SQL is parsed incorrectly when `trailing_commas` is not set

[Taylor-lagrange]

When parser not set trailing_commas=true in ParserOptions or use BigQueryDialect, the following SQL will be wrongly parse instead of throw an error.

SELECT foo, bar, FROM baz

-- Will be wrongly parse instead of throw an error.

SELECT foo, bar, FROM AS baz

In theory it should throw a error

relevant code

#[test]
fn parse_range_select() {
    let statements = Parser::parse_sql(&GenericDialect {}, "SELECT foo, bar, FROM baz").unwrap();
    println!("{}", statements[0]);
}

[Taylor-lagrange]

Maybe we should detect keyword in parse_comma_separated even if trailing_commas is not set

[alamb]

Maybe @ankrgyl has some comments about this (I believe he added support for trailing_commas)

[ankrgyl]

Sounds like it may be a bug in the trailing_commas logic!

[Taylor-lagrange]

May be we should add a else branch in Parser::parse_comma_separated. If trailing commas are not allowed, an error will be reported if commas followed by keywords.

[LucaCappelletti94]

Completed by #1212, SELECT foo, bar, FROM baz now fails with Expected an expression, found: FROM in dialects without trailing-comma support. GenericDialect accepts it on purpose since #1921 turned on supports_projection_trailing_commas.