Add NLL test for #45045

Closes #45045

src/test/ui/nll/borrowed-match-issue-45045.rs

@@ -0,0 +1,30 @@
+// 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.
+
+// Regression test for issue #45045
+
+#![feature(nll)]
+
+enum Xyz {
+    A,
+    B,
+}
+
+fn main() {
+    let mut e = Xyz::A;
+    let f = &mut e;
+    let g = f;
+    match e {
+        Xyz::A => println!("a"),
+        //~^ cannot use `e` because it was mutably borrowed [E0503]
+        Xyz::B => println!("b"),
+    };
+    *g = Xyz::B;
+}

src/test/ui/nll/borrowed-match-issue-45045.stderr

@@ -0,0 +1,11 @@
+error[E0503]: cannot use `e` because it was mutably borrowed
+  --> $DIR/borrowed-match-issue-45045.rs:25:9
+   |
+22 |     let f = &mut e;
+   |             ------ borrow of `e` occurs here
+...
+25 |         Xyz::A => println!("a"),
+   |         ^^^^^^ use of borrowed `e`
+
+error: aborting due to previous error
+