Declarative macros 2.0 without hygiene.

src/doc/unstable-book/src/language-features/decl-macro.md

@@ -0,0 +1,10 @@
+# `decl_macro`
+
+The tracking issue for this feature is: [#39412]
+
+[#39412]: https://github.com/rust-lang/rust/issues/39412
+
+------------------------
+
+
+

src/librustc/hir/lowering.rs

@@ -1502,10 +1502,11 @@ impl<'a> LoweringContext<'a> {
     pub fn lower_item(&mut self, i: &Item) -> Option<hir::Item> {
         let mut name = i.ident.name;
         let attrs = self.lower_attrs(&i.attrs);
-        if let ItemKind::MacroDef(ref tts) = i.node {
+        if let ItemKind::MacroDef(ref def) = i.node {
-            if i.attrs.iter().any(|attr| attr.path == "macro_export") {
+            if !def.legacy || i.attrs.iter().any(|attr| attr.path == "macro_export") {
+                let (body, legacy) = (def.stream(), def.legacy);
                 self.exported_macros.push(hir::MacroDef {
-                    name: name, attrs: attrs, id: i.id, span: i.span, body: tts.stream(),
+                    name: name, attrs: attrs, id: i.id, span: i.span, body: body, legacy: legacy,
                 });
             }
             return None;

src/librustc/hir/mod.rs

@@ -536,6 +536,7 @@ pub struct MacroDef {
     pub id: NodeId,
     pub span: Span,
     pub body: TokenStream,
+    pub legacy: bool,
 }
 
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]

src/librustc/ich/impls_hir.rs

@@ -332,6 +332,7 @@ impl_stable_hash_for!(struct hir::MacroDef {
     attrs,
     id,
     span,
+    legacy,
     body
 });
 

src/librustc_metadata/cstore_impl.rs

@@ -388,6 +388,7 @@ impl CrateStore for cstore::CStore {
             attrs: attrs.iter().cloned().collect(),
             node: ast::ItemKind::MacroDef(ast::MacroDef {
                 tokens: body.into(),
+                legacy: true,
             }),
             vis: ast::Visibility::Inherited,
         })

src/librustc_resolve/build_reduced_graph.rs

@@ -77,7 +77,7 @@ struct LegacyMacroImports {
 impl<'a> Resolver<'a> {
     /// Defines `name` in namespace `ns` of module `parent` to be `def` if it is not yet defined;
     /// otherwise, reports an error.
-    fn define<T>(&mut self, parent: Module<'a>, ident: Ident, ns: Namespace, def: T)
+    pub fn define<T>(&mut self, parent: Module<'a>, ident: Ident, ns: Namespace, def: T)
         where T: ToNameBinding<'a>,
     {
         let binding = def.to_name_binding(self.arenas);
@@ -730,7 +730,7 @@ impl<'a, 'b> Visitor<'a> for BuildReducedGraphVisitor<'a, 'b> {
     fn visit_item(&mut self, item: &'a Item) {
         let macro_use = match item.node {
             ItemKind::MacroDef(..) => {
-                self.resolver.define_macro(item, &mut self.legacy_scope);
+                self.resolver.define_macro(item, self.expansion, &mut self.legacy_scope);
                 return
             }
             ItemKind::Mac(..) => {

src/librustc_resolve/lib.rs

@@ -1058,6 +1058,13 @@ impl<'a> NameBinding<'a> {
             _ => true,
         }
     }
+
+    fn is_macro_def(&self) -> bool {
+        match self.kind {
+            NameBindingKind::Def(Def::Macro(..)) => true,
+            _ => false,
+        }
+    }
 }
 
 /// Interns the names of the primitive types.
@@ -1377,8 +1384,9 @@ impl<'a> Resolver<'a> {
                 vis: ty::Visibility::Public,
             }),
 
-            // `#![feature(proc_macro)]` implies `#[feature(extern_macros)]`
+            // The `proc_macro` and `decl_macro` features imply `use_extern_macros`
-            use_extern_macros: features.use_extern_macros || features.proc_macro,
+            use_extern_macros:
+                features.use_extern_macros || features.proc_macro || features.decl_macro,
 
             crate_loader: crate_loader,
             macro_names: FxHashSet(),

src/librustc_resolve/macros.rs

@@ -687,7 +687,10 @@ impl<'a> Resolver<'a> {
         });
     }
 
-    pub fn define_macro(&mut self, item: &ast::Item, legacy_scope: &mut LegacyScope<'a>) {
+    pub fn define_macro(&mut self,
+                        item: &ast::Item,
+                        expansion: Mark,
+                        legacy_scope: &mut LegacyScope<'a>) {
         self.local_macro_def_scopes.insert(item.id, self.current_module);
         let ident = item.ident;
         if ident.name == "macro_rules" {
@@ -699,16 +702,24 @@ impl<'a> Resolver<'a> {
                                                &self.session.features,
                                                item));
         self.macro_map.insert(def_id, ext);
-        *legacy_scope = LegacyScope::Binding(self.arenas.alloc_legacy_binding(LegacyBinding {
-            parent: Cell::new(*legacy_scope), name: ident.name, def_id: def_id, span: item.span,
-        }));
-        self.macro_names.insert(ident.name);
 
-        if attr::contains_name(&item.attrs, "macro_export") {
+        let def = match item.node { ast::ItemKind::MacroDef(ref def) => def, _ => unreachable!() };
-            let def = Def::Macro(def_id, MacroKind::Bang);
+        if def.legacy {
-            self.macro_exports.push(Export { name: ident.name, def: def, span: item.span });
+            self.macro_names.insert(ident.name);
+            *legacy_scope = LegacyScope::Binding(self.arenas.alloc_legacy_binding(LegacyBinding {
+                parent: Cell::new(*legacy_scope), name: ident.name, def_id: def_id, span: item.span,
+            }));
+            if attr::contains_name(&item.attrs, "macro_export") {
+                let def = Def::Macro(def_id, MacroKind::Bang);
+                self.macro_exports.push(Export { name: ident.name, def: def, span: item.span });
+            } else {
+                self.unused_macros.insert(def_id);
+            }
         } else {
-            self.unused_macros.insert(def_id);
+            let module = self.current_module;
+            let def = Def::Macro(def_id, MacroKind::Bang);
+            let vis = self.resolve_visibility(&item.vis);
+            self.define(module, ident, MacroNS, (def, vis, item.span, expansion));
         }
     }
 

src/librustc_resolve/resolve_imports.rs

@@ -803,7 +803,7 @@ impl<'a, 'b:'a> ImportResolver<'a, 'b> {
             };
 
             if binding.vis == ty::Visibility::Public &&
-               (binding.is_import() || binding.is_extern_crate()) {
+               (binding.is_import() || binding.is_macro_def()) {
                 let def = binding.def();
                 if def != Def::Err {
                     if !def.def_id().is_local() {

src/libsyntax/ast.rs

@@ -1022,6 +1022,7 @@ impl Mac_ {
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub struct MacroDef {
     pub tokens: ThinTokenStream,
+    pub legacy: bool,
 }
 
 impl MacroDef {

src/libsyntax/ext/tt/macro_rules.rs

@@ -162,6 +162,12 @@ pub fn compile(sess: &ParseSess, features: &RefCell<Features>, def: &ast::Item)
     let lhs_nm = ast::Ident::with_empty_ctxt(Symbol::gensym("lhs"));
     let rhs_nm = ast::Ident::with_empty_ctxt(Symbol::gensym("rhs"));
 
+    // Parse the macro_rules! invocation
+    let body = match def.node {
+        ast::ItemKind::MacroDef(ref body) => body,
+        _ => unreachable!(),
+    };
+
     // The pattern that macro_rules matches.
     // The grammar for macro_rules! is:
     // $( $lhs:tt => $rhs:tt );+
@@ -174,7 +180,7 @@ pub fn compile(sess: &ParseSess, features: &RefCell<Features>, def: &ast::Item)
                 quoted::TokenTree::Token(DUMMY_SP, token::FatArrow),
                 quoted::TokenTree::MetaVarDecl(DUMMY_SP, rhs_nm, ast::Ident::from_str("tt")),
             ],
-            separator: Some(token::Semi),
+            separator: Some(if body.legacy { token::Semi } else { token::Comma }),
             op: quoted::KleeneOp::OneOrMore,
             num_captures: 2,
         })),
@@ -187,12 +193,7 @@ pub fn compile(sess: &ParseSess, features: &RefCell<Features>, def: &ast::Item)
         })),
     ];
 
-    // Parse the macro_rules! invocation
+    let argument_map = match parse(sess, body.stream(), &argument_gram, None, true) {
-    let body = match def.node {
-        ast::ItemKind::MacroDef(ref body) => body.stream(),
-        _ => unreachable!(),
-    };
-    let argument_map = match parse(sess, body, &argument_gram, None, true) {
         Success(m) => m,
         Failure(sp, tok) => {
             let s = parse_failure_msg(tok);

src/libsyntax/feature_gate.rs

@@ -309,9 +309,12 @@ declare_features! (
     // The `unadjusted` ABI. Perma unstable.
     (active, abi_unadjusted, "1.16.0", None),
 
-    // Macros 1.1
+    // Procedural macros 2.0.
     (active, proc_macro, "1.16.0", Some(38356)),
 
+    // Declarative macros 2.0 (`macro`).
+    (active, decl_macro, "1.17.0", Some(39412)),
+
     // Allows attributes on struct literal fields.
     (active, struct_field_attributes, "1.16.0", Some(38814)),
 
@@ -1229,6 +1232,11 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                 }
             }
 
+            ast::ItemKind::MacroDef(ast::MacroDef { legacy: false, .. }) => {
+                let msg = "`macro` is experimental";
+                gate_feature_post!(&self, decl_macro, i.span, msg);
+            }
+
             _ => {}
         }
 

src/libsyntax/fold.rs

@@ -522,6 +522,7 @@ pub fn noop_fold_mac<T: Folder>(Spanned {node, span}: Mac, fld: &mut T) -> Mac {
 pub fn noop_fold_macro_def<T: Folder>(def: MacroDef, fld: &mut T) -> MacroDef {
     MacroDef {
         tokens: fld.fold_tts(def.tokens.into()).into(),
+        legacy: def.legacy,
     }
 }
 

src/libsyntax/parse/parser.rs

@@ -3758,33 +3758,59 @@ impl<'a> Parser<'a> {
     fn eat_macro_def(&mut self, attrs: &[Attribute], vis: &Visibility)
                      -> PResult<'a, Option<P<Item>>> {
         let lo = self.span;
-        match self.token {
+        let (ident, def) = match self.token {
-            token::Ident(ident) if ident.name == "macro_rules" => {
+            token::Ident(ident) if ident.name == keywords::Macro.name() => {
-                if self.look_ahead(1, |t| *t == token::Not) {
+                self.bump();
-                    let prev_span = self.prev_span;
+                let ident = self.parse_ident()?;
-                    self.complain_if_pub_macro(vis, prev_span);
+                let tokens = if self.check(&token::OpenDelim(token::Brace)) {
-                    self.bump();
+                    match self.parse_token_tree() {
-                    self.bump();
+                        TokenTree::Delimited(_, ref delimited) => delimited.stream(),
+                        _ => unreachable!(),
+                    }
+                } else if self.check(&token::OpenDelim(token::Paren)) {
+                    let args = self.parse_token_tree();
+                    let body = if self.check(&token::OpenDelim(token::Brace)) {
+                        self.parse_token_tree()
+                    } else {
+                        self.unexpected()?;
+                        unreachable!()
+                    };
+                    TokenStream::concat(vec![
+                        args.into(),
+                        TokenTree::Token(lo.to(self.prev_span), token::FatArrow).into(),
+                        body.into(),
+                    ])
+                } else {
+                    self.unexpected()?;
+                    unreachable!()
+                };
+
+                (ident, ast::MacroDef { tokens: tokens.into(), legacy: false })
+            }
+            token::Ident(ident) if ident.name == "macro_rules" &&
+                                   self.look_ahead(1, |t| *t == token::Not) => {
+                let prev_span = self.prev_span;
+                self.complain_if_pub_macro(vis, prev_span);
+                self.bump();
+                self.bump();
+
+                let ident = self.parse_ident()?;
+                let (delim, tokens) = self.expect_delimited_token_tree()?;
+                if delim != token::Brace {
+                    if !self.eat(&token::Semi) {
+                        let msg = "macros that expand to items must either \
+                                   be surrounded with braces or followed by a semicolon";
+                        self.span_err(self.prev_span, msg);
+                    }
                 }
+
+                (ident, ast::MacroDef { tokens: tokens, legacy: true })
             }
             _ => return Ok(None),
         };
 
-        let id = self.parse_ident()?;
-        let (delim, tts) = self.expect_delimited_token_tree()?;
-        if delim != token::Brace {
-            if !self.eat(&token::Semi) {
-                let msg = "macros that expand to items must either be surrounded with braces \
-                           or followed by a semicolon";
-                self.span_err(self.prev_span, msg);
-            }
-        }
-
         let span = lo.to(self.prev_span);
-        let kind = ItemKind::MacroDef(ast::MacroDef {
+        Ok(Some(self.mk_item(span, ident, ItemKind::MacroDef(def), vis.clone(), attrs.to_vec())))
-            tokens: tts,
-        });
-        Ok(Some(self.mk_item(span, id, kind, Visibility::Inherited, attrs.to_owned())))
     }
 
     fn parse_stmt_without_recovery(&mut self,