Array.groupBy unexpected behavior

Main.purs

module Main where

import Prelude

import Data.Array as A
import Effect (Effect)
import Effect.Class.Console (log)
import TryPureScript as TryPureScript
import Debug (spy)

main :: Effect Unit
main = TryPureScript.render =<< TryPureScript.withConsole do
  log $ show $ useGroupBy

useGroupBy = [0, 1, 2, 3]
  # spy "original Array"
  # A.groupBy (\l r -> do
    let _ = spy "l" l
    let _ = spy "r" r
    l + 1 == r
  )
  # spy "post groupBy"

-- Check the web console to see the values of `l` and `r`