Rename PtrKey as Interned and improve it.

In particular, there's now more protection against incorrect usage,
because you can only create one via `Interned::new_unchecked`, which
makes it more obvious that you must be careful.

There are also some tests.

compiler/rustc_resolve/src/imports.rs

@@ -11,7 +11,7 @@ use crate::{NameBinding, NameBindingKind, PathResult, PrivacyError, ToNameBindin
 
 use rustc_ast::NodeId;
 use rustc_data_structures::fx::FxHashSet;
-use rustc_data_structures::ptr_key::PtrKey;
+use rustc_data_structures::intern::Interned;
 use rustc_errors::{pluralize, struct_span_err, Applicability};
 use rustc_hir::def::{self, PartialRes};
 use rustc_hir::def_id::DefId;
@@ -134,7 +134,7 @@ impl<'a> Import<'a> {
 pub struct NameResolution<'a> {
     /// Single imports that may define the name in the namespace.
     /// Imports are arena-allocated, so it's ok to use pointers as keys.
-    single_imports: FxHashSet<PtrKey<'a, Import<'a>>>,
+    single_imports: FxHashSet<Interned<'a, Import<'a>>>,
     /// The least shadowable known binding for this name, or None if there are no known bindings.
     pub binding: Option<&'a NameBinding<'a>>,
     shadowed_glob: Option<&'a NameBinding<'a>>,
@@ -153,7 +153,7 @@ impl<'a> NameResolution<'a> {
     }
 
     crate fn add_single_import(&mut self, import: &'a Import<'a>) {
-        self.single_imports.insert(PtrKey(import));
+        self.single_imports.insert(Interned::new_unchecked(import));
     }
 }
 
@@ -850,7 +850,7 @@ impl<'a, 'b> ImportResolver<'a, 'b> {
                     Err(Determined) => {
                         let key = this.new_key(target, ns);
                         this.update_resolution(parent, key, |_, resolution| {
-                            resolution.single_imports.remove(&PtrKey(import));
+                            resolution.single_imports.remove(&Interned::new_unchecked(import));
                         });
                     }
                     Ok(binding) if !binding.is_importable() => {

compiler/rustc_resolve/src/lib.rs

@@ -38,7 +38,7 @@ use rustc_ast::{ItemKind, ModKind, Path};
 use rustc_ast_lowering::ResolverAstLowering;
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
-use rustc_data_structures::ptr_key::PtrKey;
+use rustc_data_structures::intern::Interned;
 use rustc_data_structures::sync::Lrc;
 use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder};
 use rustc_expand::base::{DeriveResolutions, SyntaxExtension, SyntaxExtensionKind};
@@ -964,7 +964,7 @@ pub struct Resolver<'a> {
     /// language items.
     empty_module: Module<'a>,
     module_map: FxHashMap<DefId, Module<'a>>,
-    binding_parent_modules: FxHashMap<PtrKey<'a, NameBinding<'a>>, Module<'a>>,
+    binding_parent_modules: FxHashMap<Interned<'a, NameBinding<'a>>, Module<'a>>,
     underscore_disambiguator: u32,
 
     /// Maps glob imports to the names of items actually imported.
@@ -1115,7 +1115,7 @@ impl<'a> ResolverArenas<'a> {
         self.name_resolutions.alloc(Default::default())
     }
     fn alloc_macro_rules_scope(&'a self, scope: MacroRulesScope<'a>) -> MacroRulesScopeRef<'a> {
-        PtrKey(self.dropless.alloc(Cell::new(scope)))
+        Interned::new_unchecked(self.dropless.alloc(Cell::new(scope)))
     }
     fn alloc_macro_rules_binding(
         &'a self,
@@ -2938,7 +2938,9 @@ impl<'a> Resolver<'a> {
     }
 
     fn set_binding_parent_module(&mut self, binding: &'a NameBinding<'a>, module: Module<'a>) {
-        if let Some(old_module) = self.binding_parent_modules.insert(PtrKey(binding), module) {
+        if let Some(old_module) =
+            self.binding_parent_modules.insert(Interned::new_unchecked(binding), module)
+        {
             if !ptr::eq(module, old_module) {
                 span_bug!(binding.span, "parent module is reset for binding");
             }
@@ -2954,8 +2956,8 @@ impl<'a> Resolver<'a> {
         // is disambiguated to mitigate regressions from macro modularization.
         // Scoping for `macro_rules` behaves like scoping for `let` at module level, in general.
         match (
-            self.binding_parent_modules.get(&PtrKey(macro_rules)),
-            self.binding_parent_modules.get(&PtrKey(modularized)),
+            self.binding_parent_modules.get(&Interned::new_unchecked(macro_rules)),
+            self.binding_parent_modules.get(&Interned::new_unchecked(modularized)),
         ) {
             (Some(macro_rules), Some(modularized)) => {
                 macro_rules.nearest_parent_mod() == modularized.nearest_parent_mod()

compiler/rustc_resolve/src/macros.rs

@@ -11,7 +11,7 @@ use rustc_ast_lowering::ResolverAstLowering;
 use rustc_ast_pretty::pprust;
 use rustc_attr::StabilityLevel;
 use rustc_data_structures::fx::FxHashSet;
-use rustc_data_structures::ptr_key::PtrKey;
+use rustc_data_structures::intern::Interned;
 use rustc_data_structures::sync::Lrc;
 use rustc_errors::struct_span_err;
 use rustc_expand::base::{Annotatable, DeriveResolutions, Indeterminate, ResolverExpand};
@@ -71,7 +71,7 @@ pub enum MacroRulesScope<'a> {
 /// This helps to avoid uncontrollable growth of `macro_rules!` scope chains,
 /// which usually grow lineraly with the number of macro invocations
 /// in a module (including derives) and hurt performance.
-pub(crate) type MacroRulesScopeRef<'a> = PtrKey<'a, Cell<MacroRulesScope<'a>>>;
+pub(crate) type MacroRulesScopeRef<'a> = Interned<'a, Cell<MacroRulesScope<'a>>>;
 
 // Macro namespace is separated into two sub-namespaces, one for bang macros and
 // one for attribute-like macros (attributes, derives).