cursed code to get the sequence "!||" to be valid

a.sh

#!/bin/sh
rustc +nightly --crate-type=staticlib forty_two.rs || exit 1
gcc main.c -L. -lforty_two || exit 1
./a.out
# prints: forty_two() = 42

forty_two.rs

#![no_std]
#![no_core]
#![feature(no_core, lang_items, auto_traits)]

#[no_mangle]
pub extern "C" fn forty_two() -> u32 {
    !|| () // evaluates to 42
}

#[lang = "not"]
pub trait Not {
    type Output;
    fn not(self) -> Self::Output;
}
impl<T> Not for T {
    type Output = u32;
    fn not(self) -> u32 {
        42
    }
}

// mandatory lang items since we don't have ::core

#[lang = "sized"]
pub trait Sized {}

#[lang = "copy"]
pub unsafe trait Copy {}

#[lang = "freeze"]
unsafe auto trait Freeze {}

#[lang = "drop_in_place"]
pub unsafe fn drop_in_place<T: ?Sized>(_: *mut T) {
    loop {}
}

main.c

#include <stdint.h>
#include <stdio.h>

extern uint32_t forty_two();

int main() {
    printf("forty_two() = %d\n", forty_two());
}