Removed the promotable field from CheckCrateVisitor and replaced it with the structs Promotable and NotPromotable.

src/test/compile-fail/closure_promotion.rs

@@ -0,0 +1,17 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![allow(const_err)]
+
+// nll successfully compiles this. It is a bug.
+// See https://github.com/rust-lang/rust/issues/52384
+fn main() {
+    let x: &'static _ = &|| { let z = 3; z }; //~ ERROR does not live long enough
+}