New upstream version 1.30.0~beta.7+dfsg1

[rustc.git] / src / librustc / ty / query / config.rs

// Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use dep_graph::SerializedDepNodeIndex;
use dep_graph::DepNode;
use hir::def_id::{CrateNum, DefId, DefIndex};
use mir::interpret::GlobalId;
use traits::query::{
    CanonicalPredicateGoal, CanonicalProjectionGoal, CanonicalTyGoal, CanonicalTypeOpEqGoal,
    CanonicalTypeOpNormalizeGoal, CanonicalTypeOpProvePredicateGoal, CanonicalTypeOpSubtypeGoal,
};
use ty::{self, ParamEnvAnd, Ty, TyCtxt};
use ty::subst::Substs;
use ty::query::queries;
use ty::query::Query;
use ty::query::QueryCache;
use util::profiling::ProfileCategory;

use std::hash::Hash;
use std::fmt::Debug;
use syntax_pos::symbol::InternedString;
use rustc_data_structures::sync::Lock;
use rustc_data_structures::stable_hasher::HashStable;
use ich::StableHashingContext;

// Query configuration and description traits.

pub trait QueryConfig<'tcx> {
    const NAME: &'static str;
    const CATEGORY: ProfileCategory;

    type Key: Eq + Hash + Clone + Debug;
    type Value: Clone + for<'a> HashStable<StableHashingContext<'a>>;
}

pub(super) trait QueryAccessors<'tcx>: QueryConfig<'tcx> {
    fn query(key: Self::Key) -> Query<'tcx>;

    // Don't use this method to access query results, instead use the methods on TyCtxt
    fn query_cache<'a>(tcx: TyCtxt<'a, 'tcx, '_>) -> &'a Lock<QueryCache<'tcx, Self>>;

    fn to_dep_node(tcx: TyCtxt<'_, 'tcx, '_>, key: &Self::Key) -> DepNode;

    // Don't use this method to compute query results, instead use the methods on TyCtxt
    fn compute(tcx: TyCtxt<'_, 'tcx, '_>, key: Self::Key) -> Self::Value;

    fn handle_cycle_error(tcx: TyCtxt<'_, 'tcx, '_>) -> Self::Value;
}

pub(super) trait QueryDescription<'tcx>: QueryAccessors<'tcx> {
    fn describe(tcx: TyCtxt, key: Self::Key) -> String;

    #[inline]
    fn cache_on_disk(_: Self::Key) -> bool {
        false
    }

    fn try_load_from_disk(_: TyCtxt<'_, 'tcx, 'tcx>,
                          _: SerializedDepNodeIndex)
                          -> Option<Self::Value> {
        bug!("QueryDescription::load_from_disk() called for an unsupported query.")
    }
}

impl<'tcx, M: QueryAccessors<'tcx, Key=DefId>> QueryDescription<'tcx> for M {
    default fn describe(tcx: TyCtxt, def_id: DefId) -> String {
        if !tcx.sess.verbose() {
            format!("processing `{}`", tcx.item_path_str(def_id))
        } else {
            let name = unsafe { ::std::intrinsics::type_name::<M>() };
            format!("processing `{}` applied to `{:?}`", name, def_id)
        }
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::normalize_projection_ty<'tcx> {
    fn describe(
        _tcx: TyCtxt,
        goal: CanonicalProjectionGoal<'tcx>,
    ) -> String {
        format!("normalizing `{:?}`", goal)
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::implied_outlives_bounds<'tcx> {
    fn describe(_tcx: TyCtxt, goal: CanonicalTyGoal<'tcx>) -> String {
        format!("computing implied outlives bounds for `{:?}`", goal)
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::dropck_outlives<'tcx> {
    fn describe(_tcx: TyCtxt, goal: CanonicalTyGoal<'tcx>) -> String {
        format!("computing dropck types for `{:?}`", goal)
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::normalize_ty_after_erasing_regions<'tcx> {
    fn describe(_tcx: TyCtxt, goal: ParamEnvAnd<'tcx, Ty<'tcx>>) -> String {
        format!("normalizing `{:?}`", goal)
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::evaluate_obligation<'tcx> {
    fn describe(_tcx: TyCtxt, goal: CanonicalPredicateGoal<'tcx>) -> String {
        format!("evaluating trait selection obligation `{}`", goal.value.value)
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::type_op_eq<'tcx> {
    fn describe(_tcx: TyCtxt, goal: CanonicalTypeOpEqGoal<'tcx>) -> String {
        format!("evaluating `type_op_eq` `{:?}`", goal)
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::type_op_subtype<'tcx> {
    fn describe(_tcx: TyCtxt, goal: CanonicalTypeOpSubtypeGoal<'tcx>) -> String {
        format!("evaluating `type_op_subtype` `{:?}`", goal)
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::type_op_prove_predicate<'tcx> {
    fn describe(_tcx: TyCtxt, goal: CanonicalTypeOpProvePredicateGoal<'tcx>) -> String {
        format!("evaluating `type_op_prove_predicate` `{:?}`", goal)
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::type_op_normalize_ty<'tcx> {
    fn describe(_tcx: TyCtxt, goal: CanonicalTypeOpNormalizeGoal<'tcx, Ty<'tcx>>) -> String {
        format!("normalizing `{:?}`", goal)
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::type_op_normalize_predicate<'tcx> {
    fn describe(
        _tcx: TyCtxt,
        goal: CanonicalTypeOpNormalizeGoal<'tcx, ty::Predicate<'tcx>>,
    ) -> String {
        format!("normalizing `{:?}`", goal)
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::type_op_normalize_poly_fn_sig<'tcx> {
    fn describe(
        _tcx: TyCtxt,
        goal: CanonicalTypeOpNormalizeGoal<'tcx, ty::PolyFnSig<'tcx>>,
    ) -> String {
        format!("normalizing `{:?}`", goal)
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::type_op_normalize_fn_sig<'tcx> {
    fn describe(_tcx: TyCtxt, goal: CanonicalTypeOpNormalizeGoal<'tcx, ty::FnSig<'tcx>>) -> String {
        format!("normalizing `{:?}`", goal)
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::is_copy_raw<'tcx> {
    fn describe(_tcx: TyCtxt, env: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> String {
        format!("computing whether `{}` is `Copy`", env.value)
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::is_sized_raw<'tcx> {
    fn describe(_tcx: TyCtxt, env: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> String {
        format!("computing whether `{}` is `Sized`", env.value)
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::is_freeze_raw<'tcx> {
    fn describe(_tcx: TyCtxt, env: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> String {
        format!("computing whether `{}` is freeze", env.value)
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::needs_drop_raw<'tcx> {
    fn describe(_tcx: TyCtxt, env: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> String {
        format!("computing whether `{}` needs drop", env.value)
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::layout_raw<'tcx> {
    fn describe(_tcx: TyCtxt, env: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> String {
        format!("computing layout of `{}`", env.value)
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::super_predicates_of<'tcx> {
    fn describe(tcx: TyCtxt, def_id: DefId) -> String {
        format!("computing the supertraits of `{}`",
                tcx.item_path_str(def_id))
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::erase_regions_ty<'tcx> {
    fn describe(_tcx: TyCtxt, ty: Ty<'tcx>) -> String {
        format!("erasing regions from `{:?}`", ty)
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::type_param_predicates<'tcx> {
    fn describe(tcx: TyCtxt, (_, def_id): (DefId, DefId)) -> String {
        let id = tcx.hir.as_local_node_id(def_id).unwrap();
        format!("computing the bounds for type parameter `{}`",
                tcx.hir.ty_param_name(id))
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::coherent_trait<'tcx> {
    fn describe(tcx: TyCtxt, def_id: DefId) -> String {
        format!("coherence checking all impls of trait `{}`",
                tcx.item_path_str(def_id))
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::upstream_monomorphizations<'tcx> {
    fn describe(_: TyCtxt, k: CrateNum) -> String {
        format!("collecting available upstream monomorphizations `{:?}`", k)
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::crate_inherent_impls<'tcx> {
    fn describe(_: TyCtxt, k: CrateNum) -> String {
        format!("all inherent impls defined in crate `{:?}`", k)
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::crate_inherent_impls_overlap_check<'tcx> {
    fn describe(_: TyCtxt, _: CrateNum) -> String {
        "check for overlap between inherent impls defined in this crate".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::crate_variances<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "computing the variances for items in this crate".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::inferred_outlives_crate<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "computing the inferred outlives predicates for items in this crate".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::mir_shims<'tcx> {
    fn describe(tcx: TyCtxt, def: ty::InstanceDef<'tcx>) -> String {
        format!("generating MIR shim for `{}`",
                tcx.item_path_str(def.def_id()))
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::privacy_access_levels<'tcx> {
    fn describe(_: TyCtxt, _: CrateNum) -> String {
        "privacy access levels".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::typeck_item_bodies<'tcx> {
    fn describe(_: TyCtxt, _: CrateNum) -> String {
        "type-checking all item bodies".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::reachable_set<'tcx> {
    fn describe(_: TyCtxt, _: CrateNum) -> String {
        "reachability".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::const_eval<'tcx> {
    fn describe(tcx: TyCtxt, key: ty::ParamEnvAnd<'tcx, GlobalId<'tcx>>) -> String {
        format!("const-evaluating `{}`", tcx.item_path_str(key.value.instance.def.def_id()))
    }

    #[inline]
    fn cache_on_disk(_key: Self::Key) -> bool {
        true
    }

    #[inline]
    fn try_load_from_disk<'a>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                              id: SerializedDepNodeIndex)
                              -> Option<Self::Value> {
        tcx.queries.on_disk_cache.try_load_query_result(tcx, id).map(Ok)
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::mir_keys<'tcx> {
    fn describe(_: TyCtxt, _: CrateNum) -> String {
        "getting a list of all mir_keys".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::symbol_name<'tcx> {
    fn describe(_tcx: TyCtxt, instance: ty::Instance<'tcx>) -> String {
        format!("computing the symbol for `{}`", instance)
    }

    #[inline]
    fn cache_on_disk(_: Self::Key) -> bool {
        true
    }

    #[inline]
    fn try_load_from_disk<'a>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                              id: SerializedDepNodeIndex)
                              -> Option<Self::Value> {
        tcx.queries.on_disk_cache.try_load_query_result(tcx, id)
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::describe_def<'tcx> {
    fn describe(_: TyCtxt, _: DefId) -> String {
        bug!("describe_def")
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::def_span<'tcx> {
    fn describe(_: TyCtxt, _: DefId) -> String {
        bug!("def_span")
    }
}


impl<'tcx> QueryDescription<'tcx> for queries::lookup_stability<'tcx> {
    fn describe(_: TyCtxt, _: DefId) -> String {
        bug!("stability")
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::lookup_deprecation_entry<'tcx> {
    fn describe(_: TyCtxt, _: DefId) -> String {
        bug!("deprecation")
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::item_attrs<'tcx> {
    fn describe(_: TyCtxt, _: DefId) -> String {
        bug!("item_attrs")
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::is_reachable_non_generic<'tcx> {
    fn describe(_: TyCtxt, _: DefId) -> String {
        bug!("is_reachable_non_generic")
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::fn_arg_names<'tcx> {
    fn describe(_: TyCtxt, _: DefId) -> String {
        bug!("fn_arg_names")
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::impl_parent<'tcx> {
    fn describe(_: TyCtxt, _: DefId) -> String {
        bug!("impl_parent")
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::trait_of_item<'tcx> {
    fn describe(_: TyCtxt, _: DefId) -> String {
        bug!("trait_of_item")
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::const_is_rvalue_promotable_to_static<'tcx> {
    fn describe(tcx: TyCtxt, def_id: DefId) -> String {
        format!("const checking if rvalue is promotable to static `{}`",
            tcx.item_path_str(def_id))
    }

    #[inline]
    fn cache_on_disk(_: Self::Key) -> bool {
        true
    }

    #[inline]
    fn try_load_from_disk<'a>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                          id: SerializedDepNodeIndex)
                          -> Option<Self::Value> {
        tcx.queries.on_disk_cache.try_load_query_result(tcx, id)
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::rvalue_promotable_map<'tcx> {
    fn describe(tcx: TyCtxt, def_id: DefId) -> String {
        format!("checking which parts of `{}` are promotable to static",
                tcx.item_path_str(def_id))
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::is_mir_available<'tcx> {
    fn describe(tcx: TyCtxt, def_id: DefId) -> String {
        format!("checking if item is mir available: `{}`",
            tcx.item_path_str(def_id))
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::codegen_fulfill_obligation<'tcx> {
    fn describe(tcx: TyCtxt, key: (ty::ParamEnv<'tcx>, ty::PolyTraitRef<'tcx>)) -> String {
        format!("checking if `{}` fulfills its obligations", tcx.item_path_str(key.1.def_id()))
    }

    #[inline]
    fn cache_on_disk(_: Self::Key) -> bool {
        true
    }

    #[inline]
    fn try_load_from_disk<'a>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                              id: SerializedDepNodeIndex)
                              -> Option<Self::Value> {
        tcx.queries.on_disk_cache.try_load_query_result(tcx, id)
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::trait_impls_of<'tcx> {
    fn describe(tcx: TyCtxt, def_id: DefId) -> String {
        format!("trait impls of `{}`", tcx.item_path_str(def_id))
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::is_object_safe<'tcx> {
    fn describe(tcx: TyCtxt, def_id: DefId) -> String {
        format!("determine object safety of trait `{}`", tcx.item_path_str(def_id))
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::is_const_fn<'tcx> {
    fn describe(tcx: TyCtxt, def_id: DefId) -> String {
        format!("checking if item is const fn: `{}`", tcx.item_path_str(def_id))
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::dylib_dependency_formats<'tcx> {
    fn describe(_: TyCtxt, _: CrateNum) -> String {
        "dylib dependency formats of crate".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::is_panic_runtime<'tcx> {
    fn describe(_: TyCtxt, _: CrateNum) -> String {
        "checking if the crate is_panic_runtime".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::is_compiler_builtins<'tcx> {
    fn describe(_: TyCtxt, _: CrateNum) -> String {
        "checking if the crate is_compiler_builtins".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::has_global_allocator<'tcx> {
    fn describe(_: TyCtxt, _: CrateNum) -> String {
        "checking if the crate has_global_allocator".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::has_panic_handler<'tcx> {
    fn describe(_: TyCtxt, _: CrateNum) -> String {
        "checking if the crate has_panic_handler".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::extern_crate<'tcx> {
    fn describe(_: TyCtxt, _: DefId) -> String {
        "getting crate's ExternCrateData".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::lint_levels<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "computing the lint levels for items in this crate".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::specializes<'tcx> {
    fn describe(_tcx: TyCtxt, _: (DefId, DefId)) -> String {
        "computing whether impls specialize one another".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::in_scope_traits_map<'tcx> {
    fn describe(_tcx: TyCtxt, _: DefIndex) -> String {
        "traits in scope at a block".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::is_no_builtins<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "test whether a crate has #![no_builtins]".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::panic_strategy<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "query a crate's configured panic strategy".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::is_profiler_runtime<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "query a crate is #![profiler_runtime]".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::is_sanitizer_runtime<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "query a crate is #![sanitizer_runtime]".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::reachable_non_generics<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "looking up the exported symbols of a crate".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::native_libraries<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "looking up the native libraries of a linked crate".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::foreign_modules<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "looking up the foreign modules of a linked crate".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::plugin_registrar_fn<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "looking up the plugin registrar for a crate".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::derive_registrar_fn<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "looking up the derive registrar for a crate".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::crate_disambiguator<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "looking up the disambiguator a crate".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::crate_hash<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "looking up the hash a crate".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::original_crate_name<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "looking up the original name a crate".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::extra_filename<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "looking up the extra filename for a crate".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::implementations_of_trait<'tcx> {
    fn describe(_tcx: TyCtxt, _: (CrateNum, DefId)) -> String {
        "looking up implementations of a trait in a crate".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::all_trait_implementations<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "looking up all (?) trait implementations".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::link_args<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "looking up link arguments for a crate".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::resolve_lifetimes<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "resolving lifetimes".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::named_region_map<'tcx> {
    fn describe(_tcx: TyCtxt, _: DefIndex) -> String {
        "looking up a named region".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::is_late_bound_map<'tcx> {
    fn describe(_tcx: TyCtxt, _: DefIndex) -> String {
        "testing if a region is late bound".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::object_lifetime_defaults_map<'tcx> {
    fn describe(_tcx: TyCtxt, _: DefIndex) -> String {
        "looking up lifetime defaults for a region".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::dep_kind<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "fetching what a dependency looks like".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::crate_name<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "fetching what a crate is named".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::get_lib_features<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        format!("calculating the lib features map")
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::defined_lib_features<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        format!("calculating the lib features defined in a crate")
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::get_lang_items<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "calculating the lang items map".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::defined_lang_items<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "calculating the lang items defined in a crate".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::missing_lang_items<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "calculating the missing lang items in a crate".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::visible_parent_map<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "calculating the visible parent map".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::missing_extern_crate_item<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "seeing if we're missing an `extern crate` item for this crate".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::used_crate_source<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "looking at the source for a crate".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::postorder_cnums<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "generating a postorder list of CrateNums".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::maybe_unused_extern_crates<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "looking up all possibly unused extern crates".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::stability_index<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "calculating the stability index for the local crate".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::all_traits<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "fetching all foreign and local traits".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::all_crate_nums<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "fetching all foreign CrateNum instances".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::exported_symbols<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "exported_symbols".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::collect_and_partition_mono_items<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "collect_and_partition_mono_items".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::codegen_unit<'tcx> {
    fn describe(_tcx: TyCtxt, _: InternedString) -> String {
        "codegen_unit".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::output_filenames<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "output_filenames".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::vtable_methods<'tcx> {
    fn describe(tcx: TyCtxt, key: ty::PolyTraitRef<'tcx> ) -> String {
        format!("finding all methods for trait {}", tcx.item_path_str(key.def_id()))
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::features_query<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "looking up enabled feature gates".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::typeck_tables_of<'tcx> {
    #[inline]
    fn cache_on_disk(def_id: Self::Key) -> bool {
        def_id.is_local()
    }

    fn try_load_from_disk(tcx: TyCtxt<'_, 'tcx, 'tcx>,
                          id: SerializedDepNodeIndex)
                          -> Option<Self::Value> {
        let typeck_tables: Option<ty::TypeckTables<'tcx>> = tcx
            .queries.on_disk_cache
            .try_load_query_result(tcx, id);

        typeck_tables.map(|tables| tcx.alloc_tables(tables))
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::optimized_mir<'tcx> {
    #[inline]
    fn cache_on_disk(def_id: Self::Key) -> bool {
        def_id.is_local()
    }

    fn try_load_from_disk<'a>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                              id: SerializedDepNodeIndex)
                              -> Option<Self::Value> {
        let mir: Option<::mir::Mir<'tcx>> = tcx.queries.on_disk_cache
                                               .try_load_query_result(tcx, id);
        mir.map(|x| tcx.alloc_mir(x))
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::substitute_normalize_and_test_predicates<'tcx> {
    fn describe(tcx: TyCtxt, key: (DefId, &'tcx Substs<'tcx>)) -> String {
        format!("testing substituted normalized predicates:`{}`", tcx.item_path_str(key.0))
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::target_features_whitelist<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "looking up the whitelist of target features".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::instance_def_size_estimate<'tcx> {
    fn describe(tcx: TyCtxt, def: ty::InstanceDef<'tcx>) -> String {
        format!("estimating size for `{}`", tcx.item_path_str(def.def_id()))
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::generics_of<'tcx> {
    #[inline]
    fn cache_on_disk(def_id: Self::Key) -> bool {
        def_id.is_local()
    }

    fn try_load_from_disk<'a>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                              id: SerializedDepNodeIndex)
                              -> Option<Self::Value> {
        let generics: Option<ty::Generics> = tcx.queries.on_disk_cache
                                                .try_load_query_result(tcx, id);
        generics.map(|x| tcx.alloc_generics(x))
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::program_clauses_for<'tcx> {
    fn describe(_tcx: TyCtxt, _: DefId) -> String {
        "generating chalk-style clauses".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::program_clauses_for_env<'tcx> {
    fn describe(_tcx: TyCtxt, _: ty::ParamEnv<'tcx>) -> String {
        "generating chalk-style clauses for param env".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::wasm_import_module_map<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "wasm import module map".to_string()
    }
}

impl<'tcx> QueryDescription<'tcx> for queries::dllimport_foreign_items<'tcx> {
    fn describe(_tcx: TyCtxt, _: CrateNum) -> String {
        "wasm import module map".to_string()
    }
}

macro_rules! impl_disk_cacheable_query(
    ($query_name:ident, |$key:tt| $cond:expr) => {
        impl<'tcx> QueryDescription<'tcx> for queries::$query_name<'tcx> {
            #[inline]
            fn cache_on_disk($key: Self::Key) -> bool {
                $cond
            }

            #[inline]
            fn try_load_from_disk<'a>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                      id: SerializedDepNodeIndex)
                                      -> Option<Self::Value> {
                tcx.queries.on_disk_cache.try_load_query_result(tcx, id)
            }
        }
    }
);

impl_disk_cacheable_query!(unsafety_check_result, |def_id| def_id.is_local());
impl_disk_cacheable_query!(borrowck, |def_id| def_id.is_local());
impl_disk_cacheable_query!(mir_borrowck, |def_id| def_id.is_local());
impl_disk_cacheable_query!(mir_const_qualif, |def_id| def_id.is_local());
impl_disk_cacheable_query!(check_match, |def_id| def_id.is_local());
impl_disk_cacheable_query!(def_symbol_name, |_| true);
impl_disk_cacheable_query!(type_of, |def_id| def_id.is_local());
impl_disk_cacheable_query!(predicates_of, |def_id| def_id.is_local());
impl_disk_cacheable_query!(used_trait_imports, |def_id| def_id.is_local());
impl_disk_cacheable_query!(codegen_fn_attrs, |_| true);
impl_disk_cacheable_query!(specialization_graph_of, |_| true);