diff --git a/compiler/rustc_expand/src/expand.rs b/compiler/rustc_expand/src/expand.rs
index 9fd524ef45cd0..a1037ac0145f8 100644
--- a/compiler/rustc_expand/src/expand.rs
+++ b/compiler/rustc_expand/src/expand.rs
@@ -86,7 +86,7 @@ macro_rules! ast_fragments {
                 }
             }
 
-            fn make_from<'a>(self, result: Box<dyn MacResult + 'a>) -> Option<AstFragment> {
+            fn make_from(self, result: Box<dyn MacResult + '_>) -> Option<AstFragment> {
                 match self {
                     AstFragmentKind::OptExpr =>
                         result.make_expr().map(Some).map(AstFragment::OptExpr),
@@ -136,7 +136,7 @@ macro_rules! ast_fragments {
                 T::fragment_to_output(self)
             }
 
-            pub(crate) fn mut_visit_with<F: MutVisitor>(&mut self, vis: &mut F) {
+            pub(crate) fn mut_visit_with(&mut self, vis: &mut impl MutVisitor) {
                 match self {
                     AstFragment::OptExpr(opt_expr) => {
                         if let Some(expr) = opt_expr.take() {
@@ -316,9 +316,9 @@ impl AstFragmentKind {
         }
     }
 
-    pub(crate) fn expect_from_annotatables<I: IntoIterator<Item = Annotatable>>(
+    pub(crate) fn expect_from_annotatables(
         self,
-        items: I,
+        items: impl IntoIterator<Item = Annotatable>,
     ) -> AstFragment {
         let mut items = items.into_iter();
         match self {
@@ -1218,10 +1218,10 @@ trait InvocationCollectorNode: HasAttrs + HasNodeId + Sized {
     fn descr() -> &'static str {
         unreachable!()
     }
-    fn walk_flat_map<V: MutVisitor>(self, _visitor: &mut V) -> Self::OutputTy {
+    fn walk_flat_map(self, _collector: &mut InvocationCollector<'_, '_>) -> Self::OutputTy {
         unreachable!()
     }
-    fn walk<V: MutVisitor>(&mut self, _visitor: &mut V) {
+    fn walk(&mut self, _collector: &mut InvocationCollector<'_, '_>) {
         unreachable!()
     }
     fn is_mac_call(&self) -> bool {
@@ -1276,8 +1276,8 @@ impl InvocationCollectorNode for P<ast::Item> {
     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
         fragment.make_items()
     }
-    fn walk_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
-        walk_flat_map_item(visitor, self)
+    fn walk_flat_map(self, collector: &mut InvocationCollector<'_, '_>) -> Self::OutputTy {
+        walk_flat_map_item(collector, self)
     }
     fn is_mac_call(&self) -> bool {
         matches!(self.kind, ItemKind::MacCall(..))
@@ -1431,8 +1431,8 @@ impl InvocationCollectorNode for AstNodeWrapper<P<ast::AssocItem>, TraitItemTag>
     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
         fragment.make_trait_items()
     }
-    fn walk_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
-        walk_flat_map_assoc_item(visitor, self.wrapped, AssocCtxt::Trait)
+    fn walk_flat_map(self, collector: &mut InvocationCollector<'_, '_>) -> Self::OutputTy {
+        walk_flat_map_assoc_item(collector, self.wrapped, AssocCtxt::Trait)
     }
     fn is_mac_call(&self) -> bool {
         matches!(self.wrapped.kind, AssocItemKind::MacCall(..))
@@ -1472,8 +1472,8 @@ impl InvocationCollectorNode for AstNodeWrapper<P<ast::AssocItem>, ImplItemTag>
     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
         fragment.make_impl_items()
     }
-    fn walk_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
-        walk_flat_map_assoc_item(visitor, self.wrapped, AssocCtxt::Impl { of_trait: false })
+    fn walk_flat_map(self, collector: &mut InvocationCollector<'_, '_>) -> Self::OutputTy {
+        walk_flat_map_assoc_item(collector, self.wrapped, AssocCtxt::Impl { of_trait: false })
     }
     fn is_mac_call(&self) -> bool {
         matches!(self.wrapped.kind, AssocItemKind::MacCall(..))
@@ -1513,8 +1513,8 @@ impl InvocationCollectorNode for AstNodeWrapper<P<ast::AssocItem>, TraitImplItem
     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
         fragment.make_trait_impl_items()
     }
-    fn walk_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
-        walk_flat_map_assoc_item(visitor, self.wrapped, AssocCtxt::Impl { of_trait: true })
+    fn walk_flat_map(self, collector: &mut InvocationCollector<'_, '_>) -> Self::OutputTy {
+        walk_flat_map_assoc_item(collector, self.wrapped, AssocCtxt::Impl { of_trait: true })
     }
     fn is_mac_call(&self) -> bool {
         matches!(self.wrapped.kind, AssocItemKind::MacCall(..))
@@ -1551,8 +1551,8 @@ impl InvocationCollectorNode for P<ast::ForeignItem> {
     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
         fragment.make_foreign_items()
     }
-    fn walk_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
-        walk_flat_map_foreign_item(visitor, self)
+    fn walk_flat_map(self, collector: &mut InvocationCollector<'_, '_>) -> Self::OutputTy {
+        walk_flat_map_foreign_item(collector, self)
     }
     fn is_mac_call(&self) -> bool {
         matches!(self.kind, ForeignItemKind::MacCall(..))
@@ -1573,8 +1573,8 @@ impl InvocationCollectorNode for ast::Variant {
     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
         fragment.make_variants()
     }
-    fn walk_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
-        walk_flat_map_variant(visitor, self)
+    fn walk_flat_map(self, collector: &mut InvocationCollector<'_, '_>) -> Self::OutputTy {
+        walk_flat_map_variant(collector, self)
     }
 }
 
@@ -1586,8 +1586,8 @@ impl InvocationCollectorNode for ast::WherePredicate {
     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
         fragment.make_where_predicates()
     }
-    fn walk_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
-        walk_flat_map_where_predicate(visitor, self)
+    fn walk_flat_map(self, collector: &mut InvocationCollector<'_, '_>) -> Self::OutputTy {
+        walk_flat_map_where_predicate(collector, self)
     }
 }
 
@@ -1599,8 +1599,8 @@ impl InvocationCollectorNode for ast::FieldDef {
     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
         fragment.make_field_defs()
     }
-    fn walk_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
-        walk_flat_map_field_def(visitor, self)
+    fn walk_flat_map(self, collector: &mut InvocationCollector<'_, '_>) -> Self::OutputTy {
+        walk_flat_map_field_def(collector, self)
     }
 }
 
@@ -1612,8 +1612,8 @@ impl InvocationCollectorNode for ast::PatField {
     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
         fragment.make_pat_fields()
     }
-    fn walk_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
-        walk_flat_map_pat_field(visitor, self)
+    fn walk_flat_map(self, collector: &mut InvocationCollector<'_, '_>) -> Self::OutputTy {
+        walk_flat_map_pat_field(collector, self)
     }
 }
 
@@ -1625,8 +1625,8 @@ impl InvocationCollectorNode for ast::ExprField {
     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
         fragment.make_expr_fields()
     }
-    fn walk_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
-        walk_flat_map_expr_field(visitor, self)
+    fn walk_flat_map(self, collector: &mut InvocationCollector<'_, '_>) -> Self::OutputTy {
+        walk_flat_map_expr_field(collector, self)
     }
 }
 
@@ -1638,8 +1638,8 @@ impl InvocationCollectorNode for ast::Param {
     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
         fragment.make_params()
     }
-    fn walk_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
-        walk_flat_map_param(visitor, self)
+    fn walk_flat_map(self, collector: &mut InvocationCollector<'_, '_>) -> Self::OutputTy {
+        walk_flat_map_param(collector, self)
     }
 }
 
@@ -1651,8 +1651,8 @@ impl InvocationCollectorNode for ast::GenericParam {
     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
         fragment.make_generic_params()
     }
-    fn walk_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
-        walk_flat_map_generic_param(visitor, self)
+    fn walk_flat_map(self, collector: &mut InvocationCollector<'_, '_>) -> Self::OutputTy {
+        walk_flat_map_generic_param(collector, self)
     }
 }
 
@@ -1664,8 +1664,8 @@ impl InvocationCollectorNode for ast::Arm {
     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
         fragment.make_arms()
     }
-    fn walk_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
-        walk_flat_map_arm(visitor, self)
+    fn walk_flat_map(self, collector: &mut InvocationCollector<'_, '_>) -> Self::OutputTy {
+        walk_flat_map_arm(collector, self)
     }
 }
 
@@ -1677,8 +1677,8 @@ impl InvocationCollectorNode for ast::Stmt {
     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
         fragment.make_stmts()
     }
-    fn walk_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
-        walk_flat_map_stmt(visitor, self)
+    fn walk_flat_map(self, collector: &mut InvocationCollector<'_, '_>) -> Self::OutputTy {
+        walk_flat_map_stmt(collector, self)
     }
     fn is_mac_call(&self) -> bool {
         match &self.kind {
@@ -1751,8 +1751,8 @@ impl InvocationCollectorNode for ast::Crate {
     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
         fragment.make_crate()
     }
-    fn walk<V: MutVisitor>(&mut self, visitor: &mut V) {
-        walk_crate(visitor, self)
+    fn walk(&mut self, collector: &mut InvocationCollector<'_, '_>) {
+        walk_crate(collector, self)
     }
     fn expand_cfg_false(
         &mut self,
@@ -1777,8 +1777,8 @@ impl InvocationCollectorNode for ast::Ty {
     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
         fragment.make_ty()
     }
-    fn walk<V: MutVisitor>(&mut self, visitor: &mut V) {
-        walk_ty(visitor, self)
+    fn walk(&mut self, collector: &mut InvocationCollector<'_, '_>) {
+        walk_ty(collector, self)
     }
     fn is_mac_call(&self) -> bool {
         matches!(self.kind, ast::TyKind::MacCall(..))
@@ -1800,8 +1800,8 @@ impl InvocationCollectorNode for ast::Pat {
     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
         fragment.make_pat()
     }
-    fn walk<V: MutVisitor>(&mut self, visitor: &mut V) {
-        walk_pat(visitor, self)
+    fn walk(&mut self, collector: &mut InvocationCollector<'_, '_>) {
+        walk_pat(collector, self)
     }
     fn is_mac_call(&self) -> bool {
         matches!(self.kind, PatKind::MacCall(..))
@@ -1826,8 +1826,8 @@ impl InvocationCollectorNode for ast::Expr {
     fn descr() -> &'static str {
         "an expression"
     }
-    fn walk<V: MutVisitor>(&mut self, visitor: &mut V) {
-        walk_expr(visitor, self)
+    fn walk(&mut self, collector: &mut InvocationCollector<'_, '_>) {
+        walk_expr(collector, self)
     }
     fn is_mac_call(&self) -> bool {
         matches!(self.kind, ExprKind::MacCall(..))
@@ -1850,8 +1850,8 @@ impl InvocationCollectorNode for AstNodeWrapper<P<ast::Expr>, OptExprTag> {
     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
         fragment.make_opt_expr()
     }
-    fn walk_flat_map<V: MutVisitor>(mut self, visitor: &mut V) -> Self::OutputTy {
-        walk_expr(visitor, &mut self.wrapped);
+    fn walk_flat_map(mut self, collector: &mut InvocationCollector<'_, '_>) -> Self::OutputTy {
+        walk_expr(collector, &mut self.wrapped);
         Some(self.wrapped)
     }
     fn is_mac_call(&self) -> bool {
@@ -1885,8 +1885,8 @@ impl InvocationCollectorNode for AstNodeWrapper<P<ast::Expr>, MethodReceiverTag>
     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
         AstNodeWrapper::new(fragment.make_method_receiver_expr(), MethodReceiverTag)
     }
-    fn walk<V: MutVisitor>(&mut self, visitor: &mut V) {
-        walk_expr(visitor, &mut self.wrapped)
+    fn walk(&mut self, collector: &mut InvocationCollector<'_, '_>) {
+        walk_expr(collector, &mut self.wrapped)
     }
     fn is_mac_call(&self) -> bool {
         matches!(self.wrapped.kind, ast::ExprKind::MacCall(..))