Impl GenKill for old dataflow framework's GenKillSet

This impl is temporary and will be removed along with the old dataflow
framework. It allows us to reuse the transfer function of new dataflow
analyses when defining old ones

src/librustc_mir/dataflow/generic/mod.rs

@@ -395,5 +395,16 @@ impl<T: Idx> GenKill<T> for BitSet<T> {
     }
 }
 
+// For compatibility with old framework
+impl<T: Idx> GenKill<T> for crate::dataflow::GenKillSet<T> {
+    fn gen(&mut self, elem: T) {
+        self.gen(elem);
+    }
+
+    fn kill(&mut self, elem: T) {
+        self.kill(elem);
+    }
+}
+
 #[cfg(test)]
 mod tests;