do not fetch variance for items when equating
Fixes#41849. Problem was that evaluating the constant expression
required evaluating a trait, which would equate types, which would
request variance information, which it would then discard. However,
computing the variance information would require determining the type of
a field, which would evaluate the constant expression.
(This problem will potentially arise *later* as we move to more sophisticated
constants, however, where we need to check subtyping. We can tackle that
when we come to it.)
r? @eddyb
Added blank lines around example
Added comment to Add example referencing the Output type
Removed whitespace from lines 272 and 273
Removed Debug derivation from Add examples
Added Debug derivation
Fixes#41849. Problem was that evaluating the constant expression
required evaluating a trait, which would equate types, which would
request variance information, which it would then discard. However,
computing the variance information would require determining the type of
a field, which would evaluate the constant expression.
(This problem will potentially arise *later* as we move to more sophisticated
constants, however, where we need to check subtyping. We can tackle that
when we come to it.)
Add disabled android host builders
Introduce the concept of disabled builder. A disabled builder is one that is not run by travis. It is intended to be run by the user who wants a rustc for a tier 2 or 3 platform. Off corse, there is no guarantee that it will work.
ci: Update android ndk and sdk
Make install-sdk.sh and install-ndk.sh more generic so future updates can be made directly on Dockerfile. Update ndk to r13b, which will be necessary to make host builds for android (in the future). Update sdk to r25.2.5 (maybe some emulator performance improvement).
More Queries for Crate Metadata
This covers a little bit of clean up and the following parts of #41417:
* `fn item_attrs(&self, def_id: DefId) -> Vec<ast::Attribute>;`
* `fn fn_arg_names(&self, did: DefId) -> Vec<ast::Name>;`
* `fn trait_of_item(&self, def_id: DefId) -> Option<DefId>;`
* `fn impl_parent(&self, impl_def_id: DefId) -> Option<DefId>;`
* ` fn is_foreign_item(&self, did: DefId) -> bool;`
* `fn is_exported_symbol(&self, def_id: DefId) -> bool;`
r? @nikomatsakis
Add `eprint!` and `eprintln!` macros to the prelude.
These are exactly the same as `print!` and `println!` except that they write to stderr instead of stdout. Issues #39228 and #40528; previous PR #39229; accepted RFC rust-lang/rfcs#1869; proposed revision to The Book rust-lang/book#615.
I have _not_ revised this any since the original submission; I will do that later this week. I wanted to get this PR in place since it's been quite a while since the RFC was merged.
Known outstanding review comments:
* [x] @steveklabnik requested a new chapter for the unstable version of The Book -- please see if the proposed revisions to the second edition cover it.
* [x] @nodakai asked if it were possible to merge the internal methods `_print` and `_eprint` - not completely, since they both refer to different internal globals which we don't want to expose, but I will see if some duplication can be factored out.
Please let me know if I missed anything.
[Doc] Improve `thread::spawn` documentation
Part of #29378
- Add two examples to `thread::spawn` doumentation that show common uses of threads.
- Add a link to `thread::Builder` in the `thread::spawn` documentation for configuring threads.
- Add a link to `thread::spawn` in `thread::Builder` in order to avoid documentation duplication.
r? @steveklabnik
[DOC] Improve the thread::park and thread::unpark documentation
Part of #29378 .
Takes care of the documentation for `park`, `park_duration` and also improves the `unpark` example.
- `park should` have its module documentation inlined here, and cleaned up.
- `park_timeout` could use links to `park`.
Improve docs on Arc<T> and Send/Sync
This is something I always forget, so let's actually
explain in the docs.
I didn't fully link up everything here, but I'd like to make sure that the wording is okay before I bother.
Add more ways to create a PathBuf to docs
The best way to do this wasn't in the documentation, and the ways that
were there needed some extra text to elaborate.
Fixes#40159
/cc @nagisa
This commit adds a new `-Z` flag to the compiler for use when bootstrapping the
compiler itself. We want to be able to use crates.io crates, but we also want
the usage of such crates to be as ergonomic as possible! To that end compiler
crates are a little tricky in that the crates.io crates are not annotated as
unstable, nor do they expect to pull in unstable dependencies.
To cover all these situations it's intended that the compiler will forever now
bootstrap with `-Z force-unstable-if-unmarked`. This flags serves a dual purpose
of forcing crates.io crates to themselves be unstable while also allowing them
to use other "unstable" crates.io crates. This should mean that adding a
dependency to compiler no longer requires upstream modification with
unstable/staged_api attributes for inclusion!
* Factor out the nigh-identical bodies of `_print` and `_eprint` to a helper
function `print_to` (I was sorely tempted to call it `_doprnt`).
* Update the issue number for the unstable `eprint` feature.
* Add entries to the "unstable book" for `eprint` and `eprint_internal`.
* Style corrections to the documentation.
Improve cleaning of the bottom of the backtrace
Following https://github.com/rust-lang/rust/pull/40264. It only cleans the bottom of the trace (after the main). It handles correctly the normal main, tests, benchmarks and threads.
I kept `skipped_before` since it will be used later for the cleaning of the top.
Make [u8]::reverse() 5x faster
Since LLVM doesn't vectorize the loop for us, do unaligned reads of a larger type and use LLVM's bswap intrinsic to do the reversing of the actual bytes. cfg!-restricted to x86 and x86_64, as I assume it wouldn't help on things like ARMv5.
Also makes [u16]::reverse() a more modest 1.5x faster by loading/storing u32 and swapping the u16s with ROT16.
Thank you ptr::*_unaligned for making this easy :)
Benchmark results (from my i5-2500K):
```text
# Before
test slice::reverse_u8 ... bench: 273,836 ns/iter (+/- 15,592) = 3829 MB/s
test slice::reverse_u16 ... bench: 139,793 ns/iter (+/- 17,748) = 7500 MB/s
test slice::reverse_u32 ... bench: 74,997 ns/iter (+/- 5,130) = 13981 MB/s
test slice::reverse_u64 ... bench: 47,452 ns/iter (+/- 2,213) = 22097 MB/s
# After
test slice::reverse_u8 ... bench: 52,170 ns/iter (+/- 3,962) = 20099 MB/s
test slice::reverse_u16 ... bench: 93,330 ns/iter (+/- 4,412) = 11235 MB/s
test slice::reverse_u32 ... bench: 74,731 ns/iter (+/- 1,425) = 14031 MB/s
test slice::reverse_u64 ... bench: 47,556 ns/iter (+/- 3,025) = 22049 MB/s
```
If you're curious about the assembly, instead of doing this
```
movzx eax, byte ptr [rdi]
movzx ecx, byte ptr [rsi]
mov byte ptr [rdi], cl
mov byte ptr [rsi], al
```
it does this
```
mov rax, qword ptr [rdx]
mov rbx, qword ptr [r11 + rcx - 8]
bswap rbx
mov qword ptr [rdx], rbx
bswap rax
mov qword ptr [r11 + rcx - 8], rax
```
