ANTLR Warning suppression workaround

On p.285 of the ANTLR book it implies that you cannot suppress warnings in ANTLR v3 like you could in v2.

However, it appears that a semantic predicate works nicely as a workaround:

// Strings
SQ_STRING: '\''! ({true}? ESC_SEQ | ~'\'')* '\''!;
DQ_STRING: '"'!  ({true}? ESC_SEQ | ~'"')* '"'!;
BQ_STRING: '`'!  ({true}? ESC_SEQ | ~'`')* '`'!;
fragment ESC_SEQ: '\\' ~('\n'|'\r');

The generated code now contains LL(2) lookahead for no reason, and some redundant code. For example, code that originally read

   if ( (LA19_0 == '\"') )
  {
     alt19 = 1;
  }

Now says

   if ( (LA19_0 == '\"') )
  {
     int LA19_1 = input.LA(2);
     if ( (true) )
     {
         alt19 = 1;
     }
  }

However, its behavior appears to be the same.

The compiler will emit some "unreachable code" warnings. In C# you can disable them like this:

grammar Expr;
options {
  language=CSharp;
}
@lexer::members {
  #pragma warning disable 0162
}
@parser::members {
  #pragma warning disable 0162
}