Move QueryState/ActiveKeyStatus.

From `rustc_query_state` to `rustc_middle`.

compiler/rustc_middle/src/query/mod.rs

@@ -1,8 +1,10 @@
 use rustc_hir::def_id::LocalDefId;
-pub use rustc_query_system::query::{QueryMode, QueryState};
+pub use rustc_query_system::query::QueryMode;
 
 pub use self::keys::{AsLocalKey, Key, LocalCrate};
-pub use self::plumbing::{IntoQueryParam, TyCtxtAt, TyCtxtEnsureDone, TyCtxtEnsureOk};
+pub use self::plumbing::{
+    ActiveKeyStatus, IntoQueryParam, QueryState, TyCtxtAt, TyCtxtEnsureDone, TyCtxtEnsureOk,
+};
 pub use crate::queries::Providers;
 use crate::ty::TyCtxt;
 

compiler/rustc_middle/src/query/plumbing.rs

@@ -1,6 +1,8 @@
 use std::ops::Deref;
 
 use rustc_data_structures::fingerprint::Fingerprint;
+use rustc_data_structures::hash_table::HashTable;
+use rustc_data_structures::sharded::Sharded;
 use rustc_data_structures::sync::{AtomicU64, WorkerLocal};
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::hir_id::OwnerId;
@@ -8,7 +10,7 @@ use rustc_macros::HashStable;
 use rustc_query_system::dep_graph::{DepNodeIndex, SerializedDepNodeIndex};
 use rustc_query_system::ich::StableHashingContext;
 pub(crate) use rustc_query_system::query::QueryJobId;
-use rustc_query_system::query::{CycleError, CycleErrorHandling, QueryCache};
+use rustc_query_system::query::{CycleError, CycleErrorHandling, QueryCache, QueryJob};
 use rustc_span::{ErrorGuaranteed, Span};
 pub use sealed::IntoQueryParam;
 
@@ -20,6 +22,37 @@ use crate::queries::{
 use crate::query::on_disk_cache::{CacheEncoder, EncodedDepNodeIndex, OnDiskCache};
 use crate::ty::TyCtxt;
 
+/// For a particular query, keeps track of "active" keys, i.e. keys whose
+/// evaluation has started but has not yet finished successfully.
+///
+/// (Successful query evaluation for a key is represented by an entry in the
+/// query's in-memory cache.)
+pub struct QueryState<'tcx, K> {
+    pub active: Sharded<HashTable<(K, ActiveKeyStatus<'tcx>)>>,
+}
+
+impl<'tcx, K> Default for QueryState<'tcx, K> {
+    fn default() -> QueryState<'tcx, K> {
+        QueryState { active: Default::default() }
+    }
+}
+
+/// For a particular query and key, tracks the status of a query evaluation
+/// that has started, but has not yet finished successfully.
+///
+/// (Successful query evaluation for a key is represented by an entry in the
+/// query's in-memory cache.)
+pub enum ActiveKeyStatus<'tcx> {
+    /// Some thread is already evaluating the query for this key.
+    ///
+    /// The enclosed [`QueryJob`] can be used to wait for it to finish.
+    Started(QueryJob<'tcx>),
+
+    /// The query panicked. Queries trying to wait on this will raise a fatal error which will
+    /// silently panic.
+    Poisoned,
+}
+
 pub type WillCacheOnDiskForKeyFn<'tcx, Key> = fn(tcx: TyCtxt<'tcx>, key: &Key) -> bool;
 
 pub type TryLoadFromDiskFn<'tcx, Key, Value> = fn(