Macro match_each_list_builder 

macro_rules! match_each_list_builder {
    ($dyn_builder:expr, | $builder:ident | $body:expr) => { ... };
}

Matches a &mut dyn ArrayBuilder against every concrete list builder type, i.e. every ListBuilder<O> and ListViewBuilder<O, S> instantiation over the OffsetBuilderPType offset/size types (u32, u64, i32, i64).

Binds the downcast builder as $builder and evaluates $body with it, yielding Some($body); yields None when the builder is not a list builder. List encodings dispatch through this matcher because the concrete list builders are generic over their offset/size integer types, which cannot be named through a dyn ArrayBuilder. The matcher is exhaustive because OffsetBuilderPType is sealed, so no other instantiations can be constructed.