Note! This crate is experimental and under development. It may include bugs that alter the behavior of your code in unexpected ways. You should review the expanded code from the macro before use, and report any bugs you may find to the bug tracker at https://github.com/frxstrem/cain/issues.

The cain! macro is a macro that rewrites sequential Rust branch statements into nested branches.

This can be useful in cases where you want to have branches with different types that behave similarly, for example concrete types with a common trait, without having to use runtime trait objects like Box<dyn Trait>.

The disadvantage of this is that the amount of code grows exponentially relative to the number of sequential branches in the expanded code.

MSRV

The minimal supported Rust version for cain is 1.57.0 (December 2021).

Example

The code:

fn foo(): Result<i32, bool> { .. }

let a = cain! {
  let value = match foo() {
    Ok(n) => n,
    Err(b) => b,
  };

  value.to_string()
};

Will be expanded by the cain! macro into the code:

fn foo(): Result<i32, bool> { .. }

let a = {
  match foo() {
    Ok(n) => {
      let value = n;
      n.to_string()
    },
    Err(b) => {
      let value = b;
      b.to_string()
    }
  }
};