Expected 'AS' in alias when SELECT

[Catwoolfii]

I'm just starting to try Proton and maybe I'm missing something or misunderstanding something.
I'm trying to run a request with pseudocode and getting an exception. This behavior is not reproduced in any version of Clickhouse.

How to reproduce

1. Executing a query:
   SELECT x.* FROM (SELECT 'test' name) x

When executing query following exception is received:

Syntax error: failed at position 32 ('name'):

SELECT x.* FROM (SELECT 'test' name) x

Expected one of: NOT, BETWEEN, IS, AS, FROM, WHERE, PARTITION BY, SHUFFLE BY, GROUP BY, WITH, HAVING, WINDOW, ORDER BY, LIMIT, EMIT, SETTINGS, UNION

2. Executing a query when an alias is created with the 'AS' keyword:
   SELECT x.* FROM (SELECT 'test' AS name) AS x

When executing query following output is received:

┌─name─┐
│ test │
└──────┘

1 row in set. Elapsed: 0.001 sec.

Additional context
I expect that such queries should be executed without exceptions, since the keyword 'AS' is optional.

[Sake169]

yes, it may need an enhancement, i tried the clickhouse in the same query, it can work well,

[yl-lisen]

Thank you for your experience @Catwoolfii .
For some reasons, we must use explicit aliases for tables via AS keyword.
Usually, we always recommend using AS to define aliases everywhere, which is more understandable.