Suggestion: improve error message on wrong use of scale_x_datetime

[adisarid]

The following code yields an error message

date_issues <- tibble(dates = lubridate::ymd(c("2019-09-19", "2019-09-20", "2019-09-21")), values = 1:3)

ggplot(date_issues, aes(x = dates, y = values)) + 
   geom_line() + 
   scale_x_datetime(date_minor_breaks = "1 day")

The error is:

Error: Invalid input: time_trans works with objects of class POSIXct only

The reason is that we are using the wrong scale function. We should be using scale_x_date instead of scale_x_datetime.

A "suggestion flavored" error message would help the user understand and fix the issue. E.g.:

Error: Invalid input: time_trans works with objects of class POSIXct only. 
   Did you consider using scale_x_date() instead of scale_x_datetime()?

[lazappi]

I have had a go at doing this in a branch here https://github.com/lazappi/ggplot2/tree/issue-3533. My solution was to catch the error in ScaleContinuous and modify the message.

https://github.com/lazappi/ggplot2/blob/6c1fde5f2977002c6fe06c07192f02cfd8f5bd56/R/scale-.r#L552-L561

I could submit this as a pull request but not sure what the developers think of the solution? My main concern is that if the error occurs for some other reason then the new message won't be appropriate.