import with

type
  Bob = object
    y: int
  Test = object
    x: Bob

proc `$`(x: Bob): string =
  "Bob[" & $x.y & "]"

# This could be defined by a user, or it could be absent
#proc toHtml(x: Bob): string =
#  $x.y

proc toCss(x: Bob): string =
  "(This is CSS: " & $x.y & ")"

# This would be automatically generated by autotemplate
proc toHtml(x: Test): string =
  proc tt(x: auto): string =
    when compiles(toHtml(x)):
      toHtml(x)
    else:
      $x
  proc `$`(x: auto): string =
    tt(x)
  with x:
    "Hello: " & $x & " world"

proc toCss(x: Test): string =
  proc tt(x: auto): string =
    when compiles(toCss(x)):
      toCss(x)
    else:
      $x
  proc `$`(x: auto): string =
    tt(x)
  with x:
    "Hello: " & $x & " world"

echo Test(x: Bob(y: 42)).toHtml # This should output: Hello: Bob[42] world
echo Test(x: Bob(y: 42)).toCss # This should output: Hello: (This is CSS: 42) world