Macro agnes::Fields

macro_rules! Fields {
    (@fields()) => { ... };
    (@fields(
        $label:ident: $dtype:ident $(= $name:expr)*,
        $($rest_label:ident: $rest_dtype:ident $(= $rest_name:expr)*,)*)
    ) => { ... };
    ($($label:ident: $dtype:ident $(= $name:expr)*),*$(,)*) => { ... };
    ($existing:ident .. $($label:ident: $dtype:ident),*$(,)*) => { ... };
    ($($label:ident: $dtype:ident),*$(,)* .. $existing:ident) => { ... };
}

Create a FieldCons cons-list based on a list of provided labels and data types. Used by tablespace macro.