//! A derived type nothing reads, kept runnable so the `Default` claim in
//! docs/derive.md cannot quietly stop being true.
//!
//! `Reading` derives no `Default`, and it does not need one: the program only
//! ever writes it. The region between the markers below *is* the version in
//! docs/derive.md; `docs_quote_the_example_verbatim` in tests/docs.rs fails if
//! the two stop matching.
//!
//! `cargo run --example derive --features derive`
// docs:begin
// docs:end