dplyr problem when using comment()

[jdlng]

dplyr seems to have a problem when I use comment() to describe my variables:

test <- data.frame(A = c(1,1,0,0), B = c(2,2,3,3))
summarise(group_by(test, A), mean(B))
Source: local data frame [2 x 2]

A mean(B)
1 0 3
2 1 2

comment(test$B) <- "2nd Var"
summarise(group_by(test, A), mean(B))

Error: column 'B' has unsupported type