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//! This crate provides the `if_chain!` macro -- a macro for composing
//! long chains of if-else if-else statements.
//!
//! It is intended to provide an alternative to writing if chains with `match`,
//! such as:
//!
//! ```ignore
//! match () {
//!     _ if some_condition => ...,
//!     _ if some_other_condition => ...,
//!     _ if some_third_condition => ...,
//!     _ => ...,
//! }
//! ```
//!
//! # Example usage
//!
//! While it is mainly intended for long chains, `if_chain!` can be used
//! for simple if-else situations, such as:
//!
//! ```ignore
//! if_chain! {
//! | some_condition => (/* some_condition is true */),
//! | _ => (/* the else branch */)
//! }
//! ```
//!
//! The earlier `match` example can be rewritten as:
//!
//! ```ignore
//! if_chain! {
//! | some_condition => ...,
//! | some_other_condition => ...,
//! | some_third_condition => ...,
//! }
//! ```
//!
//! Note that the `else` branch is not required, since `if_chain!` simply gets
//! expanded into:
//!
//! ```ignore
//! if some_condition {
//!     ...
//! } else if some_other_condition }
//!     ...
//! } else if some_third_condition {
//!     ...
//! }
//! ```

#![cfg_attr(not(test), no_std)]

/// A macro for writing if chains
#[macro_export]
macro_rules! if_chain {
    (| $cond:expr => $branch:expr
     $(, | $cond_alt:expr => $branch_alt:expr )*
     $(, | _ => $fallback:expr)? $(,)? ) => {
        if $cond {
            $branch
        }

        $(
            else if $cond_alt {
                $branch_alt
            }
        )*

        $(
            else {
                $fallback
            }
        )?
    }
}

#[cfg(test)]
mod tests {
    #[test]
    fn single() {
        if_chain! {
        | 'c' != 'd' => (),
        }
    }

    #[test]
    fn multiple() {
        let x = 2;

        if_chain! {
        | x == 1 => {
            todo!()
        },
        | x == 1 => unreachable!(),
        | _ => println!("idk what x is.."),
        }
    }

    #[test]
    #[should_panic]
    fn test_with_panic() {
        let x = 9;

        if_chain! {
        | x % 2 == 0 => {
            (/* x is even */)
        },
        | _ => panic!("x is odd")
        }
    }
}