Creates parser that uses wrong fieldname when referencing field causing CS1001

[mrt181]

• I have reproduced my issue using the latest version of ANTLR
• I have asked at github
• Responses from the above seem to indicate that my issue could be an ANTLR bug
• I have done a search of the existing issues to make sure I'm not sending in a duplicate

I am using this file (had to add .txt to it to upload it here):
SqlBase.g4.txt

This creates the SqlBaseParser with Error CS1001 : Identifier expected on line 7895.

	((DereferenceContext)_localctx).base = _prevctx;

The field that should be referenced is on line 7097

	public PrimaryExpressionContext @base;

Updating line 7895 to @base fixes the compile error.
Updating the grammer file to use base_ instead of base fixes the compile error. (kaby76/Antlr4BuildTasks#81)

[ericvergnaud]

Hi, thanks for this.
I prefer the latter because it's simpler, but it does end up increasing the set of forbidden keywords, notably when targeting multiple languages.