anchor.diff:      Assert.IsTrue ((x3.R2 = x1))
       Assert.IsTrue ((y3.R2 = x1))
    
  +
   [<Struct>]
   [<CustomComparison; CustomEquality>]
   type ComparisonStructRecord =
  
positive.code:         mutable M2: int
      }                  
      
  let [<Test>] ``can mutate struct record fields`` () =
      Check.QuickThrowOnFailure <|
      fun (i1:int) (i2:int) (m1:int) (m2:int) ->
  
negative.code:             ({ r1 with A = r1.B} <> r2) |@ "{r1 with A = r1.B} <> r2" .&.
              (r1.Equals r2)              |@ "r1.Equals r2"
  
  
  [<Struct>]
  type StructRecord =
      {   C: int
          D: int
      }
  
  
  let [<Test>] ``can compare struct records`` () =
      Check.QuickThrowOnFailure <|
  