The commit should have changed comments as well.
At the time of writting, it passes the tidy and check tool.
Revisions asked by eddyb :
- Renamed of all the occurences of {visit/super}_mir
- Renamed test structures `CachedMir` to `Cached`
Fixing the missing import on `AggregateKind`
The move gathering code is sensitive to type-equality - that is rather
un-robust and I plan to fix it eventually, but that's a more invasive
change. And we want to fix the visitor anyway.
Fixes#42903.
* Emit `EndRegion` for every code-extent for which we observe a
borrow. To do this, we needed to thread source info back through
to `fn in_scope`, which makes this commit a bit more painful than
one might have expected.
* There is `end_region` emission in `Builder::pop_scope` and in
`Builder::exit_scope`; the first handles falling out of a scope
normally, the second handles e.g. `break`.
* Remove `EndRegion` statements during the erase_regions mir
transformation.
* Preallocate the terminator block, and throw an `Unreachable` marker
on it from the outset. Then overwrite that Terminator as necessary
on demand.
* Instead of marking the scope as needs_cleanup after seeing a
borrow, just treat every scope in the chain as being part of the
diverge_block (after any *one* of them has separately signalled
that it needs cleanup, e.g. due to having a destructor to run).
* Allow for resume terminators to be patched when looking up drop flags.
(In particular, `MirPatch::new` has an explicit code path,
presumably previously unreachable, that patches up such resume
terminators.)
* Make `Scope` implement `Debug` trait.
* Expanded a stray comment: we do not emit StorageDead on diverging
paths, but that end behavior might not be desirable.
Overall goal: reduce the amount of context a mir pass needs so that it
resembles a query.
- The hooks are no longer "threaded down" to the pass, but rather run
automatically from the top-level (we also thread down the current pass
number, so that the files are sorted better).
- The hook now receives a *single* callback, rather than a callback per-MIR.
- The traits are no longer lifetime parameters, which moved to the
methods -- given that we required
`for<'tcx>` objecs, there wasn't much point to that.
- Several passes now store a `String` instead of a `&'l str` (again, no
point).
