error: function pointer assumed to be nullable, even though it isn't
  --> $DIR/fn_null_check.rs:13:8
   |
LL |     if (fn_ptr as *mut ()).is_null() {}
   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: try wrapping your function pointer type in `Option<T>` instead, and using `is_none` to check for null pointer value
   = note: `-D clippy::fn-null-check` implied by `-D warnings`

error: function pointer assumed to be nullable, even though it isn't
  --> $DIR/fn_null_check.rs:14:8
   |
LL |     if (fn_ptr as *const u8).is_null() {}
   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: try wrapping your function pointer type in `Option<T>` instead, and using `is_none` to check for null pointer value

error: function pointer assumed to be nullable, even though it isn't
  --> $DIR/fn_null_check.rs:15:8
   |
LL |     if (fn_ptr as *const ()) == std::ptr::null() {}
   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: try wrapping your function pointer type in `Option<T>` instead, and using `is_none` to check for null pointer value

error: function pointer assumed to be nullable, even though it isn't
  --> $DIR/fn_null_check.rs:16:8
   |
LL |     if (fn_ptr as *const ()) == (0 as *const ()) {}
   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: try wrapping your function pointer type in `Option<T>` instead, and using `is_none` to check for null pointer value

error: function pointer assumed to be nullable, even though it isn't
  --> $DIR/fn_null_check.rs:17:8
   |
LL |     if (fn_ptr as *const ()) == ZPTR {}
   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: try wrapping your function pointer type in `Option<T>` instead, and using `is_none` to check for null pointer value

error: aborting due to 5 previous errors