error[E0080]: evaluation of constant value failed
  --> $DIR/partial_ptr_overwrite.rs:8:9
   |
LL |         *(ptr as *mut u8) = 123;
   |         ^^^^^^^^^^^^^^^^^^^^^^^ unable to overwrite parts of a pointer in memory at alloc4
   |
   = 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 previous error

For more information about this error, try `rustc --explain E0080`.