Use the macro namespace for custom derives.

2 files changed, 16 insertions, 3 deletions

diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index 99b883d26d8..11c6f87a655 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -508,6 +508,8 @@ pub enum SyntaxExtension {
     /// the block.
     ///
     IdentTT(Box<IdentMacroExpander>, Option<Span>, bool),
+
+    CustomDerive(Box<MultiItemModifier>),
 }
 
 pub type NamedSyntaxExtension = (Name, SyntaxExtension);
@@ -524,7 +526,6 @@ pub trait Resolver {
     fn find_attr_invoc(&mut self, attrs: &mut Vec<Attribute>) -> Option<Attribute>;
     fn resolve_macro(&mut self, scope: Mark, path: &ast::Path, force: bool)
                      -> Result<Rc<SyntaxExtension>, Determinacy>;
-    fn resolve_derive_mode(&mut self, ident: ast::Ident) -> Option<Rc<MultiItemModifier>>;
 }
 
 #[derive(Copy, Clone, Debug)]
@@ -545,7 +546,6 @@ impl Resolver for DummyResolver {
     fn add_expansions_at_stmt(&mut self, _id: ast::NodeId, _macros: Vec<Mark>) {}
 
     fn find_attr_invoc(&mut self, _attrs: &mut Vec<Attribute>) -> Option<Attribute> { None }
-    fn resolve_derive_mode(&mut self, _ident: ast::Ident) -> Option<Rc<MultiItemModifier>> { None }
     fn resolve_macro(&mut self, _scope: Mark, _path: &ast::Path, _force: bool)
                      -> Result<Rc<SyntaxExtension>, Determinacy> {
         Err(Determinacy::Determined)
diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index 3a5b3ab8328..6aeb46fd522 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -364,7 +364,15 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                 let tok_result = mac.expand(self.cx, attr.span, attr_toks, item_toks);
                 self.parse_expansion(tok_result, kind, name, attr.span)
             }
-            _ => unreachable!(),
+            SyntaxExtension::CustomDerive(_) => {
+                self.cx.span_err(attr.span, &format!("`{}` is a derive mode", name));
+                kind.dummy(attr.span)
+            }
+            _ => {
+                let msg = &format!("macro `{}` may not be used in attributes", name);
+                self.cx.span_err(attr.span, &msg);
+                kind.dummy(attr.span)
+            }
         }
     }
 
@@ -439,6 +447,11 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                 return kind.dummy(span);
             }
 
+            SyntaxExtension::CustomDerive(..) => {
+                self.cx.span_err(path.span, &format!("`{}` is a derive mode", extname));
+                return kind.dummy(span);
+            }
+
             SyntaxExtension::ProcMacro(ref expandfun) => {
                 if ident.name != keywords::Invalid.name() {
                     let msg =