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

#![cfg_attr(rustfmt, rustfmt_skip)] // https://github.com/rust-lang-nursery/rustfmt/issues/2754

// Vendored from the static-cond crate as macro re-exports are not available in stable Rust.
// https://github.com/durka/static-cond/blob/36aa2dd/src/lib.rs
//
// Code is dual licensed under MIT/Apache-2.0
// Copyright (c) 2016 Alex Burka
#[macro_export]
#[doc(hidden)]
macro_rules! static_cond {
    // private rule to define and call the local macro
    (@go $lhs:tt $rhs:tt $arm1:tt $arm2:tt) => {
        // note that the inner macro has no captures (it can't, because there's no way to escape `$`)
        macro_rules! __static_cond {
            ($lhs $lhs) => $arm1;
            ($lhs $rhs) => $arm2
        }

        __static_cond!($lhs $rhs);
    };

    // no else condition provided: fall through with empty else
    (if $lhs:tt == $rhs:tt $then:tt) => {
        static_cond!(if $lhs == $rhs $then else { });
    };
    (if $lhs:tt != $rhs:tt $then:tt) => {
        static_cond!(if $lhs != $rhs $then else { });
    };

    // we evaluate a conditional by generating a new macro (in an inner scope, so name shadowing is
    // not a big concern) and calling it
    (if $lhs:tt == $rhs:tt $then:tt else $els:tt) => {
        static_cond!(@go $lhs $rhs $then $els);
    };
    (if $lhs:tt != $rhs:tt $then:tt else $els:tt) => {
        static_cond!(@go $lhs $rhs $els $then);
    };
}