performance_cv() fails with method = "loo" (object ‘test_resd’ not found)

[ManuelSpinola]

When using the performance_cv() function with method = "loo" on a linear model, the function throws an error indicating that the object test_resd is not found.

model <- lm(mpg ~ wt + cyl, data = mtcars)

performance_cv(model, method = "loo")
Error in performance_cv(model, method = "loo") :
object 'test_resd' not found

[mattansb]

This error is due to this orphan expression:

performance/R/performance_cv.R

Line 93 in a6dcc28

mean(test_resd^2, na.rm = TRUE)

However, removing it raises another unrelated error. @bwiernik can you try and figure this one out? Seems the loo method is untested.

[bwiernik]

Will try to take a look