Macro swc_common::make_impl_block

macro_rules! make_impl_block {
    (
        @NAME,
        Done {
            $($done:tt)*
        },

        $(#[$attr:meta])*
        $name:ident:

        $($rest:tt)+
    ) => { ... };
    (
        @VALUE,
        Cur {
            $($cur:tt)+
        },
        Done {
            $($done:tt)*
        },

        ,

        $($rest:tt)*
    ) => { ... };
    (
        @VALUE,
        Cur {
            $($cur:tt)*
        },
        Done {
            $($done:tt)*
        },

        $tok:tt

        $($rest:tt)+
    ) => { ... };
    (
        @VALUE,
        Cur {
            $($cur:tt)*
        },
        Done {
            $($done:tt)*
        },

        $tok:tt
    ) => { ... };
    (
        @NAME,
        Done {
            $STRUCT:ident;
            $(
                $(#[$attr:meta])*
                $name:ident: ( $($val:tt)* ),
            )*
        },
    ) => { ... };
}

Create a impl block with some bitflags.