Improve code generated for `starts_with(<literal char>)`
This PR includes two minor improvements to the code generated when checking for string prefix/suffix.
The first commit simplifies the str/str operation, by taking advantage of the raw UTF-8 representation.
The second commit replaces the current str/char matching logic with a char->str encoding and then the previous method.
The resulting code should be equivalent in the generic case (one char is being encoded versus one char being decoded), but it becomes easy to optimize in the case of a literal char, which in most cases a developer might expect to be at least as simple as that of a literal string.
This PR should fix#41993
Stabilize the `core::panic` module
`std::panic` is already stable.
`core::panic::PanicInfo` and `core::panic::Location` are stable and can be used through that path because of a bug in stability checking: #15702
Stabilize `std::{rc,sync}::Weak::{weak_count, strong_count}`
* Original PR: #56696
* Tracking issue: #57977Closes: #57977
Supporting comments:
> Although these were added for testing, it is occasionally useful to have a way to probe optimistically for whether a weak pointer has become dangling, without actually taking the overhead of manipulating atomics. Are there any plans to stabilize this?
_Originally posted by @bdonlan in https://github.com/rust-lang/rust/issues/57977#issuecomment-516970921_
> Having this stabilized would help. Currently, the only way to check if a weak pointer has become dangling is to call `upgrade`, which is by far expensive.
_Originally posted by @glebpom in https://github.com/rust-lang/rust/issues/57977#issuecomment-526934709_
Not sure if stabilizing these warrants a full RFC, so throwing this out here as a start for now.
Note: per CONTRIBUTING.md, I ran the tidy checks, but they seem to be failing on unchanged files (primarily in `src/stdsimd`).
Restore original implementation of Vec::retain
This PR reverts #48065, which aimed to optimize `Vec::retain` by making use of `Vec::drain_filter`. Unfortunately at that time, `drain_filter` was unsound.
The soundness hole in `Vec::drain_filter` was fixed in #61224 by guaranteeing that cleanup logic runs via a nested `Drop`, even in the event of a panic. Implementing this nested drop affects codegen (apparently?) and results in slower code.
Fixes#65970
Enable `loop` and `while` in constants behind a feature flag
This PR is an initial implementation of #52000. It adds a `const_loop` feature gate, which allows `while` and `loop` expressions through both HIR and MIR const-checkers if enabled. `for` expressions remain forbidden by the HIR const-checker, since they desugar to a call to `IntoIterator::into_iter`, which will be rejected anyways.
`while` loops also require [`#![feature(const_if_match)]`](https://github.com/rust-lang/rust/pull/66507), since they have a conditional built into them. The diagnostics from the HIR const checker will suggest this to the user.
r? @oli-obk
cc @rust-lang/wg-const-eval
This PR reverts #48065, which aimed to optimize `Vec::retain` by
making use of `Vec::drain_filter`. Unfortunately at that time,
`drain_filter` was unsound.
The soundness hole in `Vec::drain_filter` was fixed in #61224 by
guaranteeing that cleanup logic runs via a nested `Drop`, even in
the event of a panic. Implementing this nested drop affects codegen
(apparently?) and results in slower code.
Fixes#65970
Require stable/unstable annotations for the constness of all stable fns with a const modifier
r? @RalfJung @Centril
Every `#[stable]` const fn now needs either a `#[rustc_const_unstable]` attribute or a `#[rustc_const_stable]` attribute. You can't silently stabilize the constness of a function anymore.
SGX: Change ELF entrypoint
This fixes [rust-sgx issue #148](https://github.com/fortanix/rust-sgx/issues/148).
A new entry point is created for the ELF file generated by `rustc`, separate from the enclave entry point. When the ELF file is executed as a Linux binary, the error message below is written to stderr.
> Error: This file is an SGX enclave which cannot be executed as a standard Linux binary.
> See the installation guide at https://edp.fortanix.com/docs/installation/guide/ on how to use 'cargo run' or follow the steps at https://edp.fortanix.com/docs/tasks/deployment/ for manual deployment.
When the ELF file is converted to an SGXS using `elf2sgxs`, the old entry point is still set as the enclave entry point. In a future pull request in the rust-sgx repository, `elf2sgxs` will be modified to remove the code in the ELF entry point, since this code is not needed in the enclave.
Rollup of 7 pull requests
Successful merges:
- #67026 (Improve diagnostics and code for exhaustiveness of empty matches)
- #67235 (VecDeque: drop remaining items on destructor panic)
- #67254 (dont ICE in case of invalid drop fn)
- #67256 (Reduce allocs for validation errors)
- #67274 (be explicit that mem::uninitialized is the same as MaybeUninit::uninit().assume_init())
- #67278 (`coerce_inner`: use initial `expected_ty`)
- #67280 (docs: std::convert::From: Fix typo)
Failed merges:
r? @ghost
Improve diagnostics and code for exhaustiveness of empty matches
There was a completely separate check and diagnostics for the case of an empty match. This led to slightly different error messages and duplicated code.
This improves code reuse and generally clarifies what happens for empty matches. This also clarifies the action of the `exhaustive_patterns` feature, and ensures that this feature doesn't change diagnostics in places it doesn't need to.
