By the fundamental thm of calc, the derivative of a definite integral wrt to the upper limit is the integrand evaluated at the upper limit.

$\displaystyle \frac{d}{dy} \int^{y}_{0} f(x) dx = f(y)$

What if I integrate wrt to the integrand?

$\displaystyle \frac{d}{df(x)} \int^{y}_{0} f(x) dx = ?$

Thanks!