syntax: Use `MultiItemModifier` for built-in derives

2 files changed, 22 insertions, 25 deletions

diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index 9979f5d0a0e..4a357b0f312 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -1,6 +1,6 @@
 pub use SyntaxExtension::*;
 
-use crate::ast::{self, Attribute, Name, PatKind, MetaItem};
+use crate::ast::{self, Attribute, Name, PatKind};
 use crate::attr::HasAttrs;
 use crate::source_map::{SourceMap, Spanned, respan};
 use crate::edition::Edition;
@@ -519,9 +519,6 @@ impl MacResult for DummyResult {
     }
 }
 
-pub type BuiltinDeriveFn =
-    for<'cx> fn(&'cx mut ExtCtxt<'_>, Span, &MetaItem, &Annotatable, &mut dyn FnMut(Annotatable));
-
 /// Represents different kinds of macro invocations that can be resolved.
 #[derive(Clone, Copy, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub enum MacroKind {
@@ -607,7 +604,7 @@ pub enum SyntaxExtension {
                     Vec<Symbol> /* inert attribute names */, Edition),
 
     /// An attribute-like procedural macro that derives a builtin trait.
-    BuiltinDerive(BuiltinDeriveFn),
+    BuiltinDerive(Box<dyn MultiItemModifier + sync::Sync + sync::Send>),
 
     /// A declarative macro, e.g., `macro m() {}`.
     DeclMacro {
diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index 715303db173..892c59bbc04 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -893,29 +893,29 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             edition: ext.edition(self.cx.parse_sess.edition),
         };
 
-        match *ext {
-            ProcMacroDerive(ref ext, ..) => {
-                invoc.expansion_data.mark.set_expn_info(expn_info);
-                let span = span.with_ctxt(self.cx.backtrace());
-                let dummy = ast::MetaItem { // FIXME(jseyfried) avoid this
-                    path: Path::from_ident(Ident::invalid()),
-                    span: DUMMY_SP,
-                    node: ast::MetaItemKind::Word,
+        match ext {
+            ProcMacroDerive(expander, ..) | BuiltinDerive(expander) => {
+                let meta = match ext {
+                    ProcMacroDerive(..) => ast::MetaItem { // FIXME(jseyfried) avoid this
+                        path: Path::from_ident(Ident::invalid()),
+                        span: DUMMY_SP,
+                        node: ast::MetaItemKind::Word,
+                    },
+                    _ => {
+                        expn_info.allow_internal_unstable = Some(vec![
+                            sym::rustc_attrs,
+                            Symbol::intern("derive_clone_copy"),
+                            Symbol::intern("derive_eq"),
+                            // RustcDeserialize and RustcSerialize
+                            Symbol::intern("libstd_sys_internals"),
+                        ].into());
+                        attr.meta()?
+                    }
                 };
-                let items = ext.expand(self.cx, span, &dummy, item);
-                Some(invoc.fragment_kind.expect_from_annotatables(items))
-            }
-            BuiltinDerive(func) => {
-                expn_info.allow_internal_unstable = Some(vec![
-                    sym::rustc_attrs,
-                    Symbol::intern("derive_clone_copy"),
-                    Symbol::intern("derive_eq"),
-                    Symbol::intern("libstd_sys_internals"), // RustcDeserialize and RustcSerialize
-                ].into());
+
                 invoc.expansion_data.mark.set_expn_info(expn_info);
                 let span = span.with_ctxt(self.cx.backtrace());
-                let mut items = Vec::new();
-                func(self.cx, span, &attr.meta()?, &item, &mut |a| items.push(a));
+                let items = expander.expand(self.cx, span, &meta, item);
                 Some(invoc.fragment_kind.expect_from_annotatables(items))
             }
             _ => {