Introduce ModernIdent type to unify macro 2.0 hygiene handling

xizheyin · xizheyin · commit 868ecfb2b426 · 2025-07-27T16:32:15.000+08:00
Signed-off-by: xizheyin &lt;xizheyin@smail.nju.edu.cn&gt;
diff --git a/compiler/rustc_resolve/src/build_reduced_graph.rs b/compiler/rustc_resolve/src/build_reduced_graph.rs
@@ -27,7 +27,7 @@ use rustc_middle::bug;
 use rustc_middle::metadata::ModChild;
 use rustc_middle::ty::{Feed, Visibility};
 use rustc_span::hygiene::{ExpnId, LocalExpnId, MacroKind};
-use rustc_span::{Ident, Span, Symbol, kw, sym};
+use rustc_span::{Ident, Macros20NormalizedIdent, Span, Symbol, kw, sym};
 use thin_vec::ThinVec;
 use tracing::debug;
 
@@ -938,7 +938,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
         self.r.potentially_unused_imports.push(import);
         let imported_binding = self.r.import(binding, import);
         if parent == self.r.graph_root {
-            let ident = ident.normalize_to_macros_2_0();
+            let ident = Macros20NormalizedIdent::new(ident);
             if let Some(entry) = self.r.extern_prelude.get(&ident)
                 && expansion != LocalExpnId::ROOT
                 && orig_name.is_some()
diff --git a/compiler/rustc_resolve/src/check_unused.rs b/compiler/rustc_resolve/src/check_unused.rs
@@ -33,7 +33,7 @@ use rustc_session::lint::BuiltinLintDiag;
 use rustc_session::lint::builtin::{
     MACRO_USE_EXTERN_CRATE, UNUSED_EXTERN_CRATES, UNUSED_IMPORTS, UNUSED_QUALIFICATIONS,
 };
-use rustc_span::{DUMMY_SP, Ident, Span, kw};
+use rustc_span::{DUMMY_SP, Ident, Macros20NormalizedIdent, Span, kw};
 
 use crate::imports::{Import, ImportKind};
 use crate::{LexicalScopeBinding, NameBindingKind, Resolver, module_to_string};
@@ -203,7 +203,7 @@ impl<'a, 'ra, 'tcx> UnusedImportCheckVisitor<'a, 'ra, 'tcx> {
             if self
                 .r
                 .extern_prelude
-                .get(&extern_crate.ident)
+                .get(&unsafe { Macros20NormalizedIdent::new_without_normalize(extern_crate.ident) })
                 .is_none_or(|entry| entry.introduced_by_item)
             {
                 continue;
diff --git a/compiler/rustc_resolve/src/diagnostics.rs b/compiler/rustc_resolve/src/diagnostics.rs
@@ -32,7 +32,7 @@ use rustc_span::edit_distance::find_best_match_for_name;
 use rustc_span::edition::Edition;
 use rustc_span::hygiene::MacroKind;
 use rustc_span::source_map::SourceMap;
-use rustc_span::{BytePos, Ident, Span, Symbol, SyntaxContext, kw, sym};
+use rustc_span::{BytePos, Ident, Macros20NormalizedIdent, Span, Symbol, SyntaxContext, kw, sym};
 use thin_vec::{ThinVec, thin_vec};
 use tracing::{debug, instrument};
 
@@ -322,8 +322,10 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         // Check if the target of the use for both bindings is the same.
         let duplicate = new_binding.res().opt_def_id() == old_binding.res().opt_def_id();
         let has_dummy_span = new_binding.span.is_dummy() || old_binding.span.is_dummy();
-        let from_item =
-            self.extern_prelude.get(&ident).is_none_or(|entry| entry.introduced_by_item);
+        let from_item = self
+            .extern_prelude
+            .get(&unsafe { Macros20NormalizedIdent::new_without_normalize(ident) })
+            .is_none_or(|entry| entry.introduced_by_item);
         // Only suggest removing an import if both bindings are to the same def, if both spans
         // aren't dummy spans. Further, if both bindings are imports, then the ident must have
         // been introduced by an item.
@@ -532,7 +534,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         module.for_each_child(self, |_this, ident, _ns, binding| {
             let res = binding.res();
             if filter_fn(res) && ctxt.is_none_or(|ctxt| ctxt == ident.span.ctxt()) {
-                names.push(TypoSuggestion::typo_from_ident(ident, res));
+                names.push(TypoSuggestion::typo_from_ident(ident.0, res));
             }
         });
     }
@@ -1100,7 +1102,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 Scope::ExternPrelude => {
                     suggestions.extend(this.extern_prelude.iter().filter_map(|(ident, _)| {
                         let res = Res::Def(DefKind::Mod, CRATE_DEF_ID.to_def_id());
-                        filter_fn(res).then_some(TypoSuggestion::typo_from_ident(*ident, res))
+                        filter_fn(res).then_some(TypoSuggestion::typo_from_ident(ident.0, res))
                     }));
                 }
                 Scope::ToolPrelude => {
@@ -1246,7 +1248,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     };
                     segms.append(&mut path_segments.clone());
 
-                    segms.push(ast::PathSegment::from_ident(ident));
+                    segms.push(ast::PathSegment::from_ident(ident.0));
                     let path = Path { span: name_binding.span, segments: segms, tokens: None };
 
                     if child_accessible
@@ -1319,7 +1321,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 if let Some(def_id) = name_binding.res().module_like_def_id() {
                     // form the path
                     let mut path_segments = path_segments.clone();
-                    path_segments.push(ast::PathSegment::from_ident(ident));
+                    path_segments.push(ast::PathSegment::from_ident(ident.0));
 
                     let alias_import = if let NameBindingKind::Import { import, .. } =
                         name_binding.kind
@@ -1455,7 +1457,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 if needs_disambiguation {
                     crate_path.push(ast::PathSegment::path_root(rustc_span::DUMMY_SP));
                 }
-                crate_path.push(ast::PathSegment::from_ident(ident));
+                crate_path.push(ast::PathSegment::from_ident(ident.0));
 
                 suggestions.extend(self.lookup_import_candidates_from_module(
                     lookup_ident,
diff --git a/compiler/rustc_resolve/src/imports.rs b/compiler/rustc_resolve/src/imports.rs
@@ -499,7 +499,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 let imported_binding = self.import(binding, *import);
                 let _ = self.try_define(
                     import.parent_scope.module,
-                    ident,
+                    ident.0,
                     key.ns,
                     imported_binding,
                     warn_ambiguity,
@@ -1522,7 +1522,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     .is_some_and(|binding| binding.warn_ambiguity_recursive());
                 let _ = self.try_define(
                     import.parent_scope.module,
-                    key.ident,
+                    key.ident.0,
                     key.ns,
                     imported_binding,
                     warn_ambiguity,
@@ -1555,7 +1555,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     next_binding = binding;
                 }
 
-                children.push(ModChild { ident, res, vis: binding.vis, reexport_chain });
+                children.push(ModChild { ident: ident.0, res, vis: binding.vis, reexport_chain });
             }
         });
 
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -1473,7 +1473,10 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                     })
                     .collect();
                 if let [target] = targets.as_slice() {
-                    return Some(TypoSuggestion::single_item_from_ident(target.0.ident, target.1));
+                    return Some(TypoSuggestion::single_item_from_ident(
+                        target.0.ident.0,
+                        target.1,
+                    ));
                 }
             }
         }
@@ -2492,7 +2495,7 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                                             Res::Def(DefKind::Mod, crate_id.as_def_id());
 
                                         filter_fn(crate_mod).then(|| {
-                                            TypoSuggestion::typo_from_ident(*ident, crate_mod)
+                                            TypoSuggestion::typo_from_ident(ident.0, crate_mod)
                                         })
                                     })
                             }));
@@ -2654,7 +2657,7 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                 if let Some(module_def_id) = name_binding.res().module_like_def_id() {
                     // form the path
                     let mut path_segments = path_segments.clone();
-                    path_segments.push(ast::PathSegment::from_ident(ident));
+                    path_segments.push(ast::PathSegment::from_ident(ident.0));
                     let doc_visible = doc_visible
                         && (module_def_id.is_local() || !r.tcx.is_doc_hidden(module_def_id));
                     if module_def_id == def_id {
@@ -2693,7 +2696,7 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
             enum_module.for_each_child(self.r, |_, ident, _, name_binding| {
                 if let Res::Def(DefKind::Ctor(CtorOf::Variant, kind), def_id) = name_binding.res() {
                     let mut segms = enum_import_suggestion.path.segments.clone();
-                    segms.push(ast::PathSegment::from_ident(ident));
+                    segms.push(ast::PathSegment::from_ident(ident.0));
                     let path = Path { span: name_binding.span, segments: segms, tokens: None };
                     variants.push((path, def_id, kind));
                 }
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
@@ -71,7 +71,7 @@ use rustc_query_system::ich::StableHashingContext;
 use rustc_session::lint::builtin::PRIVATE_MACRO_USE;
 use rustc_session::lint::{BuiltinLintDiag, LintBuffer};
 use rustc_span::hygiene::{ExpnId, LocalExpnId, MacroKind, SyntaxContext, Transparency};
-use rustc_span::{DUMMY_SP, Ident, Span, Symbol, kw, sym};
+use rustc_span::{DUMMY_SP, Ident, Macros20NormalizedIdent, Span, Symbol, kw, sym};
 use smallvec::{SmallVec, smallvec};
 use tracing::debug;
 
@@ -531,7 +531,7 @@ impl ModuleKind {
 struct BindingKey {
     /// The identifier for the binding, always the `normalize_to_macros_2_0` version of the
     /// identifier.
-    ident: Ident,
+    ident: Macros20NormalizedIdent,
     ns: Namespace,
     /// When we add an underscore binding (with ident `_`) to some module, this field has
     /// a non-zero value that uniquely identifies this binding in that module.
@@ -543,7 +543,7 @@ struct BindingKey {
 
 impl BindingKey {
     fn new(ident: Ident, ns: Namespace) -> Self {
-        BindingKey { ident: ident.normalize_to_macros_2_0(), ns, disambiguator: 0 }
+        BindingKey { ident: Macros20NormalizedIdent::new(ident), ns, disambiguator: 0 }
     }
 
     fn new_disambiguated(
@@ -552,7 +552,7 @@ impl BindingKey {
         disambiguator: impl FnOnce() -> u32,
     ) -> BindingKey {
         let disambiguator = if ident.name == kw::Underscore { disambiguator() } else { 0 };
-        BindingKey { ident: ident.normalize_to_macros_2_0(), ns, disambiguator }
+        BindingKey { ident: Macros20NormalizedIdent::new(ident), ns, disambiguator }
     }
 }
 
@@ -659,7 +659,7 @@ impl<'ra> Module<'ra> {
     fn for_each_child<'tcx, R, F>(self, resolver: &mut R, mut f: F)
     where
         R: AsMut<Resolver<'ra, 'tcx>>,
-        F: FnMut(&mut R, Ident, Namespace, NameBinding<'ra>),
+        F: FnMut(&mut R, Macros20NormalizedIdent, Namespace, NameBinding<'ra>),
     {
         for (key, name_resolution) in resolver.as_mut().resolutions(self).borrow().iter() {
             if let Some(binding) = name_resolution.borrow().best_binding() {
@@ -681,7 +681,7 @@ impl<'ra> Module<'ra> {
                     return;
                 }
                 if let Res::Def(DefKind::Trait | DefKind::TraitAlias, def_id) = binding.res() {
-                    collected_traits.push((name, binding, r.as_mut().get_module(def_id)))
+                    collected_traits.push((name.0, binding, r.as_mut().get_module(def_id)))
                 }
             });
             *traits = Some(collected_traits.into_boxed_slice());
@@ -1040,7 +1040,7 @@ pub struct Resolver<'ra, 'tcx> {
     graph_root: Module<'ra>,
 
     prelude: Option<Module<'ra>>,
-    extern_prelude: FxIndexMap<Ident, ExternPreludeEntry<'ra>>,
+    extern_prelude: FxIndexMap<Macros20NormalizedIdent, ExternPreludeEntry<'ra>>,
 
     /// N.B., this is used only for better diagnostics, not name resolution itself.
     field_names: LocalDefIdMap<Vec<Ident>>,
@@ -1467,19 +1467,28 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         let mut invocation_parents = FxHashMap::default();
         invocation_parents.insert(LocalExpnId::ROOT, InvocationParent::ROOT);
 
-        let mut extern_prelude: FxIndexMap<Ident, ExternPreludeEntry<'_>> = tcx
+        let mut extern_prelude: FxIndexMap<Macros20NormalizedIdent, ExternPreludeEntry<'_>> = tcx
             .sess
             .opts
             .externs
             .iter()
             .filter(|(_, entry)| entry.add_prelude)
-            .map(|(name, _)| (Ident::from_str(name), Default::default()))
+            .map(|(name, _)| {
+                (
+                    unsafe {
+                        Macros20NormalizedIdent::new_without_normalize(Ident::from_str(name))
+                    },
+                    Default::default(),
+                )
+            })
             .collect();
 
         if !attr::contains_name(attrs, sym::no_core) {
-            extern_prelude.insert(Ident::with_dummy_span(sym::core), Default::default());
+            extern_prelude
+                .insert(Macros20NormalizedIdent::with_dummy_span(sym::core), Default::default());
             if !attr::contains_name(attrs, sym::no_std) {
-                extern_prelude.insert(Ident::with_dummy_span(sym::std), Default::default());
+                extern_prelude
+                    .insert(Macros20NormalizedIdent::with_dummy_span(sym::std), Default::default());
             }
         }
 
@@ -1983,7 +1992,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             // Avoid marking `extern crate` items that refer to a name from extern prelude,
             // but not introduce it, as used if they are accessed from lexical scope.
             if used == Used::Scope {
-                if let Some(entry) = self.extern_prelude.get(&ident.normalize_to_macros_2_0()) {
+                if let Some(entry) = self.extern_prelude.get(&Macros20NormalizedIdent::new(ident)) {
                     if !entry.introduced_by_item && entry.binding == Some(used_binding) {
                         return;
                     }
@@ -2146,7 +2155,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             return None;
         }
 
-        let norm_ident = ident.normalize_to_macros_2_0();
+        let norm_ident = Macros20NormalizedIdent::new(ident);
         let binding = self.extern_prelude.get(&norm_ident).cloned().and_then(|entry| {
             Some(if let Some(binding) = entry.binding {
                 if finalize {
diff --git a/compiler/rustc_resolve/src/macros.rs b/compiler/rustc_resolve/src/macros.rs
@@ -535,11 +535,11 @@ impl<'ra, 'tcx> ResolverExpand for Resolver<'ra, 'tcx> {
         target_trait.for_each_child(self, |this, ident, ns, _binding| {
             // FIXME: Adjust hygiene for idents from globs, like for glob imports.
             if let Some(overriding_keys) = this.impl_binding_keys.get(&impl_def_id)
-                && overriding_keys.contains(&BindingKey::new(ident, ns))
+                && overriding_keys.contains(&BindingKey::new(ident.0, ns))
             {
                 // The name is overridden, do not produce it from the glob delegation.
             } else {
-                idents.push((ident, None));
+                idents.push((ident.0, None));
             }
         });
         Ok(idents)
diff --git a/compiler/rustc_span/src/lib.rs b/compiler/rustc_span/src/lib.rs
@@ -66,7 +66,8 @@ pub use span_encoding::{DUMMY_SP, Span};
 
 pub mod symbol;
 pub use symbol::{
-    ByteSymbol, Ident, MacroRulesNormalizedIdent, STDLIB_STABLE_CRATES, Symbol, kw, sym,
+    ByteSymbol, Ident, MacroRulesNormalizedIdent, Macros20NormalizedIdent, STDLIB_STABLE_CRATES,
+    Symbol, kw, sym,
 };
 
 mod analyze_source_file;
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
@@ -3,6 +3,7 @@
 //! type, and vice versa.
 
 use std::hash::{Hash, Hasher};
+use std::ops::{Deref, DerefMut};
 use std::{fmt, str};
 
 use rustc_arena::DroplessArena;
@@ -2562,16 +2563,17 @@ impl fmt::Display for IdentPrinter {
 }
 
 /// An newtype around `Ident` that calls [Ident::normalize_to_macro_rules] on
-/// construction.
-// FIXME(matthewj, petrochenkov) Use this more often, add a similar
-// `ModernIdent` struct and use that as well.
+/// construction for "local variable hygiene" comparisons.
+///
+/// Use this type when you need to compare identifiers according to macro_rules hygiene.
+/// This ensures compile-time safety and avoids manual normalization calls.
 #[derive(Copy, Clone, Eq, PartialEq, Hash)]
 pub struct MacroRulesNormalizedIdent(Ident);
 
 impl MacroRulesNormalizedIdent {
     #[inline]
     pub fn new(ident: Ident) -> Self {
-        Self(ident.normalize_to_macro_rules())
+        MacroRulesNormalizedIdent(ident.normalize_to_macro_rules())
     }
 }
 
@@ -2587,6 +2589,57 @@ impl fmt::Display for MacroRulesNormalizedIdent {
     }
 }
 
+/// An newtype around `Ident` that calls [Ident::normalize_to_macros_2_0] on
+/// construction for "item hygiene" comparisons.
+///
+/// Identifiers with same string value become same if they came from the same macro 2.0 macro
+/// (e.g., `macro` item, but not `macro_rules` item) and stay different if they came from
+/// different macro 2.0 macros.
+#[derive(Copy, Clone, Eq, PartialEq, Hash)]
+pub struct Macros20NormalizedIdent(pub Ident);
+
+impl Macros20NormalizedIdent {
+    #[inline]
+    pub fn new(ident: Ident) -> Self {
+        Macros20NormalizedIdent(ident.normalize_to_macros_2_0())
+    }
+
+    // For search in index map for `Ident` as a index key
+    pub unsafe fn new_without_normalize(ident: Ident) -> Self {
+        Macros20NormalizedIdent(ident)
+    }
+
+    // dummy_span does not need to be normalized, so we can use `Ident` directly
+    pub fn with_dummy_span(name: Symbol) -> Self {
+        Macros20NormalizedIdent(Ident::with_dummy_span(name))
+    }
+}
+
+impl fmt::Debug for Macros20NormalizedIdent {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Debug::fmt(&self.0, f)
+    }
+}
+
+impl fmt::Display for Macros20NormalizedIdent {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Display::fmt(&self.0, f)
+    }
+}
+
+impl Deref for Macros20NormalizedIdent {
+    type Target = Ident;
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl DerefMut for Macros20NormalizedIdent {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
+
 /// An interned UTF-8 string.
 ///
 /// Internally, a `Symbol` is implemented as an index, and all operations

Original file line number	Diff line number	Diff line change
`@@ -535,11 +535,11 @@ impl<'ra, 'tcx> ResolverExpand for Resolver<'ra, 'tcx> {`
`535`	`535`	`target_trait.for_each_child(self, \|this, ident, ns, _binding\| {`
`536`	`536`	`// FIXME: Adjust hygiene for idents from globs, like for glob imports.`
`537`	`537`	`if let Some(overriding_keys) = this.impl_binding_keys.get(&impl_def_id)`
`538`		`- && overriding_keys.contains(&BindingKey::new(ident, ns))`
	`538`	`+ && overriding_keys.contains(&BindingKey::new(ident.0, ns))`
`539`	`539`	`{`
`540`	`540`	`// The name is overridden, do not produce it from the glob delegation.`
`541`	`541`	`} else {`
`542`		`- idents.push((ident, None));`
	`542`	`+ idents.push((ident.0, None));`
`543`	`543`	`}`
`544`	`544`	`});`
`545`	`545`	`Ok(idents)`