Auto merge of #89016 - lcnr:non_blanket_impls, r=nikomatsakis,michaelwoerister

fix non_blanket_impls iteration order

We sometimes iterate over all `non_blanket_impls`, not sure if this is observable outside
of error messages (i.e. as incremental bugs). This should fix the underlying issue of #86986.

second attempt of #88718

r? `@nikomatsakis`

Author: bors

compiler/rustc_metadata/src/dependency_format.rs

@@ -277,7 +277,7 @@ fn attempt_static(tcx: TyCtxt<'_>) -> Option<DependencyList> {
     let all_crates_available_as_rlib = tcx
         .crates(())
         .iter()
-        .cloned()
+        .copied()
         .filter_map(|cnum| {
             if tcx.dep_kind(cnum).macros_only() {
                 return None;
@@ -291,10 +291,11 @@ fn attempt_static(tcx: TyCtxt<'_>) -> Option<DependencyList> {
 
     // All crates are available in an rlib format, so we're just going to link
     // everything in explicitly so long as it's actually required.
-    let last_crate = tcx.crates(()).len();
-    let mut ret = (1..last_crate + 1)
-        .map(|cnum| {
-            if tcx.dep_kind(CrateNum::new(cnum)) == CrateDepKind::Explicit {
+    let mut ret = tcx
+        .crates(())
+        .iter()
+        .map(|&cnum| {
+            if tcx.dep_kind(cnum) == CrateDepKind::Explicit {
                 Linkage::Static
             } else {
                 Linkage::NotLinked

compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs

@@ -304,17 +304,7 @@ pub fn provide(providers: &mut Providers) {
             // traversal, but not globally minimal across all crates.
             let bfs_queue = &mut VecDeque::new();
 
-            // Preferring shortest paths alone does not guarantee a
-            // deterministic result; so sort by crate num to avoid
-            // hashtable iteration non-determinism. This only makes
-            // things as deterministic as crate-nums assignment is,
-            // which is to say, its not deterministic in general. But
-            // we believe that libstd is consistently assigned crate
-            // num 1, so it should be enough to resolve #46112.
-            let mut crates: Vec<CrateNum> = (*tcx.crates(())).to_owned();
-            crates.sort();
-
-            for &cnum in crates.iter() {
+            for &cnum in tcx.crates(()) {
                 // Ignore crates without a corresponding local `extern crate` item.
                 if tcx.missing_extern_crate_item(cnum) {
                     continue;
@@ -323,35 +313,31 @@ pub fn provide(providers: &mut Providers) {
                 bfs_queue.push_back(DefId { krate: cnum, index: CRATE_DEF_INDEX });
             }
 
-            // (restrict scope of mutable-borrow of `visible_parent_map`)
-            {
-                let visible_parent_map = &mut visible_parent_map;
-                let mut add_child = |bfs_queue: &mut VecDeque<_>, child: &Export, parent: DefId| {
-                    if child.vis != ty::Visibility::Public {
-                        return;
-                    }
+            let mut add_child = |bfs_queue: &mut VecDeque<_>, child: &Export, parent: DefId| {
+                if child.vis != ty::Visibility::Public {
+                    return;
+                }
 
-                    if let Some(child) = child.res.opt_def_id() {
-                        match visible_parent_map.entry(child) {
-                            Entry::Occupied(mut entry) => {
-                                // If `child` is defined in crate `cnum`, ensure
-                                // that it is mapped to a parent in `cnum`.
-                                if child.is_local() && entry.get().is_local() {
-                                    entry.insert(parent);
-                                }
-                            }
-                            Entry::Vacant(entry) => {
+                if let Some(child) = child.res.opt_def_id() {
+                    match visible_parent_map.entry(child) {
+                        Entry::Occupied(mut entry) => {
+                            // If `child` is defined in crate `cnum`, ensure
+                            // that it is mapped to a parent in `cnum`.
+                            if child.is_local() && entry.get().is_local() {
                                 entry.insert(parent);
-                                bfs_queue.push_back(child);
                             }
                         }
+                        Entry::Vacant(entry) => {
+                            entry.insert(parent);
+                            bfs_queue.push_back(child);
+                        }
                     }
-                };
+                }
+            };
 
-                while let Some(def) = bfs_queue.pop_front() {
-                    for child in tcx.item_children(def).iter() {
-                        add_child(bfs_queue, child, def);
-                    }
+            while let Some(def) = bfs_queue.pop_front() {
+                for child in tcx.item_children(def).iter() {
+                    add_child(bfs_queue, child, def);
                 }
             }
 

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -1708,9 +1708,10 @@ impl EncodeContext<'a, 'tcx> {
 
     fn encode_crate_deps(&mut self) -> Lazy<[CrateDep]> {
         empty_proc_macro!(self);
-        let crates = self.tcx.crates(());
 
-        let mut deps = crates
+        let deps = self
+            .tcx
+            .crates(())
             .iter()
             .map(|&cnum| {
                 let dep = CrateDep {
@@ -1724,8 +1725,6 @@ impl EncodeContext<'a, 'tcx> {
             })
             .collect::<Vec<_>>();
 
-        deps.sort_by_key(|&(cnum, _)| cnum);
-
         {
             // Sanity-check the crate numbers
             let mut expected_cnum = 1;

compiler/rustc_middle/src/ich/hcx.rs

@@ -1,9 +1,9 @@
 use crate::ich;
 use crate::middle::cstore::CrateStore;
-use crate::ty::{fast_reject, TyCtxt};
+use crate::ty::TyCtxt;
 
 use rustc_ast as ast;
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::sync::Lrc;
 use rustc_hir as hir;
@@ -14,9 +14,6 @@ use rustc_span::source_map::SourceMap;
 use rustc_span::symbol::Symbol;
 use rustc_span::{BytePos, CachingSourceMapView, SourceFile, Span, SpanData};
 
-use smallvec::SmallVec;
-use std::cmp::Ord;
-
 fn compute_ignored_attr_names() -> FxHashSet<Symbol> {
     debug_assert!(!ich::IGNORED_ATTRIBUTES.is_empty());
     ich::IGNORED_ATTRIBUTES.iter().copied().collect()
@@ -241,39 +238,3 @@ impl<'a> rustc_span::HashStableContext for StableHashingContext<'a> {
 }
 
 impl rustc_session::HashStableContext for StableHashingContext<'a> {}
-
-pub fn hash_stable_trait_impls<'a>(
-    hcx: &mut StableHashingContext<'a>,
-    hasher: &mut StableHasher,
-    blanket_impls: &[DefId],
-    non_blanket_impls: &FxHashMap<fast_reject::SimplifiedType, Vec<DefId>>,
-) {
-    {
-        let mut blanket_impls: SmallVec<[_; 8]> =
-            blanket_impls.iter().map(|&def_id| hcx.def_path_hash(def_id)).collect();
-
-        if blanket_impls.len() > 1 {
-            blanket_impls.sort_unstable();
-        }
-
-        blanket_impls.hash_stable(hcx, hasher);
-    }
-
-    {
-        let mut keys: SmallVec<[_; 8]> =
-            non_blanket_impls.keys().map(|k| (k, k.map_def(|d| hcx.def_path_hash(d)))).collect();
-        keys.sort_unstable_by(|&(_, ref k1), &(_, ref k2)| k1.cmp(k2));
-        keys.len().hash_stable(hcx, hasher);
-        for (key, ref stable_key) in keys {
-            stable_key.hash_stable(hcx, hasher);
-            let mut impls: SmallVec<[_; 8]> =
-                non_blanket_impls[key].iter().map(|&impl_id| hcx.def_path_hash(impl_id)).collect();
-
-            if impls.len() > 1 {
-                impls.sort_unstable();
-            }
-
-            impls.hash_stable(hcx, hasher);
-        }
-    }
-}

compiler/rustc_middle/src/ich/mod.rs

@@ -1,8 +1,6 @@
 //! ICH - Incremental Compilation Hash
 
-pub use self::hcx::{
-    hash_stable_trait_impls, NodeIdHashingMode, StableHashingContext, StableHashingContextProvider,
-};
+pub use self::hcx::{NodeIdHashingMode, StableHashingContext, StableHashingContextProvider};
 use rustc_span::symbol::{sym, Symbol};
 
 mod hcx;

compiler/rustc_middle/src/traits/specialization_graph.rs

@@ -1,9 +1,7 @@
-use crate::ich::{self, StableHashingContext};
 use crate::ty::fast_reject::SimplifiedType;
 use crate::ty::fold::TypeFoldable;
 use crate::ty::{self, TyCtxt};
-use rustc_data_structures::fx::FxHashMap;
-use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
+use rustc_data_structures::fx::FxIndexMap;
 use rustc_errors::ErrorReported;
 use rustc_hir::def_id::{DefId, DefIdMap};
 use rustc_span::symbol::Ident;
@@ -50,19 +48,19 @@ impl Graph {
 
 /// Children of a given impl, grouped into blanket/non-blanket varieties as is
 /// done in `TraitDef`.
-#[derive(Default, TyEncodable, TyDecodable, Debug)]
+#[derive(Default, TyEncodable, TyDecodable, Debug, HashStable)]
 pub struct Children {
     // Impls of a trait (or specializations of a given impl). To allow for
     // quicker lookup, the impls are indexed by a simplified version of their
     // `Self` type: impls with a simplifiable `Self` are stored in
-    // `nonblanket_impls` keyed by it, while all other impls are stored in
+    // `non_blanket_impls` keyed by it, while all other impls are stored in
     // `blanket_impls`.
     //
     // A similar division is used within `TraitDef`, but the lists there collect
     // together *all* the impls for a trait, and are populated prior to building
     // the specialization graph.
     /// Impls of the trait.
-    pub nonblanket_impls: FxHashMap<SimplifiedType, Vec<DefId>>,
+    pub non_blanket_impls: FxIndexMap<SimplifiedType, Vec<DefId>>,
 
     /// Blanket impls associated with the trait.
     pub blanket_impls: Vec<DefId>,
@@ -235,11 +233,3 @@ pub fn ancestors(
         })
     }
 }
-
-impl<'a> HashStable<StableHashingContext<'a>> for Children {
-    fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
-        let Children { ref nonblanket_impls, ref blanket_impls } = *self;
-
-        ich::hash_stable_trait_impls(hcx, hasher, blanket_impls, nonblanket_impls);
-    }
-}

compiler/rustc_middle/src/ty/trait_def.rs

@@ -1,4 +1,3 @@
-use crate::ich::{self, StableHashingContext};
 use crate::traits::specialization_graph;
 use crate::ty::fast_reject;
 use crate::ty::fold::TypeFoldable;
@@ -7,8 +6,7 @@ use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir::definitions::DefPathHash;
 
-use rustc_data_structures::fx::FxHashMap;
-use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
+use rustc_data_structures::fx::FxIndexMap;
 use rustc_errors::ErrorReported;
 use rustc_macros::HashStable;
 
@@ -66,11 +64,11 @@ pub enum TraitSpecializationKind {
     AlwaysApplicable,
 }
 
-#[derive(Default, Debug)]
+#[derive(Default, Debug, HashStable)]
 pub struct TraitImpls {
     blanket_impls: Vec<DefId>,
     /// Impls indexed by their simplified self type, for fast lookup.
-    non_blanket_impls: FxHashMap<fast_reject::SimplifiedType, Vec<DefId>>,
+    non_blanket_impls: FxIndexMap<fast_reject::SimplifiedType, Vec<DefId>>,
 }
 
 impl TraitImpls {
@@ -249,11 +247,3 @@ pub(super) fn trait_impls_of_provider(tcx: TyCtxt<'_>, trait_id: DefId) -> Trait
 
     impls
 }
-
-impl<'a> HashStable<StableHashingContext<'a>> for TraitImpls {
-    fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
-        let TraitImpls { ref blanket_impls, ref non_blanket_impls } = *self;
-
-        ich::hash_stable_trait_impls(hcx, hasher, blanket_impls, non_blanket_impls);
-    }
-}

compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs

@@ -50,7 +50,7 @@ impl ChildrenExt for Children {
         let trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
         if let Some(st) = fast_reject::simplify_type(tcx, trait_ref.self_ty(), false) {
             debug!("insert_blindly: impl_def_id={:?} st={:?}", impl_def_id, st);
-            self.nonblanket_impls.entry(st).or_default().push(impl_def_id)
+            self.non_blanket_impls.entry(st).or_default().push(impl_def_id)
         } else {
             debug!("insert_blindly: impl_def_id={:?} st=None", impl_def_id);
             self.blanket_impls.push(impl_def_id)
@@ -65,7 +65,7 @@ impl ChildrenExt for Children {
         let vec: &mut Vec<DefId>;
         if let Some(st) = fast_reject::simplify_type(tcx, trait_ref.self_ty(), false) {
             debug!("remove_existing: impl_def_id={:?} st={:?}", impl_def_id, st);
-            vec = self.nonblanket_impls.get_mut(&st).unwrap();
+            vec = self.non_blanket_impls.get_mut(&st).unwrap();
         } else {
             debug!("remove_existing: impl_def_id={:?} st=None", impl_def_id);
             vec = &mut self.blanket_impls;
@@ -218,15 +218,15 @@ impl ChildrenExt for Children {
 }
 
 fn iter_children(children: &mut Children) -> impl Iterator<Item = DefId> + '_ {
-    let nonblanket = children.nonblanket_impls.iter_mut().flat_map(|(_, v)| v.iter());
+    let nonblanket = children.non_blanket_impls.iter().flat_map(|(_, v)| v.iter());
     children.blanket_impls.iter().chain(nonblanket).cloned()
 }
 
 fn filtered_children(
     children: &mut Children,
     st: SimplifiedType,
 ) -> impl Iterator<Item = DefId> + '_ {
-    let nonblanket = children.nonblanket_impls.entry(st).or_default().iter();
+    let nonblanket = children.non_blanket_impls.entry(st).or_default().iter();
     children.blanket_impls.iter().chain(nonblanket).cloned()
 }