WIP: expand attribute macros in extern {} blocks

src/libsyntax/ast.rs

@@ -2172,6 +2172,8 @@ pub enum ForeignItemKind {
     Static(P<Ty>, bool),
     /// A foreign type
     Ty,
+    /// A macro invocation (not really supported)
+    Macro(Mac),
 }
 
 impl ForeignItemKind {
@@ -2180,6 +2182,7 @@ impl ForeignItemKind {
             ForeignItemKind::Fn(..) => "foreign function",
             ForeignItemKind::Static(..) => "foreign static item",
             ForeignItemKind::Ty => "foreign type",
+            ForeignItemKind::Macro(..) => "macro in foreign module",
         }
     }
 }

src/libsyntax/ext/base.rs

@@ -38,6 +38,7 @@ pub enum Annotatable {
     Item(P<ast::Item>),
     TraitItem(P<ast::TraitItem>),
     ImplItem(P<ast::ImplItem>),
+    ForeignItem(P<ast::ForeignItem>),
 }
 
 impl HasAttrs for Annotatable {
@@ -46,6 +47,7 @@ impl HasAttrs for Annotatable {
             Annotatable::Item(ref item) => &item.attrs,
             Annotatable::TraitItem(ref trait_item) => &trait_item.attrs,
             Annotatable::ImplItem(ref impl_item) => &impl_item.attrs,
+            Annotatable::ForeignItem(ref foreign_item) => &foreign_item.attrs,
         }
     }
 
@@ -54,6 +56,8 @@ impl HasAttrs for Annotatable {
             Annotatable::Item(item) => Annotatable::Item(item.map_attrs(f)),
             Annotatable::TraitItem(trait_item) => Annotatable::TraitItem(trait_item.map_attrs(f)),
             Annotatable::ImplItem(impl_item) => Annotatable::ImplItem(impl_item.map_attrs(f)),
+            Annotatable::ForeignItem(ref foreign_item) =>
+                Annotatable::ForeignItem(foreign_item.map_attrs(f)),
         }
     }
 }
@@ -64,6 +68,7 @@ impl Annotatable {
             Annotatable::Item(ref item) => item.span,
             Annotatable::TraitItem(ref trait_item) => trait_item.span,
             Annotatable::ImplItem(ref impl_item) => impl_item.span,
+            Annotatable::ForeignItem(ref foreign_item) => foreign_item.span,
         }
     }
 
@@ -98,6 +103,13 @@ impl Annotatable {
         }
     }
 
+    pub fn expect_foreign_item(self) -> ast::ForeignItem {
+        match self {
+            Annotatable::ForeignItem(i) => i.into_inner(),
+            _ => panic!("expected foreign item")
+        }
+    }
+
     pub fn derive_allowed(&self) -> bool {
         match *self {
             Annotatable::Item(ref item) => match item.node {
@@ -308,6 +320,9 @@ pub trait MacResult {
         None
     }
 
+    /// Create zero or more items in an `extern {}` block
+    fn make_foreign_items(self: Box<Self>) -> Option<SmallVector<ast::ForeignItem>> { None }
+
     /// Create a pattern.
     fn make_pat(self: Box<Self>) -> Option<P<ast::Pat>> {
         None
@@ -356,6 +371,7 @@ make_MacEager! {
     items: SmallVector<P<ast::Item>>,
     impl_items: SmallVector<ast::ImplItem>,
     trait_items: SmallVector<ast::TraitItem>,
+    foreign_items: SmallVector<ast::ForeignItem>,
     stmts: SmallVector<ast::Stmt>,
     ty: P<ast::Ty>,
 }
@@ -377,6 +393,10 @@ impl MacResult for MacEager {
         self.trait_items
     }
 
+    fn make_foreign_items(self: Box<Self>) -> Option<SmallVector<ast::ForeignItem>> {
+        self.foreign_items
+    }
+
     fn make_stmts(self: Box<Self>) -> Option<SmallVector<ast::Stmt>> {
         match self.stmts.as_ref().map_or(0, |s| s.len()) {
             0 => make_stmts_default!(self),
@@ -493,6 +513,14 @@ impl MacResult for DummyResult {
         }
     }
 
+    fn make_foreign_items(self: Box<Self>) -> Option<SmallVector<ast::ForeignItem>> {
+        if self.expr_only {
+            None
+        } else {
+            Some(SmallVector::new())
+        }
+    }
+
     fn make_stmts(self: Box<DummyResult>) -> Option<SmallVector<ast::Stmt>> {
         Some(SmallVector::one(ast::Stmt {
             id: ast::DUMMY_NODE_ID,

src/libsyntax/ext/expand.rs

@@ -133,6 +133,8 @@ expansions! {
         "trait item", .make_trait_items, lift .fold_trait_item, lift .visit_trait_item;
     ImplItems: SmallVector<ast::ImplItem> [SmallVector, ast::ImplItem],
         "impl item",  .make_impl_items,  lift .fold_impl_item,  lift .visit_impl_item;
+    ForeignItems: SmallVector<ast::ForeignItem> [SmallVector, ast::ForeignItem],
+        "foreign item", .make_foreign_items, lift .fold_foreign_item, lift .visit_foreign_item;
 }
 
 impl ExpansionKind {
@@ -434,6 +436,11 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             Annotatable::ImplItem(item) => {
                 Annotatable::ImplItem(item.map(|item| cfg.fold_impl_item(item).pop().unwrap()))
             }
+            Annotatable::ForeignItem(item) => {
+                Annotatable::ForeignItem(
+                    item.map(|item| cfg.fold_foreign_item(item).pop().unwrap())
+                )
+            }
         }
     }
 
@@ -500,6 +507,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                     Annotatable::Item(item) => token::NtItem(item),
                     Annotatable::TraitItem(item) => token::NtTraitItem(item.into_inner()),
                     Annotatable::ImplItem(item) => token::NtImplItem(item.into_inner()),
+                    Annotatable::ForeignItem(item) => token::NtForeignItem(item.into_inner()),
                 })).into();
                 let tok_result = mac.expand(self.cx, attr.span, attr.tokens, item_tok);
                 self.parse_expansion(tok_result, kind, &attr.path, attr.span)
@@ -758,6 +766,15 @@ impl<'a> Parser<'a> {
                 }
                 Expansion::ImplItems(items)
             }
+            ExpansionKind::ForeignItems => {
+                let mut items = SmallVector::new();
+                while self.token != token::Eof {
+                    if let Some(item) = self.parse_foreign_item()? {
+                        items.push(item);
+                    }
+                }
+                Expansion::ForeignItems(items)
+            }
             ExpansionKind::Stmts => {
                 let mut stmts = SmallVector::new();
                 while self.token != token::Eof &&
@@ -1089,6 +1106,18 @@ impl<'a, 'b> Folder for InvocationCollector<'a, 'b> {
         noop_fold_foreign_mod(self.cfg.configure_foreign_mod(foreign_mod), self)
     }
 
+    fn fold_foreign_item(&mut self, foreign_item: ast::ForeignItem) -> SmallVector<ast::ForeignItem> {
+        let (attr, traits, foreign_item) = self.classify_item(foreign_item);
+
+        if attr.is_some() || !traits.is_empty()  {
+            let item = Annotatable::ForeignItem(P(foreign_item));
+            return self.collect_attr(attr, traits, item, ExpansionKind::ForeignItems)
+                .make_foreign_items();
+        }
+
+        return noop_fold_foreign_item(foreign_item, self);
+    }
+
     fn fold_item_kind(&mut self, item: ast::ItemKind) -> ast::ItemKind {
         match item {
             ast::ItemKind::MacroDef(..) => item,

src/libsyntax/ext/placeholders.rs

@@ -60,6 +60,10 @@ pub fn placeholder(kind: ExpansionKind, id: ast::NodeId) -> Expansion {
             defaultness: ast::Defaultness::Final,
             tokens: None,
         })),
+        ExpansionKind::ForeignItems => Expansion::ForeignItems(SmallVector::one(ast::ForeignItem {
+            id, span, ident, vis, attrs,
+            node: ast::ForeignItemKind::Macro(mac_placeholder()),
+        })),
         ExpansionKind::Pat => Expansion::Pat(P(ast::Pat {
             id, span, node: ast::PatKind::Mac(mac_placeholder()),
         })),

src/libsyntax/feature_gate.rs

@@ -1556,6 +1556,9 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                     gate_feature_post!(&self, extern_types, i.span,
                                        "extern types are experimental");
             }
+            ast::ForeignItemKind::Macro(..) => {
+                // FIXME: do we allow macro invocs in `extern {}`?
+            }
         }
 
         visit::walk_foreign_item(self, i)

src/libsyntax/fold.rs

@@ -60,10 +60,14 @@ pub trait Folder : Sized {
         noop_fold_use_tree(use_tree, self)
     }
 
-    fn fold_foreign_item(&mut self, ni: ForeignItem) -> ForeignItem {
+    fn fold_foreign_item(&mut self, ni: ForeignItem) -> SmallVector<ForeignItem> {
         noop_fold_foreign_item(ni, self)
     }
 
+    fn fold_foreign_item_simple(&mut self, ni: ForeignItem) -> ForeignItem {
+        noop_fold_foreign_item_simple(ni, self)
+    }
+
     fn fold_item(&mut self, i: P<Item>) -> SmallVector<P<Item>> {
         noop_fold_item(i, self)
     }
@@ -413,7 +417,7 @@ pub fn noop_fold_foreign_mod<T: Folder>(ForeignMod {abi, items}: ForeignMod,
                                         fld: &mut T) -> ForeignMod {
     ForeignMod {
         abi,
-        items: items.move_map(|x| fld.fold_foreign_item(x)),
+        items: items.move_flat_map(|x| fld.fold_foreign_item(x)),
     }
 }
 
@@ -1070,7 +1074,12 @@ pub fn noop_fold_item_simple<T: Folder>(Item {id, ident, attrs, node, vis, span,
     }
 }
 
-pub fn noop_fold_foreign_item<T: Folder>(ni: ForeignItem, folder: &mut T) -> ForeignItem {
+pub fn noop_fold_foreign_item<T: Folder>(ni: ForeignItem, folder: &mut T)
+-> SmallVector<ForeignItem> {
+    SmallVector::one(folder.fold_foreign_item_simple(ni))
+}
+
+pub fn noop_fold_foreign_item_simple<T: Folder>(ni: ForeignItem, folder: &mut T) -> ForeignItem {
     ForeignItem {
         id: folder.new_id(ni.id),
         vis: folder.fold_vis(ni.vis),
@@ -1084,6 +1093,7 @@ pub fn noop_fold_foreign_item<T: Folder>(ni: ForeignItem, folder: &mut T) -> For
                 ForeignItemKind::Static(folder.fold_ty(t), m)
             }
             ForeignItemKind::Ty => ForeignItemKind::Ty,
+            ForeignItemKind::Macro(mac) => ForeignItemKind::Macro(folder.fold_mac(mac)),
         },
         span: folder.new_span(ni.span)
     }

src/libsyntax/parse/parser.rs

@@ -6776,7 +6776,7 @@ impl<'a> Parser<'a> {
     }
 
     /// Parse a foreign item.
-    fn parse_foreign_item(&mut self) -> PResult<'a, Option<ForeignItem>> {
+    pub fn parse_foreign_item(&mut self) -> PResult<'a, Option<ForeignItem>> {
         let attrs = self.parse_outer_attributes()?;
         let lo = self.span;
         let visibility = self.parse_visibility(false)?;

src/libsyntax/parse/token.rs

@@ -539,6 +539,7 @@ pub enum Nonterminal {
     NtArm(ast::Arm),
     NtImplItem(ast::ImplItem),
     NtTraitItem(ast::TraitItem),
+    NtForeignItem(ast::ForeignItem),
     NtGenerics(ast::Generics),
     NtWhereClause(ast::WhereClause),
     NtArg(ast::Arg),
@@ -561,6 +562,7 @@ impl fmt::Debug for Nonterminal {
             NtArm(..) => f.pad("NtArm(..)"),
             NtImplItem(..) => f.pad("NtImplItem(..)"),
             NtTraitItem(..) => f.pad("NtTraitItem(..)"),
+            NtForeignItem(..) => f.pad("NtForeignItem(..)"),
             NtGenerics(..) => f.pad("NtGenerics(..)"),
             NtWhereClause(..) => f.pad("NtWhereClause(..)"),
             NtArg(..) => f.pad("NtArg(..)"),

src/libsyntax/print/pprust.rs

@@ -1126,6 +1126,9 @@ impl<'a> State<'a> {
                 self.end()?; // end the head-ibox
                 self.end() // end the outer cbox
             }
+            ast::ForeignItemKind::Macro(..) => {
+                // FIXME: stub for now
+            }
         }
     }
 

src/libsyntax/visit.rs

@@ -459,6 +459,7 @@ pub fn walk_foreign_item<'a, V: Visitor<'a>>(visitor: &mut V, foreign_item: &'a
         }
         ForeignItemKind::Static(ref typ, _) => visitor.visit_ty(typ),
         ForeignItemKind::Ty => (),
+        ForeignItemKind::Macro(ref mac) => visitor.visit_mac(mac),
     }
 
     walk_list!(visitor, visit_attribute, &foreign_item.attrs);

src/test/run-pass-fulldeps/proc-macro/attr-more-places.rs

@@ -10,22 +10,25 @@
 
 // aux-build:nop-attr.rs
 // ignore-stage1
+#![feature(proc_macro)]
 
 extern crate nop_attr;
 
 use nop_attr::{nop_attr, no_output};
 
 fn main() {
     #[nop_attr]
-    println!("Hello, world!");
+    let string = "Hello, world!";
 
-    #[nop_attr]
+    println!("{}", string);
+
+    #[no_output]
     {
-        println!("Hello, world!");
+        unsafe { some_definitely_unknown_symbol_which_should_be_removed() };
     }
 }
 
 extern {
     #[no_output]
-    fn read();
+    fn some_definitely_unknown_symbol_which_should_be_removed();
 }