error: any use of this value will cause an error
  --> $DIR/const-size_of_val-align_of_val-extern-type.rs:11:31
   |
LL | const _SIZE: usize = unsafe { size_of_val(&4 as *const i32 as *const Opaque) };
   | ------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
   |                               |
   |                               `extern type` does not have known layout
   |
   = note: `#[deny(const_err)]` on by default
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
   = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>

error: any use of this value will cause an error
  --> $DIR/const-size_of_val-align_of_val-extern-type.rs:13:32
   |
LL | const _ALIGN: usize = unsafe { min_align_of_val(&4 as *const i32 as *const Opaque) };
   | -------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
   |                                |
   |                                `extern type` does not have known layout
   |
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
   = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>

error: aborting due to 2 previous errors