@Override
		public boolean equals(Object obj) {
			if ( !(obj instanceof Predicate) ) return false;
			if ( this == obj ) return true;
			Predicate p = (Predicate)obj;
			return this.ruleIndex == p.ruleIndex &&
				   this.predIndex == p.predIndex &&
				   this.isCtxDependent == p.isCtxDependent;
		}
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