Don't ICE on the use of integer addresses for ZST constants in pattern matching

src/test/ui/consts/consts-in-patterns.rs

@@ -1,7 +1,10 @@
 // run-pass
+#![feature(const_transmute)]
 
 const FOO: isize = 10;
 const BAR: isize = 3;
+const ZST: &() = unsafe { std::mem::transmute(1usize) };
+const ZST_ARR: &[u8; 0] = unsafe { std::mem::transmute(1usize) };
 
 const fn foo() -> isize { 4 }
 const BOO: isize = foo();
@@ -15,4 +18,14 @@ pub fn main() {
         _ => 3
     };
     assert_eq!(y, 2);
+    let z = match &() {
+        ZST => 9,
+        // FIXME: this should not be required
+        _ => 42,
+    };
+    assert_eq!(z, 9);
+    let z = match b"" {
+        ZST_ARR => 10,
+    };
+    assert_eq!(z, 10);
 }