[WIP] Check future proofing of macros with multiple arms using FIRST sets.

src/libcollections/lib.rs

@@ -43,6 +43,7 @@
 #![feature(pattern)]
 #![feature(placement_in)]
 #![feature(placement_new_protocol)]
+#![feature(rustc_attrs)]
 #![feature(shared)]
 #![feature(slice_patterns)]
 #![feature(specialization)]

src/librustc/lib.rs

@@ -33,6 +33,7 @@
 #![feature(libc)]
 #![feature(nonzero)]
 #![feature(quote)]
+#![feature(rustc_attrs)]
 #![feature(rustc_diagnostic_macros)]
 #![feature(rustc_private)]
 #![feature(slice_patterns)]

src/librustc_metadata/lib.rs

@@ -20,6 +20,7 @@
 #![feature(box_patterns)]
 #![feature(enumset)]
 #![feature(quote)]
+#![feature(rustc_attrs)]
 #![feature(rustc_diagnostic_macros)]
 #![feature(rustc_private)]
 #![feature(staged_api)]

src/librustc_mir/build/mod.rs

@@ -139,6 +139,7 @@ impl BlockAndExtension for BasicBlock {
 
 /// Update a block pointer and return the value.
 /// Use it like `let x = unpack!(block = self.foo(block, foo))`.
+#[rustc_unsafe_macro]
 macro_rules! unpack {
     ($x:ident = $c:expr) => {
         {

src/librustc_mir/lib.rs

@@ -22,6 +22,7 @@ Rust MIR: a lowered representation of Rust. Also: an experiment!
 
 #![feature(associated_consts)]
 #![feature(box_patterns)]
+#![feature(rustc_attrs)]
 #![feature(rustc_diagnostic_macros)]
 #![feature(rustc_private)]
 #![feature(staged_api)]

src/libsyntax/ext/base.rs

@@ -715,12 +715,12 @@ impl<'a> ExtCtxt<'a> {
         }
     }
 
-    pub fn insert_macro(&mut self, def: ast::MacroDef) {
+    pub fn insert_macro(&mut self, def: ast::MacroDef, imported: bool) {
         if def.export {
             self.exported_macros.push(def.clone());
         }
         if def.use_locally {
-            let ext = macro_rules::compile(self, &def);
+            let ext = macro_rules::compile(self, &def, imported);
             self.syntax_env.insert(def.ident.name, ext);
         }
     }

src/libsyntax/ext/expand.rs

@@ -279,6 +279,7 @@ fn expand_mac_invoc<T>(mac: ast::Mac, ident: Option<Ident>, attrs: Vec<ast::Attr
                     }
                 });
 
+                let check = !attr::contains_name(&attrs, "rustc_unsafe_macro");
                 // DON'T mark before expansion.
                 fld.cx.insert_macro(ast::MacroDef {
                     ident: ident,
@@ -290,7 +291,7 @@ fn expand_mac_invoc<T>(mac: ast::Mac, ident: Option<Ident>, attrs: Vec<ast::Attr
                     export: attr::contains_name(&attrs, "macro_export"),
                     allow_internal_unstable: attr::contains_name(&attrs, "allow_internal_unstable"),
                     attrs: attrs,
-                });
+                }, check);
 
                 // macro_rules! has a side effect but expands to nothing.
                 fld.cx.bt_pop();
@@ -911,7 +912,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                     // We need to error on `#[macro_use] extern crate` when it isn't at the
                     // crate root, because `$crate` won't work properly.
                     for def in self.cx.loader.load_crate(item, self.at_crate_root) {
-                        self.cx.insert_macro(def);
+                        self.cx.insert_macro(def, false);
                     }
                 } else {
                     let at_crate_root = ::std::mem::replace(&mut self.at_crate_root, false);