code: protected boolean isErrorToken(Token token) {
  		String tokenTypeName = tokenDefProvider.getTokenDefMap().get(token.getType());
  		return "RULE_ANY_OTHER".equals(tokenTypeName);			
  	}
docs: Return <code>true</code> if the token should be considered to be an error token.
  If the token that is created from the prefix before the cursor position is an error
  token, no proposals shall be computed that don't use a prefix.
  @return <code>true</true> if the token should be considered to be an error token.