Macro impl_fast_iter_print_tuple 

macro_rules! impl_fast_iter_print_tuple {
    (@impl) => { ... };
    (@impl $T:ident $v:ident $($U:ident $u:ident)*) => { ... };
    (@inner [$($T:ident $v:ident)*] $U:ident $u:ident $($Rest:tt)*) => { ... };
    (@inner [$($T:ident $v:ident)*]) => { ... };
    ($($t:tt)*) => { ... };
}