// *** before: ***
fn parse(_input: &str) -> Value {
unimplemented!() // one word for "not yet" and for "never will be"
}
// *** in version 1.40: ***
fn parse(_input: &str) -> Value {
todo!() // says it plainly: the place is taken, the work is ahead
}
fn describe(_v: &Value) -> String {
unimplemented!("this type will never get a description")
}