add test for edition 2018

Author: csmoe

src/test/ui/editions/edition-deny-overflowing-literals-2018.rs

@@ -0,0 +1,16 @@
+// Copyright 2012 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.
+
+// edition:2018
+
+fn main() {
+    let x: u8 = 256;
+    //~^ error: literal out of range for u8
+}

src/test/ui/editions/edition-deny-overflowing-literals-2018.stderr

@@ -0,0 +1,10 @@
+error: literal out of range for u8
+  --> $DIR/edition-deny-overflowing-literals-2018.rs:14:17
+   |
+LL |     let x: u8 = 256;
+   |                 ^^^
+   |
+   = note: #[deny(overflowing_literals)] on by default
+
+error: aborting due to previous error
+