Add VecDeque::range* methods
This patch adds `VecDeque::range` and `VecDeque::range_mut` to provide
iterators over a sub-range of a `VecDeque`. This behavior can be
emulated with `skip` and `take`, but directly providing a `Range` is
more ergonomic. This also partially makes up for `VecDeque`'s lack of
`SliceIndex` support.
Move A|Rc::as_ptr from feature(weak_into_raw) to feature(rc_as_ptr)
These were stabilized alongside the Weak versions, but having `feature = "weak_.."` on a fn definition for the non-weak pointers is potentially very misleading, especially in a review context where the impl header may not be immediately visible.
r? @RalfJung
@bors rollup=always
This patch adds `VecDeque::range` and `VecDeque::range_mut` to provide
iterators over a sub-range of a `VecDeque`. This behavior can be
emulated with `skip` and `take`, but directly providing a `Range` is
more ergonomic. This also partially makes up for `VecDeque`'s lack of
`SliceIndex` support.
Remove unnecessary release from Arc::try_unwrap
The thread that recovers the unique access to Arc inner value (e.g., drop
when ref-count strong reaches zero, successful try_unwrap), ensures that
other operations on Arc inner value happened before by synchronizing
with release operations performed when decrementing the reference counter.
When try_unwrap succeeds, the current thread recovers the unique access
to Arc inner value, so release is unnecessary.
r? @Amanieu
added .collect() into String from Box<str>
I have not created an rfc, because i felt like this is a very minor change.
i have just set a random feature name and rust version as stability attribute, i expect to have to change that, i just don't know what the policy on that is. all guides i could find focused on contributing to the compiler, not contributing to the standard library.
drawbacks: more code in the standard library, could be replaced with specialization: base-implementation for AsRef\<str> and specialization for String and Cow. i can write that code if ppl want it.
advantages: using "real strings" i.e. Box\<str> is as ergonomic as string slices (&str) and string buffers (String) with iterators.
The thread that recovers the unique access to Arc inner value (e.g., drop
when ref-count strong reaches zero, successful try_unwrap), ensures that
other operations on Arc inner value happened before by synchronizing
with release operations performed when decrementing the reference counter.
When try_unwrap succeeds, the current thread recovers the unique access
to Arc inner value, so release is unnecessary.
Use &raw in A|Rc::as_ptr
This PR uses `&raw` for offsetting `*mut [A]RcInner<T> -> *mut T`.
Additionally, this updates the implementation of `Weak::as_ptr` to support unsized `T`, though it does not yet relax the bounds of `Weak::as_ptr`/`into_raw`/`from_raw` to accept unsized `T`.
to feature(rc_as_ptr)
These were stabilized alongside the Weak versions,
but having `feature = "weak_.."` on a fn definition
for the non-weak pointers is potentially very confusing.
Update Box::from_raw example to generalize better
I know very little about rust, so I saw the example here
```
use std::alloc::{alloc, Layout};
unsafe {
let ptr = alloc(Layout:🆕:<i32>()) as *mut i32;
*ptr = 5;
let x = Box::from_raw(ptr);
}
```
and tried to generalize it by writing,
```
let layout = Layout:🆕:<T>();
let new_obj = unsafe {
let ptr = alloc(layout) as *mut T;
*ptr = obj;
Box::from_raw(ptr)
};
```
for some more complicated `T`, which ended up crashing with SIGSEGV,
because it tried to `drop_in_place` the previous object in `ptr` which is
of course garbage. I think that changing this example to use `.write` instead
would be a good idea to suggest the correct generalization. It is also more
consistent with other documentation items in this file, which use `.write`.
I also added a comment to explain it, but I'm not too attached to that,
and can see it being too verbose in this place.
Shortcuts for min/max on double-ended BTreeMap/BTreeSet iterators
Closes#59947: a performance tweak that might benefit some. Optimizes `min` and `max ` on all btree double-ended iterators that do not drop, i.e. the iterators created by:
- `BTreeMap::iter`
- `BTreeMap::iter_mut`
- `BTreeMap::keys` and `BTreeSet::iter`
- `BTreeMap::range` and `BTreeSet::range`
- `BTreeMap::range_mut`
Also in these (currently) single-ended iterators, but obviously for `min` only:
- `BTreeSet::difference`
- `BTreeSet::intersection`
- `BTreeSet::symmetric_difference`
- `BTreeSet::union`
Did not do this in iterators created by `into_iter` to preserve drop order, as outlined in #62316.
Did not do this in iterators created by `drain_filter`, possibly to preserve drop order, possibly to preserve predicate invocation, mostly to not have to think about it too hard (I guess maybe it wouldn't be a change for `min`, which is the only shortcut possible in this single-ended iterator).
`improper_ctypes_definitions` lint
Addresses #19834, #66220, and #66373.
This PR takes another attempt at #65134 (reverted in #66378). Instead of modifying the existing `improper_ctypes` lint to consider `extern "C" fn` definitions in addition to `extern "C" {}` declarations, this PR adds a new lint - `improper_ctypes_definitions` - which only applies to `extern "C" fn` definitions.
In addition, the `improper_ctype_definitions` lint differs from `improper_ctypes` by considering `*T` and `&T` (where `T: Sized`) FFI-safe (addressing #66220).
There wasn't a clear consensus in #66220 (where the issues with #65134 were primarily discussed) on the approach to take, but there has [been some discussion in Zulip](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/.2366220.20improper_ctypes.20definitions.20vs.20declarations/near/198903086). I fully expect that we'll want to iterate on this before landing.
cc @varkor + @shepmaster (from #19834) @hanna-kruppe (active in discussing #66220), @SimonSapin (#65134 caused problems for Servo, want to make sure that this PR doesn't)
This commit adds a new lint - `improper_ctypes_definitions` - which
functions identically to `improper_ctypes`, but on `extern "C" fn`
definitions (as opposed to `improper_ctypes`'s `extern "C" {}`
declarations).
Signed-off-by: David Wood <david@davidtw.co>
I know very little about rust, so I saw this example and tried to generalize it by writing,
```
let layout = Layout:🆕:<T>();
let new_obj = unsafe {
let ptr = alloc(layout) as *mut T;
*ptr = obj;
Box::from_raw(ptr)
};
```
for some more complicated `T`, which ended up crashing with SIGSEGV,
because it tried to `drop_in_place` the previous object in `ptr` which is
of course garbage. I also added a comment that explains why `.write`
is used, but I think adding that comment is optional and may be too verbose
here. I do however think that changing this example is a good idea to
suggest the correct generalization. `.write` is also used in most of the rest
of the documentation here, even if the example is `i32`, so it would additionally
be more consistent.
Mention that BTreeMap::new() doesn't allocate
I think it would be nice to mention this, so you don't have to dig through the src to look at the definition of new().
