Don't ICE on horrible transmutes in pattern constants

src/test/ui/const-eval/ref_to_int_match.rs

@@ -0,0 +1,30 @@
+// Copyright 2017 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.
+
+fn main() {
+    match 40u64 {
+        0...10 => {},
+        10...BAR => {}, //~ ERROR lower range bound must be less than or equal to upper
+        _ => {},
+    }
+}
+
+union Foo {
+    f: Int,
+    r: &'static u32,
+}
+
+#[cfg(target_pointer_width="64")]
+type Int = u64;
+
+#[cfg(target_pointer_width="32")]
+type Int = u32;
+
+const BAR: Int = unsafe { Foo { r: &42 }.f }; 

src/test/ui/const-eval/ref_to_int_match.stderr

@@ -0,0 +1,9 @@
+error[E0030]: lower range bound must be less than or equal to upper
+  --> $DIR/ref_to_int_match.rs:14:9
+   |
+LL |         10...BAR => {}, //~ ERROR lower range bound must be less than or equal to upper
+   |         ^^ lower bound larger than upper bound
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0030`.