Function incorrect_check

fn incorrect_check<'a, 'tcx: 'a>(
    cx: &'a LateContext<'tcx>,
    e: &'a Expr<'a>,
) -> Option<PtrNullChecksDiag<'tcx>>

This function checks if the expression is from a series of consecutive casts, ie. (my_fn as *const _ as *mut _).cast_mut() and whether the original expression is either a fn ptr, a reference, or a function call whose definition is annotated with #![rustc_never_returns_null_ptr]. If this situation is present, the function returns the appropriate diagnostic.