Circular dependencies in initial condition are are not an error

[richfitz]

gen <- odin::odin({
  deriv(S) <- Births - b * S - beta * S * I / N + delta * R
  deriv(I) <- beta * S * I / N - (b + sigma) * I
  deriv(R) <- sigma * I - b * R-delta * R
  
  N <- S + I + R
  
  initial(S) <- N0 - I0
  initial(I) <- I0
  initial(R) <- R
  
  b <- 1/75
  I0 <- user(1)
  N0 <- 1e7
  Births <- N * b
  beta <- user(24)
  sigma <- user(12)
  delta <- user(0.2)
})

The initial(R) <- R line here should be an error