Introduce ModernIdent type to unify macro 2.0 hygiene handling #144439

xizheyin · 2025-07-25T09:15:03Z

This pr introduce ModernIdent type to unify macro 2.0 hygiene handling

Added ModernIdent type. Wraps Ident and automatically calls normalize_to_macros_2_0()
Unified identifier normalization. Replaced scattered ident.normalize_to_macros_2_0() calls with ModernIdent::new(ident)

r? @petrochenkov

rustbot · 2025-07-25T09:15:09Z

HIR ty lowering was modified

cc @fmease

fee1-dead · 2025-07-25T16:29:23Z

What problem is this intended to solve? ModernIdent seems like a quite confusing name.

compiler/rustc_span/src/symbol.rs

compiler/rustc_hir_analysis/src/coherence/inherent_impls_overlap.rs

compiler/rustc_span/src/symbol.rs

compiler/rustc_resolve/src/macros.rs

compiler/rustc_resolve/src/lib.rs

compiler/rustc_resolve/src/build_reduced_graph.rs

compiler/rustc_resolve/src/late.rs

compiler/rustc_span/src/symbol.rs

petrochenkov · 2025-07-25T17:01:09Z

In general, I have mixed feelings about both this and MacroRulesNormalizedIdent.
It clearly can potentially catch some mistakes or inefficiencies (like it did in fn define_macro, I think), on the other hand it can only be used opportunistically because most places either do not care about the normalization, or care but the normalization should be different in different cases (like in rib.bindings, I guess).

xizheyin

In this version, I removed some unnecessary uses.
The modifications are mainly centered around two fields.

BindingKey::ident
Resolver::extern_prelude

xizheyin · 2025-07-27T08:39:38Z

compiler/rustc_span/src/symbol.rs

+    // For search in index map for `Ident` as a index key
+    pub unsafe fn new_without_normalize(ident: Ident) -> Self {
+        Macros20NormalizedIdent(ident)
+    }


In the last commit, I implemented Borrow to look up in IndexMap<Macro20NormalizedIdent> with Ident as key. But in the new version, I implemented this function to temporarily convert the Ident to Macro20NormalizedIdent without normalizing it to match the type. And I also apply this function to some Idents that were not normalized using normalize_to_macros_2_0() in the original code.

I'll mark three places where I use this function and I'm not sure if I should use new or it.

I don't see any justified uses of new_without_normalize, it can be removed.

xizheyin · 2025-07-27T08:40:05Z

compiler/rustc_resolve/src/check_unused.rs

@@ -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) })


Here use new_without_normalize for indexing

This should use Macros20NormalizedIdent::new.

xizheyin · 2025-07-27T08:40:27Z

compiler/rustc_resolve/src/diagnostics.rs

+        let from_item = self
+            .extern_prelude
+            .get(&unsafe { Macros20NormalizedIdent::new_without_normalize(ident) })
+            .is_none_or(|entry| entry.introduced_by_item);


Here also for Indexing

This should use Macros20NormalizedIdent::new.

xizheyin · 2025-07-27T08:42:24Z

compiler/rustc_resolve/src/lib.rs

-            .map(|(name, _)| (Ident::from_str(name), Default::default()))
+            .map(|(name, _)| {
+                (
+                    unsafe {
+                        Macros20NormalizedIdent::new_without_normalize(Ident::from_str(name))
+                    },
+                    Default::default(),


Here will return extern_prelude which petrochenkov suggest to convert to Macro20NormalizedIdent.

This should use Macros20NormalizedIdent::with_dummy_span, please rebase on master.

compiler/rustc_resolve/src/lib.rs

Signed-off-by: xizheyin <[email protected]>

xizheyin · 2025-08-04T03:14:00Z

I rebased it @rustbot ready

petrochenkov · 2025-08-05T14:42:44Z

compiler/rustc_span/src/symbol.rs

+    }
+}
+
+impl Deref for Macros20NormalizedIdent {


This is mostly for norm_ident.as_str(), right?
Then it's probably better to just add that method to normalized idents.
Idents are not normally passed by reference besides that special case.

And I also don't see anything taking &mut Ident, so better to avoid DerefMut too.

petrochenkov · 2025-08-05T14:55:56Z

compiler/rustc_resolve/src/build_reduced_graph.rs

@@ -969,7 +969,7 @@ 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);


Suggested change

let ident = Macros20NormalizedIdent::new(ident);

let norm_ident = Macros20NormalizedIdent::new(ident);

Let's use a more disambiguated naming in contexts where both normalized and non-normalized idents exist.

petrochenkov · 2025-08-05T15:12:48Z

compiler/rustc_resolve/src/lib.rs

@@ -690,7 +690,7 @@ impl<'ra> Module<'ra> {
                    return;
                }
                if let Res::Def(DefKind::Trait | DefKind::TraitAlias, def_id) = binding.res() {
-                    collected_traits.push((name, binding, r.as_ref().get_module(def_id)))
+                    collected_traits.push((name.0, binding, r.as_ref().get_module(def_id)))


ModuleData::traits always contain normalized idents and can use Macros20NormalizedIdent.

rustbot assigned petrochenkov Jul 25, 2025

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xizheyin commented Jul 25, 2025

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xizheyin force-pushed the symbol-rs branch from bc34960 to 868ecfb Compare July 27, 2025 08:32

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xizheyin force-pushed the symbol-rs branch from 868ecfb to d2ad9c8 Compare July 28, 2025 02:41

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Introduce ModernIdent type to unify macro 2.0 hygiene handling

00a5785

Signed-off-by: xizheyin <[email protected]>

xizheyin force-pushed the symbol-rs branch from d2ad9c8 to 00a5785 Compare August 4, 2025 03:13

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Aug 4, 2025

petrochenkov reviewed Aug 5, 2025

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petrochenkov added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Aug 5, 2025

	let ident = Macros20NormalizedIdent::new(ident);
	let norm_ident = Macros20NormalizedIdent::new(ident);

Introduce ModernIdent type to unify macro 2.0 hygiene handling #144439

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Introduce ModernIdent type to unify macro 2.0 hygiene handling #144439

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xizheyin commented Jul 25, 2025

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petrochenkov commented Jul 25, 2025

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xizheyin commented Aug 4, 2025

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