fix least significant digits of f128 associated constants
While the numbers are parsed to the correct value, the decimal numbers in the source were rounded to zero instead of to the nearest, making the literals different from the values shown in the documentation.
Rollup of 6 pull requests
Successful merges:
- #124921 (offset_from: always allow pointers to point to the same address)
- #127407 (Make parse error suggestions verbose and fix spans)
- #127684 (consolidate miri-unleashed tests for mutable refs into one file)
- #127729 (Stop using the `gen` identifier in the compiler)
- #127736 (Add myself to the review rotation)
- #127758 (coverage: Restrict `ExpressionUsed` simplification to `Code` mappings)
r? `@ghost`
`@rustbot` modify labels: rollup
offset_from: always allow pointers to point to the same address
This PR implements the last remaining part of the t-opsem consensus in https://github.com/rust-lang/unsafe-code-guidelines/issues/472: always permits offset_from when both pointers have the same address, no matter how they are computed. This is required to achieve *provenance monotonicity*.
Tracking issue: https://github.com/rust-lang/rust/issues/117945
### What is provenance monotonicity and why does it matter?
Provenance monotonicity is the property that adding arbitrary provenance to any no-provenance pointer must never make the program UB. More specifically, in the program state, data in memory is stored as a sequence of [abstract bytes](https://rust-lang.github.io/unsafe-code-guidelines/glossary.html#abstract-byte), where each byte can optionally carry provenance. When a pointer is stored in memory, all of the bytes it is stored in carry that provenance. Provenance monotonicity means: if we take some byte that does not have provenance, and give it some arbitrary provenance, then that cannot change program behavior or introduce UB into a UB-free program.
We care about provenance monotonicity because we want to allow the optimizer to remove provenance-stripping operations. Removing a provenance-stripping operation effectively means the program after the optimization has provenance where the program before the optimization did not -- since the provenance removal does not happen in the optimized program. IOW, the compiler transformation added provenance to previously provenance-free bytes. This is exactly what provenance monotonicity lets us do.
We care about removing provenance-stripping operations because `*ptr = *ptr` is, in general, (likely) a provenance-stripping operation. Specifically, consider `ptr: *mut usize` (or any integer type), and imagine the data at `*ptr` is actually a pointer (i.e., we are type-punning between pointers and integers). Then `*ptr` on the right-hand side evaluates to the data in memory *without* any provenance (because [integers do not have provenance](https://rust-lang.github.io/rfcs/3559-rust-has-provenance.html#integers-do-not-have-provenance)). Storing that back to `*ptr` means that the abstract bytes `ptr` points to are the same as before, except their provenance is now gone. This makes `*ptr = *ptr` a provenance-stripping operation (Here we assume `*ptr` is fully initialized. If it is not initialized, evaluating `*ptr` to a value is UB, so removing `*ptr = *ptr` is trivially correct.)
### What does `offset_from` have to do with provenance monotonicity?
With `ptr = without_provenance(N)`, `ptr.offset_from(ptr)` is always well-defined and returns 0. By provenance monotonicity, I can now add provenance to the two arguments of `offset_from` and it must still be well-defined. Crucially, I can add *different* provenance to the two arguments, and it must still be well-defined. In other words, this must always be allowed: `ptr1.with_addr(N).offset_from(ptr2.with_addr(N))` (and it returns 0). But the current spec for `offset_from` says that the two pointers must either both be derived from an integer or both be derived from the same allocation, which is not in general true for arbitrary `ptr1`, `ptr2`.
To obtain provenance monotonicity, this PR hence changes the spec for offset_from to say that if both pointers have the same address, the function is always well-defined.
### What further consequences does this have?
It means the compiler can no longer transform `end2 = begin.offset(end.offset_from(begin))` into `end2 = end`. However, it can still be transformed into `end2 = begin.with_addr(end.addr())`, which later parts of the backend (when provenance has been erased) can trivially turn into `end2 = end`.
The only alternative I am aware of is a fundamentally different handling of zero-sized accesses, where a "no provenance" pointer is not allowed to do zero-sized accesses and instead we have a special provenance that indicates "may be used for zero-sized accesses (and nothing else)". `offset` and `offset_from` would then always be UB on a "no provenance" pointer, and permit zero-sized offsets on a "zero-sized provenance" pointer. This achieves provenance monotonicity. That is, however, a breaking change as it contradicts what we landed in https://github.com/rust-lang/rust/pull/117329. It's also a whole bunch of extra UB, which doesn't seem worth it just to achieve that transformation.
### What about the backend?
LLVM currently doesn't have an intrinsic for pointer difference, so we anyway cast to integer and subtract there. That's never UB so it is compatible with any relaxation we may want to apply.
If LLVM gets a `ptrsub` in the future, then plausibly it will be consistent with `ptradd` and [consider two equal pointers to be inbounds](https://github.com/rust-lang/rust/pull/124921#issuecomment-2205795829).
These constifications were blocked on classification functions being
added. Now that those methods are available, constify them.
This brings things more in line with `f32` and `f64`.
Remove memory leaks in doctests in `core`, `alloc`, and `std`
cc `@RalfJung` https://github.com/rust-lang/rust/issues/126067https://github.com/rust-lang/miri/issues/3670
Should be no actual *documentation* changes[^1], all added/modified lines in the doctests are hidden with `#`,
This PR splits the existing memory leaks in doctests in `core`, `alloc`, and `std` into two general categories:
1. "Non-focused" memory leaks that are incidental to the thing being documented, and/or are easy to remove, i.e. they are only there because preventing the leak would make the doctest less clear and/or concise.
- These doctests simply have a comment like `# // Prevent leaks for Miri.` above the added line that removes the memory leak.
- [^2]Some of these would perhaps be better as part of the public documentation part of the doctest, to clarify that a memory leak can happen if it is not otherwise mentioned explicitly in the documentation (specifically the ones in `(A)Rc::increment_strong_count(_in)`).
2. "Focused" memory leaks that are intentional and documented, and/or are possibly fragile to remove.
- These doctests have a `# // FIXME` comment above the line that removes the memory leak, with a note that once `-Zmiri-disable-leak-check` can be applied at test granularity, these tests should be "un-unleakified" and have `-Zmiri-disable-leak-check` enabled.
- Some of these are possibly fragile (e.g. unleaking the result of `Vec::leak`) and thus should definitely not be made part of the documentation.
This should be all of the leaks currently in `core` and `alloc`. I only found one leak in `std`, and it was in the first category (excluding the modules `@RalfJung` mentioned in https://github.com/rust-lang/rust/issues/126067 , and reducing the number of iterations of [one test](https://github.com/rust-lang/rust/blob/master/library/std/src/sync/once_lock.rs#L49-L94) from 1000 to 10)
[^1]: assuming [^2] is not added
[^2]: backlink
Stabilize const unchecked conversion from u32 to char
Closes https://github.com/rust-lang/rust/issues/89259.
The functions in this PR were left out of the initial set of `feature(const_char_convert)` stabilizations in https://github.com/rust-lang/rust/pull/102470, but have since been unblocked by https://github.com/rust-lang/rust/pull/118979.
If `unsafe { from_u32_unchecked(u) }` is called in const with a value for which `from_u32(u)` returns None, we get the following compile error.
```rust
fn main() {
let _ = const { unsafe { char::from_u32_unchecked(0xd800) } };
}
```
```console
error[E0080]: it is undefined behavior to use this value
--> src/main.rs:2:19
|
2 | let _ = const { unsafe { char::from_u32_unchecked(0xd800) } };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered 0x0000d800, but expected a valid unicode scalar value (in `0..=0x10FFFF` but not in `0xD800..=0xDFFF`)
|
= note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
= note: the raw bytes of the constant (size: 4, align: 4) {
00 d8 00 00 │ ....
}
note: erroneous constant encountered
--> src/main.rs:2:13
|
2 | let _ = const { unsafe { char::from_u32_unchecked(0xd800) } };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
```
Improved slice documentation
Improve slice documentation to include assert_eq checks for all the cases where there were existing examples. I think it makes things more clear when the documentation explicitly checks against values and shows the reader what it does.
I also started a rust internals discussion about it here: https://internals.rust-lang.org/t/improve-slice-documentaion/21168
Since the libs and lang teams completed an FCP to allow for const
`strlen` ([1]), currently implemented with `const_eval_select`, there is
no longer any reason to avoid this specific function or use it only in
const.
Rename it to reflect this status change.
[1]: https://github.com/rust-lang/rust/issues/113219#issuecomment-2016939401
Stabilize const_cstr_from_ptr (CStr::from_ptr, CStr::count_bytes)
Completed the pair of FCPs https://github.com/rust-lang/rust/issues/113219#issuecomment-2016939401 + https://github.com/rust-lang/rust/issues/114441#issuecomment-2016942566.
`CStr::from_ptr` is covered by just the first FCP on its own. `CStr::count_bytes` requires the approval of both FCPs. The second paragraph of the first link and the last paragraph of the second link explain the relationship between the two FCPs. As both have been approved, we can proceed with stabilizing `const` on both of these already-stable functions.
A `rustc_const_stable` attribute by itself has nonintuitive purpose when
placed in a public module.
Separately, it would probably be okay to rename `const_strlen` to just
`strlen` to make it more clear this is our general-purpose
implementation of strlen now, not something specifically for const
(avoiding confusion like in PR 127444).
as_simd: fix doc comment to be in line with align_to
In #121201, the guarantees about `align_offset` and `align_to` were changed. This PR aims to correct the doc comment of `as_simd` to be in line with the new `align_to`.
Tagging #86656 for good measure.
core: Limit remaining f16 doctests to x86_64 linux
On s390x, every use of the f16 data type will currently ICE due to https://github.com/llvm/llvm-project/issues/50374, causing doctest failures on the platform.
Most doctests were already restricted to certain platforms, so fix this by likewise restricting the remaining five.
Suggest borrowing on fn argument that is `impl AsRef`
When encountering a move conflict, on an expression that is `!Copy` passed as an argument to an `fn` that is `impl AsRef`, suggest borrowing the expression.
```
error[E0382]: use of moved value: `bar`
--> f204.rs:14:15
|
12 | let bar = Bar;
| --- move occurs because `bar` has type `Bar`, which does not implement the `Copy` trait
13 | foo(bar);
| --- value moved here
14 | let baa = bar;
| ^^^ value used here after move
|
help: borrow the value to avoid moving it
|
13 | foo(&bar);
| +
```
Fix#41708
On s390x, every use of the f16 data type will currently ICE
due to https://github.com/llvm/llvm-project/issues/50374,
causing doctest failures on the platform.
Most doctests were already restricted to certain platforms,
so fix this by likewise restricting the remaining five.
std: Set `has_reliable_f16` to false for MIPS targets in build.rs
This PR makes std tests link for MIPS again (they broke with https://github.com/rust-lang/rust/pull/126608) by avoiding the following link errors. Step-by-step instructions on how to reproduce these errors in docker can be found below.
std.9e27ea-cgu.12:(.text._ZN3std3num8test_num17edc3E+0x38): undefined reference to `__gnu_f2h_ieee'
std.9e27ea-cgu.12:(.text._ZN3std3num8test_num17hdc3E+0x38): undefined reference to `__gnu_h2f_ieee'
This PR just adds one line of config in existing f16 infrastructure. It also disables four doctests that fails with the same link errors.
## Step-by-step to reproduce linking error
1. Prepare:
```sh
docker run -it ubuntu:24.10
apt update && apt install -y \
libc6-mips-cross \
libc6-mipsel-cross \
libc6-mips64-cross \
libc6-mips64el-cross \
gcc-mips-linux-gnu \
gcc-mipsel-linux-gnu \
gcc-mips64-linux-gnuabi64 \
gcc-mips64el-linux-gnuabi64 \
git curl python3 build-essential
git clone --depth 1 https://github.com/rust-lang/rust.git
cd rust
```
2. Try to link std tests for any of these 4 MIPS targets by running any one of these commands:
```sh
CC_mips_unknown_linux_gnu=mips-linux-gnu-gcc \
CARGO_TARGET_MIPS_UNKNOWN_LINUX_GNU_LINKER=mips-linux-gnu-gcc \
./x test library/std --target mips-unknown-linux-gnu
CC_mipsel_unknown_linux_gnu=mipsel-linux-gnu-gcc \
CARGO_TARGET_MIPSEL_UNKNOWN_LINUX_GNU_LINKER=mipsel-linux-gnu-gcc \
./x test library/std --target mipsel-unknown-linux-gnu
CC_mips64_unknown_linux_gnuabi64=mips64-linux-gnuabi64-gcc \
CARGO_TARGET_MIPS64_UNKNOWN_LINUX_GNUABI64_LINKER=mips64-linux-gnuabi64-gcc \
./x test library/std --target mips64-unknown-linux-gnuabi64
CC_mips64el_unknown_linux_gnuabi64=mips64el-linux-gnuabi64-gcc \
CARGO_TARGET_MIPS64EL_UNKNOWN_LINUX_GNUABI64_LINKER=mips64el-linux-gnuabi64-gcc \
./x test library/std --target mips64el-unknown-linux-gnuabi64
```
### Expected
No link error. After this PR there are no link errors.
### Actual
```
error: linking with `mips-linux-gnu-gcc` failed: exit status: 1
|
= note: LC_ALL="C" PATH="/rust/build/x86_64-unknown-linux-gnu/stage1/lib/rustlib/x86_64-unknown-linux-gnu/bin:/rust/build/x86_64-unknown-linux-gnu/stage1/lib/rustlib/x86_64-unknown-linux-gnu/bin:/rust/build/x86_64-unknown-linux-gnu/stage1/lib/rustlib/x86_64-unknown-linux-gnu/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin" VSLANG="1033" "mips-linux-gnu-gcc" "/tmp/rustcEtKsay/symbols.o" "/rust/build/x86_64-unknown-linux-gnu/stage1-std/mips-unknown-linux-gnu/release/deps/std-1cffa50fa8c43b63.std.9ee227e919a554fa-cgu.00.rcgu.o" "/rust/build/x86_64-unknown-linux-gnu/stage1-std/mips-unknown-linux-gnu/release/deps/std-1cffa50fa8c43b63.std.9ee227e919a554fa-cgu.01.rcgu.o" "/rust/build/x86_64-unknown-linux-gnu/stage1-std/mips-unknown-linux-gnu/release/deps/std-1cffa50fa8c43b63.std.9ee227e919a554fa-cgu.02.rcgu.o" "/rust/build/x86_64-unknown-linux-gnu/stage1-std/mips-unknown-linux-gnu/release/deps/std-1cffa50fa8c43b63.std.9ee227e919a554fa-cgu.03.rcgu.o" "/rust/build/x86_64-unknown-linux-gnu/stage1-std/mips-unknown-linux-gnu/release/deps/std-1cffa50fa8c43b63.std.9ee227e919a554fa-cgu.04.rcgu.o" "/rust/build/x86_64-unknown-linux-gnu/stage1-std/mips-unknown-linux-gnu/release/deps/std-1cffa50fa8c43b63.std.9ee227e919a554fa-cgu.05.rcgu.o" "/rust/build/x86_64-unknown-linux-gnu/stage1-std/mips-unknown-linux-gnu/release/deps/std-1cffa50fa8c43b63.std.9ee227e919a554fa-cgu.06.rcgu.o" "/rust/build/x86_64-unknown-linux-gnu/stage1-std/mips-unknown-linux-gnu/release/deps/std-1cffa50fa8c43b63.std.9ee227e919a554fa-cgu.07.rcgu.o" "/rust/build/x86_64-unknown-linux-gnu/stage1-std/mips-unknown-linux-gnu/release/deps/std-1cffa50fa8c43b63.std.9ee227e919a554fa-cgu.08.rcgu.o" "/rust/build/x86_64-unknown-linux-gnu/stage1-std/mips-unknown-linux-gnu/release/deps/std-1cffa50fa8c43b63.std.9ee227e919a554fa-cgu.09.rcgu.o" "/rust/build/x86_64-unknown-linux-gnu/stage1-std/mips-unknown-linux-gnu/release/deps/std-1cffa50fa8c43b63.std.9ee227e919a554fa-cgu.10.rcgu.o" "/rust/build/x86_64-unknown-linux-gnu/stage1-std/mips-unknown-linux-gnu/release/deps/std-1cffa50fa8c43b63.std.9ee227e919a554fa-cgu.11.rcgu.o" "/rust/build/x86_64-unknown-linux-gnu/stage1-std/mips-unknown-linux-gnu/release/deps/std-1cffa50fa8c43b63.std.9ee227e919a554fa-cgu.12.rcgu.o" "/rust/build/x86_64-unknown-linux-gnu/stage1-std/mips-unknown-linux-gnu/release/deps/std-1cffa50fa8c43b63.std.9ee227e919a554fa-cgu.13.rcgu.o" "/rust/build/x86_64-unknown-linux-gnu/stage1-std/mips-unknown-linux-gnu/release/deps/std-1cffa50fa8c43b63.std.9ee227e919a554fa-cgu.14.rcgu.o" "/rust/build/x86_64-unknown-linux-gnu/stage1-std/mips-unknown-linux-gnu/release/deps/std-1cffa50fa8c43b63.std.9ee227e919a554fa-cgu.15.rcgu.o" "-Wl,--as-needed" "-L" "/rust/build/x86_64-unknown-linux-gnu/stage1-std/mips-unknown-linux-gnu/release/deps" "-L" "/rust/build/x86_64-unknown-linux-gnu/stage1-std/release/deps" "-L" "/rust/build/x86_64-unknown-linux-gnu/stage1/lib/rustlib/mips-unknown-linux-gnu/lib" "-Wl,-Bstatic" "/rust/build/x86_64-unknown-linux-gnu/stage1-std/mips-unknown-linux-gnu/release/deps/librand_xorshift-deb32232a867c543.rlib" "/rust/build/x86_64-unknown-linux-gnu/stage1-std/mips-unknown-linux-gnu/release/deps/librand-5a391600dce9d98f.rlib" "/rust/build/x86_64-unknown-linux-gnu/stage1-std/mips-unknown-linux-gnu/release/deps/librand_core-a11cfba3d86c5298.rlib" "/rust/build/x86_64-unknown-linux-gnu/stage1/lib/rustlib/mips-unknown-linux-gnu/lib/libtest-65b05caf5a9b99a4.rlib" "/rust/build/x86_64-unknown-linux-gnu/stage1/lib/rustlib/mips-unknown-linux-gnu/lib/libgetopts-ba692b2f798aef60.rlib" "/rust/build/x86_64-unknown-linux-gnu/stage1/lib/rustlib/mips-unknown-linux-gnu/lib/libunicode_width-20ec8b475126cb0b.rlib" "/rust/build/x86_64-unknown-linux-gnu/stage1/lib/rustlib/mips-unknown-linux-gnu/lib/librustc_std_workspace_std-c17f739fee51cc86.rlib" "-L" "/rust/build/x86_64-unknown-linux-gnu/stage1/lib/rustlib/mips-unknown-linux-gnu/lib" "-Wl,-Bdynamic" "-lstd-124ee57a4c00deda" "-Wl,-Bstatic" "/rust/build/x86_64-unknown-linux-gnu/stage1-std/mips-unknown-linux-gnu/release/deps/libcompiler_builtins-bd55a137b89bc81f.rlib" "-Wl,-Bdynamic" "-lgcc_s" "-lutil" "-lrt" "-lpthread" "-lm" "-ldl" "-lc" "-Wl,--eh-frame-hdr" "-Wl,-z,noexecstack" "-L" "/rust/build/x86_64-unknown-linux-gnu/stage1/lib/rustlib/mips-unknown-linux-gnu/lib" "-o" "/rust/build/x86_64-unknown-linux-gnu/stage1-std/mips-unknown-linux-gnu/release/deps/std-1cffa50fa8c43b63" "-Wl,--gc-sections" "-pie" "-Wl,-z,relro,-z,now" "-Wl,-O1" "-nodefaultlibs" "-Wl,-z,origin" "-Wl,-rpath,$ORIGIN/../lib"
= note: /usr/lib/gcc-cross/mips-linux-gnu/12/../../../../mips-linux-gnu/bin/ld: /rust/build/x86_64-unknown-linux-gnu/stage1-std/mips-unknown-linux-gnu/release/deps/std-1cffa50fa8c43b63.std.9ee227e919a554fa-cgu.12.rcgu.o: in function `std::num::test_num':
std.9ee227e919a554fa-cgu.12:(.text._ZN3std3num8test_num17haed2ea710c1afdc3E+0x38): undefined reference to `__gnu_f2h_ieee'
/usr/lib/gcc-cross/mips-linux-gnu/12/../../../../mips-linux-gnu/bin/ld: std.9ee227e919a554fa-cgu.12:(.text._ZN3std3num8test_num17haed2ea710c1afdc3E+0x3c): undefined reference to `__gnu_f2h_ieee'
/usr/lib/gcc-cross/mips-linux-gnu/12/../../../../mips-linux-gnu/bin/ld: std.9ee227e919a554fa-cgu.12:(.text._ZN3std3num8test_num17haed2ea710c1afdc3E+0x44): undefined reference to `__gnu_h2f_ieee'
...
collect2: error: ld returned 1 exit status
error: could not compile `std` (lib test) due to 1 previous error
```
Mark format! with must_use hint
Uses unstable feature https://github.com/rust-lang/rust/issues/94745
Part of #126475
First contribution to rust, please let me know if the blessing of tests is correct
Thanks `@bjorn3` for the help
Rollup of 8 pull requests
Successful merges:
- #127179 (Print `TypeId` as hex for debugging)
- #127189 (LinkedList's Cursor: method to get a ref to the cursor's list)
- #127236 (doc: update config file path in platform-support/wasm32-wasip1-threads.md)
- #127297 (Improve std::Path's Hash quality by avoiding prefix collisions)
- #127308 (Attribute cleanups)
- #127354 (Describe Sized requirements for mem::offset_of)
- #127409 (Emit a wrap expr span_bug only if context is not tainted)
- #127447 (once_lock: make test not take as long in Miri)
r? `@ghost`
`@rustbot` modify labels: rollup
Describe Sized requirements for mem::offset_of
The container doesn't have to be sized, but the field must be sized (at least until https://github.com/rust-lang/rust/issues/126151 is stable).
Print `TypeId` as hex for debugging
In <https://github.com/rust-lang/rust/pull/127134>, the `Debug` impl for `TypeId` was changed to print a single integer rather than a tuple. Change this again to print as hex for more concise and consistent formatting, as was suggested.
Result:
TypeId(0x1378bb1c0a0202683eb65e7c11f2e4d7)
Don't check the capacity every time (and also for `Extend` for tuples, as this is how `unzip()` is implemented).
I did this with an unsafe method on `Extend` that doesn't check for growth (`extend_one_unchecked()`). I've marked it as perma-unstable currently, although we may want to expose it in the future so collections outside of std can benefit from it. Then specialize `Extend for (A, B)` for `TrustedLen` to call it.
It may seem that an alternative way of implementing this is to have a semi-public trait (`#[doc(hidden)]` public, so collections outside of core can implement it) for `extend()` inside tuples, and specialize it from collections. However, it is impossible due to limitations of `min_specialization`.
A concern that may arise with the current approach is that implementing `extend_one_unchecked()` correctly must also incur implementing `extend_reserve()`, otherwise you can have UB. This is a somewhat non-local safety invariant. However, I believe this is fine, since to have actual UB you must have unsafe code inside your `extend_one_unchecked()` that makes incorrect assumption, *and* not implement `extend_reserve()`. I've also documented this requirement.
offset_from, offset: clearly separate safety requirements the user needs to prove from corollaries that automatically follow
By landing https://github.com/rust-lang/rust/pull/116675 we decided that objects larger than `isize::MAX` cannot exist in the address space of a Rust program, which lets us simplify these rules.
For `offset_from`, we can even state that the *absolute* distance fits into an `isize`, and therefore exclude `isize::MIN`. This PR also changes Miri to treat an `isize::MIN` difference like the other isize-overflowing cases.
Add `new_range_api` for RFC 3550
Initial implementation for #125687
This includes a `From<legacy::RangeInclusive> for RangeInclusive` impl for convenience, instead of the `TryFrom` impl from the RFC. Having `From` is highly convenient and the debug assert should find almost all misuses.
This includes re-exports of all existing `Range` types under `core::range`, plus the range-related traits (`RangeBounds`, `Step`, `OneSidedRange`) and the `Bound` enum.
Currently the iterators are just wrappers around the old range types.
Tracking issues:
- https://github.com/rust-lang/rust/issues/123741
- https://github.com/rust-lang/rust/issues/125687
Improve readability of some fmt code examples
Some indent was weird. Some examples were too long (overall better to keep it to maximum 80 columns, but only changed the most outstanding ones).
r? ```@Amanieu```
Improve dead code analysis
Fixes#120770
1. check impl items later if self ty is private although the trait method is public, cause we must use the ty firstly if it's private
2. mark the adt live if it appears in pattern, like generic argument, this implies the use of the adt
3. based on the above, we can handle the case that private adts impl Default, so that we don't need adding rustc_trivial_field_reads on Default, and the logic in should_ignore_item
r? ``@pnkfelix``
This includes a `From<legacy::RangeInclusive> for RangeInclusive` impl for convenience, instead of the `TryFrom` impl from the RFC.
Having `From` is highly convenient and the assertion is unlikely to be a problem in practice.
This includes re-exports of all existing `Range` types under `core::range`, plus the range-related traits (`RangeBounds`, `Step`, `OneSidedRange`) and the `Bound` enum.
Currently the iterators are just wrappers around the old range types,
and most other trait impls delegate to the old rage types as well.
Also includes an `.iter()` shorthand for `.clone().into_iter()`
