separate_wider_delim changes input column names when using names_sep with cols_remove=FALSE

[markpurver]

The separate_wider_delim function changes the input column names from cols to strrep(cols, 2) when you use names_sep with cols_remove=FALSE, e.g. column "a" becomes column "aa".

separate_wider_delim(tibble(a="x y"), cols=a, delim=" ", names_sep="", cols_remove=FALSE)

[sda030]

Duplicate of #1499