This is meant to ease development of multi-stage dataflow analyses
where the output from one analysis is used to initialize the state
for the next; in such a context, you cannot start with `bottom_value`
for all the bits.
If the gen/kill bits are set there, the effects of `start_block_effects`
will not be seen when using `FlowAtLocation` etc. to go over the MIR.
EverInitializedLvals is the only pass that got this wrong, but this
fixes the footgun for everyone.
We now visit just the stuff in the CFG, and we add liveness
constraints for all the random types, regions etc that appear within
rvalues and statements.
In particular, if we see a variable is DROP-LIVE, but it is not
MAYBE-INIT, then we can ignore the drop. This leavess attempt to use
more complex refinements of the idea (e.g., for subpaths or subfields)
to future work.
Region inference can create borrows for an empty region if the borrow is
dead. In that case, there's no reason to track the borrow, but because
there's no such thing as an EndRegion(ReEmpty) these borrows used to live
for the entire function.
Fixes#46161.
Also, factor out `do_mir_borrowck`, which is the code that actually
performs the MIR borrowck from within the scope of an inference context.
This change should be a pure refactoring.
`EndRegion` do not always correspond to borrow-data entries
Remove assertion that the argument to every `EndRegion` correspond to some dataflow-tracked borrow-data entry.
Fix#44828
(The comment thread on the aforementioned issue discusses why its best to just remove this assertion.)
some dataflow-tracked borrow-data entry.
Fix#44828
(The comment thread on the aforementioned issue discusses why its best
to just remove this assertion.)
