lang/rust doesn't play nice with portupgrade -a and probably pkg

[John]

Hi,

I periodically use portupgrade -a to upgrade the ports (after checking
UPDATING) and it upgrades practically all ports painlessly. But for the
last 6 months or so, the upgrade of rust always bails saying it can't
upgrade for example) to 1_0_10 because 1_0_9 is already installed. But 
with every other port, increments in version are handled by
pkg/portupgrade.

wish I had the full error output, I'll save it the next time it happens.
In the meantime, can anyone clue me in as to what's happening?

thanks,
-- 
  John
  tech-lists at zyxst.net