> 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`.

> df %>% distinct(y = a + 1)
Error: Problem adding computed columns in `distinct()`.
x Problem with `mutate()` input `y`.
x object 'a' not found
i Input `y` is `a + 1`.

