Clarified why `Sized` bound not implicit on trait's implicit `Self` type.
This part of the documentation was a little confusing to me on first read. I've added a couple lines for further explanation. Hopefully this makes things a bit clearer for new readers.
Add std/core::iter::repeat_with
Adds an iterator primitive `repeat_with` which is the "lazy" version of `repeat` but also more flexible since you can build up state with the `FnMut`. The design is mostly taken from `repeat`.
r? @rust-lang/libs
cc @withoutboats, @scottmcm
Update ops range example to avoid confusion between indexes and values.
Makes clearer the numbers in the range refer to indexes, not the values at those indexes.
Correct a few stability attributes
* `core_float_bits`, `duration_core`, `path_component_asref`, and `repr_align` were stabalized in 1.25.0 not 1.24.0.
* Impls for `NonNull` involving unstable things should remain unstable.
* `Duration` should remain stable since 1.3.0 so it appears correctly in the `std` docs.
* `cursor_mut_vec` is an impl on only stable things so should be marked stable.
Add Range[Inclusive]::is_empty
During https://github.com/rust-lang/rfcs/pull/1980, it was discussed that figuring out whether a range is empty was subtle, and thus there should be a clear and obvious way to do it. It can't just be ExactSizeIterator::is_empty (also unstable) because not all ranges are ExactSize -- such as `Range<i64>` and `RangeInclusive<usize>`.
Things to ponder:
- Unless this is stabilized first, this makes stabilizing ExactSizeIterator::is_empty more icky, since this hides that.
- This is only on `Range` and `RangeInclusive`, as those are the only ones where it's interesting. But one could argue that it should be on more for consistency, or on RangeArgument instead.
- The bound on this is PartialOrd, since that works ok (see tests for float examples) and is consistent with `contains`. But ranges like `NAN..=NAN`_are_ kinda weird.
- [x] ~~There's not a real issue number on this yet~~
Document the behaviour of infinite iterators on potentially-computable methods
It’s not entirely clear from the current documentation what behaviour
calling a method such as `min` on an infinite iterator like `RangeFrom`
is. One might expect this to terminate, but in fact, for infinite
iterators, `min` is always nonterminating (at least in the standard
library). This adds a quick note about this behaviour for clarification.
Add fetch_nand to atomics
I think this is all fine but I have little familiarity with the atomic code (or libcore in general) so I may have accidentally done something wrong here...
cc #13226 (the tracking issue)
During the RFC, it was discussed that figuring out whether a range is empty was subtle, and thus there should be a clear and obvious way to do it. It can't just be ExactSizeIterator::is_empty (also unstable) because not all ranges are ExactSize -- not even Range<i32> or RangeInclusive<usize>.
`match`ing on an `Option<Ordering>` seems cause some confusion for LLVM; switching to just using comparison operators removes a few jumps from the simple `for` loops I was trying.
Implement TrustedLen for Take<Repeat> and Take<RangeFrom>
This will allow optimization of simple `repeat(x).take(n).collect()` iterators, which are currently not vectorized and have capacity checks.
This will only support a few aggregates on `Repeat` and `RangeFrom`, which might be enough for simple cases, but doesn't optimize more complex ones. Namely, Cycle, StepBy, Filter, FilterMap, Peekable, SkipWhile, Skip, FlatMap, Fuse and Inspect are not marked `TrustedLen` when the inner iterator is infinite.
Previous discussion can be found in #47082
r? @alexcrichton
Add filtering options to `rustc_on_unimplemented`
- Add filtering options to `rustc_on_unimplemented` for local traits, filtering on `Self` and type arguments.
- Add a way to provide custom notes.
- Tweak binops text.
- Add filter to detect wether `Self` is local or belongs to another crate.
- Add filter to `Iterator` diagnostic for `&str`.
Partly addresses #44755 with a different syntax, as a first approach. Fixes#46216, fixes#37522, CC #34297, #46806.
BREAKING CHANGE: (or perhaps, *bugfix*)
In #![no_std] applications, the following calls to `panic!` used
to behave differently; they now behave the same.
Old behavior:
panic!("{{"); // panics with "{{"
panic!("{{",); // panics with "{"
New behavior:
panic!("{{"); // panics with "{{"
panic!("{{",); // panics with "{{"
This only affects calls to `panic!` (and by proxy `assert`
and `debug_assert`) with a single string literal followed by
a trailing comma, and only in `#![no_std]` applications.
