add oversized-ref test back

Author: RalfJung

tests/ui/consts/extra-const-ub/detect-extra-ub.rs

@@ -91,4 +91,12 @@ const VALID_ENUM2: Result<&'static [u8], ()> = { let e = Err(()); e };
 // Htting the (non-integer) array code in validation with an immediate local.
 const VALID_ARRAY: [Option<i32>; 0] = { let e = [None; 0]; e };
 
+// Detecting oversized references.
+const OVERSIZED_REF: () = { unsafe {
+    let slice: *const [u8] = transmute((1usize, usize::MAX));
+    let _val = &*slice;
+    //[with_flag]~^ ERROR: evaluation of constant value failed
+    //[with_flag]~| slice is bigger than largest supported object
+} };
+
 fn main() {}

tests/ui/consts/extra-const-ub/detect-extra-ub.with_flag.stderr

@@ -52,6 +52,12 @@ LL |     let _val = *(&mem as *const Align as *const [*const u8; 2]);
    = help: this code performed an operation that depends on the underlying bytes representing a pointer
    = help: the absolute address of a pointer is not known at compile-time, so such operations are not supported
 
-error: aborting due to 7 previous errors
+error[E0080]: evaluation of constant value failed
+  --> $DIR/detect-extra-ub.rs:97:16
+   |
+LL |     let _val = &*slice;
+   |                ^^^^^^^ constructing invalid value: encountered invalid reference metadata: slice is bigger than largest supported object
+
+error: aborting due to 8 previous errors
 
 For more information about this error, try `rustc --explain E0080`.