Try to sort single_imports before usage to have a stable result

The `FxIndexSet` solution seems costly.

Author: ismailarilik

compiler/rustc_resolve/src/ident.rs

@@ -984,9 +984,14 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
 
         // --- From now on we either have a glob resolution or no resolution. ---
 
+        // It is sorted before usage so ordering is not important.
+        #[allow(rustc::potential_query_instability)]
+        let mut single_imports: Vec<_> = resolution.single_imports.clone().into_iter().collect();
+        single_imports.sort_by_key(|import| import.0.id());
+
         // Check if one of single imports can still define the name,
         // if it can then our result is not determined and can be invalidated.
-        for single_import in &resolution.single_imports {
+        for single_import in &single_imports {
             if ignore_import == Some(*single_import) {
                 // This branch handles a cycle in single imports.
                 //

compiler/rustc_resolve/src/imports.rs

@@ -4,7 +4,7 @@ use std::cell::Cell;
 use std::mem;
 
 use rustc_ast::NodeId;
-use rustc_data_structures::fx::{FxHashSet, FxIndexSet};
+use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::intern::Interned;
 use rustc_errors::codes::*;
 use rustc_errors::{Applicability, MultiSpan, pluralize, struct_span_code_err};
@@ -220,7 +220,7 @@ impl<'ra> ImportData<'ra> {
 pub(crate) struct NameResolution<'ra> {
     /// Single imports that may define the name in the namespace.
     /// Imports are arena-allocated, so it's ok to use pointers as keys.
-    pub single_imports: FxIndexSet<Import<'ra>>,
+    pub single_imports: FxHashSet<Import<'ra>>,
     /// The least shadowable known binding for this name, or None if there are no known bindings.
     pub binding: Option<NameBinding<'ra>>,
     pub shadowed_glob: Option<NameBinding<'ra>>,
@@ -482,7 +482,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 let key = BindingKey::new(target, ns);
                 let _ = this.try_define(import.parent_scope.module, key, dummy_binding, false);
                 this.update_resolution(import.parent_scope.module, key, false, |_, resolution| {
-                    resolution.single_imports.shift_remove(&import);
+                    resolution.single_imports.remove(&import);
                 })
             });
             self.record_use(target, dummy_binding, Used::Other);
@@ -837,7 +837,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                         }
                         let key = BindingKey::new(target, ns);
                         this.update_resolution(parent, key, false, |_, resolution| {
-                            resolution.single_imports.shift_remove(&import);
+                            resolution.single_imports.remove(&import);
                         });
                     }
                 }