diff options
Diffstat (limited to 'third_party/rust/pin-project/examples/struct-default-expanded.rs')
| -rw-r--r-- | third_party/rust/pin-project/examples/struct-default-expanded.rs | 155 |
1 files changed, 155 insertions, 0 deletions
diff --git a/third_party/rust/pin-project/examples/struct-default-expanded.rs b/third_party/rust/pin-project/examples/struct-default-expanded.rs new file mode 100644 index 0000000000..d6610993d3 --- /dev/null +++ b/third_party/rust/pin-project/examples/struct-default-expanded.rs @@ -0,0 +1,155 @@ +// Original code (./struct-default.rs): +// +// ```rust +// #![allow(dead_code)] +// +// use pin_project::pin_project; +// +// #[pin_project] +// struct Struct<T, U> { +// #[pin] +// pinned: T, +// unpinned: U, +// } +// +// fn main() {} +// ``` + +#![allow(dead_code, unused_imports, unused_parens, unknown_lints, renamed_and_removed_lints)] +#![allow(clippy::needless_lifetimes)] + +use pin_project::pin_project; + +// #[pin_project] +struct Struct<T, U> { + // #[pin] + pinned: T, + unpinned: U, +} + +const _: () = { + struct __StructProjection<'pin, T, U> + where + Struct<T, U>: 'pin, + { + pinned: ::pin_project::__private::Pin<&'pin mut (T)>, + unpinned: &'pin mut (U), + } + struct __StructProjectionRef<'pin, T, U> + where + Struct<T, U>: 'pin, + { + pinned: ::pin_project::__private::Pin<&'pin (T)>, + unpinned: &'pin (U), + } + + impl<T, U> Struct<T, U> { + fn project<'pin>( + self: ::pin_project::__private::Pin<&'pin mut Self>, + ) -> __StructProjection<'pin, T, U> { + unsafe { + let Self { pinned, unpinned } = self.get_unchecked_mut(); + __StructProjection { + pinned: ::pin_project::__private::Pin::new_unchecked(pinned), + unpinned, + } + } + } + fn project_ref<'pin>( + self: ::pin_project::__private::Pin<&'pin Self>, + ) -> __StructProjectionRef<'pin, T, U> { + unsafe { + let Self { pinned, unpinned } = self.get_ref(); + __StructProjectionRef { + pinned: ::pin_project::__private::Pin::new_unchecked(pinned), + unpinned, + } + } + } + } + + // Ensure that it's impossible to use pin projections on a #[repr(packed)] + // struct. + // + // Taking a reference to a packed field is UB, and applying + // `#[forbid(unaligned_references)]` makes sure that doing this is a hard error. + // + // If the struct ends up having #[repr(packed)] applied somehow, + // this will generate an (unfriendly) error message. Under all reasonable + // circumstances, we'll detect the #[repr(packed)] attribute, and generate + // a much nicer error above. + // + // See https://github.com/taiki-e/pin-project/pull/34 for more details. + #[forbid(unaligned_references, safe_packed_borrows)] + fn __assert_not_repr_packed<T, U>(this: &Struct<T, U>) { + let _ = &this.pinned; + let _ = &this.unpinned; + } + + // Automatically create the appropriate conditional `Unpin` implementation. + // + // Basically this is equivalent to the following code: + // + // ```rust + // impl<T, U> Unpin for Struct<T, U> where T: Unpin {} + // ``` + // + // However, if struct is public and there is a private type field, + // this would cause an E0446 (private type in public interface). + // + // When RFC 2145 is implemented (rust-lang/rust#48054), + // this will become a lint, rather then a hard error. + // + // As a workaround for this, we generate a new struct, containing all of + // the pinned fields from our #[pin_project] type. This struct is declared + // within a function, which makes it impossible to be named by user code. + // This guarantees that it will use the default auto-trait impl for Unpin - + // that is, it will implement Unpin iff all of its fields implement Unpin. + // This type can be safely declared as 'public', satisfying the privacy + // checker without actually allowing user code to access it. + // + // This allows users to apply the #[pin_project] attribute to types + // regardless of the privacy of the types of their fields. + // + // See also https://github.com/taiki-e/pin-project/pull/53. + struct __Struct<'pin, T, U> { + __pin_project_use_generics: ::pin_project::__private::AlwaysUnpin< + 'pin, + (::pin_project::__private::PhantomData<T>, ::pin_project::__private::PhantomData<U>), + >, + __field0: T, + } + impl<'pin, T, U> ::pin_project::__private::Unpin for Struct<T, U> where + __Struct<'pin, T, U>: ::pin_project::__private::Unpin + { + } + // A dummy impl of `UnsafeUnpin`, to ensure that the user cannot implement it. + // + // To ensure that users don't accidentally write a non-functional `UnsafeUnpin` + // impls, we emit one ourselves. If the user ends up writing an `UnsafeUnpin` + // impl, they'll get a "conflicting implementations of trait" error when + // coherence checks are run. + #[doc(hidden)] + unsafe impl<'pin, T, U> ::pin_project::UnsafeUnpin for Struct<T, U> where + __Struct<'pin, T, U>: ::pin_project::__private::Unpin + { + } + + // Ensure that struct does not implement `Drop`. + // + // If you attempt to provide an Drop impl, the blanket impl will + // then apply to your type, causing a compile-time error due to + // the conflict with the second impl. + trait StructMustNotImplDrop {} + #[allow(clippy::drop_bounds, drop_bounds)] + impl<T: ::pin_project::__private::Drop> StructMustNotImplDrop for T {} + impl<T, U> StructMustNotImplDrop for Struct<T, U> {} + // A dummy impl of `PinnedDrop`, to ensure that users don't accidentally + // write a non-functional `PinnedDrop` impls. + #[doc(hidden)] + impl<T, U> ::pin_project::__private::PinnedDrop for Struct<T, U> { + unsafe fn drop(self: ::pin_project::__private::Pin<&mut Self>) {} + } +}; + +fn main() {} |