum) -> bool {
        fatal_cycle
        desc { "checking if the crate is_compiler_builtins" }
    }
    query has_global_allocator(_: CrateNum) -> bool {
        // This query depends on untracked global state in CStore
        eval_always
        fatal_cycle
        desc { "checking if the crate has_global_allocator" }
    }
    query has_panic_handler(_: CrateNum) -> bool {
        fatal_cycle
        desc { "checking if the crate has_panic_handler" }
    }
    query is_profiler_runtime(_: CrateNum) -> bool {
        fatal_cycle
        desc { "query a crate is `#![profiler_runtime]`" }
    }
    query panic_strategy(_: CrateNum) -> PanicStrategy {
        fatal_cycle
        desc { "query a crate's configured panic strategy" }
    }
    query is_no_builtins(_: CrateNum) -> bool {
        fatal_cycle
        desc { "test whether a crate has `#![no_builtins]`" }
    }
    query symbol_mangling_version(_: CrateNum) -> SymbolManglingVersion {
        fatal_cycle
        desc { "query a crate's symbol mangling version" }
    }

    query extern_crate(def_id: DefId) -> Option<&'tcx ExternCrate> {
        eval_always
        desc { "getting crate's ExternCrateData" }
    }

    query specializes(_: (DefId, DefId)) -> bool {
        desc { "computing whether impls specialize one another" }
    }
    query in_scope_traits_map(_: LocalDefId)
        -> Option<&'tcx FxHashMap<ItemLocalId, Box<[TraitCandidate]>>> {
        desc { "traits in scope at a block" }
    }

    query module_exports(def_id: LocalDefId) -> Option<&'tcx [Export<LocalDefId>]> {
        desc { |tcx| "looking up items exported by `{}`", tcx.def_path_str(def_id.to_def_id()) }
    }

    query impl_defaultness(def_id: DefId) -> hir::Defaultness {
        desc { |tcx| "looking up whether `{}` is a default impl", tcx.def_path_str(def_id) }
    }

    query impl_constness(def_id: DefId) -> hir::Constness {
        desc { |tcx| "looking up whether `{}` is a const impl", tcx.def_path_str(def_id) }
    }

    query check_item_well_formed(key: LocalDefId) -> () {
        desc { |tcx| "checking that `{}` is well-formed", tcx.def_path_str(key.to_def_id()) }
    }
    query check_trait_item_well_formed(key: LocalDefId) -> () {
        desc { |tcx| "checking that `{}` is well-formed", tcx.def_path_str(key.to_def_id()) }
    }
    query check_impl_item_well_formed(key: LocalDefId) -> () {
        desc { |tcx| "checking that `{}` is well-formed", tcx.def_path_str(key.to_def_id()) }
    }

    // The `DefId`s of all non-generic functions and statics in the given crate
    // that can be reached from outside the crate.
    //
    // We expect this items to be available for being linked to.
    //
    // This query can also be called for `LOCAL_CRATE`. In this case it will
    // compute which items will be reachable to other crates, taking into account
    // the kind of crate that is currently compiled. Crates with only a
    // C interface have fewer reachable things.
    //
    // Does not include external symbols that don't have a corresponding DefId,
    // like the compiler-generated `main` function and so on.
    query reachable_non_generics(_: CrateNum)
        -> DefIdMap<SymbolExportLevel> {
        storage(ArenaCacheSelector<'tcx>)
        desc { "looking up the exported symbols of a crate" }
    }
    query is_reachable_non_generic(def_id: DefId) -> bool {
        desc { |tcx| "checking whether `{}` is an exported symbol", tcx.def_path_str(def_id) }
    }
    query is_unreachable_local_definition(def_id: LocalDefId) -> bool {
        desc { |tcx|
            "checking whether `{}` is reachable from outside the crate",
            tcx.def_path_str(def_id.to_def_id()),
        }
    }

    /// The entire set of monomorphizations the local crate can safely link
    /// to because they are exported from upstream crates. Do not depend on
    /// this directly, as its value changes anytime a monomorphization gets
    /// added or removed in any upstream crate. Instead use the narrower
    /// `upstream_monomorphizations_for`, `upstream_drop_glue_for`, or, even
    /// better, `Instance::upstream_monomorphization()`.
    query upstream_monomorphizations(_: ()) -> DefIdMap<FxHashMap<SubstsRef<'tcx>, CrateNum>> {
        storage(ArenaCacheSelector<'tcx>)
        desc { "collecting available upstream monomorphizations" }
    }

    /// Returns the set of upstream monomorphizations available for the
    /// generic function identified by the given `def_id`. The query makes
    /// sure to make a stable selection if the same monomorphization is
    /// available in multiple upstream crates.
    ///
    /// You likely want to call `Instance::upstream_monomorphization()`
    /// instead of invoking this query directly.
    query upstream_monomorphizations_for(def_id: DefId)
        -> Option<&'tcx FxHashMap<SubstsRef<'tcx>, CrateNum>> {
            desc { |tcx|
                "collecting available upstream monomorphizations for `{}`",
                tcx.def_path_str(def_id),
            }
        }

    /// Returns the upstream crate that exports drop-glue for the given
    /// type (`substs` is expected to be a single-item list containing the
    /// type one wants drop-glue for).
    ///
    /// This is a subset of `upstream_monomorphizations_for` in order to
    /// increase dep-tracking granularity. Otherwise adding or removing any
    /// type with drop-glue in any upstream crate would invalidate all
    /// functions calling drop-glue of an upstream type.
    ///
    /// You likely want to call `Instance::upstream_monomorphization()`
    /// instead of invoking this query directly.
    ///
    /// NOTE: This query could easily be extended to also support other
    ///       common functions that have are large set of monomorphizations
    ///       (like `Clone::clone` for example).
    query upstream_drop_glue_for(substs: SubstsRef<'tcx>) -> Option<CrateNum> {
        desc { "available upstream drop-glue for `{:?}`", substs }
    }

    query foreign_modules(_: CrateNum) -> Lrc<FxHashMap<DefId, ForeignModule>> {
        desc { "looking up the foreign modules of a linked crate" }
    }

    /// Identifies the entry-point (e.g., the `main` function) for a given
    /// crate, returning `None` if there is no entry point (such as for library crates).
    query entry_fn(_: ()) -> Option<(DefId, EntryFnType)> {
        desc { "looking up the entry function of a crate" }
    }
    query plugin_registrar_fn(_: ()) -> Option<LocalDefId> {
        desc { "looking up the plugin registrar for a crate" }
    }
    query proc_macro_decls_static(_: ()) -> Option<LocalDefId> {
        desc { "looking up the derive registrar for a crate" }
    }
    // The macro which defines `rustc_metadata::provide_extern` depends on this query's name.
    // Changing the name should cause a compiler error, but in case that changes, be aware.
    query crate_hash(_: CrateNum) -> Svh {
        eval_always
        desc { "looking up the hash a crate" }
    }
    query crate_host_hash(_: CrateNum) -> Option<Svh> {
        eval_always
        desc { "looking up the hash of a host version of a crate" }
    }
    query extra_filename(_: CrateNum) -> String {
        eval_always
        desc { "looking up the extra filename for a crate" }
    }
    query crate_extern_paths(_: CrateNum) -> Vec<PathBuf> {
        eval_always
        desc { "looking up the paths for extern crates" }
    }

    /// Given a crate and a trait, look up all impls of that trait in the crate.
    /// Return `(impl_id, self_ty)`.
    query implementations_of_trait(_: (CrateNum, DefId))
        -> &'tcx [(DefId, Option<ty::fast_reject::SimplifiedType>)] {
        desc { "looking up implementations of a trait in a crate" }
    }

    /// Given a crate, look up all trait impls in that crate.
    /// Return `(impl_id, self_ty)`.
    query all_trait_implementations(_: CrateNum)
        -> &'tcx [(DefId, Option<ty::fast_reject::SimplifiedType>)] {
        desc { "looking up all (?) trait implementations" }
    }

    query is_dllimport_foreign_item(def_id: DefId) -> bool {
        desc { |tcx| "is_dllimport_foreign_item({})", tcx.def_path_str(def_id) }
    }
    query is_statically_included_foreign_item(def_id: DefId) -> bool {
        desc { |tcx| "is_statically_included_foreign_item({})", tcx.def_path_str(def_id) }
    }
    query native_library_kind(def_id: DefId)
        -> Option<NativeLibKind> {
        desc { |tcx| "native_library_kind({})", tcx.def_path_str(def_id) }
    }

    /// Does lifetime resolution, but does not descend into trait items. This
    /// should only be used for resolving lifetimes of on trait definitions,
    /// and is used to avoid cycles. Importantly, `resolve_lifetimes` still visits
    /// the same lifetimes and is responsible for diagnostics.
    /// See `rustc_resolve::late::lifetimes for details.
    query resolve_lifetimes_trait_definition(_: LocalDefId) -> ResolveLifetimes {
        storage(ArenaCacheSelector<'tcx>)
        desc { "resolving lifetimes for a trait definition" }
    }
    /// Does lifetime resolution on items. Importantly, we can't resolve
    /// lifetimes directly on things like trait methods, because of trait params.
    /// See `rustc_resolve::late::lifetimes for details.
    query resolve_lifetimes(_: LocalDefId) -> ResolveLifetimes {
        storage(ArenaCacheSelector<'tcx>)
        desc { "resolving lifetimes" }
    }
    query named_region_map(_: LocalDefId) ->
        Option<&'tcx FxHashMap<ItemLocalId, Region>> {
        desc { "looking up a named region" }
    }
    query is_late_bound_map(_: LocalDefId) ->
        Option<(LocalDefId, &'tcx FxHashSet<ItemLocalId>)> {
        desc { "testing if a region is late bound" }
    }
    /// For a given item (like a struct), gets the default lifetimes to be used
    /// for each parameter if a trait object were to be passed for that parameter.
    /// For example, for `struct Foo<'a, T, U>`, this would be `['static, 'static]`.
    /// For `struct Foo<'a, T: 'a, U>`, this would instead be `['a, 'static]`.
    query object_lifetime_defaults_map(_: LocalDefId)
        -> Option<Vec<ObjectLifetimeDefault>> {
        desc { "looking up lifetime defaults for a region on an item" }
    }
    query late_bound_vars_map(_: LocalDefId)
        -> Option<&'tcx FxHashMap<ItemLocalId, Vec<ty::BoundVariableKind>>> {
        desc { "looking up late bound vars" }
    }

    query lifetime_scope_map(_: LocalDefId) -> Option<FxHashMap<ItemLocalId, LifetimeScopeForPath>> {
        desc { "finds the lifetime scope for an HirId of a PathSegment" }
    }

    query visibility(def_id: DefId) -> ty::Visibility {
        desc { |tcx| "computing visibility of `{}`", tcx.def_path_str(def_id) }
    }

    /// Computes the set of modules from which this type is visibly uninhabited.
    /// To check whether a type is uninhabited at all (not just from a given module), you could
    /// check whether the forest is empty.
    query type_uninhabited_from(
        key: ty::ParamEnvAnd<'tcx, Ty<'tcx>>
    ) -> ty::inhabitedness::DefIdForest {
        desc { "computing the inhabitedness of `{:?}`", key }
    }

    query dep_kind(_: CrateNum) -> CrateDepKind {
        eval_always
        desc { "fetching what a dependency looks like" }
    }
    query crate_name(_: CrateNum) -> Symbol {
        eval_always
        desc { "fetching what a crate is named" }
    }
    query item_children(def_id: DefId) -> &'tcx [Export<hir::HirId>] {
        desc { |tcx| "collecting child items of `{}`", tcx.def_path_str(def_id) }
    }
    query extern_mod_stmt_cnum(def_id: LocalDefId) -> Option<CrateNum> {
        desc { |tcx| "computing crate imported by `{}`", tcx.def_path_str(def_id.to_def_id()) }
    }

    query get_lib_features(_: ()) -> LibFeatures {
        storage(ArenaCacheSelector<'tcx>)
        eval_always
        desc { "calculating the lib features map" }
    }
    query defined_lib_features(_: CrateNum)
        -> &'tcx [(Symbol, Option<Symbol>)] {
        desc { "calculating the lib features defined in a crate" }
    }
    /// Returns the lang items defined in another crate by loading it from metadata.
    query get_lang_items(_: ()) -> LanguageItems {
        storage(ArenaCacheSelector<'tcx>)
        eval_always
        desc { "calculating the lang items map" }
    }

    /// Returns all diagnostic items defined in all crates.
    query all_diagnostic_items(_: ()) -> FxHashMap<Symbol, DefId> {
        storage(ArenaCacheSelector<'tcx>)
        eval_always
        desc { "calculating the diagnostic items map" }
    }

    /// Returns the lang items defined in another crate by loading it from metadata.
    query defined_lang_items(_: CrateNum) -> &'tcx [(DefId, usize)] {
        desc { "calculating the lang items defined in a crate" }
    }

    /// Returns the diagnostic items defined in a crate.
    query diagnostic_items(_: CrateNum) -> FxHashMap<Symbol, DefId> {
        storage(ArenaCacheSelector<'tcx>)
        desc { "calculating the diagnostic items map in a crate" }
    }

    query missing_lang_items(_: CrateNum) -> &'tcx [LangItem] {
        desc { "calculating the missing lang items in a crate" }
    }
    query visible_parent_map(_: ()) -> DefIdMap<DefId> {
        storage(ArenaCacheSelector<'tcx>)
        desc { "calculating the visible parent map" }
    }
    query trimmed_def_paths(_: ()) -> FxHashMap<DefId, Symbol> {
        storage(ArenaCacheSelector<'tcx>)
        desc { "calculating trimmed def paths" }
    }
    query missing_extern_crate_item(_: CrateNum) -> bool {
        eval_always
        desc { "seeing if we're missing an `extern crate` item for this crate" }
    }
    query used_crate_source(_: CrateNum) -> Lrc<CrateSource> {
        eval_always
        desc { "looking at the source for a crate" }
    }
    query postorder_cnums(_: ()) -> &'tcx [CrateNum] {
        eval_always
        desc { "generating a postorder list of CrateNums" }
    }
    /// Returns whether or not the crate with CrateNum 'cnum'
    /// is marked as a private dependency
    query is_private_dep(c: CrateNum) -> bool {
        eval_always
        desc { "check whether crate {} is a private dependency", c }
    }
    query allocator_kind(_: ()) -> Option<AllocatorKind> {
        eval_always
        desc { "allocator kind for the current crate" }
    }

    query upvars_mentioned(def_id: DefId) -> Option<&'tcx FxIndexMap<hir::HirId, hir::Upvar>> {
        desc { |tcx| "collecting upvars mentioned in `{}`", tcx.def_path_str(def_id) }
        eval_always
    }
    query maybe_unused_trait_import(def_id: LocalDefId) -> bool {
        desc { |tcx| "maybe_unused_trait_import for `{}`", tcx.def_path_str(def_id.to_def_id()) }
    }
    query maybe_unused_extern_crates(_: ()) -> &'tcx [(LocalDefId, Span)] {
        desc { "looking up all possibly unused extern crates" }
    }
    query names_imported_by_glob_use(def_id: LocalDefId) -> &'tcx FxHashSet<Symbol> {
        desc { |tcx| "names_imported_by_glob_use for `{}`", tcx.def_path_str(def_id.to_def_id()) }
    }

    query stability_index(_: ()) -> stability::Index<'tcx> {
        storage(ArenaCacheSelector<'tcx>)
        eval_always
        desc { "calculating the stability index for the local crate" }
    }
    query crates(_: ()) -> &'tcx [CrateNum] {
        eval_always
        desc { "fetching all foreign CrateNum instances" }
    }

    /// A vector of every trait accessible in the whole crate
    /// (i.e., including those from subcrates). This is used only for
    /// error reporting.
    query all_traits(_: ()) -> &'tcx [DefId] {
        desc { "fetching all foreign and local traits" }
    }

    /// The list of symbols exported from the given crate.
    ///
    /// - All names contained in `exported_symbols(cnum)` are guaranteed to
    ///   correspond to a publicly visible symbol in `cnum` machine code.
    /// - The `exported_symbols` sets of different crates do not intersect.
    query exported_symbols(_: CrateNum)
        -> &'tcx [(ExportedSymbol<'tcx>, SymbolExportLevel)] {
        desc { "exported_symbols" }
    }

    query collect_and_partition_mono_items(_: ()) -> (&'tcx DefIdSet, &'tcx [CodegenUnit<'tcx>]) {
        eval_always
        desc { "collect_and_partition_mono_items" }
    }
    query is_codegened_item(def_id: DefId) -> bool {
        desc { |tcx| "determining whether `{}` needs codegen", tcx.def_path_str(def_id) }
    }

    /// All items participating in code generation together with items inlined into them.
    query codegened_and_inlined_items(_: ()) -> &'tcx DefIdSet {
        eval_always
       desc { "codegened_and_inlined_items" }
    }

    query codegen_unit(_: Symbol) -> &'tcx CodegenUnit<'tcx> {
        desc { "codegen_unit" }
    }
    query unused_generic_params(key: DefId) -> FiniteBitSet<u32> {
        cache_on_disk_if { key.is_local() }
        desc {
            |tcx| "determining which generic parameters are unused by `{}`",
                tcx.def_path_str(key)
        }
    }
    query backend_optimization_level(_: ()) -> OptLevel {
        desc { "optimization level used by backend" }
    }

    query output_filenames(_: ()) -> Arc<OutputFilenames> {
        eval_always
        desc { "output_filenames" }
    }

    /// Do not call this query directly: invoke `normalize` instead.
    query normalize_projection_ty(
        goal: CanonicalProjectionGoal<'tcx>
    ) -> Result<
        &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, NormalizationResult<'tcx>>>,
        NoSolution,
    > {
        desc { "normalizing `{:?}`", goal }
    }

    /// Do not call this query directly: invoke `normalize_erasing_regions` instead.
    query normalize_generic_arg_after_erasing_regions(
        goal: ParamEnvAnd<'tcx, GenericArg<'tcx>>
    ) -> GenericArg<'tcx> {
        desc { "normalizing `{}`", goal.value }
    }

    /// Do not call this query directly: invoke `normalize_erasing_regions` instead.
    query normalize_mir_const_after_erasing_regions(
        goal: ParamEnvAnd<'tcx, mir::ConstantKind<'tcx>>
    ) -> mir::ConstantKind<'tcx> {
        desc { "normalizing `{}`", goal.value }
    }

    query implied_outlives_bounds(
        goal: CanonicalTyGoal<'tcx>
    ) -> Result<
        &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, Vec<OutlivesBound<'tcx>>>>,
        NoSolution,
    > {
        desc { "computing implied outlives bounds for `{:?}`", goal }
    }

    /// Do not call this query directly: invoke `infcx.at().dropck_outlives()` instead.
    query dropck_outlives(
        goal: CanonicalTyGoal<'tcx>
    ) -> Result<
        &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, DropckOutlivesResult<'tcx>>>,
        NoSolution,
    > {
        desc { "computing dropck types for `{:?}`", goal }
    }

    /// Do not call this query directly: invoke `infcx.predicate_may_hold()` or
    /// `infcx.predicate_must_hold()` instead.
    query evaluate_obligation(
        goal: CanonicalPredicateGoal<'tcx>
    ) -> Result<traits::EvaluationResult, traits::OverflowError> {
        desc { "evaluating trait selection obligation `{}`", goal.value.value }
    }

    query evaluate_goal(
        goal: traits::CanonicalChalkEnvironmentAndGoal<'tcx>
    ) -> Result<
        &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, ()>>,
        NoSolution
    > {
        desc { "evaluating trait selection obligation `{}`", goal.value }
    }

    /// Do not call this query directly: part of the `Eq` type-op
    query type_op_ascribe_user_type(
        goal: CanonicalTypeOpAscribeUserTypeGoal<'tcx>
    ) -> Result<
        &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, ()>>,
        NoSolution,
    > {
        desc { "evaluating `type_op_ascribe_user_type` `{:?}`", goal }
    }

    /// Do not call this query directly: part of the `Eq` type-op
    query type_op_eq(
        goal: CanonicalTypeOpEqGoal<'tcx>
    ) -> Result<
        &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, ()>>,
        NoSolution,
    > {
        desc { "evaluating `type_op_eq` `{:?}`", goal }
    }

    /// Do not call this query directly: part of the `Subtype` type-op
    query type_op_subtype(
        goal: CanonicalTypeOpSubtypeGoal<'tcx>
    ) -> Result<
        &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, ()>>,
        NoSolution,
    > {
        desc { "evaluating `type_op_subtype` `{:?}`", goal }
    }

    /// Do not call this query directly: part of the `ProvePredicate` type-op
    query type_op_prove_predicate(
        goal: CanonicalTypeOpProvePredicateGoal<'tcx>
    ) -> Result<
        &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, ()>>,
        NoSolution,
    > {
        desc { "evaluating `type_op_prove_predicate` `{:?}`", goal }
    }

    /// Do not call this query directly: part of the `Normalize` type-op
    query type_op_normalize_ty(
        goal: CanonicalTypeOpNormalizeGoal<'tcx, Ty<'tcx>>
    ) -> Result<
        &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, Ty<'tcx>>>,
        NoSolution,
    > {
        desc { "normalizing `{:?}`", goal }
    }

    /// Do not call this query directly: part of the `Normalize` type-op
    query type_op_normalize_predicate(
        goal: CanonicalTypeOpNormalizeGoal<'tcx, ty::Predicate<'tcx>>
    ) -> Result<
        &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, ty::Predicate<'tcx>>>,
        NoSolution,
    > {
        desc { "normalizing `{:?}`", goal }
    }

    /// Do not call this query directly: part of the `Normalize` type-op
    query type_op_normalize_poly_fn_sig(
        goal: CanonicalTypeOpNormalizeGoal<'tcx, ty::PolyFnSig<'tcx>>
    ) -> Result<
        &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, ty::PolyFnSig<'tcx>>>,
        NoSolution,
    > {
        desc { "normalizing `{:?}`", goal }
    }

    /// Do not call this query directly: part of the `Normalize` type-op
    query type_op_normalize_fn_sig(
        goal: CanonicalTypeOpNormalizeGoal<'tcx, ty::FnSig<'tcx>>
    ) -> Result<
        &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, ty::FnSig<'tcx>>>,
        NoSolution,
    > {
        desc { "normalizing `{:?}`", goal }
    }

    query subst_and_check_impossible_predicates(key: (DefId, SubstsRef<'tcx>)) -> bool {
        desc { |tcx|
            "impossible substituted predicates:`{}`",
            tcx.def_path_str(key.0)
        }
    }

    query method_autoderef_steps(
        goal: CanonicalTyGoal<'tcx>
    ) -> MethodAutoderefStepsResult<'tcx> {
        desc { "computing autoderef types for `{:?}`", goal }
    }

    query supported_target_features(_: CrateNum) -> FxHashMap<String, Option<Symbol>> {
        storage(ArenaCacheSelector<'tcx>)
        eval_always
        desc { "looking up supported target features" }
    }

    /// Get an estimate of the size of an InstanceDef based on its MIR for CGU partitioning.
    query instance_def_size_estimate(def: ty::InstanceDef<'tcx>)
        -> usize {
        desc { |tcx| "estimating size for `{}`", tcx.def_path_str(def.def_id()) }
    }

    query features_query(_: ()) -> &'tcx rustc_feature::Features {
        eval_always
        desc { "looking up enabled feature gates" }
    }

    /// Attempt to resolve the given `DefId` to an `Instance`, for the
    /// given generics args (`SubstsRef`), returning one of:
    ///  * `Ok(Some(instance))` on success
    ///  * `Ok(None)` when the `SubstsRef` are still too generic,
    ///    and therefore don't allow finding the final `Instance`
    ///  * `Err(ErrorReported)` when the `Instance` resolution process
    ///    couldn't complete due to errors elsewhere - this is distinct
    ///    from `Ok(None)` to avoid misleading diagnostics when an error
    ///    has already been/will be emitted, for the original cause
    query resolve_instance(
        key: ty::ParamEnvAnd<'tcx, (DefId, SubstsRef<'tcx>)>
    ) -> Result<Option<ty::Instance<'tcx>>, ErrorReported> {
        desc { "resolving instance `{}`", ty::Instance::new(key.value.0, key.value.1) }
    }

    query resolve_instance_of_const_arg(
        key: ty::ParamEnvAnd<'tcx, (LocalDefId, DefId, SubstsRef<'tcx>)>
    ) -> Result<Option<ty::Instance<'tcx>>, ErrorReported> {
        desc {
            "resolving instance of the const argument `{}`",
            ty::Instance::new(key.value.0.to_def_id(), key.value.2),
        }
    }

    query normalize_opaque_types(key: &'tcx ty::List<ty::Predicate<'tcx>>) -> &'tcx ty::List<ty::Predicate<'tcx>> {
        desc { "normalizing opaque types in {:?}", key }
    }

    /// Checks whether a type is definitely uninhabited. This is
    /// conservative: for some types that are uninhabited we return `false`,
    /// but we only return `true` for types that are definitely uninhabited.
    /// `ty.conservative_is_privately_uninhabited` implies that any value of type `ty`
    /// will be `Abi::Uninhabited`. (Note that uninhabited types may have nonzero
    /// size, to account for partial initialisation. See #49298 for details.)
    query conservative_is_privately_uninhabited(key: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
        desc { "conservatively checking if {:?} is privately uninhabited", key }
    }

    query limits(key: ()) -> Limits {
        desc { "looking up limits" }
    }

    /// Performs an HIR-based well-formed check on the item with the given `HirId`. If
    /// we get an `Umimplemented` error that matches the provided `Predicate`, return
    /// the cause of the newly created obligation.
    ///
    /// This is only used by error-reporting code to get a better cause (in particular, a better
    /// span) for an *existing* error. Therefore, it is best-effort, and may never handle
    /// all of the cases that the normal `ty::Ty`-based wfcheck does. This is fine,
    /// because the `ty::Ty`-based wfcheck is always run.
    query diagnostic_hir_wf_check(key: (ty::Predicate<'tcx>, traits::WellFormedLoc)) -> Option<traits::ObligationCause<'tcx>> {
        eval_always
        no_hash
        desc { "performing HIR wf-checking for predicate {:?} at item {:?}", key.0, key.1 }
    }
}