General Relativity predicts the bending of light due to gravity. But, does this explanation require light to be corpuscular? Can the EM waves of classical electromagnetism be bend in Einstein's gravity? Or does the fact that light bends due to gravity alone prove that it is photons(corpuscles) in General Relativity?
In relativity (both flavours) light rays follow null geodesics. That is when you calculate the proper length of any part of the light's trajectory it comes out zero. More precisely the trajectory of a light ray is described by the null geodesic equation.
So to calculate the bending of light you simply have to solve the null geodesic equation. No resort to quantum mechanics or the particulate nature of the light is required.
Light is not unique in this respect. In the weak field limit the trajectory of gravitational waves is also described by the null geodesic equation. In fact massless particles also follow the same trajectory, though the key property here is not that they are particles but that they are massless.