private static @Nullable PsiExpression getOnlyExpression(@NotNull PsiSwitchExpression switchExpression) {
    PsiCodeBlock body = switchExpression.getBody();
    if (body == null) return null;
    PsiStatement[] statements = body.getStatements();
    if (statements.length != 1 || !(statements[0] instanceof PsiSwitchLabeledRuleStatement rule)) return null;
    PsiStatement ruleBody = rule.getBody();
    if (!(ruleBody instanceof PsiExpressionStatement expressionStatement)) return null;
    return expressionStatement.getExpression();
  }
private static @Nullable PsiExpression getOnlyExpression(@NotNull PsiSwitchExpression switchExpression)