resolve: Reserve a few very special names in macro namespace

2 files changed, 14 insertions, 0 deletions

diff --git a/src/librustc_resolve/macros.rs b/src/librustc_resolve/macros.rs
index 351963bff5b..7733ce475e3 100644
--- a/src/librustc_resolve/macros.rs
+++ b/src/librustc_resolve/macros.rs
@@ -1083,6 +1083,9 @@ impl<'a, 'cl> Resolver<'a, 'cl> {
                 self.define(module, ident, MacroNS,
                             (def, vis, item.span, expansion, IsMacroExport));
             } else {
+                if !attr::contains_name(&item.attrs, "rustc_doc_only_macro") {
+                    self.check_reserved_macro_name(ident, MacroNS);
+                }
                 self.unused_macros.insert(def_id);
             }
         } else {
diff --git a/src/librustc_resolve/resolve_imports.rs b/src/librustc_resolve/resolve_imports.rs
index 68709f6891a..dfbea0ffe22 100644
--- a/src/librustc_resolve/resolve_imports.rs
+++ b/src/librustc_resolve/resolve_imports.rs
@@ -452,6 +452,16 @@ impl<'a, 'crateloader> Resolver<'a, 'crateloader> {
         })
     }
 
+    crate fn check_reserved_macro_name(&self, ident: Ident, ns: Namespace) {
+        // Reserve some names that are not quite covered by the general check
+        // performed on `Resolver::builtin_attrs`.
+        if ns == MacroNS &&
+           (ident.name == "cfg" || ident.name == "cfg_attr" || ident.name == "derive") {
+            self.session.span_err(ident.span,
+                                  &format!("name `{}` is reserved in macro namespace", ident));
+        }
+    }
+
     // Define the name or return the existing binding if there is a collision.
     pub fn try_define(&mut self,
                       module: Module<'a>,
@@ -459,6 +469,7 @@ impl<'a, 'crateloader> Resolver<'a, 'crateloader> {
                       ns: Namespace,
                       binding: &'a NameBinding<'a>)
                       -> Result<(), &'a NameBinding<'a>> {
+        self.check_reserved_macro_name(ident, ns);
         self.update_resolution(module, ident, ns, |this, resolution| {
             if let Some(old_binding) = resolution.binding {
                 if binding.is_glob_import() {