Scoped rules builder

RulesBuilder.fs

type ScopeAndRules = | ScopeAndRules of string * int list

type RulesBuilder() =
    member x.Yield(v) = []
    [<CustomOperation("scope", MaintainsVariableSpace=true)>]
    member x.Scope(source, scope) = ScopeAndRules(scope, []) :: source
    [<CustomOperation("rule", MaintainsVariableSpace=true)>]
    member x.Rule(source, rule) =
        match source with
        | ScopeAndRules(scope, rules) :: tail -> ScopeAndRules(scope, rule :: rules) :: tail
        | _ -> failwith "You need to defian a scope before adding a rule"
    member x.Run(source) =
        source
        |> List.rev 
        |> List.map (fun (ScopeAndRules(s, r)) ->  s, (List.rev r))

 
let rules = new RulesBuilder()

let x = rules {

    scope "test"
    rule 1
    rule 2

    scope "test2"
    rule 3
    rule 4

}

module myFirm
    open xxx;

    [<FirmRules("FirmId")>]
    let rules = rules {
        scope "test"
        rule 1
        rule 2

        scope "test2"
        rule 3
        rule 4
    }