test <- function() {
  "Double quotes remain as they are"
  "Single quotes are converted to double quotes"
  "even if the string contains an escaped ' single quote"
  'but not if it contains a "double quote'

  "multi-line quotes
  remain multi-line
  "

  "That also holds true
  if
  single quotes are used
  ."

  "strings with embedded\nline breaks are handled correctly"

  "\\"
  "\\'"
  "\\\\"
  "\\\\'"
  "'\\\\'"

  # Comments are always preserved

  function_calls(get_spaces = around_equal)

  no_space(after_opening(), paren((1 + 2)))
  no_space (before_opening (), paren ((1 + 2)))
  no_space(before(closing), paren((1 + 2)))
  multi(
    line,
    call
  )
  multi_line_empty_call()

  one_space(after, comma("in", "function",  args))

  {
    braced
    expression
  }

  braced("unnamed", {
    "function"
    call
  })

  braced(named = {
    "function"
    call
  })

  braced("unnamed reduces space",    {
  })

  braced("unnamed adds space space", {
  })

  braced(named_reduces_space =    {
  })

  braced(named_adds_space =    {
  })

  braced({
    empty_removes_space
  })

  a %/% b
  a %% b
  a && b
  a || b
  a == b
  a != b
  a <= b
  a >= b
  a <- b
  a -> b
  a <- b
  a < b
  a > b
  a * b
  a / b
  a^b
  a & b
  a | b
  a := b

  a + b
  a - b
  a + +b
  a + -b
  a + +b
  a - +b
  a - -b
  a + --b
  a - -+b
  call(+a)
  call(-a)
  call(5, +a)
  call(5, -a)

  # Only with conservative settings:
  call(
    preserves, distance,
    after,     commas,
    given_has, one
  )

  if (TRUE) {
    FALSE
  }

  if (TRUE) {
    FALSE
  } else {
    TRUE
  }

  while (TRUE) {
    FALSE
  }

  single_line ("function", call)

  multiline (
    "function", call)

  nested (function_call ("in", one, line))

  nested (function_call (
    "in",
    multiple, lines))

  nested(
    function_call (with),
    many,
    first_level_args)

  nested(
    function_call (with),  # a comment and
    many # more
    ,     first_level_args)

  difficult(nested(
    "function", call
  ),
  with, more, args
  )
}


# formula
lm(a ~ b + c, data = NA)
lm(a ~ . - 1, data = NA)
a ~ b:c
a ~ b:c
a   ~   b:c

~a
~gg
b ~   k
call(1, ~qq)