diff --git a/src/librustc_expand/base.rs b/src/librustc_expand/base.rs
index 9debae19fa5..af02070828a 100644
--- a/src/librustc_expand/base.rs
+++ b/src/librustc_expand/base.rs
@@ -62,7 +62,7 @@ fn attrs(&self) -> &[Attribute] {
         }
     }
 
-    fn visit_attrs<F: FnOnce(&mut Vec<Attribute>)>(&mut self, f: F) {
+    fn visit_attrs(&mut self, f: impl FnOnce(&mut Vec<Attribute>)) {
         match self {
             Annotatable::Item(item) => item.visit_attrs(f),
             Annotatable::TraitItem(trait_item) => trait_item.visit_attrs(f),
diff --git a/src/libsyntax/attr/mod.rs b/src/libsyntax/attr/mod.rs
index 419297678d2..a78fbe276fa 100644
--- a/src/libsyntax/attr/mod.rs
+++ b/src/libsyntax/attr/mod.rs
@@ -657,15 +657,15 @@ fn from_tokens<I>(tokens: &mut iter::Peekable<I>) -> Option<NestedMetaItem>
 }
 
 pub trait HasAttrs: Sized {
-    fn attrs(&self) -> &[ast::Attribute];
-    fn visit_attrs<F: FnOnce(&mut Vec<ast::Attribute>)>(&mut self, f: F);
+    fn attrs(&self) -> &[Attribute];
+    fn visit_attrs(&mut self, f: impl FnOnce(&mut Vec<Attribute>));
 }
 
 impl<T: HasAttrs> HasAttrs for Spanned<T> {
-    fn attrs(&self) -> &[ast::Attribute] {
+    fn attrs(&self) -> &[Attribute] {
         self.node.attrs()
     }
-    fn visit_attrs<F: FnOnce(&mut Vec<ast::Attribute>)>(&mut self, f: F) {
+    fn visit_attrs(&mut self, f: impl FnOnce(&mut Vec<Attribute>)) {
         self.node.visit_attrs(f);
     }
 }
@@ -674,7 +674,7 @@ impl HasAttrs for Vec<Attribute> {
     fn attrs(&self) -> &[Attribute] {
         self
     }
-    fn visit_attrs<F: FnOnce(&mut Vec<Attribute>)>(&mut self, f: F) {
+    fn visit_attrs(&mut self, f: impl FnOnce(&mut Vec<Attribute>)) {
         f(self)
     }
 }
@@ -683,7 +683,7 @@ impl HasAttrs for AttrVec {
     fn attrs(&self) -> &[Attribute] {
         self
     }
-    fn visit_attrs<F: FnOnce(&mut Vec<Attribute>)>(&mut self, f: F) {
+    fn visit_attrs(&mut self, f: impl FnOnce(&mut Vec<Attribute>)) {
         visit_clobber(self, |this| {
             let mut vec = this.into();
             f(&mut vec);
@@ -696,7 +696,7 @@ impl<T: HasAttrs + 'static> HasAttrs for P<T> {
     fn attrs(&self) -> &[Attribute] {
         (**self).attrs()
     }
-    fn visit_attrs<F: FnOnce(&mut Vec<Attribute>)>(&mut self, f: F) {
+    fn visit_attrs(&mut self, f: impl FnOnce(&mut Vec<Attribute>)) {
         (**self).visit_attrs(f);
     }
 }
@@ -714,7 +714,7 @@ fn attrs(&self) -> &[Attribute] {
         }
     }
 
-    fn visit_attrs<F: FnOnce(&mut Vec<Attribute>)>(&mut self, f: F) {
+    fn visit_attrs(&mut self, f: impl FnOnce(&mut Vec<Attribute>)) {
         match self {
             StmtKind::Local(local) => local.visit_attrs(f),
             StmtKind::Item(..) => {}
@@ -733,21 +733,11 @@ fn attrs(&self) -> &[ast::Attribute] {
         self.kind.attrs()
     }
 
-    fn visit_attrs<F: FnOnce(&mut Vec<ast::Attribute>)>(&mut self, f: F) {
+    fn visit_attrs(&mut self, f: impl FnOnce(&mut Vec<Attribute>)) {
         self.kind.visit_attrs(f);
     }
 }
 
-impl HasAttrs for GenericParam {
-    fn attrs(&self) -> &[ast::Attribute] {
-        &self.attrs
-    }
-
-    fn visit_attrs<F: FnOnce(&mut Vec<Attribute>)>(&mut self, f: F) {
-        self.attrs.visit_attrs(f);
-    }
-}
-
 macro_rules! derive_has_attrs {
     ($($ty:path),*) => { $(
         impl HasAttrs for $ty {
@@ -755,7 +745,7 @@ fn attrs(&self) -> &[Attribute] {
                 &self.attrs
             }
 
-            fn visit_attrs<F: FnOnce(&mut Vec<Attribute>)>(&mut self, f: F) {
+            fn visit_attrs(&mut self, f: impl FnOnce(&mut Vec<Attribute>)) {
                 self.attrs.visit_attrs(f);
             }
         }
@@ -764,5 +754,5 @@ fn visit_attrs<F: FnOnce(&mut Vec<Attribute>)>(&mut self, f: F) {
 
 derive_has_attrs! {
     Item, Expr, Local, ast::ForeignItem, ast::StructField, ast::AssocItem, ast::Arm,
-    ast::Field, ast::FieldPat, ast::Variant, ast::Param
+    ast::Field, ast::FieldPat, ast::Variant, ast::Param, GenericParam
 }