Add some runtime sanity checks

Author: oli-obk

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

@@ -8,12 +8,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// compile-pass
+// run-pass
 
 #![feature(const_str_len, const_str_as_bytes)]
 
-#![crate_type = "lib"]
-
 const S: &str = "foo";
 pub const B: &[u8] = S.as_bytes();
 
@@ -24,3 +22,12 @@ pub fn foo() -> [u8; S.len()] {
     }
     buf
 }
+
+fn main() {
+    assert_eq!(&foo()[..], b"foo");
+    assert_eq!(foo().len(), S.len());
+    const LEN: usize = S.len();
+    assert_eq!(LEN, S.len());
+    assert_eq!(B, foo());
+    assert_eq!(B, b"foo");
+}