Extra parentheses causing DQL errors?

[mpdude]

Q	A
Version	2.19.5

I noticed today that in some places, the DQL parser can be picky about extra parentheses used around expressions.

For example, the following is a working query:

SELECT CONCAT(CASE s.id WHEN 1 THEN 'foo' WHEN 2 THEN 'bar' ELSE 'baz' END, 'suffix') FROM Something s

... but adding extra parentheses around the case expression (for better readability) makes it invalid:

SELECT CONCAT((CASE s.id WHEN 1 THEN 'foo' WHEN 2 THEN 'bar' ELSE 'baz' END), 'suffix') FROM Something s

[Syntax Error] line 0, col 14: Error: Expected StateFieldPathExpression | string | InputParameter | FunctionsReturningStrings | AggregateExpression, got '('

This led me to believe that maybe I should be careful about parentheses in general, but both of the following are OK:

SELECT 'bar' FROM Something s
SELECT ('bar') FROM Something s

... but not e. g. within a CONCAT expression:

SELECT CONCAT('foo', ('bar')) FROM Something s (fails)

All corresponding constructs are valid in SQL, and I always just assumed (without thinking deeper about it) that extra parentheses should not pose a problem.

Did I miss something, or is this just a glitch in the grammar/parser 🤪?