Set<Object> (@Nullable PsiExpression expression) { if (expression == null) return Collections.emptySet(); DataflowPoint point = myData.get(new JavaExpressionAnchor(expression)); if (point == null) return Collections.emptySet(); Set<Object> values = point.myPossibleValues; return values == null ? Collections.emptySet() : Collections.unmodifiableSet(values); }