test_that("c.term", {
  expect_error(c(NA_term_, recursive = TRUE))
  expect_identical(
    c(NA_term_, "b", "a[1]", ""),
    c(NA, "b", "a[1]", "")
  )
  expect_identical(
    c(NA_character_, "b", "a[1]", ""),
    c(NA_character_, "b", "a[1]", "")
  )
})