Unify walk_closure_binder

Author: maxcabrajac

compiler/rustc_ast/src/visitors.rs

@@ -396,7 +396,8 @@ macro_rules! make_ast_visitor {
                     $vis.visit_ident($ident)
                 ,
                     $vis.visit_ident(*$ident)
-                ) }
+                )
+            }
         }
 
         macro_rules! return_result {
@@ -416,6 +417,18 @@ macro_rules! make_ast_visitor {
             }
         }
 
+        macro_rules! visit_list {
+            ($visitor: expr, $visit: ident, $flat_map: ident, $list: expr) => {
+                if_mut_expr!(
+                    $list.flat_map_in_place(|x| $visitor.$flat_map(x))
+                ,
+                    for elem in $list {
+                        try_v!($visitor.$visit(elem));
+                    }
+                )
+            }
+        }
+
         pub fn walk_ident<$($lt,)? V: $trait$(<$lt>)?>(
             vis: &mut V,
             ident: if_mut_ty!(ref_t!(Ident), Ident)
@@ -527,6 +540,20 @@ macro_rules! make_ast_visitor {
             return_result!(V)
         }
 
+        pub fn walk_closure_binder<$($lt,)? V: $trait$(<$lt>)?>(
+            vis: &mut V,
+            binder: ref_t!(ClosureBinder)
+        ) -> result!(V) {
+            match binder {
+                ClosureBinder::NotPresent => {}
+                // TODO: skipped span
+                ClosureBinder::For { generic_params, span: _ } => {
+                    visit_list!(vis, visit_generic_param, flat_map_generic_param, generic_params)
+                }
+            }
+            return_result!(V)
+        }
+
         make_walk_flat_map!{Arm, walk_flat_map_arm, visit_arm}
         make_walk_flat_map!{ExprField, walk_flat_map_expr_field, visit_expr_field}
         make_walk_flat_map!{FieldDef, walk_flat_map_field_def, visit_field_def}
@@ -1117,19 +1144,6 @@ pub mod visit {
         V::Result::output()
     }
 
-    pub fn walk_closure_binder<'a, V: Visitor<'a>>(
-        visitor: &mut V,
-        binder: &'a ClosureBinder,
-    ) -> V::Result {
-        match binder {
-            ClosureBinder::NotPresent => {}
-            ClosureBinder::For { generic_params, span: _ } => {
-                walk_list!(visitor, visit_generic_param, generic_params)
-            }
-        }
-        V::Result::output()
-    }
-
     pub fn walk_where_predicate<'a, V: Visitor<'a>>(
         visitor: &mut V,
         predicate: &'a WherePredicate,
@@ -2144,15 +2158,6 @@ pub mod mut_visit {
         }
     }
 
-    fn walk_closure_binder<T: MutVisitor>(vis: &mut T, binder: &mut ClosureBinder) {
-        match binder {
-            ClosureBinder::NotPresent => {}
-            ClosureBinder::For { span: _, generic_params } => {
-                generic_params.flat_map_in_place(|param| vis.flat_map_generic_param(param));
-            }
-        }
-    }
-
     fn walk_coroutine_kind<T: MutVisitor>(vis: &mut T, coroutine_kind: &mut CoroutineKind) {
         match coroutine_kind {
             CoroutineKind::Async { span, closure_id, return_impl_trait_id }