PartiQL.g4 should be declared as a parser grammar

[kaby76]

Description

I maintain grammar-g4, the large library of Antlr4 grammars. Someone mentioned a problem with using the PartiQL grammar with the Go target. After looking at this grammar carefully, I highly recommend that you change the declaration statement of PartiQL.g4 to be parser grammar PartiQLParser;, and rename the file PartiQLParser.g4.

The problem is that PartiQL.g4 is a combined grammar, but you also declare a split grammar for the lexer, PartiQLTokens.g4. If someone adds a lexer rule, or a string literal to PartiQL.g4, a second lexer class will be generated. A parser can only reference one token stream at a time, which means it may not work as intended. Since PartiQL.g4 only contains parser rules, it should be declared as a parser grammar.

[RCHowell]

Thank you very much for this issue! This is super insightful and we appreciate the advice on maintaining better grammars.

[RCHowell]

This suggestion was merged in #1474