1An unknown intrinsic function was declared.23Erroneous code example:45```compile_fail,E00936#![feature(intrinsics)]7#![allow(internal_features)]89#[rustc_intrinsic]10unsafe fn foo(); // error: unrecognized intrinsic function: `foo`1112fn main() {13    unsafe {14        foo();15    }16}17```1819Please check you didn't make a mistake in the function's name. All intrinsic20functions are defined in `library/core/src/intrinsics` in the Rust source code.