Make `Cell::new` method come first in documentation
Methods to create a thing usually comes first in `std` documentation, and `Cell` has been an exception. Also, `T: Copy` specialized methods should not be on top of the page. (This had led me to miss that most of its methods are not bounded by `Copy`...)
rewrite documentation for unimplemented! to clarify use
The current docs for `unimplemented!` seem to miss the point of this macro.
> This can be useful if you are prototyping and are just looking to have your code type-check, or if you're implementing a trait that requires multiple methods, and you're only planning on using one of them.
You could also return a `()` if you just want your code to type-check.
I think `unimplemented!` is useful for when you want your program to exit when it reaches an unimplemented area.
I rewrote the explanation and gave examples of both forms of this macro that I think clarify its use a little better.
Revert #63649 - "Upgrade Emscripten targets to use upstream LLVM backend"
This change caused the runtime of the linux-asmjs builder to nearly double from 2+ hours to about 4 hours, which happens to be the bors timeout. (It made it in barely under 4 hours when it was merged.) This is causing timeouts on all new changes.
This reverts commit 7870050796, reversing
changes made to 2e7244807a.
Stabilize `Option::as_deref` and `Option::as_deref_mut`
The tracking issue https://github.com/rust-lang/rust/issues/50264 still has unresolved question for the corresponding `Result` methods.
- Refactors the Emscripten target spec to share code with other wasm
targets.
- Replaces the incorrect wasm32 C call ABI with the old asmjs
version, which is correct for both wasm32 and JS.
- Updates the varargs ABI used by Emscripten and deletes the old one.
- Removes the obsolete wasm32-experimental-emscripten target.
- Temporarily makes Emscripten targets use panic=abort by default
because supporting unwinding will require an LLVM patch.
Stabilize todo macro
The `todo!` macro is just another name for `unimplemented!`.
Tracking issue: https://github.com/rust-lang/rust/issues/59277
This PR needs a FCP to merge.
r? @withoutboats
Inline `{min,max}_value` even in debug builds
I think it is worth to inline `{min,max}_value` even in debug builds.
See this godbolt link: https://godbolt.org/z/-COkVS
use try_fold instead of try_for_each to reduce compile time
as it was stated in #64572 that the biggest gain was due to less code was generated I tried to reduce the number of functions to inline by using try_fold direct instead of calling try_for_each that calls try_fold.
as there is some gains with using the try_fold function this is maybe a way forward.
when I tried to compile the clap-rs benchmark I get times gains only some % from #64572
there is more function that use eg. fold that calls try_fold that also can be changed but the question is how mush "duplication" that is tolerated in std to give faster compile times
can someone start a perf run?
cc @nnethercote @scottmcm @bluss
r? @ghost
Remove manual unrolling from slice::Iter(Mut)::try_fold
While this definitely helps sometimes (particularly for trivial closures), it's also a pessimization sometimes, so it's better to leave this to (hypothetical) future LLVM improvements instead of forcing this on everyone.
I think it's better for the advice to be that sometimes you need to unroll manually than you sometimes need to not-unroll manually (like #64545).
---
For context see https://github.com/rust-lang/rust/pull/64572#issuecomment-532961046
Improve wording in documentation of MaybeUninit
Changes
> variables are properly initialized **at** their respective type
into
> variables are properly initialized **as** their respective type
reserve `impl<T> From<!> for T`
this is necessary for never-type stabilization.
cc #57012#35121
I think we wanted a crater run for this @nikomatsakis?
r? @nikomatsakis
use `sign` variable in abs and wrapping_abs methods
This also makes the code easier to understand by hinting at the significance of `self >> ($BITS - 1)`.
Also, now `overflowing_abs` simply uses `wrapping_abs`, which is clearer and avoids a potential performance regression in the LLVM IR.
This PR follows from the discussion from #63786.
r? @eddyb
cc @nikic
Document the unstable iter_order_by library feature
Tracking issue: #64295
Follow-up for: #62205
References the tracking issue and adds a page to the unstable book for the new unstable `iter_order_by` feature.
While this definitely helps sometimes (particularly for trivial closures), it's also a pessimization sometimes, so it's better to leave this to (hypothetical) future LLVM improvements instead of forcing this on everyone.
I think it's better for the advice to be that sometimes you need to unroll manually than you sometimes need to not-unroll manually (like #64545).
Add `cmp::{min_by, min_by_key, max_by, max_by_key}`
This adds the following functions to `core::cmp`:
- `min_by`
- `min_by_key`
- `max_by`
- `max_by_key`
`min_by` and `max_by` are somewhat trivial to implement, but not entirely because `min_by` returns the first value in case the two are equal (and `max_by` the second). `min` and `max` can be implemented in terms of `min_by` and `max_by`, but not as easily the other way around.
To give an example of why I think these functions could be useful: the `Iterator::{min_by, min_by_key, max_by, max_by_key}` methods all currently hard-code the behavior mentioned above which is an ever so small duplication of logic. If we delegate them to `cmp::{min_by, max_by}` methods instead, we get the correct behavior for free. (edit: this is now included in the PR)
I added `min_by_key` / `max_by_key` for consistency's sake but I wouldn't mind removing them. I don't have a particular use case in mind for them, and `min_by` / `max_by` seem to be more useful.
Tracking issue: #64460
PR: documentation spin loop hint
The documentation for 'spin loop hint' explains that yield is better if the lock holder is running on the same CPU. I suggest that 'CPU or core' would be clearer.
