ParserAlias ignores backticks whaen checking for restricted keywords

[zhicwu]

Is the behavior below expected? Looks like SQL parsing issue? select null `tuple` works but select null `array` won't, unless as is used explicitly.

$ clickhouse-client
ClickHouse client version 23.3.2.37 (official build).
Connecting to localhost:9000 as user default.
Connected to ClickHouse server version 23.3.2 revision 54462.

ch-server :) select range(1,2) `array`

Syntax error: failed at position 19 ('`array`'):

select range(1,2) `array`

Expected one of: token, OpeningRoundBracket, FILTER, OVER, OR, AND, BETWEEN, NOT BETWEEN, LIKE, ILIKE, NOT LIKE, NOT ILIKE, REGEXP, IN, NOT IN, GLOBAL IN, GLOBAL NOT IN, MOD, DIV, IS NULL, IS NOT NULL, alias, AS, identifier, Comma, FROM, PREWHERE, WHERE, GROUP BY, WITH, HAVING, WINDOW, ORDER BY, LIMIT, OFFSET, SETTINGS, UNION, EXCEPT, INTERSECT, INTO OUTFILE, FORMAT, end of query

ch-server :) select range(1,2) as `array`

SELECT range(1, 2) AS array

Query id: 19ea4aa4-80ee-4dc2-9b9b-d6329d86bfa5

┌─array─┐
│ [1]   │
└───────┘

1 row in set. Elapsed: 0.004 sec. 

[tavplubix]

Looks like it's because ARRAY is a restricted keyword (TUPLE is not) and ParserAlias::parseImpl ignores backticks (it should not):

ClickHouse/src/Parsers/ExpressionElementParsers.cpp

Lines 1425 to 1446 in f0b514a

	ParserKeyword s_as("AS");
	ParserIdentifier id_p;
	bool has_as_word = s_as.ignore(pos, expected);
	if (!allow_alias_without_as_keyword && !has_as_word)
	return false;
	if (!id_p.parse(pos, node, expected))
	return false;
	if (!has_as_word)
	{
	/** In this case, the alias can not match the keyword -
	* so that in the query "SELECT x FROM t", the word FROM was not considered an alias,
	* and in the query "SELECT x FR FROM t", the word FR was considered an alias.
	*/
	const String name = getIdentifierName(node);
	for (const char ** keyword = restricted_keywords; *keyword != nullptr; ++keyword)
	if (0 == strcasecmp(name.data(), *keyword))
	return false;