error_derive 0.2.0

Macros for deriving Error implementations through custom_derive!.
Documentation 
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//! Utility module.


/// enum_derive_util macro, copy-pasted from enum_derive (commit 7172f80).
/// (Can't be used directly since Rust doesn't support macro re-exports).
#[doc(hidden)]
#[macro_export]
macro_rules! enum_derive_util {
    (@as_expr $e:expr) => {$e};
    (@as_item $($i:item)+) => {$($i)+};
    (@first_expr $head:expr, $($tail:expr),*) => {$head};
    (@first_expr $head:expr) => {$head};

    (
        @collect_unitary_variants ($callback:ident { $($args:tt)* }),
        ($(,)*) -> ($($var_names:ident,)*)
    ) => {
        enum_derive_util! {
            @as_item
            $callback!{ $($args)* ($($var_names),*) }
        }
    };

    (
        @collect_unitary_variants $fixed:tt,
        (#[$_attr:meta] $($tail:tt)*) -> ($($var_names:tt)*)
    ) => {
        enum_derive_util! {
            @collect_unitary_variants $fixed,
            ($($tail)*) -> ($($var_names)*)
        }
    };

    (
        @collect_unitary_variants $fixed:tt,
        ($var:ident $(= $_val:expr)*, $($tail:tt)*) -> ($($var_names:tt)*)
    ) => {
        enum_derive_util! {
            @collect_unitary_variants $fixed,
            ($($tail)*) -> ($($var_names)* $var,)
        }
    };

    (
        @collect_unitary_variants ($name:ident),
        ($var:ident $_struct:tt, $($tail:tt)*) -> ($($var_names:tt)*)
    ) => {
        const _error: () = "cannot parse unitary variants from enum with non-unitary variants";
    };

    (
        @collect_unary_variants ($callback:ident { $($args:tt)* }),
        ($(,)*) -> ($($out:tt)*)
    ) => {
        enum_derive_util! {
            @as_item
            $callback!{ $($args)* ($($out)*) }
        }
    };

    (
        @collect_unary_variants $fixed:tt,
        (#[$_attr:meta] $($tail:tt)*) -> ($($out:tt)*)
    ) => {
        enum_derive_util! {
            @collect_unary_variants $fixed,
            ($($tail)*) -> ($($out)*)
        }
    };

    (
        @collect_unary_variants $fixed:tt,
        ($var_name:ident($var_ty:ty), $($tail:tt)*) -> ($($out:tt)*)
    ) => {
        enum_derive_util! {
            @collect_unary_variants $fixed,
            ($($tail)*) -> ($($out)* $var_name($var_ty),)
        }
    };

    (
        @collect_unary_variants $fixed:tt,
        ($var_name:ident(pub $var_ty:ty), $($tail:tt)*) -> ($($out:tt)*)
    ) => {
        enum_derive_util! {
            @collect_unary_variants $fixed,
            ($($tail)*) -> ($($out)* $var_name($var_ty),)
        }
    };

    (
        @collect_unary_variants ($name:ident),
        ($var:ident $_struct:tt, $($tail:tt)*) -> ($($_out:tt)*)
    ) => {
        const _error: () = "cannot parse unary variants from enum with non-unary tuple variants";
    };
}