syntax_ext: remove leftover span_err_if_not_stage0 macro.

Author: eddyb

src/libsyntax_ext/deriving/default.rs

@@ -76,8 +76,8 @@ fn default_substructure(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructur
             }
         }
         StaticEnum(..) => {
-            span_err_if_not_stage0!(cx, trait_span, E0665,
-                                    "`Default` cannot be derived for enums, only structs");
+            span_err!(cx, trait_span, E0665,
+                      "`Default` cannot be derived for enums, only structs");
             // let compilation continue
             cx.expr_usize(trait_span, 0)
         }

src/libsyntax_ext/deriving/mod.rs

@@ -19,17 +19,6 @@ use syntax::ptr::P;
 use syntax::symbol::Symbol;
 use syntax_pos::Span;
 
-macro_rules! span_err_if_not_stage0 {
-    ($cx:expr, $sp:expr, $code:ident, $text:tt) => {
-        #[cfg(not(stage0))] {
-            span_err!($cx, $sp, $code, $text)
-        }
-        #[cfg(stage0)] {
-            $cx.span_err($sp, $text)
-        }
-    }
-}
-
 macro path_local($x:ident) {
     generic::ty::Path::new_local(stringify!($x))
 }