Add two regression tests for const eval

src/test/compile-fail/const-err4.rs

@@ -0,0 +1,24 @@
+// 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.
+
+#[derive(Copy, Clone)]
+union Foo {
+    a: isize,
+    b: (),
+}
+
+enum Bar {
+    Boo = [unsafe { Foo { b: () }.a }; 4][3],
+    //~^ ERROR constant evaluation of enum discriminant resulted in non-integer
+}
+
+fn main() {
+    assert_ne!(Bar::Boo as isize, 0);
+}

src/test/run-pass/const-repeated-values.rs

@@ -0,0 +1,19 @@
+// 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.
+
+const FOO: isize = 42;
+
+enum Bar {
+    Boo = *[&FOO; 4][3],
+}
+
+fn main() {
+    assert_eq!(Bar::Boo as isize, 42);
+}