> ui_line("line")
Message: line

> ui_todo("to do")
Message: * to do

> ui_done("done")
Message: v done

> ui_oops("oops")
Message: x oops

> ui_info("info")
Message: i info

> ui_code_block(c("x <- 1", "y <- 2"))
Message:   x <- 1
  y <- 2

> ui_stop("an error")
Error: an error

> ui_warn("a warning")
Warning: a warning

