1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133

//! A macro for defining #[cfg] if-else statements.
//!
//! The macro provided by this crate, `cfg_if`, is similar to the `if/elif` C
//! preprocessor macro by allowing definition of a cascade of `#[cfg]` cases,
//! emitting the implementation which matches first.
//!
//! This allows you to conveniently provide a long list #[cfg]'d blocks of code
//! without having to rewrite each clause multiple times.
//!
//! # Example
//!
//! ```
//! #[macro_use]
//! extern crate cfg_if;
//!
//! cfg_if! {
//!     if #[cfg(unix)] {
//!         fn foo() { /* unix specific functionality */ }
//!     } else if #[cfg(target_pointer_width = "32")] {
//!         fn foo() { /* non-unix, 32-bit functionality */ }
//!     } else {
//!         fn foo() { /* fallback implementation */ }
//!     }
//! }
//!
//! # fn main() {}
//! ```

#![no_std]

#![doc(html_root_url = "http://alexcrichton.com/cfg-if")]
#![deny(missing_docs)]
#![cfg_attr(test, deny(warnings))]

#[macro_export]
macro_rules! cfg_if {
    ($(
        if #[cfg($($meta:meta),*)] { $($it:item)* }
    ) else * else {
        $($it2:item)*
    }) => {
        __cfg_if_items! {
            () ;
            $( ( ($($meta),*) ($($it)*) ), )*
            ( () ($($it2)*) ),
        }
    };
    (
        if #[cfg($($i_met:meta),*)] { $($i_it:item)* }
        $(
            else if #[cfg($($e_met:meta),*)] { $($e_it:item)* }
        )*
    ) => {
        __cfg_if_items! {
            () ;
            ( ($($i_met),*) ($($i_it)*) ),
            $( ( ($($e_met),*) ($($e_it)*) ), )*
            ( () () ),
        }
    }
}

#[macro_export]
#[doc(hidden)]
macro_rules! __cfg_if_items {
    (($($not:meta,)*) ; ) => {};
    (($($not:meta,)*) ; ( ($($m:meta),*) ($($it:item)*) ), $($rest:tt)*) => {
        __cfg_if_apply! { cfg(all($($m,)* not(any($($not),*)))), $($it)* }
        __cfg_if_items! { ($($not,)* $($m,)*) ; $($rest)* }
    }
}

#[macro_export]
#[doc(hidden)]
macro_rules! __cfg_if_apply {
    ($m:meta, $($it:item)*) => {
        $(#[$m] $it)*
    }
}

#[cfg(test)]
mod tests {
    cfg_if! {
        if #[cfg(test)] {
            use core::option::Option as Option2;
            fn works1() -> Option2<u32> { Some(1) }
        } else {
            fn works1() -> Option<u32> { None }
        }
    }

    cfg_if! {
        if #[cfg(foo)] {
            fn works2() -> bool { false }
        } else if #[cfg(test)] {
            fn works2() -> bool { true }
        } else {
            fn works2() -> bool { false }
        }
    }

    cfg_if! {
        if #[cfg(foo)] {
            fn works3() -> bool { false }
        } else {
            fn works3() -> bool { true }
        }
    }

    cfg_if! {
        if #[cfg(test)] {
            use core::option::Option as Option3;
            fn works4() -> Option3<u32> { Some(1) }
        }
    }

    cfg_if! {
        if #[cfg(foo)] {
            fn works5() -> bool { false }
        } else if #[cfg(test)] {
            fn works5() -> bool { true }
        }
    }

    #[test]
    fn it_works() {
        assert!(works1().is_some());
        assert!(works2());
        assert!(works3());
        assert!(works4().is_some());
        assert!(works5());
    }
}