syntax: Use `MultiItemModifier` for built-in derives

1 files changed, 20 insertions, 4 deletions

diff --git a/src/libsyntax_ext/deriving/mod.rs b/src/libsyntax_ext/deriving/mod.rs
index ac41f30e6b3..2f09ab2087e 100644
--- a/src/libsyntax_ext/deriving/mod.rs
+++ b/src/libsyntax_ext/deriving/mod.rs
@@ -1,8 +1,8 @@
 //! The compiler code necessary to implement the `#[derive]` extensions.
 
 use rustc_data_structures::sync::Lrc;
-use syntax::ast;
-use syntax::ext::base::{Annotatable, ExtCtxt, SyntaxExtension, Resolver};
+use syntax::ast::{self, MetaItem};
+use syntax::ext::base::{Annotatable, ExtCtxt, SyntaxExtension, Resolver, MultiItemModifier};
 use syntax::ext::build::AstBuilder;
 use syntax::ext::hygiene::{Mark, SyntaxContext};
 use syntax::ptr::P;
@@ -39,9 +39,25 @@ pub mod partial_ord;
 #[path="cmp/ord.rs"]
 pub mod ord;
 
-
 pub mod generic;
 
+struct BuiltinDerive(
+    fn(&mut ExtCtxt<'_>, Span, &MetaItem, &Annotatable, &mut dyn FnMut(Annotatable))
+);
+
+impl MultiItemModifier for BuiltinDerive {
+    fn expand(&self,
+              ecx: &mut ExtCtxt<'_>,
+              span: Span,
+              meta_item: &MetaItem,
+              item: Annotatable)
+              -> Vec<Annotatable> {
+        let mut items = Vec::new();
+        (self.0)(ecx, span, meta_item, &item, &mut |a| items.push(a));
+        items
+    }
+}
+
 macro_rules! derive_traits {
     ($( $name:expr => $func:path, )+) => {
         pub fn is_builtin_trait(name: ast::Name) -> bool {
@@ -55,7 +71,7 @@ macro_rules! derive_traits {
             $(
                 resolver.add_builtin(
                     ast::Ident::with_empty_ctxt(Symbol::intern($name)),
-                    Lrc::new(SyntaxExtension::BuiltinDerive($func))
+                    Lrc::new(SyntaxExtension::BuiltinDerive(Box::new(BuiltinDerive($func))))
                 );
             )*
         }