Support "soft" feature-gating using a lint

Use it for feature-gating `#[bench]`

1 files changed, 4 insertions, 2 deletions

diff --git a/src/libcore/macros.rs b/src/libcore/macros.rs
index f9dc53874ac..680fcd12c4f 100644
--- a/src/libcore/macros.rs
+++ b/src/libcore/macros.rs
@@ -1281,8 +1281,10 @@ pub(crate) mod builtin {
     pub macro test($item:item) { /* compiler built-in */ }
 
     /// Attribute macro applied to a function to turn it into a benchmark test.
-    #[unstable(feature = "test", issue = "50297",
-               reason = "`bench` is a part of custom test frameworks which are unstable")]
+    #[cfg_attr(not(boostrap_stdarch_ignore_this), unstable(soft, feature = "test", issue = "50297",
+               reason = "`bench` is a part of custom test frameworks which are unstable"))]
+    #[cfg_attr(boostrap_stdarch_ignore_this, unstable(feature = "test", issue = "50297",
+               reason = "`bench` is a part of custom test frameworks which are unstable"))]
     #[allow_internal_unstable(test, rustc_attrs)]
     #[rustc_builtin_macro]
     #[rustc_macro_transparency = "semitransparent"]