A disjunction, or sum type, defines a constraint consisting of two or more options that are allowed.

The disjunction’s options are values called its elements. They are written separated by the pipe symbol (|).

A disjunction allows values that unify successfully with at least one of its elements. When a value constrained by a disjunction is exported it must unify successfully with only one of the disjunction’s elements.

#Conn: {
	address:  string
	port:     int
	protocol: "tcp" | "udp" | "sctp" | "dccp"
}

lossy: #Conn & {
	address:  "203.0.113.42"
	port:     8888
	protocol: "udp" // acceptable value
}
error: #Conn & {
	address:  "203.0.113.42"
	port:     8888
	protocol: "IP" // invalid value
}

$ cue eval -ic file.cue
lossy: {
    address:  "203.0.113.42"
    port:     8888
    protocol: "udp"
}
error: {
    address:  "203.0.113.42"
    port:     8888
    protocol: _|_ // error.protocol: 4 errors in empty disjunction: (and 4 more errors)
}