Macro do_expand_alias

macro_rules! do_expand_alias {
    ($array:ty, $variant_name:ident, (
        $(Array, $array_alias:ident,)?
        $(ArrayBuilder, $array_builder_alias:ident,)?
        $(Scalar, $scalar_alias:ident,)?
        $(ScalarRef, $scalar_ref_alias:ident,)?
        $(VARIANT_NAME, $variant_name_alias:ident,)?
    )) => { ... };
}

Helper macro for expanding type aliases and constants. Internally used by dispatch_ macros.