Once upon a time (commit 9bd35c07c26) there were two kinds of
projection: one for places, and one for constants. It therefore made
sense to share the `Projection` struct for both. Although the different
use-cases used different concrete types, sharing was made possible by
type-parameterisation of `Projection`.
Since then, however, the usage of projections in constants has
disappeared, meaning that (forgetting lifetimes for a moment) the
parameterised type is only every instantiated under one guise. So it may
as well be a concrete type.
Borrowck error reporting cleanup
* Don't show variables created by desugarings in borrowck errors
* Move "conflict error" reporting to it's own module, so that `error_reporting` contains only common error reporting methods.
* Remove unused `ScopeTree` parameter.
r? @pnkfelix
`InternedString::intern(x)` is preferable to
`Symbol::intern(x).as_interned_str()`, because the former involves one
call to `with_interner` while the latter involves two.
The case within InternedString::decode() is particularly hot, and this
change reduces the number of `with_interner` calls by up to 13%.
Multi-variant layouts for generators
This allows generators to overlap fields using variants, but doesn't do any such overlapping yet. It creates one variant for every state of the generator (unresumed, returned, panicked, plus one for every yield), and puts every stored local in each of the yield-point variants.
Required for optimizing generator layouts (#52924).
There was quite a lot of refactoring needed for this change. I've done my best in later commits to eliminate assumptions in the code that only certain kinds of types are multi-variant, and to centralize knowledge of the inner mechanics of generators in as few places as possible.
This change also emits debuginfo about the fields contained in each variant, as well as preserving debuginfo about stored locals while running in the generator.
Also, fixes#59972.
Future work:
- Use this change for an optimization pass that actually overlaps locals within the generator struct (#52924)
- In the type layout fields, don't include locals that are uninitialized for a particular variant, so miri and UB sanitizers can check our memory (see https://github.com/rust-lang/rust/issues/59972#issuecomment-483058172)
- Preserve debuginfo scopes across generator yield points
Rollup of 7 pull requests
Successful merges:
- #60287 (Use references for variances_of)
- #60327 (Search for incompatible universes in borrow errors)
- #60330 (Suggest using an inclusive range instead of an exclusive range when the endpoint overflows by 1)
- #60366 (build-gcc: Create missing cc symlink)
- #60369 (Support ZSTs in DispatchFromDyn)
- #60404 (Implement `BorrowMut<str>` for `String`)
- #60417 (Rename hir::ExprKind::Use to ::DropTemps and improve docs.)
Failed merges:
r? @ghost
Search for incompatible universes in borrow errors
If we have a borrow that has to live for `'static` we need to check for
any regions in incompatible universes when trying to find the cause.
closes#60274
Cleanup the MIR visitor
* Remove useless `BasicBlock` parameters on methods with `Location`s.
* Prefer `visit_terminator_kind` to `visit_terminator`.
* Remove `Region` from PlaceContexts. `visit_rvalue` should be used when the region is important.
* Remove unused visitor methods.
Future-proof MIR for dedicated debuginfo.
This is #56231 without the last commit (the one that actually moves to `VarDebuginfo`).
Nothing should be broken, but it should no longer depend on debuginfo for anything else.
r? @nikomatsakis
update polonius-engine
This updates polonius-engine to [version 0.7.0](https://github.com/rust-lang/polonius/blob/master/RELEASES.md#v070), which adds a hybrid algorithm that starts off with performing a cheaper, location-insensitive analysis before proceeding with the full analysis.
r? @nikomatsakis
Use normal newtype_index macro for MIR dataflows
* Makes the definition of these structs contain `struct IndexName`
* Avoids having an offset by removing high values, rather than 0
* Implements some traits for us.
A comment in one match arm make a blanket statement about "reads/reservations", but in fact the whole point of this PR is that reservations are *not* handled by that particular arm anymore.
Remove adt_def from projections and downcasts in MIR
As part of optimizing generator layouts in MIR, we'd like to allow downcasting generators to variants which do not have a corresponding `def_id`, since they are created by the compiler.
This refactor hopes to allow that, without regressing perf.
r? @eddyb
