Implement default type parameters in generics.

3 files changed, 16 insertions, 5 deletions

diff --git a/src/libsyntax/ext/build.rs b/src/libsyntax/ext/build.rs
index 3b43c96a184..9ad4f4f7fac 100644
--- a/src/libsyntax/ext/build.rs
+++ b/src/libsyntax/ext/build.rs
@@ -66,7 +66,10 @@ pub trait AstBuilder {
     fn ty_field_imm(&self, span: Span, name: Ident, ty: P<ast::Ty>) -> ast::TypeField;
     fn strip_bounds(&self, bounds: &Generics) -> Generics;
 
-    fn typaram(&self, id: ast::Ident, bounds: OptVec<ast::TyParamBound>) -> ast::TyParam;
+    fn typaram(&self,
+               id: ast::Ident,
+               bounds: OptVec<ast::TyParamBound>,
+               default: Option<P<ast::Ty>>) -> ast::TyParam;
 
     fn trait_ref(&self, path: ast::Path) -> ast::TraitRef;
     fn typarambound(&self, path: ast::Path) -> ast::TyParamBound;
@@ -354,8 +357,16 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
         })
     }
 
-    fn typaram(&self, id: ast::Ident, bounds: OptVec<ast::TyParamBound>) -> ast::TyParam {
-        ast::TyParam { ident: id, id: ast::DUMMY_NODE_ID, bounds: bounds }
+    fn typaram(&self,
+               id: ast::Ident,
+               bounds: OptVec<ast::TyParamBound>,
+               default: Option<P<ast::Ty>>) -> ast::TyParam {
+        ast::TyParam {
+            ident: id,
+            id: ast::DUMMY_NODE_ID,
+            bounds: bounds,
+            default: default
+        }
     }
 
     // these are strange, and probably shouldn't be used outside of
diff --git a/src/libsyntax/ext/deriving/generic.rs b/src/libsyntax/ext/deriving/generic.rs
index 3c9401b109f..9ebb771f5da 100644
--- a/src/libsyntax/ext/deriving/generic.rs
+++ b/src/libsyntax/ext/deriving/generic.rs
@@ -375,7 +375,7 @@ impl<'a> TraitDef<'a> {
             // require the current trait
             bounds.push(cx.typarambound(trait_path.clone()));
 
-            trait_generics.ty_params.push(cx.typaram(ty_param.ident, bounds));
+            trait_generics.ty_params.push(cx.typaram(ty_param.ident, bounds, None));
         }
 
         // Create the reference to the trait.
diff --git a/src/libsyntax/ext/deriving/ty.rs b/src/libsyntax/ext/deriving/ty.rs
index b22dcfe0da2..893a1c68426 100644
--- a/src/libsyntax/ext/deriving/ty.rs
+++ b/src/libsyntax/ext/deriving/ty.rs
@@ -196,7 +196,7 @@ fn mk_ty_param(cx: &ExtCtxt, span: Span, name: &str, bounds: &[Path],
             let path = b.to_path(cx, span, self_ident, self_generics);
             cx.typarambound(path)
         }));
-    cx.typaram(cx.ident_of(name), bounds)
+    cx.typaram(cx.ident_of(name), bounds, None)
 }
 
 fn mk_generics(lifetimes: ~[ast::Lifetime],  ty_params: ~[ast::TyParam]) -> Generics {