How to use Table Aliases?

[richb-hanover]

I would like to use (I think they're called) Table Aliases to simplify code. That is, I would like to use:

from l=TableA
join r=TableB [==Col1]
select [
  l.Col1,
  r.Col1,
]
filter [l.Col1 != r.Col1]

• If I use this form, the Playground gives an error: Unknown name l.Col1 in the filter expression.

• If I move the filter between the join and select, I get a long Cannot lower to IR expr:... message.

What am I missing? Thanks.

[max-sixty]

Good find, this looks like quite a bad bug. Moving to an issue: #1253