87558.rs: add feature(unboxed_closures)

Author: Alexendoo

ices/87558.rs

@@ -1,5 +1,9 @@
+#![feature(unboxed_closures)]
+
 struct ErrorKind;
 struct Error(ErrorKind);
 impl Fn(&isize) for Error {
     fn from() {}
 }
+
+fn main() {}