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Put the RFC behind a feature gate result_ffi_guarantees 
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8 files changed

+499
-28
lines changed

8 files changed

+499
-28
lines changed

‎compiler/rustc_feature/src/unstable.rs

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@@ -585,6 +585,9 @@ declare_features! (
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(incomplete, repr128, "1.16.0", Some(56071)),
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/// Allows `repr(simd)` and importing the various simd intrinsics.
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(unstable, repr_simd, "1.4.0", Some(27731)),
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/// Allows enums like Result<T, E> to be used across FFI, if T's niche value can
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/// be used to describe E or vise-versa.
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(unstable, result_ffi_guarantees, "CURRENT_RUSTC_VERSION", Some(110503)),
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/// Allows bounding the return type of AFIT/RPITIT.
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(incomplete, return_type_notation, "1.70.0", Some(109417)),
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/// Allows `extern "rust-cold"`.

‎compiler/rustc_lint/src/types.rs

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@@ -1142,6 +1142,10 @@ pub(crate) fn repr_nullable_ptr<'tcx>(
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[var_one, var_two] => match (&var_one.fields.raw[..], &var_two.fields.raw[..]) {
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([], [field]) | ([field], []) => field.ty(tcx, args),
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([field1], [field2]) => {
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if !tcx.features().result_ffi_guarantees {
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return None;
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}
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let ty1 = field1.ty(tcx, args);
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let ty2 = field2.ty(tcx, args);
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‎compiler/rustc_span/src/symbol.rs

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@@ -1509,6 +1509,7 @@ symbols! {
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require,
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residual,
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result,
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result_ffi_guarantees,
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resume,
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return_position_impl_trait_in_trait,
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return_type_notation,

‎src/doc/unstable-book/src/language-features/result-ffi-guarantees.md

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@@ -0,0 +1,14 @@
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# `result_ffi_guarantees`
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The tracking issue for this feature is: [#110503]
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[#110503]: https://github.com/rust-lang/rust/issues/110503
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------------------------
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This feature adds the possibility of using `Result<T, E>` in FFI if T's niche
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value can be used to describe E or vise-versa.
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See [RFC 3391] for more information.
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[RFC 3391]: https://github.com/rust-lang/rfcs/blob/master/text/3391-result_ffi_guarantees.md

‎tests/ui/feature-gates/feature-gate-result_ffi_guarantees.rs

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@@ -0,0 +1,99 @@
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#![allow(dead_code)]
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#![deny(improper_ctypes)]
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#![feature(ptr_internals)]
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use std::num;
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enum Z {}
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#[repr(transparent)]
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struct TransparentStruct<T>(T, std::marker::PhantomData<Z>);
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#[repr(transparent)]
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enum TransparentEnum<T> {
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Variant(T, std::marker::PhantomData<Z>),
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}
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struct NoField;
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extern "C" {
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fn result_ref_t(x: Result<&'static u8, ()>);
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//~^ ERROR `extern` block uses type `Result
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fn result_fn_t(x: Result<extern "C" fn(), ()>);
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//~^ ERROR `extern` block uses type `Result
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fn result_nonnull_t(x: Result<std::ptr::NonNull<u8>, ()>);
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//~^ ERROR `extern` block uses type `Result
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fn result_unique_t(x: Result<std::ptr::Unique<u8>, ()>);
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//~^ ERROR `extern` block uses type `Result
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fn result_nonzero_u8_t(x: Result<num::NonZero<u8>, ()>);
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//~^ ERROR `extern` block uses type `Result
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fn result_nonzero_u16_t(x: Result<num::NonZero<u16>, ()>);
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//~^ ERROR `extern` block uses type `Result
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fn result_nonzero_u32_t(x: Result<num::NonZero<u32>, ()>);
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//~^ ERROR `extern` block uses type `Result
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fn result_nonzero_u64_t(x: Result<num::NonZero<u64>, ()>);
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//~^ ERROR `extern` block uses type `Result
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fn result_nonzero_usize_t(x: Result<num::NonZero<usize>, ()>);
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//~^ ERROR `extern` block uses type `Result
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fn result_nonzero_i8_t(x: Result<num::NonZero<i8>, ()>);
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//~^ ERROR `extern` block uses type `Result
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fn result_nonzero_i16_t(x: Result<num::NonZero<i16>, ()>);
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//~^ ERROR `extern` block uses type `Result
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fn result_nonzero_i32_t(x: Result<num::NonZero<i32>, ()>);
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//~^ ERROR `extern` block uses type `Result
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fn result_nonzero_i64_t(x: Result<num::NonZero<i64>, ()>);
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//~^ ERROR `extern` block uses type `Result
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fn result_nonzero_isize_t(x: Result<num::NonZero<isize>, ()>);
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//~^ ERROR `extern` block uses type `Result
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fn result_transparent_struct_t(x: Result<TransparentStruct<num::NonZero<u8>>, ()>);
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//~^ ERROR `extern` block uses type `Result
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fn result_transparent_enum_t(x: Result<TransparentEnum<num::NonZero<u8>>, ()>);
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//~^ ERROR `extern` block uses type `Result
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fn result_phantom_t(x: Result<num::NonZero<u8>, std::marker::PhantomData<()>>);
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//~^ ERROR `extern` block uses type `Result
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fn result_1zst_exhaustive_no_variant_t(x: Result<num::NonZero<u8>, Z>);
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//~^ ERROR `extern` block uses type `Result
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fn result_1zst_exhaustive_no_field_t(x: Result<num::NonZero<u8>, NoField>);
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//~^ ERROR `extern` block uses type `Result
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fn result_ref_e(x: Result<(), &'static u8>);
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//~^ ERROR `extern` block uses type `Result
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fn result_fn_e(x: Result<(), extern "C" fn()>);
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//~^ ERROR `extern` block uses type `Result
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fn result_nonnull_e(x: Result<(), std::ptr::NonNull<u8>>);
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//~^ ERROR `extern` block uses type `Result
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fn result_unique_e(x: Result<(), std::ptr::Unique<u8>>);
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//~^ ERROR `extern` block uses type `Result
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fn result_nonzero_u8_e(x: Result<(), num::NonZero<u8>>);
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//~^ ERROR `extern` block uses type `Result
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fn result_nonzero_u16_e(x: Result<(), num::NonZero<u16>>);
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//~^ ERROR `extern` block uses type `Result
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fn result_nonzero_u32_e(x: Result<(), num::NonZero<u32>>);
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//~^ ERROR `extern` block uses type `Result
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fn result_nonzero_u64_e(x: Result<(), num::NonZero<u64>>);
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//~^ ERROR `extern` block uses type `Result
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fn result_nonzero_usize_e(x: Result<(), num::NonZero<usize>>);
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//~^ ERROR `extern` block uses type `Result
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fn result_nonzero_i8_e(x: Result<(), num::NonZero<i8>>);
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//~^ ERROR `extern` block uses type `Result
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fn result_nonzero_i16_e(x: Result<(), num::NonZero<i16>>);
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//~^ ERROR `extern` block uses type `Result
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fn result_nonzero_i32_e(x: Result<(), num::NonZero<i32>>);
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//~^ ERROR `extern` block uses type `Result
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fn result_nonzero_i64_e(x: Result<(), num::NonZero<i64>>);
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//~^ ERROR `extern` block uses type `Result
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fn result_nonzero_isize_e(x: Result<(), num::NonZero<isize>>);
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//~^ ERROR `extern` block uses type `Result
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fn result_transparent_struct_e(x: Result<(), TransparentStruct<num::NonZero<u8>>>);
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//~^ ERROR `extern` block uses type `Result
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fn result_transparent_enum_e(x: Result<(), TransparentEnum<num::NonZero<u8>>>);
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//~^ ERROR `extern` block uses type `Result
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fn result_phantom_e(x: Result<num::NonZero<u8>, std::marker::PhantomData<()>>);
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//~^ ERROR `extern` block uses type `Result
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fn result_1zst_exhaustive_no_variant_e(x: Result<Z, num::NonZero<u8>>);
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//~^ ERROR `extern` block uses type `Result
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fn result_1zst_exhaustive_no_field_e(x: Result<NoField, num::NonZero<u8>>);
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//~^ ERROR `extern` block uses type `Result
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}
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pub fn main() {}

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