How to return subset of a record

Test.purs

module Test where 

import Prim.Row 
import Record as Record

type UpdateProps r
  = ( name :: String
    , purgeHistoryDays :: String
    , purgeImmediate :: String
    , forceRestartTime :: Int
    | r
    )


type UpdateResult r
  = ("@type" :: String | r)


x :: forall r r3 r4 props rest t. 
    Union props rest (UpdateProps r)
    => Union r3 t (UpdateResult props)
    => Nub (UpdateResult props) r3
    => { | props }
    -> { | r3 }
x rec = Record.merge {"@type": "hello"} rec

y :: forall r r3 r4 props rest t. 
    Union props rest (UpdateProps ())
    => { | props }
    -> String
y rec = "asdsa"
 -- How can I get the compiler to compile as long as the return value of this function returns a subset of UpdateProps??
z :: forall r r3 r4 props rest t. 
  Union props rest (UpdateProps ())
  => { | props }
  -> { | (UpdateResult props) }          
z rec = { "@type": "hello", name: ""  }