macros: init MethodDef.unify_fieldless_variants to false

AFAICT this field is irrelevant to us, but it still must be initialized.

macros/src/lib.rs

@@ -75,6 +75,7 @@ pub fn expand_deriving_from_primitive(cx: &mut ExtCtxt,
             MethodDef {
                 name: "from_i64",
                 is_unsafe: false,
+                unify_fieldless_variants: false,
                 generics: LifetimeBounds::empty(),
                 explicit_self: None,
                 args: vec!(Literal(path_local!(i64))),
@@ -91,6 +92,7 @@ pub fn expand_deriving_from_primitive(cx: &mut ExtCtxt,
             MethodDef {
                 name: "from_u64",
                 is_unsafe: false,
+                unify_fieldless_variants: false,
                 generics: LifetimeBounds::empty(),
                 explicit_self: None,
                 args: vec!(Literal(path_local!(u64))),