How to use a data variable to name a new column name with tidy eval

tidy-eval-dynamic-colname.R

library(tidyverse)
f <- function(dat, colname) {
    varname <- rlang::as_name(rlang::enquo(colname))
    new_df <- data.frame(x = c('a','b','c')) %>%
        mutate({{varname}} := dat %>% pull({{ colname }}))
    return(new_df)
}

df1 <- data.frame(a = 1:3, b = 4:6)
df1 %>% f(a)
df1 %>% f(b)