[sanxiyn]

"place" and "live" have their respective intuitive definitions. To clarify, "place" is a set of bytes in the memory. "live" means it is used again. But both are runtime concepts, so Rust compiler needs to compute static approximation of these runtime concepts. This static approximation is what is complex and changing. But the principle is simple.

Actually, my elaboration of "place", local/field/index, is nearly complete. The only thing missing is upvar, which is local captured in closure. Pre-NLL "live" is simple: expression is live from the definition to the end of the containing statement, and declaration is live from the definition to the end of the containing block. Post-NLL "live" is connected region of control flow graph from the definition to potentially multiple last uses. Really, that is the whole story.

There are two changes currently in development. One changes definition of "place" to include field captured in closure, in addition to local captured in closure. The other is more drastic, changing definition of "live": a loan is live where the loan is origin of a variable and the variable is live. This is great, because current approximation is equivalent to union of all origins.