More sophisticated modules demo

main.cpp

#include <iostream>
import shop;

int main() {
  auto bag = shop();
  if (bag.products.size() != 2) {
    std::cout << "Bag did not have the expected size!\n";
    return 1;
  }
  if (bag.products[0].value != "fruit") {
    std::cout << "First product is not a fruit!\n";
  }
  if (bag.products[1].value != "veggie") {
    std::cout << "First product is not a veggie!\n";
  }
  std::cout << "Shopping bag had everything we expected!\n";
}

shop-unit.cpp

module;
#include <memory>
module shop;
import util;

ShoppingBag shop() {
  ShoppingBag bag;
  bag.products.push_back(produce("fruit"));
  bag.products.push_back(produce("veggie"));
  return bag;
}

shop.ixx

export module shop;

import types;

export
ShoppingBag shop();

types.ixx

module;
#include <string>
#include <vector>
export module types;

export
struct Product {
  std::string value;
};

export
struct ShoppingBag {
  std::vector<Product> products;
};

util.ixx

module;
#include <string>
export module util;

import types;

export
Product produce(const char* product) { return { .value = product }; }