A model without trunc() finishes okay, but when I add trunc() it seems to hang forever.

```
n <- 10000
df <- n - 2
stanvars <- stanvar(df,name='df')
priors = c(prior(inv_gamma(0.001,0.001), class = sigma),
prior(student_t(df, 0, 3), class = b))
myfit <-
brm(data = d, family = student,
someresp | trunc(lb = 0, ub = 24) ~ 0 + Intercept + somepred,
prior = priors,
iter = 2000, warmup = 1000, chains = 4, cores = 4,
seed = 4, stanvars = stanvars)
pp_check(myfit)
```