tsql: code corruption alias removed L025

[fmms]

Search before asking

• I searched the issues and found no similar issues.

What Happened

I have the following query

SELECT * FROM (
        SELECT col FROM dbo.tab
        UNION
        SELECT -1 AS col
) AS a

I tried to format that.

Expected Behaviour

Query is formatted and still executable.

Observed Behaviour

Query broken.

How to reproduce

PS > cat .\sqlfluff-9.config
[sqlfluff]
dialect = tsql
templater = raw
PS > cat .\sqlfluff-9.sql
SELECT * FROM (
        SELECT col FROM dbo.tab
        UNION
        SELECT -1 AS col
) AS a
PS > sqlfluff fix .\sqlfluff-9.sql --config .\sqlfluff-9.config
==== finding fixable violations ====
== [sqlfluff-9.sql] FAIL
L:   5 | P:   6 | L025 | Alias 'a' is never used in SELECT statement.
==== fixing violations ====
1 fixable linting violations found
Are you sure you wish to attempt to fix these? [Y/n]

Dialect

tsql

Version

current git

Configuration

see above

Are you willing to work on and submit a PR to address the issue?

• Yes I am willing to submit a PR!

Code of Conduct

• I agree to follow this project's Code of Conduct

[barrywhart]

Got it -- I bet I need to check for a different segment type, because using UNION wraps the select_statement in a surrounding segment type. I can probably fix it this morning, not sure if I can get a reviewer before we release 1.1.0 today.