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[wip] Implement error source dropping #1918

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[wip] Implement error source dropping #1918

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@jswrenn jswrenn commented Oct 15, 2024

Introduces Metadata<Src>. Currently blocked on gracefully supporting both referency sources and value-y sources. Perhaps derive(IntoBytes) could also emit impls of Source?

joshlf and others added 23 commits October 12, 2024 14:06
We already have the merge queue; running on push is redundant.
Upgrade our MSRV to 1.65 and remove version detection logic prior to
that version.
* Release 0.9.0-alpha.0

Upgrade our MSRV to 1.65 and remove version detection logic prior to
that version.

* Enable clippy::missing_const_for_fn

While we're here, remove defensive programming against bug in
`Layout::from_size_align` which is no longer needed on our new MSRV.
Now that our MSRV is 1.65, we can clean up some code.

Makes progress on #67
Also clean up some code for 0.9.
* Upgrade some code for MSRV 1.65

Now that our MSRV is 1.65, we can clean up some code.

Makes progress on #67

* Upgrade versions of some dependencies

Now that our MSRV is 1.65, it unlocks upgrading some dependencies'
versions.
Bumps [github/codeql-action](https://github.com/github/codeql-action) from 3.26.12 to 3.26.13.
- [Release notes](https://github.com/github/codeql-action/releases)
- [Changelog](https://github.com/github/codeql-action/blob/main/CHANGELOG.md)
- [Commits](github/codeql-action@c36620d...f779452)

---
updated-dependencies:
- dependency-name: github/codeql-action
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Bumps [Swatinem/rust-cache](https://github.com/swatinem/rust-cache) from 2.7.3 to 2.7.5.
- [Release notes](https://github.com/swatinem/rust-cache/releases)
- [Changelog](https://github.com/Swatinem/rust-cache/blob/master/CHANGELOG.md)
- [Commits](Swatinem/rust-cache@23bce25...82a92a6)

---
updated-dependencies:
- dependency-name: Swatinem/rust-cache
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Previously, we supported the `AtLeast` bound, which was used to describe
a subset relationship in which `I: AtLeast<J>` implied that `I` as at
least as restrictive as `J`. However, as described in #1866, this
incorrectly models invariants as monotonic. In reality, invariants both
provide guarantees but also *require* guarantees.

This commit takes a step in the direction of resolving #1866 by removing
`AtLeast`. Uses of `AtLeast<Shared>` are replaced by a new `Reference`
trait, which is implemented for `Shared` and `Exclusive`. This serves
two purposes: First, it makes it explicit what this bound means.
Previously, `AtLeast<Shared>` had an ambiguous meaning, while
`Reference` means precisely that an invariant is either `Shared` or
`Exclusive` and nothing else. Second, it paves the way for #1183, in
which we may add new aliasing invariants which convey ownership. In that
case, it will be important for existing methods to add `Reference`
bounds when those methods would not be sound in the face of ownership
semantics.

We also inline the items in the `invariant` module, which were
previously generated by macro. The addition of the `Reference` trait did
not play nicely with that macro, and we will likely need to go further
from the macro in order to fix #1839 – this fix will likely require
making aliasing invariants meaningfully different than other invariants,
for example by adding an associated type.

Makes progress on #1866
Explain why we only support concrete types so that future authors won't
spuriously add support for them.
`PtrInner` carries all invariants which are not controlled by type
parameters. Since `PtrInner` does not promise to uphold aliasing,
alignment, or validity, we can move some utility methods to `PtrInner`
which previously were responsible for maintaining invariants orthogonal
to their purpose.

Makes progress on #1892 (still needs to be fixed on v0.8.x)
Closes #1890
This prepares us for future changes which will significantly increase
the amount of code in the `invariant` module.

Also merge `aliasing_safety` into this new file.
When the aliasing mode is `Any`, `Ptr<'a, T>` is invariant in `'a` and
`T`. When the aliasing mode is `Shared` or `Exclusive`, `Ptr` has the
same variance as `&'a T` and `&'a mut T` respectively.

Makes progress on #1839
`AliasingSafe` is really about whether a pointer permits unsynchronized
reads - either because the referent contains no `UnsafeCell`s or because
the aliasing mode is `Exclusive`. Previously, `AliasingSafe` was not
named consistent with this meaning, and was a function of a *pair* of
types rather than of a single type. This commit fixes both oversights.

While we're here, we also add `Read` bounds in some places, allowing us
to simplify many safety comments.
For aliasing, use `Inaccessible`. For alignment and validity, use
`Unknown`.
This commit adds a framework which supports encoding in the type system
any `I -> I` mapping where `I` is any `Invariant` type. This permits us
to make `cast_unsized`'s return value smarter, and as a result, allows
us to remove a lot of `unsafe` code.

Makes progress on #1122
gherrit-pr-id: I003d5360d1b7f7882a71490813eca50b39025f14
Introduces `Metadata<Src>`. Currently blocked on gracefully supporting
both referency sources and value-y sources. Perhaps `derive(IntoBytes)`
could also emit impls of `Source`?
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3 participants