Moved failing test to src/test/ui/

Still have not figured out how to make it work

library/core/tests/mem.rs

@@ -131,18 +131,9 @@ fn test_discriminant_send_sync() {
 }
 
 #[test]
+#[cfg(not(bootstrap))]
 fn assume_init_good() {
     const TRUE: bool = unsafe { MaybeUninit::<bool>::new(true).assume_init() };
 
     assert!(TRUE);
 }
-
-#[test]
-fn assume_init_bad() {
-    const _BAD: () = unsafe {
-        MaybeUninit::<!>::uninit().assume_init();
-        //~^ ERROR the type `!` does not permit being left uninitialized
-        //~| ERROR this code causes undefined behavior when executed
-        //~| ERROR help: use `MaybeUninit<T>` instead, and only call `assume_init` after initialization is done
-    };
-}

src/test/ui/assume-type-intrinsics.rs

@@ -0,0 +1,13 @@
+#![feature(never_type)]
+#![feature(const_maybe_uninit_assume_init)]
+
+fn main() {
+    use std::mem::MaybeUninit;
+
+    const _BAD: () = unsafe {
+        MaybeUninit::<!>::uninit().assume_init();
+        //~^ ERROR: the type `!` does not permit being left uninitialized
+        //~| this code causes undefined behavior when executed
+        //~| WARN: the type `!` does not permit being left uninitialized
+    };
+}

src/test/ui/assume-type-intrinsics.stderr

@@ -0,0 +1,37 @@
+error: any use of this value will cause an error
+  --> $SRC_DIR/core/src/mem/maybe_uninit.rs:LL:COL
+   |
+LL |               intrinsics::assert_inhabited::<T>();
+   |               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |               |
+   |               attempted to instantiate uninhabited type `!`
+   |               inside `MaybeUninit::<!>::assume_init` at $SRC_DIR/core/src/mem/maybe_uninit.rs:LL:COL
+   |               inside `_BAD` at $DIR/assume-type-intrinsics.rs:8:9
+   | 
+  ::: $DIR/assume-type-intrinsics.rs:7:5
+   |
+LL | /     const _BAD: () = unsafe {
+LL | |         MaybeUninit::<!>::uninit().assume_init();
+LL | |
+LL | |
+LL | |
+LL | |
+LL | |     };
+   | |______-
+   |
+   = note: `#[deny(const_err)]` on by default
+
+warning: the type `!` does not permit being left uninitialized
+  --> $DIR/assume-type-intrinsics.rs:8:9
+   |
+LL |         MaybeUninit::<!>::uninit().assume_init();
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |         |
+   |         this code causes undefined behavior when executed
+   |         help: use `MaybeUninit<T>` instead, and only call `assume_init` after initialization is done
+   |
+   = note: `#[warn(invalid_value)]` on by default
+   = note: the `!` type has no valid value
+
+error: aborting due to previous error; 1 warning emitted
+