Inconsistent checks in gaussian_dlm_obs_lpdf code

There are two versions of the gaussian_dlm_obs distribution: one has a full covariance matrix for the observation errors, and the other one takes a diagonal covariance matrix, as a vector. I am puzzled by the fact that they don’t do the same checks on their arguments. For example, the diagonal-covariance-matrix version does check_not_nan() on the arguments, but the full-covariance-matrix version does not. Does anyone know if these differences are intentional, or are they just historical accidents?

Some of the checks were removed in For example, there’s no need to have an explicit call to check_not_nan on a matrix if there’s already a check_pos_definite, because the latter already includes it.