Make builtin derives a SyntaxExtension

This allows builtin derives to be registered and
resolved, just like other derive types.

2 files changed, 9 insertions, 3 deletions

diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index edf74e1fe19..231e2e6205c 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -10,7 +10,7 @@
 
 pub use self::SyntaxExtension::{MultiDecorator, MultiModifier, NormalTT, IdentTT};
 
-use ast::{self, Attribute, Name, PatKind};
+use ast::{self, Attribute, Name, PatKind, MetaItem};
 use attr::HasAttrs;
 use codemap::{self, CodeMap, ExpnInfo, Spanned, respan};
 use syntax_pos::{Span, ExpnId, NO_EXPANSION};
@@ -471,6 +471,9 @@ impl MacResult for DummyResult {
     }
 }
 
+pub type BuiltinDeriveFn =
+    for<'cx> fn(&'cx mut ExtCtxt, Span, &MetaItem, &Annotatable, &mut FnMut(Annotatable));
+
 /// An enum representing the different kinds of syntax extensions.
 pub enum SyntaxExtension {
     /// A syntax extension that is attached to an item and creates new items
@@ -508,6 +511,9 @@ pub enum SyntaxExtension {
     IdentTT(Box<IdentMacroExpander>, Option<Span>, bool),
 
     CustomDerive(Box<MultiItemModifier>),
+
+    /// An attribute-like procedural macro that derives a builtin trait.
+    BuiltinDerive(BuiltinDeriveFn),
 }
 
 pub type NamedSyntaxExtension = (Name, SyntaxExtension);
diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index 226625ebc8e..0e5d94e0381 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -370,7 +370,7 @@ 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)
             }
-            SyntaxExtension::CustomDerive(_) => {
+            SyntaxExtension::CustomDerive(..) | SyntaxExtension::BuiltinDerive(..) => {
                 self.cx.span_err(attr.span, &format!("`{}` is a derive mode", name));
                 kind.dummy(attr.span)
             }
@@ -440,7 +440,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                 return kind.dummy(span);
             }
 
-            SyntaxExtension::CustomDerive(..) => {
+            SyntaxExtension::CustomDerive(..) | SyntaxExtension::BuiltinDerive(..) => {
                 self.cx.span_err(path.span, &format!("`{}` is a derive mode", extname));
                 return kind.dummy(span);
             }