We used to hardcode that we wanted the liveness of *all* variables.
This can now be configured by selecting an alternative index type
V and providing a (partial) map from locals to that new type V.
As a drive-by: the ref_for_guards created by `fn declare_binding`
should not have been tagged as user_variables in the first
place. These secret internal locals are *pointers* to user variables,
but themselves are not such (IMO. For now at least.)
This adds an `UnpackedKind` type as a typesafe counterpart to `Kind`. This should make future changes to kinds (such as const generics!) more resilient, as the type-checker should catch more potential issues.
NLL fixes
First, introduce pre-statement effects to dataflow to fix#46875. Edge dataflow effects might make that redundant, but I'm not sure of the best way to integrate them with liveness etc., and if this is a hack, this is one of the cleanest hacks I've seen.
And I want a small fix to avoid the torrent of bug reports.
Second, fix linking of projections to fix#46974
r? @pnkfelix
move closure kind, signature into `ClosureSubsts`
Instead of using side-tables, store the closure-kind and signature in the substitutions themselves. This has two key effects:
- It means that the closure's type changes as inference finds out more things, which is very nice.
- As a result, it avoids the need for the `freshen_closure_like` code (though we still use it for generators).
- It avoids cyclic closures calls.
- These were never meant to be supported, precisely because they make a lot of the fancy inference that we do much more complicated. However, due to an oversight, it was previously possible -- if challenging -- to create a setup where a closure *directly* called itself (see e.g. #21410).
We have to see what the effect of this change is, though. Needs a crater run. Marking as [WIP] until that has been assessed.
r? @arielb1
Extend `dump_mir` and functions it calls in order to allow callers to
add custom information. We do this by adding an enum `PassWhere` and
an extra argument of type `FnMut(PassWhere, &mut Write) ->
io::Result<()>`. This callback is responsible for printing the extra
information when MIR is dumped at various stages.
For the "nll" pass, use the new mechanism to dump the `Region`
information after the header, but before the control flow graph for
every function.
In the interest of keeping the output somewhat concise, implement
a custom Debug impl for `Region`
Open Questions:
* What should we call what has been called `PassWhere` so far?
