The entry point of the NLL borrow checker.
- The output of
nll::compute_regions. This includes the computed
RegionInferenceContext, any closure requirements to propagate, and any generated errors.
- Computes the (non-lexical) regions from the input MIR.
- Rewrites the regions in the MIR to use NLL variables, also scraping out the set of universal regions (e.g., region parameters) declared on the function. That set will need to be given to