Macro seq_impl 

macro_rules! seq_impl {
    (
        $ty:ident < T $(: $tbound1:ident $(+ $tbound2:ident)*)? $(, $typaram:ident : $bound1:ident $(+ $bound2:ident)* )* >,
        $with_capacity:expr,
        $append:ident
    ) => { ... };
}