Function boolean

Creates a boolean shape.

Admits true and false and nothing else, closed to the single enumerated value where the constraints state one; the domain is closed by the kind alone, so the constraints cannot be contradictory.

Creates a boolean shape admitting a single value.

Reads a bare truth value as the enumeration closing the domain to it, so that a tag telling the alternatives of a union apart is stated as boolean(true) rather than as boolean({ in: true }).