Fix parsing of COLLATE after parentheses in expressions

[ghost]

Version 0.17.0 fails to parse COLLATE after an expression that's surrounded by parentheses, like (name) COLLATE "de_DE". This regression was introduced by da6a17b (#466), where an "early return" is used to return the parsed expression when the closing parenthesis isn't followed by a period, https://github.com/sqlparser-rs/sqlparser-rs/blob/4070f3ec6e616be6e9249f7202338e0f05969237/src/parser.rs#L521-L524 but this return causes the code which parses COLLATE https://github.com/sqlparser-rs/sqlparser-rs/blob/4070f3ec6e616be6e9249f7202338e0f05969237/src/parser.rs#L542-L549 to be skipped.

Replacing the early return with if-else fixes this regression, as verified by a test that I've added.

[alamb]

👍

alamb=# select (name) COLLATE "de_DE" from foo;
 name 
------
 a
 b
 c
 d
(4 rows)

[coveralls]

Pull Request Test Coverage Report for Build 2378293006

• 11 of 12 (91.67%) changed or added relevant lines in 2 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.004%) to 89.826%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/parser.rs	7	8	87.5%

Files with Coverage Reduction	New Missed Lines	%
src/parser.rs	1	83.0%

Totals
Change from base Build 2378120823:	0.004%
Covered Lines:	8326
Relevant Lines:	9269

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💛 - Coveralls