syntax: Remove `Nt(Impl,Trait,Foreign)Item`

src/librustc_ast_pretty/pprust.rs

@@ -319,10 +319,7 @@ pub fn nonterminal_to_string(nt: &Nonterminal) -> String {
         token::NtLifetime(e) => e.to_string(),
         token::NtLiteral(ref e) => expr_to_string(e),
         token::NtTT(ref tree) => tt_to_string(tree.clone()),
-        // FIXME(Centril): merge these variants.
-        token::NtImplItem(ref e) | token::NtTraitItem(ref e) => assoc_item_to_string(e),
         token::NtVis(ref e) => vis_to_string(e),
-        token::NtForeignItem(ref e) => foreign_item_to_string(e),
     }
 }
 
@@ -358,10 +355,6 @@ pub fn item_to_string(i: &ast::Item) -> String {
     to_string(|s| s.print_item(i))
 }
 
-fn assoc_item_to_string(i: &ast::AssocItem) -> String {
-    to_string(|s| s.print_assoc_item(i))
-}
-
 pub fn generic_params_to_string(generic_params: &[ast::GenericParam]) -> String {
     to_string(|s| s.print_generic_params(generic_params))
 }
@@ -404,10 +397,6 @@ pub fn param_to_string(arg: &ast::Param) -> String {
     to_string(|s| s.print_param(arg, false))
 }
 
-fn foreign_item_to_string(arg: &ast::ForeignItem) -> String {
-    to_string(|s| s.print_foreign_item(arg))
-}
-
 fn visibility_qualified(vis: &ast::Visibility, s: &str) -> String {
     format!("{}{}", to_string(|s| s.print_visibility(vis)), s)
 }

src/librustc_expand/expand.rs

@@ -669,12 +669,17 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                 SyntaxExtensionKind::Attr(expander) => {
                     self.gate_proc_macro_input(&item);
                     self.gate_proc_macro_attr_item(span, &item);
+                    // `Annotatable` can be converted into tokens directly, but we are packing it
+                    // into a nonterminal as a piece of AST to make the produced token stream
+                    // look nicer in pretty-printed form. This may be no longer necessary.
                     let item_tok = TokenTree::token(
                         token::Interpolated(Lrc::new(match item {
                             Annotatable::Item(item) => token::NtItem(item),
-                            Annotatable::TraitItem(item) => token::NtTraitItem(item),
-                            Annotatable::ImplItem(item) => token::NtImplItem(item),
-                            Annotatable::ForeignItem(item) => token::NtForeignItem(item),
+                            Annotatable::TraitItem(item)
+                            | Annotatable::ImplItem(item)
+                            | Annotatable::ForeignItem(item) => {
+                                token::NtItem(P(item.and_then(ast::AssocItem::into_item)))
+                            }
                             Annotatable::Stmt(stmt) => token::NtStmt(stmt.into_inner()),
                             Annotatable::Expr(expr) => token::NtExpr(expr),
                             Annotatable::Arm(..)

src/librustc_parse/lib.rs

@@ -314,9 +314,6 @@ pub fn nt_to_tokenstream(nt: &Nonterminal, sess: &ParseSess, span: Span) -> Toke
         Nonterminal::NtItem(ref item) => {
             prepend_attrs(sess, &item.attrs, item.tokens.as_ref(), span)
         }
-        Nonterminal::NtTraitItem(ref item) | Nonterminal::NtImplItem(ref item) => {
-            prepend_attrs(sess, &item.attrs, item.tokens.as_ref(), span)
-        }
         Nonterminal::NtIdent(ident, is_raw) => {
             Some(tokenstream::TokenTree::token(token::Ident(ident.name, is_raw), ident.span).into())
         }

src/librustc_parse/parser/item.rs

@@ -632,16 +632,10 @@ impl<'a> Parser<'a> {
     }
 
     pub fn parse_impl_item(&mut self) -> PResult<'a, Option<Option<P<AssocItem>>>> {
-        maybe_whole!(self, NtImplItem, |x| Some(Some(x)));
         self.parse_assoc_item(|_| true)
     }
 
     pub fn parse_trait_item(&mut self) -> PResult<'a, Option<Option<P<AssocItem>>>> {
-        maybe_whole!(self, NtTraitItem, |x| Some(Some(x)));
-        // This is somewhat dubious; We don't want to allow
-        // param names to be left off if there is a definition...
-        //
-        // We don't allow param names to be left off in edition 2018.
         self.parse_assoc_item(|t| t.span.rust_2018())
     }
 
@@ -834,8 +828,6 @@ impl<'a> Parser<'a> {
 
     /// Parses a foreign item (one in an `extern { ... }` block).
     pub fn parse_foreign_item(&mut self) -> PResult<'a, Option<Option<P<ForeignItem>>>> {
-        maybe_whole!(self, NtForeignItem, |item| Some(Some(item)));
-
         Ok(self.parse_item_(|_| true)?.map(|Item { attrs, id, span, vis, ident, kind, tokens }| {
             let kind = match kind {
                 ItemKind::Mac(a) => ForeignItemKind::Macro(a),

src/libsyntax/ast.rs

@@ -2441,6 +2441,13 @@ impl Item {
     }
 }
 
+impl<K: IntoItemKind> Item<K> {
+    pub fn into_item(self) -> Item {
+        let Item { attrs, id, span, vis, ident, kind, tokens } = self;
+        Item { attrs, id, span, vis, ident, kind: kind.into_item_kind(), tokens }
+    }
+}
+
 /// `extern` qualifier on a function item or function type.
 #[derive(Clone, Copy, RustcEncodable, RustcDecodable, Debug)]
 pub enum Extern {
@@ -2617,6 +2624,10 @@ impl ItemKind {
     }
 }
 
+pub trait IntoItemKind {
+    fn into_item_kind(self) -> ItemKind;
+}
+
 // FIXME(Centril): These definitions should be unmerged;
 // see https://github.com/rust-lang/rust/pull/69194#discussion_r379899975
 pub type ForeignItem = Item<AssocItemKind>;
@@ -2656,3 +2667,15 @@ impl AssocItemKind {
         }
     }
 }
+
+impl IntoItemKind for AssocItemKind {
+    fn into_item_kind(self) -> ItemKind {
+        match self {
+            AssocItemKind::Const(a, b, c) => ItemKind::Const(a, b, c),
+            AssocItemKind::Static(a, b, c) => ItemKind::Static(a, b, c),
+            AssocItemKind::Fn(a, b, c, d) => ItemKind::Fn(a, b, c, d),
+            AssocItemKind::TyAlias(a, b, c, d) => ItemKind::TyAlias(a, b, c, d),
+            AssocItemKind::Macro(a) => ItemKind::Mac(a),
+        }
+    }
+}

src/libsyntax/mut_visit.rs

@@ -711,20 +711,7 @@ pub fn noop_visit_interpolated<T: MutVisitor>(nt: &mut token::Nonterminal, vis:
         }
         token::NtPath(path) => vis.visit_path(path),
         token::NtTT(tt) => vis.visit_tt(tt),
-        token::NtImplItem(item) => visit_clobber(item, |item| {
-            // See reasoning above.
-            vis.flat_map_impl_item(item).expect_one("expected visitor to produce exactly one item")
-        }),
-        token::NtTraitItem(item) => visit_clobber(item, |item| {
-            // See reasoning above.
-            vis.flat_map_trait_item(item).expect_one("expected visitor to produce exactly one item")
-        }),
         token::NtVis(visib) => vis.visit_vis(visib),
-        token::NtForeignItem(item) => visit_clobber(item, |item| {
-            // See reasoning above.
-            vis.flat_map_foreign_item(item)
-                .expect_one("expected visitor to produce exactly one item")
-        }),
     }
 }
 

src/libsyntax/token.rs

@@ -712,12 +712,6 @@ pub enum Nonterminal {
     NtPath(ast::Path),
     NtVis(ast::Visibility),
     NtTT(TokenTree),
-    // Used only for passing items to proc macro attributes (they are not
-    // strictly necessary for that, `Annotatable` can be converted into
-    // tokens directly, but doing that naively regresses pretty-printing).
-    NtTraitItem(P<ast::AssocItem>),
-    NtImplItem(P<ast::AssocItem>),
-    NtForeignItem(P<ast::ForeignItem>),
 }
 
 // `Nonterminal` is used a lot. Make sure it doesn't unintentionally get bigger.
@@ -755,9 +749,6 @@ impl fmt::Debug for Nonterminal {
             NtMeta(..) => f.pad("NtMeta(..)"),
             NtPath(..) => f.pad("NtPath(..)"),
             NtTT(..) => f.pad("NtTT(..)"),
-            NtImplItem(..) => f.pad("NtImplItem(..)"),
-            NtTraitItem(..) => f.pad("NtTraitItem(..)"),
-            NtForeignItem(..) => f.pad("NtForeignItem(..)"),
             NtVis(..) => f.pad("NtVis(..)"),
             NtLifetime(..) => f.pad("NtLifetime(..)"),
         }

src/test/ui/proc-macro/trait-fn-args-2015.rs

@@ -0,0 +1,14 @@
+// Unnamed arguments in trait functions can be passed through proc macros on 2015 edition.
+
+// check-pass
+// aux-build:test-macros.rs
+
+#[macro_use]
+extern crate test_macros;
+
+trait Tr {
+    #[identity_attr]
+    fn method(u8);
+}
+
+fn main() {}