Xsd Choice is interpreted as Option<> * Option<_>.....

[MarkNicholls]

This has been noted many years ago with JSON, I assume that does the same thing.

type RawXml3 = XmlProvider<Schema = """
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
	<xs:complexType name="rootType">
		<xs:sequence>
			<xs:element name="vehicle">
				<xs:complexType>
					<xs:choice>
						<xs:element name="CAR"/>
						<xs:element name="BICYCLE"/>
					</xs:choice>
				</xs:complexType>
			</xs:element>
		</xs:sequence>
	</xs:complexType>
	
	<xs:element name="ROOT" type="rootType">
	</xs:element>
</xs:schema>""">

let t = RawXml3.Parse "file.xml"

match t.Vehicle.Bicycle, t.Vehicle.Car with
| Some bike, None -> 
    printfn "a bike"
| None, Some car -> 
    printfn "a car"
| None, None -> 
    printfn "not allowed"
| Some _ , Some _ -> 
    printfn "not allowed"

Not the end of the world, but not ideal, we have a state space that allows None * None and Some _ * Some _, both of which are illegal.

is there some way to turn on choice?

(The situation with multiple choices values is I think slightly worse because it maps to Car[] and Bicycle[], rather than Choice<Car,Bicycle>[], so I assume it destroys the relative ordering of Cars and Bicycles e.g.

<Car/>
<Bicycle/>
<Car/>

and

<Car/>
<Car/>
<Bicycle/>

will be indistinguishable, rarely an issue, but some XML is order sensitive)