Error code E0094

An invalid number of generic parameters was passed to an intrinsic function.

Erroneous code example:

#![allow(unused)]
#![feature(intrinsics, rustc_attrs)]
#![allow(internal_features)]

fn main() {
extern "rust-intrinsic" {
    #[rustc_safe_intrinsic]
    fn size_of<T, U>() -> usize; // error: intrinsic has wrong number
                                 //        of type parameters
}
}

Please check that you provided the right number of type parameters and verify with the function declaration in the Rust source code. Example:

#![allow(unused)]
#![feature(intrinsics, rustc_attrs)]
#![allow(internal_features)]

fn main() {
extern "rust-intrinsic" {
    #[rustc_safe_intrinsic]
    fn size_of<T>() -> usize; // ok!
}
}