Macro newtype

macro_rules! newtype {
    ($type_name: ident, $type: ty) => { ... };
    ($type_name: ident, $type: ty, $is_pub:vis) => { ... };
    ($type_name: ident, $type: ty, $access_name: ident) => { ... };
    ($type_name: ident, $type: ty, $access_name: ident, $is_pub:vis) => { ... };
    {$type_name: ident, $type: ty} => { ... };
    {$type_name: ident, $type: ty, $is_pub:vis} => { ... };
    {$type_name: ident, $type: ty, $access_name: ident} => { ... };
    {$type_name: ident, $type: ty, $access_name: ident, $is_pub:vis} => { ... };
}

A rust newtype macro inspired by kotlin’s inline class.

When we use rust newtype!(NewTypeOne, u32); It generate the struct

 #[derive(Debug, Clone)]
     struct UserHomeDirectory {
         pub v: u32,
     }

for you. The v is the default public field.

use inline_newtype::newtype;
use std::path::PathBuf;
newtype!(UserHomeDirectory, PathBuf);
newtype!(UserRuntimeDirectory, PathBuf);
let user_home_directory = UserHomeDirectory { v: PathBuf::from("hello") };
let user_runtime_directory= UserRuntimeDirectory {v: PathBuf::from("hello")};
fn test_newtype_type_func(user_home_directory: UserHomeDirectory) -> UserHomeDirectory{
         user_home_directory
}

test_newtype_type_func(user_runtime_directory);  // mismatch type

You can aslo make the newtype public just adding the pub.

use inline_newtype::newtype;
use std::path::PathBuf;
newtype!(UserHomeDirectory, PathBuf, pub);

You also can change the field name if you want.

use inline_newtype::newtype;
use std::path::PathBuf;
newtype!(UserHomeDirectory, PathBuf, path_buf);
let user_home_directory = UserHomeDirectory { path_buf: PathBuf::from("hello")};
assert_eq!(user_home_directory.path_buf, PathBuf::from("hello"));

Transform from one newtype to another

use inline_newtype::newtype;
use std::path::PathBuf;
newtype!(UserHomeDirectory, PathBuf);
newtype!(UserRuntimeDirectory, PathBuf);
let user_home_directory = UserHomeDirectory { v: PathBuf::from("hello") };
let user_runtime_directory = UserRuntimeDirectory { v: PathBuf::from("hello") };
fn transform_user_home_to_runtime_directory(
    mut user_home_directory: UserHomeDirectory,
) -> UserRuntimeDirectory {
    let mut runtime_dir = user_home_directory.v;
    runtime_dir.push("runtime_dir");
    UserRuntimeDirectory { v: runtime_dir }
}

You can also using curly brackets to declare the newtype.

use inline_newtype::newtype;
use std::path::PathBuf;
newtype! {UserHomeDirectory, PathBuf, path_buf}
let user_home_directory = UserHomeDirectory { path_buf: PathBuf::from("hello") };
assert_eq!(user_home_directory.path_buf, PathBuf::from("hello"))