Allow top-level shadowing for imported names?

[Yitzchak Gale]

Yuras Shumovich wrote:
>> Can we generalize the proposal such that subsequent imports shadow
>> preceding ones?

Herbert Valerio Riedel wrote:
> ...iirc there is a different idea...
> allowing explicitly enumerated names...
> to shadow imports from other modules which didn't explicitly name the
> same import; effectively introducing a higher-priority scope for names
> imported explicitly.

Conversely - the original proposal should be modified to remain
an error, not a warning, when the symbol was imported explicitly
on an import list and then redefined locally at the top level.
This is equivalent to defining a symbol twice in the same scope.

Thanks,
Yitz