> df %>% distinct(aa, x)
Error: `distinct()` must use existing variables.
x `aa` not found in `.data`.

> df %>% distinct(aa, bb)
Error: `distinct()` must use existing variables.
x `aa` not found in `.data`.
x `bb` not found in `.data`.

> df %>% distinct(.data$aa)
Error: `distinct()` must use existing variables.
x `aa` not found in `.data`.

