#anonymous #struct #named-arguments #destruct #instruct #macro #obstruct

macro obstruct-macros

Macros for obstruct. You probably want to depend on obstruct instead.

1 unstable release

0.1.0 Nov 4, 2023

#5 in #destruct


Used in obstruct

MIT license

20KB
291 lines

About

obstruct is an experimental implementation of anonymous structs and named arguments for Rust.

Anonymous structs

Create an anonymous struct with instruct! and destructure it with destruct!:

#![feature(associated_const_equality)]
use obstruct::{instruct, destruct};

// Create an anonymous struct.
let structured = instruct! { red: 0, green: 1.0, blue: 2 };

// Destructure that struct.
destruct! { let {red, green, blue} = structured };
assert_eq!(red, 0);
assert_eq!(green, 1.0);
assert_eq!(blue, 2);

Note that this is not (just) a tuple: the order in which fields are specified does not matter!

#![feature(associated_const_equality)]
use obstruct::{instruct, destruct};

// Create an anonymous struct.
let structured = instruct! { red: 0, green: 1.0, blue: 2 };

// Destructure that struct.
destruct! { let {blue, green, red} = structured };
assert_eq!(red, 0);
assert_eq!(green, 1.0);
assert_eq!(blue, 2);

If you attempt to access a field that doesn't exist, you will get a compile-time error:

#![feature(associated_const_equality)]
use obstruct::{instruct, destruct};

// Create an anonymous struct.
let structured = instruct! { red: 0, green: 1.0, blue: 2 };

// Destructure that struct.
destruct! { let {blue, green, oops} = structured };
//                            ^^^ --- will fail with a complex error message pointing at `oops`.

Named arguments

Create a function accepting named parameters with destruct! and call it with call!:

#![feature(associated_const_equality)]
use obstruct::{call, instruct, destruct};

// Create a function accepting anonymous arguments.
destruct!(fn do_something({red: u8, green: &'static str, blue: ()}) {
    println!("Roses are {red}");
});


// Call this function
call!(do_something, {red: 0, green: "GREEN", blue: ()});

// Or equivalently
do_something(instruct! {red: 0, green: "GREEN", blue: ()});

Again, the order in which arguments are specified does not matter:

#![feature(associated_const_equality)]
use obstruct::{call, instruct, destruct};

// Create a function accepting anonymous arguments.
destruct!(fn do_something({red: u8, green: &'static str, blue: ()}) {
    println!("Roses are {red}");
});

do_something(instruct! {blue: (), green: "GREEN", red: 0});

Again, errors are caught at compile-time:

#![feature(associated_const_equality)]
use obstruct::{call, instruct, destruct};

// Create a function accepting anonymous arguments.
destruct!(fn do_something({red: u8, green: &'static str, blue: ()}) {
    println!("Roses are {red}");
});

do_something(instruct! {blue: (), green: "GREEN", oops: 0});
//                                                 ^^^ --- will fail with a complex error message pointing at `oops`.


call!(do_something, {red: 0, green: "GREEN", oops: ()});
//                                           ^^^ --- will fail with a complex error message pointing at `oops`.

Dependencies

~0.7–1.2MB
~26K SLoC