Derive Macro TryFromList 

#[derive(TryFromList)]
{
    // Attributes available to this derive:
    #[into_list]
}

Derive TryFromList for a struct (R list → Rust).

• Named structs: extract by field name. A field whose name appears more than once in the list is an error (SexpError::DuplicateName), since the struct could keep only one of the values; other names, repeated or not, are ignored.
• Tuple structs: extract by position (0, 1, 2, …)
• Fields annotated #[into_list(ignore)] are not read and are initialized with Default::default(), so their types must be Default