Error [E0599] when trying to build

error[E0599]: no method named `split_array_ref` found for reference `&&[u8]` in the current scope\
   --> src/crypto.rs:100:35\
    |\
100 |     let (iv, ciphertext) = secret.split_array_ref();\
    |                                   ^^^^^^^^^^^^^^^\
    |\
help: there is a method `split_at` with a similar name, but with different arguments\
   --> /rustc/8f359beca4e58bc3ae795a666301a8f47023044c/library/core/src/slice/mod.rs:1870:5