Rollup merge of #66188 - Centril:fnsig, r=davidtwco

`MethodSig` -> `FnSig` & Use it in `ItemKind::Fn`

In both AST & HIR, rename `MethodSig` to `FnSig` and then proceed to use it in `ItemKind::Fn` so that the overall structure is more regular.

r? @davidtwco

src/librustc/hir/intravisit.rs

@@ -45,7 +45,7 @@ pub enum FnKind<'a> {
     ItemFn(Ident, &'a Generics, FnHeader, &'a Visibility, &'a [Attribute]),
 
     /// `fn foo(&self)`
-    Method(Ident, &'a MethodSig, Option<&'a Visibility>, &'a [Attribute]),
+    Method(Ident, &'a FnSig, Option<&'a Visibility>, &'a [Attribute]),
 
     /// `|x, y| {}`
     Closure(&'a [Attribute]),
@@ -481,13 +481,13 @@ pub fn walk_item<'v, V: Visitor<'v>>(visitor: &mut V, item: &'v Item) {
             visitor.visit_ty(typ);
             visitor.visit_nested_body(body);
         }
-        ItemKind::Fn(ref declaration, header, ref generics, body_id) => {
+        ItemKind::Fn(ref sig, ref generics, body_id) => {
             visitor.visit_fn(FnKind::ItemFn(item.ident,
                                             generics,
-                                            header,
+                                            sig.header,
                                             &item.vis,
                                             &item.attrs),
-                             declaration,
+                             &sig.decl,
                              body_id,
                              item.span,
                              item.hir_id)

src/librustc/hir/lowering/item.rs

@@ -306,7 +306,7 @@ impl LoweringContext<'_> {
                     self.lower_const_body(e)
                 )
             }
-            ItemKind::Fn(ref decl, header, ref generics, ref body) => {
+            ItemKind::Fn(FnSig { ref decl, header }, ref generics, ref body) => {
                 let fn_def_id = self.resolver.definitions().local_def_id(id);
                 self.with_new_scopes(|this| {
                     this.current_item = Some(ident.span);
@@ -317,7 +317,7 @@ impl LoweringContext<'_> {
                     // declaration (decl), not the return types.
                     let body_id = this.lower_maybe_async_body(&decl, header.asyncness.node, body);
 
-                    let (generics, fn_decl) = this.add_in_band_defs(
+                    let (generics, decl) = this.add_in_band_defs(
                         generics,
                         fn_def_id,
                         AnonymousLifetimeMode::PassThrough,
@@ -328,13 +328,8 @@ impl LoweringContext<'_> {
                             header.asyncness.node.opt_return_id()
                         ),
                     );
-
-                    hir::ItemKind::Fn(
-                        fn_decl,
-                        this.lower_fn_header(header),
-                        generics,
-                        body_id,
-                    )
+                    let sig = hir::FnSig { decl, header: this.lower_fn_header(header) };
+                    hir::ItemKind::Fn(sig, generics, body_id)
                 })
             }
             ItemKind::Mod(ref m) => hir::ItemKind::Mod(self.lower_mod(m)),
@@ -1260,11 +1255,11 @@ impl LoweringContext<'_> {
     fn lower_method_sig(
         &mut self,
         generics: &Generics,
-        sig: &MethodSig,
+        sig: &FnSig,
         fn_def_id: DefId,
         impl_trait_return_allow: bool,
         is_async: Option<NodeId>,
-    ) -> (hir::Generics, hir::MethodSig) {
+    ) -> (hir::Generics, hir::FnSig) {
         let header = self.lower_fn_header(sig.header);
         let (generics, decl) = self.add_in_band_defs(
             generics,
@@ -1277,7 +1272,7 @@ impl LoweringContext<'_> {
                 is_async,
             ),
         );
-        (generics, hir::MethodSig { header, decl })
+        (generics, hir::FnSig { header, decl })
     }
 
     fn lower_is_auto(&mut self, a: IsAuto) -> hir::IsAuto {

src/librustc/hir/map/blocks.rs

@@ -158,25 +158,25 @@ impl<'a> FnLikeNode<'a> {
 
     pub fn body(self) -> ast::BodyId {
         self.handle(|i: ItemFnParts<'a>| i.body,
-                    |_, _, _: &'a ast::MethodSig, _, body: ast::BodyId, _, _| body,
+                    |_, _, _: &'a ast::FnSig, _, body: ast::BodyId, _, _| body,
                     |c: ClosureParts<'a>| c.body)
     }
 
     pub fn decl(self) -> &'a FnDecl {
         self.handle(|i: ItemFnParts<'a>| &*i.decl,
-                    |_, _, sig: &'a ast::MethodSig, _, _, _, _| &sig.decl,
+                    |_, _, sig: &'a ast::FnSig, _, _, _, _| &sig.decl,
                     |c: ClosureParts<'a>| c.decl)
     }
 
     pub fn span(self) -> Span {
         self.handle(|i: ItemFnParts<'_>| i.span,
-                    |_, _, _: &'a ast::MethodSig, _, _, span, _| span,
+                    |_, _, _: &'a ast::FnSig, _, _, span, _| span,
                     |c: ClosureParts<'_>| c.span)
     }
 
     pub fn id(self) -> ast::HirId {
         self.handle(|i: ItemFnParts<'_>| i.id,
-                    |id, _, _: &'a ast::MethodSig, _, _, _, _| id,
+                    |id, _, _: &'a ast::FnSig, _, _, _, _| id,
                     |c: ClosureParts<'_>| c.id)
     }
 
@@ -199,7 +199,7 @@ impl<'a> FnLikeNode<'a> {
         let closure = |c: ClosureParts<'a>| {
             FnKind::Closure(c.attrs)
         };
-        let method = |_, ident: Ident, sig: &'a ast::MethodSig, vis, _, _, attrs| {
+        let method = |_, ident: Ident, sig: &'a ast::FnSig, vis, _, _, attrs| {
             FnKind::Method(ident, sig, vis, attrs)
         };
         self.handle(item, method, closure)
@@ -209,7 +209,7 @@ impl<'a> FnLikeNode<'a> {
         I: FnOnce(ItemFnParts<'a>) -> A,
         M: FnOnce(ast::HirId,
                   Ident,
-                  &'a ast::MethodSig,
+                  &'a ast::FnSig,
                   Option<&'a ast::Visibility>,
                   ast::BodyId,
                   Span,
@@ -219,16 +219,16 @@ impl<'a> FnLikeNode<'a> {
     {
         match self.node {
             map::Node::Item(i) => match i.kind {
-                ast::ItemKind::Fn(ref decl, header, ref generics, block) =>
+                ast::ItemKind::Fn(ref sig, ref generics, block) =>
                     item_fn(ItemFnParts {
                         id: i.hir_id,
                         ident: i.ident,
-                        decl: &decl,
+                        decl: &sig.decl,
                         body: block,
                         vis: &i.vis,
                         span: i.span,
                         attrs: &i.attrs,
-                        header,
+                        header: sig.header,
                         generics,
                     }),
                 _ => bug!("item FnLikeNode that is not fn-like"),

src/librustc/hir/map/def_collector.rs

@@ -100,7 +100,7 @@ impl<'a> visit::Visitor<'a> for DefCollector<'a> {
 
         // Pick the def data. This need not be unique, but the more
         // information we encapsulate into, the better
-        let def_data = match i.kind {
+        let def_data = match &i.kind {
             ItemKind::Impl(..) => DefPathData::Impl,
             ItemKind::Mod(..) if i.ident.name == kw::Invalid => {
                 return visit::walk_item(self, i);
@@ -109,19 +109,14 @@ impl<'a> visit::Visitor<'a> for DefCollector<'a> {
             ItemKind::Enum(..) | ItemKind::Struct(..) | ItemKind::Union(..) |
             ItemKind::OpaqueTy(..) | ItemKind::ExternCrate(..) | ItemKind::ForeignMod(..) |
             ItemKind::TyAlias(..) => DefPathData::TypeNs(i.ident.name),
-            ItemKind::Fn(
-                ref decl,
-                ref header,
-                ref generics,
-                ref body,
-            ) if header.asyncness.node.is_async() => {
+            ItemKind::Fn(sig, generics, body) if sig.header.asyncness.node.is_async() => {
                 return self.visit_async_fn(
                     i.id,
                     i.ident.name,
                     i.span,
-                    header,
+                    &sig.header,
                     generics,
-                    decl,
+                    &sig.decl,
                     body,
                 )
             }
@@ -228,7 +223,7 @@ impl<'a> visit::Visitor<'a> for DefCollector<'a> {
 
     fn visit_impl_item(&mut self, ii: &'a ImplItem) {
         let def_data = match ii.kind {
-            ImplItemKind::Method(MethodSig {
+            ImplItemKind::Method(FnSig {
                 ref header,
                 ref decl,
             }, ref body) if header.asyncness.node.is_async() => {

src/librustc/hir/map/mod.rs

@@ -49,21 +49,21 @@ impl<'hir> Entry<'hir> {
         match self.node {
             Node::Item(ref item) => {
                 match item.kind {
-                    ItemKind::Fn(ref fn_decl, _, _, _) => Some(fn_decl),
+                    ItemKind::Fn(ref sig, _, _) => Some(&sig.decl),
                     _ => None,
                 }
             }
 
             Node::TraitItem(ref item) => {
                 match item.kind {
-                    TraitItemKind::Method(ref method_sig, _) => Some(&method_sig.decl),
+                    TraitItemKind::Method(ref sig, _) => Some(&sig.decl),
                     _ => None
                 }
             }
 
             Node::ImplItem(ref item) => {
                 match item.kind {
-                    ImplItemKind::Method(ref method_sig, _) => Some(&method_sig.decl),
+                    ImplItemKind::Method(ref sig, _) => Some(&sig.decl),
                     _ => None,
                 }
             }
@@ -85,7 +85,7 @@ impl<'hir> Entry<'hir> {
                 match item.kind {
                     ItemKind::Const(_, body) |
                     ItemKind::Static(.., body) |
-                    ItemKind::Fn(_, _, _, body) => Some(body),
+                    ItemKind::Fn(.., body) => Some(body),
                     _ => None,
                 }
             }
@@ -605,7 +605,7 @@ impl<'hir> Map<'hir> {
                 Node::TraitItem(ref trait_item) => Some(&trait_item.generics),
                 Node::Item(ref item) => {
                     match item.kind {
-                        ItemKind::Fn(_, _, ref generics, _) |
+                        ItemKind::Fn(_, ref generics, _) |
                         ItemKind::TyAlias(_, ref generics) |
                         ItemKind::Enum(_, ref generics) |
                         ItemKind::Struct(_, ref generics) |
@@ -702,9 +702,9 @@ impl<'hir> Map<'hir> {
                 ..
             }) => true,
             Node::Item(&Item {
-                kind: ItemKind::Fn(_, header, ..),
+                kind: ItemKind::Fn(ref sig, ..),
                 ..
-            }) => header.constness == Constness::Const,
+            }) => sig.header.constness == Constness::Const,
             _ => false,
         }
     }

src/librustc/hir/mod.rs

@@ -1876,9 +1876,10 @@ pub struct MutTy {
     pub mutbl: Mutability,
 }
 
-/// Represents a method's signature in a trait declaration or implementation.
+/// Represents a function's signature in a trait declaration,
+/// trait implementation, or a free function.
 #[derive(RustcEncodable, RustcDecodable, Debug, HashStable)]
-pub struct MethodSig {
+pub struct FnSig {
     pub header: FnHeader,
     pub decl: P<FnDecl>,
 }
@@ -1921,7 +1922,7 @@ pub enum TraitItemKind {
     /// An associated constant with an optional value (otherwise `impl`s must contain a value).
     Const(P<Ty>, Option<BodyId>),
     /// A method with an optional body.
-    Method(MethodSig, TraitMethod),
+    Method(FnSig, TraitMethod),
     /// An associated type with (possibly empty) bounds and optional concrete
     /// type.
     Type(GenericBounds, Option<P<Ty>>),
@@ -1955,7 +1956,7 @@ pub enum ImplItemKind {
     /// of the expression.
     Const(P<Ty>, BodyId),
     /// A method implementation with the given signature and body.
-    Method(MethodSig, BodyId),
+    Method(FnSig, BodyId),
     /// An associated type.
     TyAlias(P<Ty>),
     /// An associated `type = impl Trait`.
@@ -2534,7 +2535,7 @@ pub enum ItemKind {
     /// A `const` item.
     Const(P<Ty>, BodyId),
     /// A function declaration.
-    Fn(P<FnDecl>, FnHeader, Generics, BodyId),
+    Fn(FnSig, Generics, BodyId),
     /// A module.
     Mod(Mod),
     /// An external module, e.g. `extern { .. }`.
@@ -2599,7 +2600,7 @@ impl ItemKind {
 
     pub fn generics(&self) -> Option<&Generics> {
         Some(match *self {
-            ItemKind::Fn(_, _, ref generics, _) |
+            ItemKind::Fn(_, ref generics, _) |
             ItemKind::TyAlias(_, ref generics) |
             ItemKind::OpaqueTy(OpaqueTy { ref generics, impl_trait_fn: None, .. }) |
             ItemKind::Enum(_, ref generics) |

src/librustc/hir/print.rs

@@ -533,10 +533,10 @@ impl<'a> State<'a> {
                 self.s.word(";");
                 self.end(); // end the outer cbox
             }
-            hir::ItemKind::Fn(ref decl, header, ref param_names, body) => {
+            hir::ItemKind::Fn(ref sig, ref param_names, body) => {
                 self.head("");
-                self.print_fn(decl,
-                              header,
+                self.print_fn(&sig.decl,
+                              sig.header,
                               Some(item.ident.name),
                               param_names,
                               &item.vis,
@@ -835,7 +835,7 @@ impl<'a> State<'a> {
     }
     pub fn print_method_sig(&mut self,
                             ident: ast::Ident,
-                            m: &hir::MethodSig,
+                            m: &hir::FnSig,
                             generics: &hir::Generics,
                             vis: &hir::Visibility,
                             arg_names: &[ast::Ident],

src/librustc/infer/error_reporting/nice_region_error/find_anon_type.rs

@@ -31,10 +31,10 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             if let Some(hir_id) = self.tcx().hir().as_local_hir_id(def_id) {
                 let fndecl = match self.tcx().hir().get(hir_id) {
                     Node::Item(&hir::Item {
-                        kind: hir::ItemKind::Fn(ref fndecl, ..),
+                        kind: hir::ItemKind::Fn(ref m, ..),
                         ..
-                    }) => &fndecl,
-                    Node::TraitItem(&hir::TraitItem {
+                    })
+                    | Node::TraitItem(&hir::TraitItem {
                         kind: hir::TraitItemKind::Method(ref m, ..),
                         ..
                     })

src/librustc/middle/reachable.rs

@@ -33,7 +33,7 @@ fn item_might_be_inlined(tcx: TyCtxt<'tcx>, item: &hir::Item, attrs: CodegenFnAt
     }
 
     match item.kind {
-        hir::ItemKind::Fn(_, header, ..) if header.is_const() => {
+        hir::ItemKind::Fn(ref sig, ..) if sig.header.is_const() => {
             return true;
         }
         hir::ItemKind::Impl(..) |
@@ -225,8 +225,8 @@ impl<'a, 'tcx> ReachableContext<'a, 'tcx> {
             // If we are building an executable, only explicitly extern
             // types need to be exported.
             if let Node::Item(item) = *node {
-                let reachable = if let hir::ItemKind::Fn(_, header, ..) = item.kind {
-                    header.abi != Abi::Rust
+                let reachable = if let hir::ItemKind::Fn(ref sig, ..) = item.kind {
+                    sig.header.abi != Abi::Rust
                 } else {
                     false
                 };

src/librustc/middle/resolve_lifetime.rs

@@ -460,8 +460,8 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
 
     fn visit_item(&mut self, item: &'tcx hir::Item) {
         match item.kind {
-            hir::ItemKind::Fn(ref decl, _, ref generics, _) => {
-                self.visit_early_late(None, decl, generics, |this| {
+            hir::ItemKind::Fn(ref sig, ref generics, _) => {
+                self.visit_early_late(None, &sig.decl, generics, |this| {
                     intravisit::walk_item(this, item);
                 });
             }
@@ -1524,8 +1524,8 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
             {
                 match parent {
                     Node::Item(item) => {
-                        if let hir::ItemKind::Fn(decl, _, _, _) = &item.kind {
-                            find_arg_use_span(&decl.inputs);
+                        if let hir::ItemKind::Fn(sig, _, _) = &item.kind {
+                            find_arg_use_span(&sig.decl.inputs);
                         }
                     },
                     Node::ImplItem(impl_item) => {