layout.hs

module Layout (myLayoutHook) where

import XMonad.Layout
import XMonad.Layout.BinarySpacePartition
import XMonad.Layout.BorderResize
import XMonad.Layout.NoBorders
import XMonad.Layout.ResizableTile
import XMonad.Layout.Spacing
import XMonad.Layout.ThreeColumns

myLayoutHook = threeCol ||| bsp
  where          
    threeCol = withBorders  $ ThreeColMid 1 (2/100) (1/2)
    bsp      = withBorders' $ borderResize emptyBSP

    withBorders  = smartBorders . defaultSpacing 4
    withBorders' = smartBorders . defaultSpacing 4 -- both layouts using the same withBorders function causes a type error
    
    defaultSpacing i = spacingRaw True (uniformBorder i) True (uniformBorder i) True
    uniformBorder i = Border i i i i

This compiles for me:

{-# LANGUAGE NoMonomorphismRestriction #-}
{-# LANGUAGE FlexibleContexts #-}
module Layout (myLayoutHook) where

import XMonad
import XMonad.Layout
import XMonad.Layout.BinarySpacePartition
import XMonad.Layout.BorderResize
import XMonad.Layout.NoBorders
import XMonad.Layout.ResizableTile
import XMonad.Layout.Spacing
import XMonad.Layout.ThreeColumns

myLayoutHook = threeCol ||| bsp
  where
    threeCol = withBorders $ ThreeColMid 1 (2/100) (1/2)
    bsp      = withBorders $ borderResize emptyBSP

    withBorders = smartBorders . defaultSpacing 4

    defaultSpacing i = spacingRaw True (uniformBorder i) True (uniformBorder i) True
    uniformBorder i = Border i i i i

There's more to the file, so these line numbers are off, but here's the type error:

    • Couldn't match type ‘XMonad.Layout.LayoutModifier.ModifiedLayout
                             BorderResize BinarySpacePartition’
                     with ‘ThreeCol’
      Expected type: XMonad.Layout.LayoutModifier.ModifiedLayout
                       BorderResize BinarySpacePartition Graphics.X11.Types.Window
        Actual type: ThreeCol Graphics.X11.Types.Window
    • In the second argument of ‘($)’, namely
        ‘ThreeColMid 1 (2 / 100) (1 / 2)’
      In the expression: withBorders $ ThreeColMid 1 (2 / 100) (1 / 2)
      In an equation for ‘threeCol’:
          threeCol = withBorders $ ThreeColMid 1 (2 / 100) (1 / 2)
   |
45 |     threeCol = withBorders $ ThreeColMid 1 (2/100) (1/2)
   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^