resolve: Avoid some unstable iteration

compiler/rustc_data_structures/src/unord.rs

@@ -259,6 +259,12 @@ impl<V: Eq + Hash> UnordSet<V> {
         self.inner.is_empty()
     }
 
+    /// If the set has only one element, returns it, otherwise returns `None`.
+    #[inline]
+    pub fn get_only(&self) -> Option<&V> {
+        if self.inner.len() == 1 { self.inner.iter().next() } else { None }
+    }
+
     #[inline]
     pub fn insert(&mut self, v: V) -> bool {
         self.inner.insert(v)

compiler/rustc_middle/src/ty/mod.rs

@@ -33,6 +33,7 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_data_structures::intern::Interned;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::steal::Steal;
+use rustc_data_structures::unord::UnordMap;
 use rustc_errors::{Diag, ErrorGuaranteed};
 use rustc_hir::LangItem;
 use rustc_hir::def::{CtorKind, CtorOf, DefKind, DocLinkResMap, LifetimeRes, Res};
@@ -168,7 +169,7 @@ pub struct ResolverGlobalCtxt {
     /// Item with a given `LocalDefId` was defined during macro expansion with ID `ExpnId`.
     pub expn_that_defined: FxHashMap<LocalDefId, ExpnId>,
     pub effective_visibilities: EffectiveVisibilities,
-    pub extern_crate_map: FxHashMap<LocalDefId, CrateNum>,
+    pub extern_crate_map: UnordMap<LocalDefId, CrateNum>,
     pub maybe_unused_trait_imports: FxIndexSet<LocalDefId>,
     pub module_children: LocalDefIdMap<Vec<ModChild>>,
     pub glob_map: FxHashMap<LocalDefId, FxHashSet<Symbol>>,

compiler/rustc_resolve/src/build_reduced_graph.rs

@@ -1115,6 +1115,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
                 }
             });
         } else {
+            #[allow(rustc::potential_query_instability)] // FIXME
             for ident in single_imports.iter().cloned() {
                 let result = self.r.maybe_resolve_ident_in_module(
                     ModuleOrUniformRoot::Module(module),

compiler/rustc_resolve/src/diagnostics.rs

@@ -6,6 +6,7 @@ use rustc_ast::{
 };
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::unord::UnordSet;
 use rustc_errors::codes::*;
 use rustc_errors::{
     Applicability, Diag, DiagCtxtHandle, ErrorGuaranteed, MultiSpan, SuggestionStyle,
@@ -1467,6 +1468,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             return;
         }
 
+        #[allow(rustc::potential_query_instability)] // FIXME
         let unused_macro = self.unused_macros.iter().find_map(|(def_id, (_, unused_ident))| {
             if unused_ident.name == ident.name { Some((def_id, unused_ident)) } else { None }
         });
@@ -2863,18 +2865,11 @@ fn show_candidates(
             } else {
                 // Get the unique item kinds and if there's only one, we use the right kind name
                 // instead of the more generic "items".
-                let mut kinds = accessible_path_strings
+                let kinds = accessible_path_strings
                     .iter()
                     .map(|(_, descr, _, _, _)| *descr)
-                    .collect::<FxHashSet<&str>>()
+                    .collect::<UnordSet<&str>>();
-                    .into_iter();
+                let kind = if let Some(kind) = kinds.get_only() { kind } else { "item" };
-                let kind = if let Some(kind) = kinds.next()
-                    && let None = kinds.next()
-                {
-                    kind
-                } else {
-                    "item"
-                };
                 let s = if kind.ends_with('s') { "es" } else { "s" };
 
                 ("one of these", kind, s, String::new(), "")

compiler/rustc_resolve/src/ident.rs

@@ -946,6 +946,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
 
         // Check if one of single imports can still define the name,
         // if it can then our result is not determined and can be invalidated.
+        #[allow(rustc::potential_query_instability)] // FIXME
         for single_import in &resolution.single_imports {
             if ignore_import == Some(*single_import) {
                 // This branch handles a cycle in single imports.

compiler/rustc_resolve/src/late.rs

@@ -18,6 +18,7 @@ use rustc_ast::visit::{
 };
 use rustc_ast::*;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
+use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_errors::codes::*;
 use rustc_errors::{
     Applicability, DiagArgValue, ErrorGuaranteed, IntoDiagArg, StashKey, Suggestions,
@@ -47,8 +48,6 @@ mod diagnostics;
 
 type Res = def::Res<NodeId>;
 
-type IdentMap<T> = FxHashMap<Ident, T>;
-
 use diagnostics::{ElisionFnParameter, LifetimeElisionCandidate, MissingLifetime};
 
 #[derive(Copy, Clone, Debug)]
@@ -273,8 +272,8 @@ impl RibKind<'_> {
 /// resolving, the name is looked up from inside out.
 #[derive(Debug)]
 pub(crate) struct Rib<'ra, R = Res> {
-    pub bindings: IdentMap<R>,
+    pub bindings: FxHashMap<Ident, R>,
-    pub patterns_with_skipped_bindings: FxHashMap<DefId, Vec<(Span, Result<(), ErrorGuaranteed>)>>,
+    pub patterns_with_skipped_bindings: UnordMap<DefId, Vec<(Span, Result<(), ErrorGuaranteed>)>>,
     pub kind: RibKind<'ra>,
 }
 
@@ -1605,12 +1604,12 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
         // for better diagnostics.
         let mut forward_ty_ban_rib_const_param_ty = Rib {
             bindings: forward_ty_ban_rib.bindings.clone(),
-            patterns_with_skipped_bindings: FxHashMap::default(),
+            patterns_with_skipped_bindings: Default::default(),
             kind: RibKind::ForwardGenericParamBan(ForwardGenericParamBanReason::ConstParamTy),
         };
         let mut forward_const_ban_rib_const_param_ty = Rib {
             bindings: forward_const_ban_rib.bindings.clone(),
-            patterns_with_skipped_bindings: FxHashMap::default(),
+            patterns_with_skipped_bindings: Default::default(),
             kind: RibKind::ForwardGenericParamBan(ForwardGenericParamBanReason::ConstParamTy),
         };
         // We'll ban these with a `ConstParamTy` rib, so just clear these ribs for better
@@ -2334,7 +2333,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
             let local_candidates = self.lifetime_elision_candidates.take();
 
             if let Some(candidates) = local_candidates {
-                let distinct: FxHashSet<_> = candidates.iter().map(|(res, _)| *res).collect();
+                let distinct: UnordSet<_> = candidates.iter().map(|(res, _)| *res).collect();
                 let lifetime_count = distinct.len();
                 if lifetime_count != 0 {
                     parameter_info.push(ElisionFnParameter {
@@ -2358,14 +2357,13 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                         }
                     }));
                 }
-                let mut distinct_iter = distinct.into_iter();
+                if !distinct.is_empty() {
-                if let Some(res) = distinct_iter.next() {
                     match elision_lifetime {
                         // We are the first parameter to bind lifetimes.
                         Elision::None => {
-                            if distinct_iter.next().is_none() {
+                            if let Some(res) = distinct.get_only() {
                                 // We have a single lifetime => success.
-                                elision_lifetime = Elision::Param(res)
+                                elision_lifetime = Elision::Param(*res)
                             } else {
                                 // We have multiple lifetimes => error.
                                 elision_lifetime = Elision::Err;
@@ -2890,6 +2888,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                         break;
                     }
 
+                    #[allow(rustc::potential_query_instability)] // FIXME
                     seen_bindings
                         .extend(parent_rib.bindings.keys().map(|ident| (*ident, ident.span)));
                 }
@@ -4004,7 +4003,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
         }
     }
 
-    fn innermost_rib_bindings(&mut self, ns: Namespace) -> &mut IdentMap<Res> {
+    fn innermost_rib_bindings(&mut self, ns: Namespace) -> &mut FxHashMap<Ident, Res> {
         &mut self.ribs[ns].last_mut().unwrap().bindings
     }
 
@@ -5202,6 +5201,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         let mut late_resolution_visitor = LateResolutionVisitor::new(self);
         late_resolution_visitor.resolve_doc_links(&krate.attrs, MaybeExported::Ok(CRATE_NODE_ID));
         visit::walk_crate(&mut late_resolution_visitor, krate);
+        #[allow(rustc::potential_query_instability)] // FIXME
         for (id, span) in late_resolution_visitor.diag_metadata.unused_labels.iter() {
             self.lint_buffer.buffer_lint(
                 lint::builtin::UNUSED_LABELS,

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -830,6 +830,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
         if let Some(rib) = &self.last_block_rib
             && let RibKind::Normal = rib.kind
         {
+            #[allow(rustc::potential_query_instability)] // FIXME
             for (ident, &res) in &rib.bindings {
                 if let Res::Local(_) = res
                     && path.len() == 1
@@ -1018,6 +1019,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
         if let Some(err_code) = err.code {
             if err_code == E0425 {
                 for label_rib in &self.label_ribs {
+                    #[allow(rustc::potential_query_instability)] // FIXME
                     for (label_ident, node_id) in &label_rib.bindings {
                         let ident = path.last().unwrap().ident;
                         if format!("'{ident}") == label_ident.to_string() {
@@ -1177,7 +1179,10 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
         let [segment] = path else { return };
         let None = following_seg else { return };
         for rib in self.ribs[ValueNS].iter().rev() {
-            for (def_id, spans) in &rib.patterns_with_skipped_bindings {
+            let patterns_with_skipped_bindings = self.r.tcx.with_stable_hashing_context(|hcx| {
+                rib.patterns_with_skipped_bindings.to_sorted(&hcx, true)
+            });
+            for (def_id, spans) in patterns_with_skipped_bindings {
                 if let DefKind::Struct | DefKind::Variant = self.r.tcx.def_kind(*def_id)
                     && let Some(fields) = self.r.field_idents(*def_id)
                 {
@@ -2052,7 +2057,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
         if self
             .r
             .extern_crate_map
-            .iter()
+            .items()
             // FIXME: This doesn't include impls like `impl Default for String`.
             .flat_map(|(_, crate_)| self.r.tcx.implementations_of_trait((*crate_, default_trait)))
             .filter_map(|(_, simplified_self_ty)| *simplified_self_ty)
@@ -2261,6 +2266,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                 };
 
                 // Locals and type parameters
+                #[allow(rustc::potential_query_instability)] // FIXME
                 for (ident, &res) in &rib.bindings {
                     if filter_fn(res) && ident.span.ctxt() == rib_ctxt {
                         names.push(TypoSuggestion::typo_from_ident(*ident, res));
@@ -2788,6 +2794,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
         let within_scope = self.is_label_valid_from_rib(rib_index);
 
         let rib = &self.label_ribs[rib_index];
+        #[allow(rustc::potential_query_instability)] // FIXME
         let names = rib
             .bindings
             .iter()
@@ -2799,6 +2806,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
             // Upon finding a similar name, get the ident that it was from - the span
             // contained within helps make a useful diagnostic. In addition, determine
             // whether this candidate is within scope.
+            #[allow(rustc::potential_query_instability)] // FIXME
             let (ident, _) = rib.bindings.iter().find(|(ident, _)| ident.name == symbol).unwrap();
             (*ident, within_scope)
         })

compiler/rustc_resolve/src/lib.rs

@@ -9,7 +9,6 @@
 // tidy-alphabetical-start
 #![allow(internal_features)]
 #![allow(rustc::diagnostic_outside_of_impl)]
-#![allow(rustc::potential_query_instability)]
 #![allow(rustc::untranslatable_diagnostic)]
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![doc(rust_logo)]
@@ -47,6 +46,7 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_data_structures::intern::Interned;
 use rustc_data_structures::steal::Steal;
 use rustc_data_structures::sync::FreezeReadGuard;
+use rustc_data_structures::unord::UnordMap;
 use rustc_errors::{Applicability, Diag, ErrCode, ErrorGuaranteed};
 use rustc_expand::base::{DeriveResolution, SyntaxExtension, SyntaxExtensionKind};
 use rustc_feature::BUILTIN_ATTRIBUTES;
@@ -1046,7 +1046,7 @@ pub struct Resolver<'ra, 'tcx> {
     graph_root: Module<'ra>,
 
     prelude: Option<Module<'ra>>,
-    extern_prelude: FxHashMap<Ident, ExternPreludeEntry<'ra>>,
+    extern_prelude: FxIndexMap<Ident, ExternPreludeEntry<'ra>>,
 
     /// N.B., this is used only for better diagnostics, not name resolution itself.
     field_names: LocalDefIdMap<Vec<Ident>>,
@@ -1079,7 +1079,7 @@ pub struct Resolver<'ra, 'tcx> {
     extra_lifetime_params_map: NodeMap<Vec<(Ident, NodeId, LifetimeRes)>>,
 
     /// `CrateNum` resolutions of `extern crate` items.
-    extern_crate_map: FxHashMap<LocalDefId, CrateNum>,
+    extern_crate_map: UnordMap<LocalDefId, CrateNum>,
     module_children: LocalDefIdMap<Vec<ModChild>>,
     trait_map: NodeMap<Vec<TraitCandidate>>,
 
@@ -1102,7 +1102,7 @@ pub struct Resolver<'ra, 'tcx> {
     /// some AST passes can generate identifiers that only resolve to local or
     /// lang items.
     empty_module: Module<'ra>,
-    module_map: FxHashMap<DefId, Module<'ra>>,
+    module_map: FxIndexMap<DefId, Module<'ra>>,
     binding_parent_modules: FxHashMap<NameBinding<'ra>, Module<'ra>>,
 
     underscore_disambiguator: u32,
@@ -1136,7 +1136,7 @@ pub struct Resolver<'ra, 'tcx> {
     macro_names: FxHashSet<Ident>,
     builtin_macros: FxHashMap<Symbol, BuiltinMacroState>,
     registered_tools: &'tcx RegisteredTools,
-    macro_use_prelude: FxHashMap<Symbol, NameBinding<'ra>>,
+    macro_use_prelude: FxIndexMap<Symbol, NameBinding<'ra>>,
     macro_map: FxHashMap<DefId, MacroData>,
     dummy_ext_bang: Arc<SyntaxExtension>,
     dummy_ext_derive: Arc<SyntaxExtension>,
@@ -1145,7 +1145,7 @@ pub struct Resolver<'ra, 'tcx> {
     ast_transform_scopes: FxHashMap<LocalExpnId, Module<'ra>>,
     unused_macros: FxHashMap<LocalDefId, (NodeId, Ident)>,
     /// A map from the macro to all its potentially unused arms.
-    unused_macro_rules: FxIndexMap<LocalDefId, FxHashMap<usize, (Ident, Span)>>,
+    unused_macro_rules: FxIndexMap<LocalDefId, UnordMap<usize, (Ident, Span)>>,
     proc_macro_stubs: FxHashSet<LocalDefId>,
     /// Traces collected during macro resolution and validated when it's complete.
     single_segment_macro_resolutions:
@@ -1259,7 +1259,7 @@ impl<'ra> ResolverArenas<'ra> {
         expn_id: ExpnId,
         span: Span,
         no_implicit_prelude: bool,
-        module_map: &mut FxHashMap<DefId, Module<'ra>>,
+        module_map: &mut FxIndexMap<DefId, Module<'ra>>,
         module_self_bindings: &mut FxHashMap<Module<'ra>, NameBinding<'ra>>,
     ) -> Module<'ra> {
         let module = Module(Interned::new_unchecked(self.modules.alloc(ModuleData::new(
@@ -1404,7 +1404,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         arenas: &'ra ResolverArenas<'ra>,
     ) -> Resolver<'ra, 'tcx> {
         let root_def_id = CRATE_DEF_ID.to_def_id();
-        let mut module_map = FxHashMap::default();
+        let mut module_map = FxIndexMap::default();
         let mut module_self_bindings = FxHashMap::default();
         let graph_root = arenas.new_module(
             None,
@@ -1421,8 +1421,8 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             ExpnId::root(),
             DUMMY_SP,
             true,
-            &mut FxHashMap::default(),
+            &mut Default::default(),
-            &mut FxHashMap::default(),
+            &mut Default::default(),
         );
 
         let mut def_id_to_node_id = IndexVec::default();
@@ -1437,7 +1437,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         let mut invocation_parents = FxHashMap::default();
         invocation_parents.insert(LocalExpnId::ROOT, InvocationParent::ROOT);
 
-        let mut extern_prelude: FxHashMap<Ident, ExternPreludeEntry<'_>> = tcx
+        let mut extern_prelude: FxIndexMap<Ident, ExternPreludeEntry<'_>> = tcx
             .sess
             .opts
             .externs
@@ -1536,7 +1536,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             macro_names: FxHashSet::default(),
             builtin_macros: Default::default(),
             registered_tools,
-            macro_use_prelude: FxHashMap::default(),
+            macro_use_prelude: Default::default(),
             macro_map: FxHashMap::default(),
             dummy_ext_bang: Arc::new(SyntaxExtension::dummy_bang(edition)),
             dummy_ext_derive: Arc::new(SyntaxExtension::dummy_derive(edition)),

compiler/rustc_resolve/src/macros.rs

@@ -323,6 +323,7 @@ impl<'ra, 'tcx> ResolverExpand for Resolver<'ra, 'tcx> {
     }
 
     fn check_unused_macros(&mut self) {
+        #[allow(rustc::potential_query_instability)] // FIXME
         for (_, &(node_id, ident)) in self.unused_macros.iter() {
             self.lint_buffer.buffer_lint(
                 UNUSED_MACROS,
@@ -333,10 +334,7 @@ impl<'ra, 'tcx> ResolverExpand for Resolver<'ra, 'tcx> {
         }
 
         for (&def_id, unused_arms) in self.unused_macro_rules.iter() {
-            let mut unused_arms = unused_arms.iter().collect::<Vec<_>>();
+            for (&arm_i, &(ident, rule_span)) in unused_arms.to_sorted_stable_ord() {
-            unused_arms.sort_by_key(|&(&arm_i, _)| arm_i);
-
-            for (&arm_i, &(ident, rule_span)) in unused_arms {
                 if self.unused_macros.contains_key(&def_id) {
                     // We already lint the entire macro as unused
                     continue;