- On borrow, calculate lifetime of asignment (using existing lifetime code)
  - Ignore reborrows?
- Visit all statements in that lifetime and locate places where the borrow is propagated/stored
  - Requires lifetime parameters on functions/&-ptrs to be present
- Assignment of the source value during the lifetime of the borrow is an error
- Dropping of the source value is an error
- Returning the borrow is an error