expand / expand_ can't handle illegal column names

[markriseley]

Expand breaks when column names contain illegal characters eg spaces. This is in contrast to dplyr which handles them just fine. Example code below:

df <- data_frame(x = 1:2, y = 1:2)
expand(df, x, y)  # succeeds
expand_(df, c("x","y"))  # succeeds
df2 <- data_frame(`x 1` = 1:2, `y 1` = 1:2)
expand(df2,`x 1`,`y 1`) # Error in parse(text = x)...
expand_(df2, c("x 1","y 1")) # Error in parse(text = x)...
expand_(df2, sapply(names(df2),as.name))  # Error in parse(text = x)...
count_(df2, sapply(names(df2),as.name))  # dplyr 'count_' succeeds

I think the culprit might be in unique_vals() in expand.R

unique_vals <- function(data, dots) {
    df <- dplyr::distinct(dplyr::select_(data, .dots = dots))
    dplyr::arrange_(df, .dots = names(df))
}

I'm not that up on how lazyeval works but should 'names(df)' be 'dots' in the above?
Alternatively how about 'sapply(names(df),as.name)' ?