Optimization applied for polymorphic variants, but not for regular variants

[cknitt]

The following ReScript code

type status1 = OPEN | CLOSED

let isOpen1 = (status: status1) =>
  switch status {
  | OPEN => true
  | CLOSED => false
  }

type status2 = [#OPEN | #CLOSED]

let isOpen2 = (status: status2) =>
  switch status {
  | #OPEN => true
  | #CLOSED => false
  }

creates the following JS output:

function isOpen1(status) {
  if (status === "OPEN") {
    return true;
  } else {
    return false;
  }
}

function isOpen2(status) {
  return status === "OPEN";
}

So there is some optimization applied for polymorphic variants that is not applied for normal variants.

https://rescript-lang.org/try?version=v11.1.0&code=C4TwDgpgBAzsCGwCuMByB7ATgW3gGwDV5MBLeAO2CgF4oB5ABQFFUoAfKAYQBk6BlJgBEAUMLwQqJGHUjkMOfEVIUqtABRxEKAFywEyNFlyFiZSgEoaAPmFRYAdxLAAxgAs9WmFADet9vWZWaisoYEwkCD8OHn4haygAM3wYSLsAX1FQSA8DBnQ8EGwsMFcSZyUzVSgAbQBiRhZ-WpiBQQBdUXFJaVk8gqLMErKKlRooDX0dHJQ+wuLS8tMVS2C-GEcXd00DHyioesD4sIi95t5W+KS8FL8MoA

[cristianoc]

One produces an if and the other produces a switch.
One could consider finding where the if optimisation is applied, and port it to the other case as well.
Perhaps the conversion of switch to if happens too later for the normal if optimisation to apply or something.

./bsc -drawlambda tst.res

(let
  (isOpen1/1004 =
     (#fn_mk
       (function status/1005
         (switch* status/1005 case int 0: true
                              case int 1: false)))
   isOpen2/1007 =
     (#fn_mk
       (function status/1008 (if (== status/1008 880069578a) true false))))
  (makeblock module/exports isOpen1/1004 isOpen2/1007))