[Python] System.DateTime.Substract not correctly transpiled

[Freymaurer]

Description

I want to use the Substract member on System.DateTime and noticed that it is transpiled to subtract and imported by from fable_modules.fable_library.date import (now, subtract). If i go into this file i can find the following code, which seems right:

# fable_modules.fable_library.date
def op_subtraction(x: datetime, y: datetime) -> TimeSpan:
    delta = x - y
    # ts.microseconds only contains the microseconds provided to the constructor
    # so we need to calculate the total microseconds ourselves
    delta_microseconds = delta.days * (24 * 3600) + delta.seconds * 10**6 + delta.microseconds
    return create_time_span(0, 0, 0, 0, 0, delta_microseconds)

So my guess is it should be transpiled to op_subtraction, instead of subtract.

Repro code

#r "nuget: Fable.Core, 4.2.0"

open Fable.Core
open System

[<AttachMembersAttribute>]
type Stopwatch() =
  member val StartTime: DateTime option = None with get, set
  member val StopTime: DateTime option = None with get, set
  member this.Start() = this.StartTime <- Some DateTime.Now
  member this.Stop() = 
    match this.StartTime with
    | Some _ -> this.StopTime <- Some DateTime.Now
    | None -> failwith "Error. Unable to call `Stop` before `Start`."
  member this.Elapsed = 
    match this.StartTime, this.StopTime with
    | Some start, Some stop -> stop.Subtract(start)
    | _, _ -> failwith "Error. Unable to call `Elapsed` without calling `Start` and `Stop` before."

let testFunc() = 
  let stopwatch = new Stopwatch()
  stopwatch.Start()
  System.Threading.Thread.Sleep(2000)
  stopwatch.Stop()
  stopwatch.Elapsed

testFunc().ToString() |> printfn "%s"

Related information

• Fable version: 4.6.0

[Freymaurer]

I just saw, that i can use stop - start instead!

member this.Elapsed = 
    match this.StartTime, this.StopTime with
    | Some start, Some stop -> stop - start // this
    | _, _ -> failwith "Error. Unable to call `Elapsed` without calling `Start` and `Stop` before."