disallow `#[repr(C)] and `#[repr(packed)]` on structs implementing DispatchFromDyn because they will change the ABI from Scalar/ScalarPair to Aggregrate, resulting in an ICE during object-safety checks or codegen
I don't really understand what it's for, but see the comment here:
https://github.com/rust-lang/rust/pull/50173#discussion_r204222336
where arielb1 said
> Does this check do anything these days? I think `$0: Trait` is always considered ambiguous
and nikomatsakis agreed we may be able to get rid of it
If object-safety checks succeed for a receiver type, make sure the
receiver’s abi is
a) a Scalar, when Self = ()
b) a ScalarPair, when Self = dyn Trait
Rename `CoerceSized` to `DispatchFromDyn`, and reverse the direction so that, for example, you write
```
impl<T: Unsize<U>, U> DispatchFromDyn<*const U> for *const T {}
```
instead of
```
impl<T: Unsize<U>, U> DispatchFromDyn<*const T> for *const U {}
```
this way the trait is really just a subset of `CoerceUnsized`.
The checks in object_safety.rs are updated for the new trait, and some documentation and method names in there are updated for the new trait name — e.g. `receiver_is_coercible` is now called `receiver_is_dispatchable`. Since the trait now works in the opposite direction, some code had to updated here for that too.
I did not update the error messages for invalid `CoerceSized` (now `DispatchFromDyn`) implementations, except to find/replace `CoerceSized` with `DispatchFromDyn`. Will ask for suggestions in the PR thread.
I’m not sure why these tests have different output now, but they do.
In all cases, the error message that is missing looks like this: “the
trait bound `dyn Trait: Trait` is not satisfied”
My guess is that the error message is going away because object-safety
now involves trait solving, and these extra error messages are no
longer leaking out.
For now, all of the receivers that we care about are just a newtyped
pointer — i.e. `Box<Self>`, `Rc<Self>`, `Pin<Box<Self>>`, `Pin<&mut
Self>`. This is much simpler to implement in codeine than the more
general case, because the ABI is the same as a pointer. So we add some
checks in typeck/coherence/builtin.rs to make sure that implementors of
CoerceSized are just newtyped pointers. In this commit, we also
implement the codegen bits.
For a trait method to be considered object-safe, the receiver type must
satisfy certain properties: first, we need to be able to get the vtable
to so we can look up the method, and second, we need to convert the
receiver from the version where `Self=dyn Trait`, to the version where
`Self=T`, `T` being some unknown, `Sized` type that implements `Trait`.
To check that the receiver satisfies those properties, we use the
following query:
forall (U) {
if (Self: Unsize<U>) {
Receiver[Self => U]: CoerceSized<Receiver>
}
}
where `Receiver` is the receiver type of the method (e.g. `Rc<Self>`),
and `Receiver[Self => U]` is the receiver type where `Self = U`, e.g.
`Rc<U>`.
forall queries like this aren’t implemented in the trait system yet, so
for now we are using a bit of a hack — see the code for explanation.
This trait is more-or-less the reverse of CoerceUnsized, and will be
used for object-safety checks. Receiver types like `Rc` will have to
implement `CoerceSized` so that methods that use `Rc<Self>` as the
receiver will be considered object-safe.
Rollup of 13 pull requests
Successful merges:
- #55280 (Add libproc_macro to rust-src distribution)
- #55469 (Regression tests for issue #54477.)
- #55504 (Use vec![x; n] instead of iter::repeat(x).take(n).collect())
- #55522 (use String::from() instead of format!() macro to construct Strings.)
- #55536 (Pass suggestions as impl Iterator instead of Vec)
- #55542 (syntax: improve a few allocations)
- #55558 (Tweak `MatcherPos::matches`)
- #55561 (Fix double_check tests on big-endian targets)
- #55573 (Make sure the `aws` executable is in $PATH on macOS)
- #55574 (Use `SmallVec` within `MoveData`.)
- #55575 (Fix invalid_const_promotion test on some archs)
- #55578 (Made doc example of `impl Default for …` use `-> Self` instead of explicit self type)
- #55582 (Remove unused import copy from publish_toolstate.py)
Fix double_check tests on big-endian targets
Since the enums get optimized down to 1 byte long, the bits set in the `usize` member don't align with the `enum` values on big-endian machines. Avoid this issue by shrinking the integer member to the
same size as the enums.
Regression tests for issue #54477.
At some point someone may want to revisit PR #53564
it would be really good to have regression tests for #54477 before that happens. :)
save-analysis: bug fix and optimisation.
The first commit fixes a bug in name resolution and save-analysis (introduced in #54145) and removes an unused parameter. This fixes the RLS tests, which are currently blocking distribution of the RLS. The second commit removes macro uses from save-analysis data, since these are never used, they just take up space.
r? @petrochenkov
Since the enums get optimized down to 1 byte long, the bits
set in the usize member don't align with the enums on big-endian
machines. Avoid this issue by shrinking the integer member to the
same size as the enums.
`create_matches` creates a `Vec<Rc<Vec<NamedMatch>>>`. Even though all the
inner `Vec`s are empty, each one is created separately.
This commit changes `create_matches` so it instead creates one empty inner
`Vec`, and shares it.
The commit also changes `MatcherPos::matches` to a boxed slice, because its
length doesn't change.
thread::unpark: Avoid notifying with mutex locked.
This means when the other thread wakes it can continue right away
instead of having to wait for the mutex.
Also add some comments explaining why the mutex needs to be locked in
the first place.
This is a follow up to https://github.com/rust-lang/rust/pull/54174
I did some tests with relacy [here](https://gist.github.com/parched/b7fb88c97755a81e5cb9f9048a15f7fb) (This PR is InnerV2). If anyone can think of some other test case worth adding let me know.
r? @RalfJung
ci: Move global credentials to web configuration
This commit moves a number of our encrypted credentials stored in
configuration files in this repository to env vars on the web UI. This
will hopefully make it easier to rotate credentials in the future as
well as quickly change them if the need arises. (quicker than landing a
PR that is).
This also updates the travis deployment process to always use the `aws`
command line tool which we're already installing on Linux and should
enable us to avoid all `dpl` gem issues as well as have greater control
over what's going where.
Fix DWARF generation for enums
The DWARF generated for Rust enums was always somewhat unusual.
Rather than using DWARF constructs directly, it would emit magic field
names like "RUST$ENCODED$ENUM$0$Name" and "RUST$ENUM$DISR". Since
PR #45225, though, even this has not worked -- the ad hoc scheme was
not updated to handle the wider variety of niche-filling layout
optimizations now available.
This patch changes the generated DWARF to use the standard tags meant
for this purpose; namely, DW_TAG_variant and DW_TAG_variant_part.
The patch to implement this went in to LLVM 7. In order to work with
older versions of LLVM, and because LLVM doesn't do anything here for
PDB, the existing code is kept as a fallback mode.
Support for this DWARF is in the Rust lldb and in gdb 8.2.
Closes#32920Closes#32924Closes#52762Closes#53153
