> df <- tibble(x = 0L, y = 0.5, z = 1)

colwise rename()
================

> df %>% rename_all()
Error: `.funs` must specify a renaming function.

> df %>% rename_if(is_integerish)
Error: `.funs` must specify a renaming function.

> df %>% rename_at(vars(x:y))
Error: `.funs` must specify a renaming function.

> df %>% rename_all(list(tolower, toupper))
Error: `.funs` must contain one renaming function, not 2.


colwise select() 
=================

> df %>% select_all(list(tolower, toupper))
Error: `.funs` must contain one renaming function, not 2.

> df %>% select_if(function(.x) 1)
Error: `.p` is invalid.
x `.p` should return a single logical.
i `.p` returns a <double> for column `x`.

> df %>% select_if(function(.x) c(TRUE, TRUE))
Error: `.p` is invalid.
x `.p` should return a single logical.
i `.p` returns a size 2 <logical> for column `x`.

