public IntervalSet getExpectedTokens() {
		return getATN().getExpectedTokens(getState(), getContext());
	}
Computes the set of input symbols which could follow the current parser
state and context, as given by {@link #getState} and {@link #getContext},
respectively.

@see ATN#getExpectedTokens(int, RuleContext)
runtime/Java/src/org/antlr/v4/runtime/Parser.java