simple-bind: one-line non-exhaustive binds in Rust

Nightly-only crate.

// Here's a brief example that demonstrates how simple-bind works.

#![feature(proc_macro, pattern_parentheses, stmt_expr_attributes)]
extern crate simple_bind;
use simple_bind::bind;

fn main() {
  enum A { Foo(i32), Bar };

  // Let's say you have a variant of an enum.
  let x = A::Foo(10);

  // Previously, if you knew `x` was `Foo` and just wanted to access the inside,
  // you had to do either:
  let y = match x { A::Foo(y) => y, _ => unreachable!() };
  // or...
  let y = if let A::Foo(y) = x { y } else { unreachable!() };

  // With simple-bind, you can instead do:
  bind!{let A::Foo(y) = x;}

  // No more nested match/if statements!
  assert_eq!(y, 10);
}

Setup

Use of this crate uses the unstable proc_macro API, so it requires nightly and a few feature gates.

Enable nightly on your repository:

rustup override set nightly

Add this line to your cargo.toml:

[dependencies]
simple-bind = "0.1.5"

To your main module file (lib.rs or main.rs), add:

#![feature(proc_macro, pattern_parentheses, stmt_expr_attributes)]
extern crate simple_bind;

Then wherever you want to use the macro, use normal imports (i.e. not #[macro_use]):

use simple_bind::bind;

Examples

fn main() {
  enum B { Quux(i32) };
  enum A { Foo(i32), Bar{y: i32}, Baz(B) };

  // Simple binds
  bind!{let A::Foo(x) = A::Foo(10);}

  // Struct binds
  let s = A::Bar{y: 1};
  bind!{let A::Bar{y} = s;}

  // Nested binds
  bind!{let A::Baz(B::Quux(x)) = A::Baz(B::Quux(10));}

  // Reference binds
  let mut s = A::Foo(10);
  bind!{let &mut A::Foo(ref mut y) = &mut s;}
  *y = 3;
}

Issues

This implementation just covers cases I've run in to, and is not exhaustive to all possible binds. If you find a problem, feel free to submit an issue or a PR!