[bug] line move and truncation

[Lars Hansen]

With Emacs of today, do
  emacs --no-site-file --no-init-file --eval=(setq-default 
truncate-lines t)
Open a file with long lines. (You may open files.el and search for 
read-directory-names).
With point on a truncated line, hit down-arrow (or C-n if you prefer that).
Then point will move down two lines (as if lines were wrapped rather 
than truncated).
Nothing seems to be wrong when you move upwards.