Generalize get_nullable_type to allow types where null is all-ones.
#94586
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Generalize get_nullable_type to accept types that have an all-ones bit pattern as their sentry "null" value. This will allow [`OwnedFd`], [`BorrowedFd`], [`OwnedSocket`], and [`BorrowedSocket`] to be marked with `#[rustc_nonnull_optimization_guaranteed]`, which will allow `Option<OwnedFd>`, `Option<BorrowedFd>`, `Option<OwnedSocket>`, and `Option<BorrowedSocket>` to be used in FFI declarations, as described in the [I/O safety RFC]. For example, it will allow a function like `open` on Unix and `WSASocketW` on Windows to be declared using `Option<OwnedFd>` and `Option<OwnedSocket>` return types, respectively. The actual change to add `#[rustc_nonnull_optimization_guaranteed]` to the abovementioned types will be a separate PR, as it'll depend on having this patch in the stage0 compiler. Also, update the diagnostics to mention that "niche optimizations" are used in libstd as well as libcore, as `rustc_layout_scalar_valid_range_start` and `rustc_layout_scalar_valid_range_end` are already in use in libstd. [`OwnedFd`]: https://github.com/rust-lang/rust/blob/c9dc44be24c58ff13ce46416c4b97ab5c1bd8429/library/std/src/os/fd/owned.rs#L49 [`BorrowedFd`]: https://github.com/rust-lang/rust/blob/c9dc44be24c58ff13ce46416c4b97ab5c1bd8429/library/std/src/os/fd/owned.rs#L29 [`OwnedSocket`]: https://github.com/rust-lang/rust/blob/c9dc44be24c58ff13ce46416c4b97ab5c1bd8429/library/std/src/os/windows/io/socket.rs#L51 [`BorrowedSocket`]: https://github.com/rust-lang/rust/blob/c9dc44be24c58ff13ce46416c4b97ab5c1bd8429/library/std/src/os/windows/io/socket.rs#L29 [I/O safety RFC]: https://github.com/rust-lang/rfcs/blob/master/text/3128-io-safety.md#ownedfd-and-borrowedfdfd-1
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…askrgr Rollup of 8 pull requests Successful merges: - rust-lang#91993 (Tweak output for non-exhaustive `match` expression) - rust-lang#92385 (Add Result::{ok, err, and, or, unwrap_or} as const) - rust-lang#94559 (Remove argument from closure in thread::Scope::spawn.) - rust-lang#94580 (Emit `unused_attributes` if a level attr only has a reason) - rust-lang#94586 (Generalize `get_nullable_type` to allow types where null is all-ones.) - rust-lang#94708 (diagnostics: only talk about `Cargo.toml` if running under Cargo) - rust-lang#94712 (promot debug_assert to assert) - rust-lang#94726 (:arrow_up: rust-analyzer) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup
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PR rust-lang#94586 added support for using `rustc_nonnull_optimization_guaranteed` on values where the "null" value is the all-ones bitpattern. Now that rust-lang#94586 has made it to the stage0 compiler, add `rustc_nonnull_optimization_guaranteed` to `OwnedFd`, `BorrowedFd`, `OwnedSocket`, and `BorrowedSocket`, since these types all exclude all-ones bitpatterns. This allows `Option<OwnedFd>`, `Option<BorrowedFd>`, `Option<OwnedSocket>`, and `Option<BorrowedSocket>` to be used in FFI declarations, as described in the [I/O safety RFC]. [I/O safety RFC]: https://github.com/rust-lang/rfcs/blob/master/text/3128-io-safety.md#ownedfd-and-borrowedfdfd-1
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…ll-optimization-guaranteed, r=joshtriplett Add rustc_nonnull_optimization_guaranteed to Owned/Borrowed Fd/Socket PR rust-lang#94586 added support for using `rustc_nonnull_optimization_guaranteed` on values where the "null" value is the all-ones bitpattern. Now that rust-lang#94586 has made it to the stage0 compiler, add `rustc_nonnull_optimization_guaranteed` to `OwnedFd`, `BorrowedFd`, `OwnedSocket`, and `BorrowedSocket`, since these types all exclude all-ones bitpatterns. This allows `Option<OwnedFd>`, `Option<BorrowedFd>`, `Option<OwnedSocket>`, and `Option<BorrowedSocket>` to be used in FFI declarations, as described in the [I/O safety RFC]. [I/O safety RFC]: https://github.com/rust-lang/rfcs/blob/master/text/3128-io-safety.md#ownedfd-and-borrowedfdfd-1
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Generalize get_nullable_type to accept types that have an all-ones bit
pattern as their sentry "null" value.
This will allow
OwnedFd,BorrowedFd,OwnedSocket, andBorrowedSocketto be marked with#[rustc_nonnull_optimization_guaranteed], which will allowOption<OwnedFd>,Option<BorrowedFd>,Option<OwnedSocket>, andOption<BorrowedSocket>to be used in FFI declarations, as describedin the I/O safety RFC.
For example, it will allow a function like
openon Unix andWSASocketWon Windows to be declared using
Option<OwnedFd>andOption<OwnedSocket>return types, respectively.
The actual change to add
#[rustc_nonnull_optimization_guaranteed]to the abovementioned types will be a separate PR, as it'll depend on
having this patch in the stage0 compiler.
Also, update the diagnostics to mention that "niche optimizations" are
used in libstd as well as libcore, as
rustc_layout_scalar_valid_range_startand
rustc_layout_scalar_valid_range_endare already in use in libstd.