Syntax: Keywords

var declares nothing: it is reserved only so that writing it gives a clear message pointing to let. A few more words, such as result in a contract, are keywords only in one place and ordinary names everywhere else.

A keyword can't name a field either: the field could never be read, since r.agent can't be written.

type Robot {
    agent: String
}

fn main() {
    print("never runs")
}

error: `agent` is a keyword, so it can't name a field: pick another name