@Override
		public SemanticContext evalPrecedence(Recognizer<?, ?> parser, RuleContext parserCallStack) {
			if (parser.precpred(parserCallStack, precedence)) {
				return Empty.Instance;
			}
			else {
				return null;
			}
		}
The default {@link SemanticContext}, which is semantically equivalent to
a predicate of the form {@code {true}?}.
runtime/Java/src/org/antlr/v4/runtime/atn/SemanticContext.java