introduce common macro for MutVisitor and Visitor to dedup code

compiler/rustc_ast/src/lib.rs

@@ -15,6 +15,7 @@
 #![feature(associated_type_defaults)]
 #![feature(box_patterns)]
 #![feature(if_let_guard)]
+#![feature(macro_metavar_expr)]
 #![feature(negative_impls)]
 #![feature(never_type)]
 #![feature(rustdoc_internals)]

compiler/rustc_ast/src/mut_visit.rs

@@ -20,7 +20,7 @@ use thin_vec::ThinVec;
 use crate::ast::*;
 use crate::ptr::P;
 use crate::tokenstream::*;
-use crate::visit::{AssocCtxt, BoundKind, FnCtxt};
+use crate::visit::{AssocCtxt, BoundKind, FnCtxt, try_visit};
 
 pub trait ExpectOne<A: Array> {
     fn expect_one(self, err: &'static str) -> A::Item;
@@ -388,6 +388,8 @@ pub trait MutVisitor: Sized {
     }
 }
 
+super::common_visitor_and_walkers!((mut) MutVisitor);
+
 /// Use a map-style function (`FnOnce(T) -> T`) to overwrite a `&mut T`. Useful
 /// when using a `flat_map_*` or `filter_map_*` method within a `visit_`
 /// method.
@@ -777,15 +779,6 @@ fn visit_defaultness<T: MutVisitor>(vis: &mut T, defaultness: &mut Defaultness)
     }
 }
 
-// No `noop_` prefix because there isn't a corresponding method in `MutVisitor`.
-fn visit_safety<T: MutVisitor>(vis: &mut T, safety: &mut Safety) {
-    match safety {
-        Safety::Unsafe(span) => vis.visit_span(span),
-        Safety::Safe(span) => vis.visit_span(span),
-        Safety::Default => {}
-    }
-}
-
 // No `noop_` prefix because there isn't a corresponding method in `MutVisitor`.
 fn visit_polarity<T: MutVisitor>(vis: &mut T, polarity: &mut ImplPolarity) {
     match polarity {
@@ -794,14 +787,6 @@ fn visit_polarity<T: MutVisitor>(vis: &mut T, polarity: &mut ImplPolarity) {
     }
 }
 
-// No `noop_` prefix because there isn't a corresponding method in `MutVisitor`.
-fn visit_constness<T: MutVisitor>(vis: &mut T, constness: &mut Const) {
-    match constness {
-        Const::Yes(span) => vis.visit_span(span),
-        Const::No => {}
-    }
-}
-
 fn walk_closure_binder<T: MutVisitor>(vis: &mut T, binder: &mut ClosureBinder) {
     match binder {
         ClosureBinder::NotPresent => {}
@@ -940,15 +925,6 @@ pub fn walk_flat_map_generic_param<T: MutVisitor>(
     smallvec![param]
 }
 
-fn walk_label<T: MutVisitor>(vis: &mut T, Label { ident }: &mut Label) {
-    vis.visit_ident(ident);
-}
-
-fn walk_lifetime<T: MutVisitor>(vis: &mut T, Lifetime { id, ident }: &mut Lifetime) {
-    vis.visit_id(id);
-    vis.visit_ident(ident);
-}
-
 fn walk_generics<T: MutVisitor>(vis: &mut T, generics: &mut Generics) {
     let Generics { params, where_clause, span } = generics;
     params.flat_map_in_place(|param| vis.flat_map_generic_param(param));
@@ -1340,13 +1316,6 @@ fn walk_const_item<T: MutVisitor>(vis: &mut T, item: &mut ConstItem) {
     walk_define_opaques(vis, define_opaque);
 }
 
-fn walk_fn_header<T: MutVisitor>(vis: &mut T, header: &mut FnHeader) {
-    let FnHeader { safety, coroutine_kind, constness, ext: _ } = header;
-    visit_constness(vis, constness);
-    coroutine_kind.as_mut().map(|coroutine_kind| vis.visit_coroutine_kind(coroutine_kind));
-    visit_safety(vis, safety);
-}
-
 pub fn walk_crate<T: MutVisitor>(vis: &mut T, krate: &mut Crate) {
     let Crate { attrs, items, spans, id, is_placeholder: _ } = krate;
     vis.visit_id(id);

compiler/rustc_ast/src/visit.rs

@@ -315,6 +315,75 @@ pub trait Visitor<'ast>: Sized {
     }
 }
 
+#[macro_export]
+macro_rules! common_visitor_and_walkers {
+    ($(($mut: ident))? $Visitor:ident$(<$lt:lifetime>)?) => {
+        // this is only used by the MutVisitor. We include this symmetry here to make writing other functions easier
+        $(${ignore($lt)}
+            #[expect(unused, rustc::pass_by_value)]
+            #[inline]
+        )?
+        fn visit_span<$($lt,)? V: $Visitor$(<$lt>)?>(visitor: &mut V, span: &$($lt)? $($mut)? Span) $(-> <V as Visitor<$lt>>::Result)? {
+            $(
+                let _ = stringify!($mut);
+                visitor.visit_span(span);
+            )?
+            $(${ignore($lt)}V::Result::output())?
+        }
+
+        // this is only used by the MutVisitor. We include this symmetry here to make writing other functions easier
+        $(${ignore($lt)}
+            #[expect(unused, rustc::pass_by_value)]
+            #[inline]
+        )?
+        fn visit_id<$($lt,)? V: $Visitor$(<$lt>)?>(visitor: &mut V, id: &$($lt)? $($mut)? NodeId) $(-> <V as Visitor<$lt>>::Result)? {
+            $(
+                let _ = stringify!($mut);
+                visitor.visit_id(id);
+            )?
+            $(${ignore($lt)}V::Result::output())?
+        }
+
+        // this is only used by the MutVisitor. We include this symmetry here to make writing other functions easier
+        fn visit_safety<$($lt,)? V: $Visitor$(<$lt>)?>(vis: &mut V, safety: &$($lt)? $($mut)? Safety) $(-> <V as Visitor<$lt>>::Result)? {
+            match safety {
+                Safety::Unsafe(span) => visit_span(vis, span),
+                Safety::Safe(span) => visit_span(vis, span),
+                Safety::Default => { $(${ignore($lt)}V::Result::output())? }
+            }
+        }
+
+        fn visit_constness<$($lt,)? V: $Visitor$(<$lt>)?>(vis: &mut V, constness: &$($lt)? $($mut)? Const) $(-> <V as Visitor<$lt>>::Result)? {
+            match constness {
+                Const::Yes(span) => visit_span(vis, span),
+                Const::No => {
+                    $(<V as Visitor<$lt>>::Result::output())?
+                }
+            }
+        }
+
+        pub fn walk_label<$($lt,)? V: $Visitor$(<$lt>)?>(visitor: &mut V, Label { ident }: &$($lt)? $($mut)? Label) $(-> <V as Visitor<$lt>>::Result)? {
+            visitor.visit_ident(ident)
+        }
+
+        pub fn walk_fn_header<$($lt,)? V: $Visitor$(<$lt>)?>(visitor: &mut V, header: &$($lt)? $($mut)? FnHeader) $(-> <V as Visitor<$lt>>::Result)? {
+            let FnHeader { safety, coroutine_kind, constness, ext: _ } = header;
+            try_visit!(visit_constness(visitor, constness));
+            if let Some(coroutine_kind) = coroutine_kind {
+                try_visit!(visitor.visit_coroutine_kind(coroutine_kind));
+            }
+            visit_safety(visitor, safety)
+        }
+
+        pub fn walk_lifetime<$($lt,)? V: $Visitor$(<$lt>)?>(visitor: &mut V, Lifetime { id, ident }: &$($lt)? $($mut)? Lifetime) $(-> <V as Visitor<$lt>>::Result)? {
+            try_visit!(visit_id(visitor, id));
+            visitor.visit_ident(ident)
+        }
+    };
+}
+
+common_visitor_and_walkers!(Visitor<'a>);
+
 pub fn walk_crate<'a, V: Visitor<'a>>(visitor: &mut V, krate: &'a Crate) -> V::Result {
     let Crate { attrs, items, spans: _, id: _, is_placeholder: _ } = krate;
     walk_list!(visitor, visit_attribute, attrs);
@@ -334,15 +403,6 @@ pub fn walk_local<'a, V: Visitor<'a>>(visitor: &mut V, local: &'a Local) -> V::R
     V::Result::output()
 }
 
-pub fn walk_label<'a, V: Visitor<'a>>(visitor: &mut V, Label { ident }: &'a Label) -> V::Result {
-    visitor.visit_ident(ident)
-}
-
-pub fn walk_lifetime<'a, V: Visitor<'a>>(visitor: &mut V, lifetime: &'a Lifetime) -> V::Result {
-    let Lifetime { id: _, ident } = lifetime;
-    visitor.visit_ident(ident)
-}
-
 pub fn walk_poly_trait_ref<'a, V>(visitor: &mut V, trait_ref: &'a PolyTraitRef) -> V::Result
 where
     V: Visitor<'a>,
@@ -926,12 +986,6 @@ pub fn walk_fn_ret_ty<'a, V: Visitor<'a>>(visitor: &mut V, ret_ty: &'a FnRetTy)
     V::Result::output()
 }
 
-pub fn walk_fn_header<'a, V: Visitor<'a>>(visitor: &mut V, fn_header: &'a FnHeader) -> V::Result {
-    let FnHeader { safety: _, coroutine_kind, constness: _, ext: _ } = fn_header;
-    visit_opt!(visitor, visit_coroutine_kind, coroutine_kind.as_ref());
-    V::Result::output()
-}
-
 pub fn walk_fn_decl<'a, V: Visitor<'a>>(
     visitor: &mut V,
     FnDecl { inputs, output }: &'a FnDecl,