Remove the anon query modifier

We still have some anon-task machinery for `DepKind::TraitSelect` tasks, but
there are no longer any queries that use the `anon` modifier.

Author: Zalathar

compiler/rustc_macros/src/query.rs

@@ -140,7 +140,6 @@ struct CacheOnDiskIf {
 /// See `rustc_middle::query::modifiers` for documentation of each query modifier.
 struct QueryModifiers {
     // tidy-alphabetical-start
-    anon: Option<Ident>,
     arena_cache: Option<Ident>,
     cache_on_disk_if: Option<CacheOnDiskIf>,
     depth_limit: Option<Ident>,
@@ -159,7 +158,6 @@ fn parse_query_modifiers(input: ParseStream<'_>) -> Result<QueryModifiers> {
     let mut desc = None;
     let mut no_force = None;
     let mut no_hash = None;
-    let mut anon = None;
     let mut eval_always = None;
     let mut depth_limit = None;
     let mut separate_provide_extern = None;
@@ -195,8 +193,6 @@ fn parse_query_modifiers(input: ParseStream<'_>) -> Result<QueryModifiers> {
             try_insert!(no_force = modifier);
         } else if modifier == "no_hash" {
             try_insert!(no_hash = modifier);
-        } else if modifier == "anon" {
-            try_insert!(anon = modifier);
         } else if modifier == "eval_always" {
             try_insert!(eval_always = modifier);
         } else if modifier == "depth_limit" {
@@ -218,7 +214,6 @@ fn parse_query_modifiers(input: ParseStream<'_>) -> Result<QueryModifiers> {
         desc,
         no_force,
         no_hash,
-        anon,
         eval_always,
         depth_limit,
         separate_provide_extern,
@@ -248,7 +243,6 @@ fn returns_error_guaranteed(ret_ty: &ReturnType) -> bool {
 fn make_modifiers_stream(query: &Query) -> proc_macro2::TokenStream {
     let QueryModifiers {
         // tidy-alphabetical-start
-        anon,
         arena_cache,
         cache_on_disk_if,
         depth_limit,
@@ -261,7 +255,6 @@ fn make_modifiers_stream(query: &Query) -> proc_macro2::TokenStream {
         // tidy-alphabetical-end
     } = &query.modifiers;
 
-    let anon = anon.is_some();
     let arena_cache = arena_cache.is_some();
     let cache_on_disk = cache_on_disk_if.is_some();
     let depth_limit = depth_limit.is_some();
@@ -280,7 +273,6 @@ fn make_modifiers_stream(query: &Query) -> proc_macro2::TokenStream {
         query_name_span =>
         // Search for (QMODLIST) to find all occurrences of this query modifier list.
         // tidy-alphabetical-start
-        anon: #anon,
         arena_cache: #arena_cache,
         cache_on_disk: #cache_on_disk,
         depth_limit: #depth_limit,
@@ -396,7 +388,6 @@ fn add_to_analyzer_stream(query: &Query, analyzer_stream: &mut proc_macro2::Toke
 
     doc_link!(
         // tidy-alphabetical-start
-        anon,
         arena_cache,
         depth_limit,
         eval_always,
@@ -487,11 +478,6 @@ pub(super) fn rustc_queries(input: TokenStream) -> TokenStream {
         });
 
         if let Some(feedable) = &modifiers.feedable {
-            assert!(
-                modifiers.anon.is_none(),
-                feedable.span(),
-                "Query {name} cannot be both `feedable` and `anon`."
-            );
             assert!(
                 modifiers.eval_always.is_none(),
                 feedable.span(),

compiler/rustc_middle/src/dep_graph/dep_node.rs

@@ -94,10 +94,14 @@ impl DepKind {
 pub struct DepNode {
     pub kind: DepKind,
 
-    /// This is _typically_ a hash of the query key, but sometimes not.
+    /// If `kind` is a query method, then its "key fingerprint" is always a
+    /// stable hash of the query key.
     ///
-    /// For example, `anon` nodes have a fingerprint that is derived from their
-    /// dependencies instead of a key.
+    /// For non-query nodes, the content of this field varies:
+    /// - Some dep kinds always use a dummy `ZERO` fingerprint.
+    /// - Some dep kinds use the stable hash of some relevant key-like value.
+    /// - Some dep kinds use the `with_anon_task` mechanism, and set their key
+    ///   fingerprint to a hash derived from the task's dependencies.
     ///
     /// In some cases the key value can be reconstructed from this fingerprint;
     /// see [`KeyFingerprintStyle`].

compiler/rustc_middle/src/dep_graph/graph.rs

@@ -375,9 +375,8 @@ impl DepGraphData {
     /// incorrectly marked green.
     ///
     /// FIXME: This could perhaps return a `WithDepNode` to ensure that the
-    /// user of this function actually performs the read; we'll have to see
-    /// how to make that work with `anon` in `execute_job_incr`, though.
-    pub fn with_anon_task_inner<'tcx, OP, R>(
+    /// user of this function actually performs the read.
+    fn with_anon_task_inner<'tcx, OP, R>(
         &self,
         tcx: TyCtxt<'tcx>,
         dep_kind: DepKind,

compiler/rustc_middle/src/query/modifiers.rs

@@ -7,11 +7,6 @@
 
 // tidy-alphabetical-start
 //
-/// # `anon` query modifier
-///
-/// Generate a dep node based not on the query key, but on the query's dependencies.
-pub(crate) struct anon;
-
 /// # `arena_cache` query modifier
 ///
 /// Query return values must impl `Copy` and be small, but some queries must return values that

compiler/rustc_middle/src/query/plumbing.rs

@@ -77,8 +77,6 @@ pub enum EnsureMode {
 pub struct QueryVTable<'tcx, C: QueryCache> {
     pub name: &'static str,
 
-    /// True if this query has the `anon` modifier.
-    pub anon: bool,
     /// True if this query has the `eval_always` modifier.
     pub eval_always: bool,
     /// True if this query has the `depth_limit` modifier.
@@ -283,7 +281,6 @@ macro_rules! define_callbacks {
                 fn $name:ident($($K:tt)*) -> $V:ty
                 {
                     // Search for (QMODLIST) to find all occurrences of this query modifier list.
-                    anon: $anon:literal,
                     arena_cache: $arena_cache:literal,
                     cache_on_disk: $cache_on_disk:literal,
                     depth_limit: $depth_limit:literal,

compiler/rustc_query_impl/src/dep_kind_vtables.rs

@@ -96,26 +96,17 @@ mod non_query {
 /// Shared implementation of the [`DepKindVTable`] constructor for queries.
 /// Called from macro-generated code for each query.
 pub(crate) fn make_dep_kind_vtable_for_query<'tcx, Q>(
-    is_anon: bool,
     is_cache_on_disk: bool,
     is_eval_always: bool,
     is_no_force: bool,
 ) -> DepKindVTable<'tcx>
 where
     Q: GetQueryVTable<'tcx>,
 {
-    let key_fingerprint_style = if is_anon {
-        KeyFingerprintStyle::Opaque
-    } else {
-        <Q::Cache as QueryCache>::Key::key_fingerprint_style()
-    };
-
     // A query dep-node can only be forced or promoted if it can recover a key
     // from its key fingerprint.
+    let key_fingerprint_style = <Q::Cache as QueryCache>::Key::key_fingerprint_style();
     let can_recover = key_fingerprint_style.is_maybe_recoverable();
-    if is_anon {
-        assert!(!can_recover);
-    }
 
     DepKindVTable {
         is_eval_always,
@@ -135,7 +126,6 @@ macro_rules! define_dep_kind_vtables {
                 fn $name:ident($K:ty) -> $V:ty
                 {
                     // Search for (QMODLIST) to find all occurrences of this query modifier list.
-                    anon: $anon:literal,
                     arena_cache: $arena_cache:literal,
                     cache_on_disk: $cache_on_disk:literal,
                     depth_limit: $depth_limit:literal,
@@ -168,7 +158,6 @@ macro_rules! define_dep_kind_vtables {
                 $crate::dep_kind_vtables::make_dep_kind_vtable_for_query::<
                     $crate::query_impl::$name::VTableGetter,
                 >(
-                    $anon,
                     $cache_on_disk,
                     $eval_always,
                     $no_force,

compiler/rustc_query_impl/src/execution.rs

@@ -424,7 +424,7 @@ fn execute_job_incr<'tcx, C: QueryCache>(
     let dep_graph_data =
         tcx.dep_graph.data().expect("should always be present in incremental mode");
 
-    if !query.anon && !query.eval_always {
+    if !query.eval_always {
         // `to_dep_node` is expensive for some `DepKind`s.
         let dep_node =
             dep_node_opt.get_or_insert_with(|| DepNode::construct(tcx, query.dep_kind, &key));
@@ -451,13 +451,6 @@ fn execute_job_incr<'tcx, C: QueryCache>(
     let prof_timer = tcx.prof.query_provider();
 
     let (result, dep_node_index) = start_query(job_id, query.depth_limit, || {
-        if query.anon {
-            // Call the query provider inside an anon task.
-            return dep_graph_data.with_anon_task_inner(tcx, query.dep_kind, || {
-                (query.invoke_provider_fn)(tcx, key)
-            });
-        }
-
         // `to_dep_node` is expensive for some `DepKind`s.
         let dep_node =
             dep_node_opt.unwrap_or_else(|| DepNode::construct(tcx, query.dep_kind, &key));
@@ -601,9 +594,6 @@ fn check_if_ensure_can_skip_execution<'tcx, C: QueryCache>(
         return EnsureCanSkip { skip_execution: false, dep_node: None };
     }
 
-    // Ensuring an anonymous query makes no sense
-    assert!(!query.anon);
-
     let dep_node = DepNode::construct(tcx, query.dep_kind, &key);
 
     let serialized_dep_node_index = match tcx.dep_graph.try_mark_green(tcx, &dep_node) {
@@ -703,8 +693,6 @@ pub(crate) fn force_query<'tcx, C: QueryCache>(
         return;
     }
 
-    debug_assert!(!query.anon);
-
     ensure_sufficient_stack(|| {
         try_execute_query::<C, true>(query, tcx, DUMMY_SP, key, Some(dep_node))
     });

compiler/rustc_query_impl/src/query_impl.rs

@@ -16,7 +16,6 @@ macro_rules! define_queries {
                 fn $name:ident($K:ty) -> $V:ty
                 {
                     // Search for (QMODLIST) to find all occurrences of this query modifier list.
-                    anon: $anon:literal,
                     arena_cache: $arena_cache:literal,
                     cache_on_disk: $cache_on_disk:literal,
                     depth_limit: $depth_limit:literal,
@@ -133,7 +132,6 @@ macro_rules! define_queries {
 
                     QueryVTable {
                         name: stringify!($name),
-                        anon: $anon,
                         eval_always: $eval_always,
                         depth_limit: $depth_limit,
                         feedable: $feedable,

src/doc/rustc-dev-guide/src/queries/incremental-compilation-in-detail.md

@@ -485,13 +485,6 @@ respect to incremental compilation:
    For example, it makes no sense to store values from upstream
    crates in the cache because they are already available in the upstream crate's metadata.
 
- - `anon` - This attribute makes the system use "anonymous" dep-nodes for the given query.
-   An anonymous dep-node is not identified by the corresponding query key.
-   Instead, its ID is computed from the IDs of its dependencies.
-   This allows the red-green system to do its change detection even if there is no
-   query key available for a given dep-node -- something which is needed for
-   handling trait selection because it is not based on queries.
-
 [mod]: ../query.html#adding-a-new-kind-of-query