diff --git a/compiler/rustc_ast/src/mut_visit.rs b/compiler/rustc_ast/src/mut_visit.rs
index 3459d39131a..7caf7c4c356 100644
--- a/compiler/rustc_ast/src/mut_visit.rs
+++ b/compiler/rustc_ast/src/mut_visit.rs
@@ -954,8 +954,14 @@ fn walk_coroutine_kind<T: MutVisitor>(vis: &mut T, coroutine_kind: &mut Coroutin
 
 fn walk_fn<T: MutVisitor>(vis: &mut T, kind: FnKind<'_>) {
     match kind {
-        FnKind::Fn(_ctxt, _ident, FnSig { header, decl, span }, _visibility, generics, body) => {
+        FnKind::Fn(
+            _ctxt,
+            _ident,
+            _vis,
+            Fn { defaultness, generics, body, sig: FnSig { header, decl, span } },
+        ) => {
             // Identifier and visibility are visited as a part of the item.
+            visit_defaultness(vis, defaultness);
             vis.visit_fn_header(header);
             vis.visit_generics(generics);
             vis.visit_fn_decl(decl);
@@ -1205,13 +1211,8 @@ impl WalkItemKind for ItemKind {
             ItemKind::Const(item) => {
                 visit_const_item(item, vis);
             }
-            ItemKind::Fn(box Fn { defaultness, generics, sig, body }) => {
-                visit_defaultness(vis, defaultness);
-                vis.visit_fn(
-                    FnKind::Fn(FnCtxt::Free, ident, sig, visibility, generics, body),
-                    span,
-                    id,
-                );
+            ItemKind::Fn(func) => {
+                vis.visit_fn(FnKind::Fn(FnCtxt::Free, ident, visibility, &mut *func), span, id);
             }
             ItemKind::Mod(safety, mod_kind) => {
                 visit_safety(vis, safety);
@@ -1329,10 +1330,9 @@ impl WalkItemKind for AssocItemKind {
             AssocItemKind::Const(item) => {
                 visit_const_item(item, visitor);
             }
-            AssocItemKind::Fn(box Fn { defaultness, generics, sig, body }) => {
-                visit_defaultness(visitor, defaultness);
+            AssocItemKind::Fn(func) => {
                 visitor.visit_fn(
-                    FnKind::Fn(FnCtxt::Assoc(ctxt), ident, sig, visibility, generics, body),
+                    FnKind::Fn(FnCtxt::Assoc(ctxt), ident, visibility, &mut *func),
                     span,
                     id,
                 );
@@ -1476,10 +1476,9 @@ impl WalkItemKind for ForeignItemKind {
                 visitor.visit_ty(ty);
                 visit_opt(expr, |expr| visitor.visit_expr(expr));
             }
-            ForeignItemKind::Fn(box Fn { defaultness, generics, sig, body }) => {
-                visit_defaultness(visitor, defaultness);
+            ForeignItemKind::Fn(func) => {
                 visitor.visit_fn(
-                    FnKind::Fn(FnCtxt::Foreign, ident, sig, visibility, generics, body),
+                    FnKind::Fn(FnCtxt::Foreign, ident, visibility, &mut *func),
                     span,
                     id,
                 );
@@ -1965,14 +1964,7 @@ impl<N: DummyAstNode, T: DummyAstNode> DummyAstNode for crate::ast_traits::AstNo
 #[derive(Debug)]
 pub enum FnKind<'a> {
     /// E.g., `fn foo()`, `fn foo(&self)`, or `extern "Abi" fn foo()`.
-    Fn(
-        FnCtxt,
-        &'a mut Ident,
-        &'a mut FnSig,
-        &'a mut Visibility,
-        &'a mut Generics,
-        &'a mut Option<P<Block>>,
-    ),
+    Fn(FnCtxt, &'a mut Ident, &'a mut Visibility, &'a mut Fn),
 
     /// E.g., `|x, y| body`.
     Closure(
diff --git a/compiler/rustc_ast/src/visit.rs b/compiler/rustc_ast/src/visit.rs
index 1d6d7330757..232fd546de9 100644
--- a/compiler/rustc_ast/src/visit.rs
+++ b/compiler/rustc_ast/src/visit.rs
@@ -65,7 +65,7 @@ impl BoundKind {
 #[derive(Copy, Clone, Debug)]
 pub enum FnKind<'a> {
     /// E.g., `fn foo()`, `fn foo(&self)`, or `extern "Abi" fn foo()`.
-    Fn(FnCtxt, &'a Ident, &'a FnSig, &'a Visibility, &'a Generics, &'a Option<P<Block>>),
+    Fn(FnCtxt, &'a Ident, &'a Visibility, &'a Fn),
 
     /// E.g., `|x, y| body`.
     Closure(&'a ClosureBinder, &'a Option<CoroutineKind>, &'a FnDecl, &'a Expr),
@@ -74,7 +74,7 @@ pub enum FnKind<'a> {
 impl<'a> FnKind<'a> {
     pub fn header(&self) -> Option<&'a FnHeader> {
         match *self {
-            FnKind::Fn(_, _, sig, _, _, _) => Some(&sig.header),
+            FnKind::Fn(_, _, _, Fn { sig, .. }) => Some(&sig.header),
             FnKind::Closure(..) => None,
         }
     }
@@ -88,7 +88,7 @@ impl<'a> FnKind<'a> {
 
     pub fn decl(&self) -> &'a FnDecl {
         match self {
-            FnKind::Fn(_, _, sig, _, _, _) => &sig.decl,
+            FnKind::Fn(_, _, _, Fn { sig, .. }) => &sig.decl,
             FnKind::Closure(_, _, decl, _) => decl,
         }
     }
@@ -374,8 +374,8 @@ impl WalkItemKind for ItemKind {
                 try_visit!(visitor.visit_ty(ty));
                 visit_opt!(visitor, visit_expr, expr);
             }
-            ItemKind::Fn(box Fn { defaultness: _, generics, sig, body }) => {
-                let kind = FnKind::Fn(FnCtxt::Free, ident, sig, vis, generics, body);
+            ItemKind::Fn(func) => {
+                let kind = FnKind::Fn(FnCtxt::Free, ident, vis, &*func);
                 try_visit!(visitor.visit_fn(kind, span, id));
             }
             ItemKind::Mod(_unsafety, mod_kind) => match mod_kind {
@@ -715,8 +715,8 @@ impl WalkItemKind for ForeignItemKind {
                 try_visit!(visitor.visit_ty(ty));
                 visit_opt!(visitor, visit_expr, expr);
             }
-            ForeignItemKind::Fn(box Fn { defaultness: _, generics, sig, body }) => {
-                let kind = FnKind::Fn(FnCtxt::Foreign, ident, sig, vis, generics, body);
+            ForeignItemKind::Fn(func) => {
+                let kind = FnKind::Fn(FnCtxt::Foreign, ident, vis, &*func);
                 try_visit!(visitor.visit_fn(kind, span, id));
             }
             ForeignItemKind::TyAlias(box TyAlias {
@@ -858,7 +858,12 @@ pub fn walk_fn_decl<'a, V: Visitor<'a>>(
 
 pub fn walk_fn<'a, V: Visitor<'a>>(visitor: &mut V, kind: FnKind<'a>) -> V::Result {
     match kind {
-        FnKind::Fn(_ctxt, _ident, FnSig { header, decl, span: _ }, _vis, generics, body) => {
+        FnKind::Fn(
+            _ctxt,
+            _ident,
+            _vis,
+            Fn { defaultness: _, sig: FnSig { header, decl, span: _ }, generics, body },
+        ) => {
             // Identifier and visibility are visited as a part of the item.
             try_visit!(visitor.visit_fn_header(header));
             try_visit!(visitor.visit_generics(generics));
@@ -892,8 +897,8 @@ impl WalkItemKind for AssocItemKind {
                 try_visit!(visitor.visit_ty(ty));
                 visit_opt!(visitor, visit_expr, expr);
             }
-            AssocItemKind::Fn(box Fn { defaultness: _, generics, sig, body }) => {
-                let kind = FnKind::Fn(FnCtxt::Assoc(ctxt), ident, sig, vis, generics, body);
+            AssocItemKind::Fn(func) => {
+                let kind = FnKind::Fn(FnCtxt::Assoc(ctxt), ident, vis, &*func);
                 try_visit!(visitor.visit_fn(kind, span, id));
             }
             AssocItemKind::Type(box TyAlias {
diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index f31e2c65c79..b932915dc29 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -2125,7 +2125,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         self.arena.alloc(self.expr_call_mut(span, e, args))
     }
 
-    fn expr_call_lang_item_fn_mut(
+    pub(super) fn expr_call_lang_item_fn_mut(
         &mut self,
         span: Span,
         lang_item: hir::LangItem,
@@ -2135,7 +2135,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         self.expr_call_mut(span, path, args)
     }
 
-    fn expr_call_lang_item_fn(
+    pub(super) fn expr_call_lang_item_fn(
         &mut self,
         span: Span,
         lang_item: hir::LangItem,
diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs
index 236ca7ba703..ea1f4a6559a 100644
--- a/compiler/rustc_ast_passes/src/ast_validation.rs
+++ b/compiler/rustc_ast_passes/src/ast_validation.rs
@@ -917,7 +917,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 walk_list!(self, visit_attribute, &item.attrs);
                 return; // Avoid visiting again.
             }
-            ItemKind::Fn(box Fn { defaultness, sig, generics, body }) => {
+            ItemKind::Fn(func @ box Fn { defaultness, generics: _, sig, body }) => {
                 self.check_defaultness(item.span, *defaultness);
 
                 let is_intrinsic =
@@ -947,7 +947,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
 
                 self.visit_vis(&item.vis);
                 self.visit_ident(&item.ident);
-                let kind = FnKind::Fn(FnCtxt::Free, &item.ident, sig, &item.vis, generics, body);
+                let kind = FnKind::Fn(FnCtxt::Free, &item.ident, &item.vis, &*func);
                 self.visit_fn(kind, item.span, item.id);
                 walk_list!(self, visit_attribute, &item.attrs);
                 return; // Avoid visiting again.
@@ -1348,19 +1348,20 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
         }
 
         if let FnKind::Fn(
-            _,
-            _,
-            FnSig { header: FnHeader { ext: Extern::Implicit(extern_span), .. }, .. },
             _,
             _,
             _,
+            Fn {
+                sig: FnSig { header: FnHeader { ext: Extern::Implicit(extern_span), .. }, .. },
+                ..
+            },
         ) = fk
         {
             self.maybe_lint_missing_abi(*extern_span, id);
         }
 
         // Functions without bodies cannot have patterns.
-        if let FnKind::Fn(ctxt, _, sig, _, _, None) = fk {
+        if let FnKind::Fn(ctxt, _, _, Fn { body: None, sig, .. }) = fk {
             Self::check_decl_no_pat(&sig.decl, |span, ident, mut_ident| {
                 if mut_ident && matches!(ctxt, FnCtxt::Assoc(_)) {
                     if let Some(ident) = ident {
@@ -1394,7 +1395,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                         .is_some();
 
         let disallowed = (!tilde_const_allowed).then(|| match fk {
-            FnKind::Fn(_, ident, _, _, _, _) => TildeConstReason::Function { ident: ident.span },
+            FnKind::Fn(_, ident, _, _) => TildeConstReason::Function { ident: ident.span },
             FnKind::Closure(..) => TildeConstReason::Closure,
         });
         self.with_tilde_const(disallowed, |this| visit::walk_fn(this, fk));
@@ -1470,15 +1471,14 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
             self.outer_trait_or_trait_impl.as_ref().and_then(TraitOrTraitImpl::constness).is_some();
 
         match &item.kind {
-            AssocItemKind::Fn(box Fn { sig, generics, body, .. })
+            AssocItemKind::Fn(func)
                 if parent_is_const
                     || ctxt == AssocCtxt::Trait
-                    || matches!(sig.header.constness, Const::Yes(_)) =>
+                    || matches!(func.sig.header.constness, Const::Yes(_)) =>
             {
                 self.visit_vis(&item.vis);
                 self.visit_ident(&item.ident);
-                let kind =
-                    FnKind::Fn(FnCtxt::Assoc(ctxt), &item.ident, sig, &item.vis, generics, body);
+                let kind = FnKind::Fn(FnCtxt::Assoc(ctxt), &item.ident, &item.vis, &*func);
                 walk_list!(self, visit_attribute, &item.attrs);
                 self.visit_fn(kind, item.span, item.id);
             }
diff --git a/compiler/rustc_ast_pretty/src/pprust/state/item.rs b/compiler/rustc_ast_pretty/src/pprust/state/item.rs
index 897c275d850..4cfcaa95233 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state/item.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state/item.rs
@@ -34,8 +34,8 @@ impl<'a> State<'a> {
         self.maybe_print_comment(span.lo());
         self.print_outer_attributes(attrs);
         match kind {
-            ast::ForeignItemKind::Fn(box ast::Fn { defaultness, sig, generics, body }) => {
-                self.print_fn_full(sig, ident, generics, vis, *defaultness, body.as_deref(), attrs);
+            ast::ForeignItemKind::Fn(func) => {
+                self.print_fn_full(ident, vis, attrs, &*func);
             }
             ast::ForeignItemKind::Static(box ast::StaticItem { ty, mutability, expr, safety }) => {
                 self.print_item_const(
@@ -199,16 +199,8 @@ impl<'a> State<'a> {
                     *defaultness,
                 );
             }
-            ast::ItemKind::Fn(box ast::Fn { defaultness, sig, generics, body }) => {
-                self.print_fn_full(
-                    sig,
-                    item.ident,
-                    generics,
-                    &item.vis,
-                    *defaultness,
-                    body.as_deref(),
-                    &item.attrs,
-                );
+            ast::ItemKind::Fn(func) => {
+                self.print_fn_full(item.ident, &item.vis, &item.attrs, &*func);
             }
             ast::ItemKind::Mod(safety, mod_kind) => {
                 self.head(Self::to_string(|s| {
@@ -542,8 +534,8 @@ impl<'a> State<'a> {
         self.maybe_print_comment(span.lo());
         self.print_outer_attributes(attrs);
         match kind {
-            ast::AssocItemKind::Fn(box ast::Fn { defaultness, sig, generics, body }) => {
-                self.print_fn_full(sig, ident, generics, vis, *defaultness, body.as_deref(), attrs);
+            ast::AssocItemKind::Fn(func) => {
+                self.print_fn_full(ident, vis, attrs, &*func);
             }
             ast::AssocItemKind::Const(box ast::ConstItem { defaultness, generics, ty, expr }) => {
                 self.print_item_const(
@@ -653,19 +645,17 @@ impl<'a> State<'a> {
 
     fn print_fn_full(
         &mut self,
-        sig: &ast::FnSig,
         name: Ident,
-        generics: &ast::Generics,
         vis: &ast::Visibility,
-        defaultness: ast::Defaultness,
-        body: Option<&ast::Block>,
         attrs: &[ast::Attribute],
+        func: &ast::Fn,
     ) {
+        let ast::Fn { defaultness, generics, sig, body } = func;
         if body.is_some() {
             self.head("");
         }
         self.print_visibility(vis);
-        self.print_defaultness(defaultness);
+        self.print_defaultness(*defaultness);
         self.print_fn(&sig.decl, sig.header, Some(name), generics);
         if let Some(body) = body {
             self.nbsp();
diff --git a/compiler/rustc_lint/src/builtin.rs b/compiler/rustc_lint/src/builtin.rs
index c03de687a33..e8a4e9a84c4 100644
--- a/compiler/rustc_lint/src/builtin.rs
+++ b/compiler/rustc_lint/src/builtin.rs
@@ -330,10 +330,12 @@ impl EarlyLintPass for UnsafeCode {
         if let FnKind::Fn(
             ctxt,
             _,
-            ast::FnSig { header: ast::FnHeader { safety: ast::Safety::Unsafe(_), .. }, .. },
             _,
-            _,
-            body,
+            ast::Fn {
+                sig: ast::FnSig { header: ast::FnHeader { safety: ast::Safety::Unsafe(_), .. }, .. },
+                body,
+                ..
+            },
         ) = fk
         {
             let decorator = match ctxt {
diff --git a/compiler/rustc_resolve/src/def_collector.rs b/compiler/rustc_resolve/src/def_collector.rs
index 87024c487df..16c0a345f87 100644
--- a/compiler/rustc_resolve/src/def_collector.rs
+++ b/compiler/rustc_resolve/src/def_collector.rs
@@ -170,9 +170,12 @@ impl<'a, 'ra, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'ra, 'tcx> {
 
     fn visit_fn(&mut self, fn_kind: FnKind<'a>, span: Span, _: NodeId) {
         match fn_kind {
-            FnKind::Fn(_ctxt, _ident, FnSig { header, decl, span: _ }, _vis, generics, body)
-                if let Some(coroutine_kind) = header.coroutine_kind =>
-            {
+            FnKind::Fn(
+                _ctxt,
+                _ident,
+                _vis,
+                Fn { sig: FnSig { header, decl, span: _ }, generics, body, .. },
+            ) if let Some(coroutine_kind) = header.coroutine_kind => {
                 self.visit_fn_header(header);
                 self.visit_generics(generics);
 
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index 68d3351f174..4842cbd556c 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -986,8 +986,8 @@ impl<'ra: 'ast, 'ast, 'tcx> Visitor<'ast> for LateResolutionVisitor<'_, 'ast, 'r
         match fn_kind {
             // Bail if the function is foreign, and thus cannot validly have
             // a body, or if there's no body for some other reason.
-            FnKind::Fn(FnCtxt::Foreign, _, sig, _, generics, _)
-            | FnKind::Fn(_, _, sig, _, generics, None) => {
+            FnKind::Fn(FnCtxt::Foreign, _, _, Fn { sig, generics, .. })
+            | FnKind::Fn(_, _, _, Fn { sig, generics, body: None, .. }) => {
                 self.visit_fn_header(&sig.header);
                 self.visit_generics(generics);
                 self.with_lifetime_rib(
@@ -1019,7 +1019,7 @@ impl<'ra: 'ast, 'ast, 'tcx> Visitor<'ast> for LateResolutionVisitor<'_, 'ast, 'r
             // Create a label rib for the function.
             this.with_label_rib(RibKind::FnOrCoroutine, |this| {
                 match fn_kind {
-                    FnKind::Fn(_, _, sig, _, generics, body) => {
+                    FnKind::Fn(_, _, _, Fn { sig, generics, body, .. }) => {
                         this.visit_generics(generics);
 
                         let declaration = &sig.decl;
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index 2db8087fd83..57679d595da 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -224,7 +224,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                 let suggestion = if self.current_trait_ref.is_none()
                     && let Some((fn_kind, _)) = self.diag_metadata.current_function
                     && let Some(FnCtxt::Assoc(_)) = fn_kind.ctxt()
-                    && let FnKind::Fn(_, _, sig, ..) = fn_kind
+                    && let FnKind::Fn(_, _, _, ast::Fn { sig, .. }) = fn_kind
                     && let Some(items) = self.diag_metadata.current_impl_items
                     && let Some(item) = items.iter().find(|i| {
                         i.ident.name == item_str.name
@@ -560,7 +560,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                 Applicability::MaybeIncorrect,
             );
             if !self.self_value_is_available(path[0].ident.span) {
-                if let Some((FnKind::Fn(_, _, sig, ..), fn_span)) =
+                if let Some((FnKind::Fn(_, _, _, ast::Fn { sig, .. }), fn_span)) =
                     &self.diag_metadata.current_function
                 {
                     let (span, sugg) = if let Some(param) = sig.decl.inputs.get(0) {
@@ -3249,7 +3249,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                     {
                         let pre = if lt.kind == MissingLifetimeKind::Ampersand
                             && let Some((kind, _span)) = self.diag_metadata.current_function
-                            && let FnKind::Fn(_, _, sig, _, _, _) = kind
+                            && let FnKind::Fn(_, _, _, ast::Fn { sig, .. }) = kind
                             && !sig.decl.inputs.is_empty()
                             && let sugg = sig
                                 .decl
@@ -3290,7 +3290,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                         } else if (lt.kind == MissingLifetimeKind::Ampersand
                             || lt.kind == MissingLifetimeKind::Underscore)
                             && let Some((kind, _span)) = self.diag_metadata.current_function
-                            && let FnKind::Fn(_, _, sig, _, _, _) = kind
+                            && let FnKind::Fn(_, _, _, ast::Fn { sig, .. }) = kind
                             && let ast::FnRetTy::Ty(ret_ty) = &sig.decl.output
                             && !sig.decl.inputs.is_empty()
                             && let arg_refs = sig
@@ -3350,7 +3350,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                         let mut owned_sugg = lt.kind == MissingLifetimeKind::Ampersand;
                         let mut sugg = vec![(lt.span, String::new())];
                         if let Some((kind, _span)) = self.diag_metadata.current_function
-                            && let FnKind::Fn(_, _, sig, _, _, _) = kind
+                            && let FnKind::Fn(_, _, _, ast::Fn { sig, .. }) = kind
                             && let ast::FnRetTy::Ty(ty) = &sig.decl.output
                         {
                             let mut lt_finder =
diff --git a/src/tools/clippy/clippy_lints/src/multiple_bound_locations.rs b/src/tools/clippy/clippy_lints/src/multiple_bound_locations.rs
index 882ab2dda7a..0e1980a6acb 100644
--- a/src/tools/clippy/clippy_lints/src/multiple_bound_locations.rs
+++ b/src/tools/clippy/clippy_lints/src/multiple_bound_locations.rs
@@ -1,5 +1,5 @@
 use rustc_ast::visit::FnKind;
-use rustc_ast::{NodeId, WherePredicateKind};
+use rustc_ast::{Fn, NodeId, WherePredicateKind};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_lint::{EarlyContext, EarlyLintPass};
 use rustc_session::declare_lint_pass;
@@ -39,7 +39,7 @@ declare_lint_pass!(MultipleBoundLocations => [MULTIPLE_BOUND_LOCATIONS]);
 
 impl EarlyLintPass for MultipleBoundLocations {
     fn check_fn(&mut self, cx: &EarlyContext<'_>, kind: FnKind<'_>, _: Span, _: NodeId) {
-        if let FnKind::Fn(_, _, _, _, generics, _) = kind
+        if let FnKind::Fn(_, _, _, Fn { generics, .. }) = kind
             && !generics.params.is_empty()
             && !generics.where_clause.predicates.is_empty()
         {
diff --git a/src/tools/rustfmt/src/items.rs b/src/tools/rustfmt/src/items.rs
index e7d0fba048b..457d0afe3b5 100644
--- a/src/tools/rustfmt/src/items.rs
+++ b/src/tools/rustfmt/src/items.rs
@@ -333,19 +333,19 @@ impl<'a> FnSig<'a> {
         defaultness: ast::Defaultness,
     ) -> FnSig<'a> {
         match *fn_kind {
-            visit::FnKind::Fn(visit::FnCtxt::Assoc(..), _, fn_sig, vis, generics, _) => {
-                let mut fn_sig = FnSig::from_method_sig(fn_sig, generics, vis);
+            visit::FnKind::Fn(visit::FnCtxt::Assoc(..), _, vis, ast::Fn { sig, generics, .. }) => {
+                let mut fn_sig = FnSig::from_method_sig(sig, generics, vis);
                 fn_sig.defaultness = defaultness;
                 fn_sig
             }
-            visit::FnKind::Fn(_, _, fn_sig, vis, generics, _) => FnSig {
+            visit::FnKind::Fn(_, _, vis, ast::Fn { sig, generics, .. }) => FnSig {
                 decl,
                 generics,
-                ext: fn_sig.header.ext,
-                constness: fn_sig.header.constness,
-                coroutine_kind: Cow::Borrowed(&fn_sig.header.coroutine_kind),
+                ext: sig.header.ext,
+                constness: sig.header.constness,
+                coroutine_kind: Cow::Borrowed(&sig.header.coroutine_kind),
                 defaultness,
-                safety: fn_sig.header.safety,
+                safety: sig.header.safety,
                 visibility: vis,
             },
             _ => unreachable!(),
@@ -3453,6 +3453,7 @@ impl Rewrite for ast::ForeignItem {
                     ref sig,
                     ref generics,
                     ref body,
+                    ..
                 } = **fn_kind;
                 if body.is_some() {
                     let mut visitor = FmtVisitor::from_context(context);
@@ -3461,7 +3462,7 @@ impl Rewrite for ast::ForeignItem {
                     let inner_attrs = inner_attributes(&self.attrs);
                     let fn_ctxt = visit::FnCtxt::Foreign;
                     visitor.visit_fn(
-                        visit::FnKind::Fn(fn_ctxt, &self.ident, sig, &self.vis, generics, body),
+                        visit::FnKind::Fn(fn_ctxt, &self.ident, &self.vis, fn_kind),
                         &sig.decl,
                         self.span,
                         defaultness,
diff --git a/src/tools/rustfmt/src/visitor.rs b/src/tools/rustfmt/src/visitor.rs
index 805e13b7803..bdcb619153d 100644
--- a/src/tools/rustfmt/src/visitor.rs
+++ b/src/tools/rustfmt/src/visitor.rs
@@ -386,7 +386,14 @@ impl<'b, 'a: 'b> FmtVisitor<'a> {
         let indent = self.block_indent;
         let block;
         let rewrite = match fk {
-            visit::FnKind::Fn(_, ident, _, _, _, Some(ref b)) => {
+            visit::FnKind::Fn(
+                _,
+                ident,
+                _,
+                ast::Fn {
+                    body: Some(ref b), ..
+                },
+            ) => {
                 block = b;
                 self.rewrite_fn_before_block(
                     indent,
@@ -539,6 +546,7 @@ impl<'b, 'a: 'b> FmtVisitor<'a> {
                         ref sig,
                         ref generics,
                         ref body,
+                        ..
                     } = **fn_kind;
                     if body.is_some() {
                         let inner_attrs = inner_attributes(&item.attrs);
@@ -547,7 +555,7 @@ impl<'b, 'a: 'b> FmtVisitor<'a> {
                             _ => visit::FnCtxt::Foreign,
                         };
                         self.visit_fn(
-                            visit::FnKind::Fn(fn_ctxt, &item.ident, sig, &item.vis, generics, body),
+                            visit::FnKind::Fn(fn_ctxt, &item.ident, &item.vis, fn_kind),
                             &sig.decl,
                             item.span,
                             defaultness,
@@ -640,12 +648,13 @@ impl<'b, 'a: 'b> FmtVisitor<'a> {
                     ref sig,
                     ref generics,
                     ref body,
+                    ..
                 } = **fn_kind;
                 if body.is_some() {
                     let inner_attrs = inner_attributes(&ai.attrs);
                     let fn_ctxt = visit::FnCtxt::Assoc(assoc_ctxt);
                     self.visit_fn(
-                        visit::FnKind::Fn(fn_ctxt, &ai.ident, sig, &ai.vis, generics, body),
+                        visit::FnKind::Fn(fn_ctxt, &ai.ident, &ai.vis, fn_kind),
                         &sig.decl,
                         ai.span,
                         defaultness,