Feature-gate the `#[unsafe_no_drop_flag]` attribute.

See RFC 320, "Non-zeroing dynamic drops."

Fix #22173

[breaking-change]

1 files changed, 10 insertions, 0 deletions

diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index 72bbe1adfaa..e3b9402ba30 100644
--- a/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@ -126,6 +126,10 @@ static KNOWN_FEATURES: &'static [(&'static str, &'static str, Status)] = &[
 
     // Allows using #![no_std]
     ("no_std", "1.0.0", Active),
+
+    // Allows using the unsafe_no_drop_flag attribute (unlikely to
+    // switch to Accepted; see RFC 320)
+    ("unsafe_no_drop_flag", "1.0.0", Active),
 ];
 
 enum Status {
@@ -474,6 +478,12 @@ impl<'a, 'v> Visitor<'v> for PostExpansionVisitor<'a> {
             self.gate_feature("no_std", attr.span,
                               "no_std is experimental");
         }
+
+        if attr.check_name("unsafe_no_drop_flag") {
+            self.gate_feature("unsafe_no_drop_flag", attr.span,
+                              "unsafe_no_drop_flag has unstable semantics \
+                               and may be removed in the future");
+        }
     }
 
     fn visit_pat(&mut self, pattern: &ast::Pat) {