rustc: Make unused_features lint warn by default

When it was un*known*_features it was reasonably to by deny by default.

cc #21798

diff --git a/src/librustc/lint/builtin.rs b/src/librustc/lint/builtin.rs
index ae537e557e7d0e9006040651335d0fdce428b949..41a4dd3657479a89833b1bff68d03c387a3e498d 100644 (file)
--- a/src/librustc/lint/builtin.rs
+++ b/src/librustc/lint/builtin.rs
@@ -1984,7 +1984,7 @@ fn id_refers_to_this_method<'tcx>(tcx: &ty::ctxt<'tcx>,
 
 declare_lint! {
     pub UNUSED_FEATURES,
-    Deny,
+    Warn,
     "unused or unknown features found in crate-level #[feature] directives"
 }