warn if detect constant deterministic assignment?

[paciorek]

In current nimble, if a user has a lot of deterministic assignments, such as

for(i in 1:n)
  x[i] <- 1

that slows down model building and compilation. I was considering adding a warning to processBUGScode but since we are trying not to spend a lot of time on current nimble given nCompiler, I wanted to check whether this is still going to be something we suggest that users avoid, and therefore whether we should do something about this in either nimble or nCompiler.

I can see two options:

• just warn the user and suggest they set via constants or inits.
• we could strip out such lines and augment inits