Macro iterator_wrap 

macro_rules! iterator_wrap {
    (impl () for
    struct $name: ident <$($typarm:tt),*> where { $($bounds: tt)* }
     item: $item: ty,
     iter: $iter: ty,
     ) => { ... };
    (
    impl (Iterator $($rest:tt)*)  for
    $(#[$derive:meta])*
     struct $name: ident <$($typarm:tt),*> where { $($bounds: tt)* }
     item: $item: ty,
     iter: $iter: ty,
     ) => { ... };
    (
impl (ExactSizeIterator $($rest:tt)*)  for
    $(#[$derive:meta])*
     struct $name: ident <$($typarm:tt),*> where { $($bounds: tt)* }
     item: $item: ty,
     iter: $iter: ty,
     ) => { ... };
    (
impl (DoubleEndedIterator $($rest:tt)*)  for
    $(#[$derive:meta])*
     struct $name: ident <$($typarm:tt),*> where { $($bounds: tt)* }
     item: $item: ty,
     iter: $iter: ty,
     ) => { ... };
}