a == 1 && a == 2 && a == 3 を真に。

hoge.cpp

#include <iostream>

struct A
{
	constexpr bool operator==(int) const
	{
		return true;
	}
};

int main()
{
	A a;
	std::cout << std::boolalpha << (a == 1 && a == 2 && a == 3) << std::endl;
}

Hoge.cs

public class Hoge
{
	public static void Main(string[] args)
	{
		var a = new Hoge();
		System.Console.WriteLine("{0}", a == 1 && a == 2 && a == 3);
	}

	public static bool operator==(Hoge hoge, int n)
	{
		return true;
	}

	public static bool operator!=(Hoge hoge, int n)
	{
		return false;
	}
}

hoge.d

import std.stdio;

struct A
{
	public bool opEquals(int n) const
	{
		return true;
	}
}

void main()
{
	A a;
	writeln(a == 1 && a == 2 && a == 3);
}

hoge.hs

data A = A deriving Eq

instance Num A where
  _ + _ = A
  _ * _ = A
  negate = id
  abs = id
  signum = id
  fromInteger _ = A

main :: IO ()
main = let a = A in print $ a == 1 && a == 2 && a == 3

hoge.rs

struct A;

impl PartialEq<i32> for A {
    fn eq(&self, _: &i32) -> bool {
        true
    }
}

fn main() {
    let a = A;
    println!("{}", a == 1 && a == 2 && a == 3);
}

hoge2.hs

main :: IO ()
main = let a = () in a == 1 && a == 2 && a == 3
       where _ == _ = True