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Rollup merge of rust-lang#129487 - GrigorenkoPV:repr_transparent_exte…
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…rnal_private_fields, r=compiler-errors

repr_transparent_external_private_fields: special-case some std types

Fixes rust-lang#129470

``@rustbot`` label +A-lint +L-repr_transparent_external_private_fields
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matthiaskrgr authored Aug 25, 2024
2 parents 52ea214 + 06f2d73 commit 5545cb7
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Showing 13 changed files with 113 additions and 1 deletion.
5 changes: 5 additions & 0 deletions compiler/rustc_feature/src/builtin_attrs.rs
Original file line number Diff line number Diff line change
Expand Up @@ -641,6 +641,11 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
ErrorFollowing, EncodeCrossCrate::Yes,
"rustc_deprecated_safe_2024 is supposed to be used in libstd only",
),
rustc_attr!(
rustc_pub_transparent, Normal, template!(Word),
WarnFollowing, EncodeCrossCrate::Yes,
"used internally to mark types with a `transparent` representation when it is guaranteed by the documentation",
),


// ==========================================================================
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3 changes: 2 additions & 1 deletion compiler/rustc_hir_analysis/src/check/check.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1259,7 +1259,8 @@ pub(super) fn check_transparent<'tcx>(tcx: TyCtxt<'tcx>, adt: ty::AdtDef<'tcx>)
ty::Tuple(list) => list.iter().try_for_each(|t| check_non_exhaustive(tcx, t)),
ty::Array(ty, _) => check_non_exhaustive(tcx, *ty),
ty::Adt(def, args) => {
if !def.did().is_local() {
if !def.did().is_local() && !tcx.has_attr(def.did(), sym::rustc_pub_transparent)
{
let non_exhaustive = def.is_variant_list_non_exhaustive()
|| def
.variants()
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4 changes: 4 additions & 0 deletions compiler/rustc_passes/messages.ftl
Original file line number Diff line number Diff line change
Expand Up @@ -657,6 +657,10 @@ passes_rustc_lint_opt_ty =
`#[rustc_lint_opt_ty]` should be applied to a struct
.label = not a struct
passes_rustc_pub_transparent =
attribute should be applied to `#[repr(transparent)]` types
.label = not a `#[repr(transparent)]` type
passes_rustc_safe_intrinsic =
attribute should be applied to intrinsic functions
.label = not an intrinsic function
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13 changes: 13 additions & 0 deletions compiler/rustc_passes/src/check_attr.rs
Original file line number Diff line number Diff line change
Expand Up @@ -245,6 +245,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
self.check_coroutine(attr, target);
}
[sym::linkage, ..] => self.check_linkage(attr, span, target),
[sym::rustc_pub_transparent, ..] => self.check_rustc_pub_transparent( attr.span, span, attrs),
[
// ok
sym::allow
Expand Down Expand Up @@ -2381,6 +2382,18 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
}
}
}

fn check_rustc_pub_transparent(&self, attr_span: Span, span: Span, attrs: &[Attribute]) {
if !attrs
.iter()
.filter(|attr| attr.has_name(sym::repr))
.filter_map(|attr| attr.meta_item_list())
.flatten()
.any(|nmi| nmi.has_name(sym::transparent))
{
self.dcx().emit_err(errors::RustcPubTransparent { span, attr_span });
}
}
}

impl<'tcx> Visitor<'tcx> for CheckAttrVisitor<'tcx> {
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9 changes: 9 additions & 0 deletions compiler/rustc_passes/src/errors.rs
Original file line number Diff line number Diff line change
Expand Up @@ -622,6 +622,15 @@ pub struct RustcStdInternalSymbol {
pub span: Span,
}

#[derive(Diagnostic)]
#[diag(passes_rustc_pub_transparent)]
pub struct RustcPubTransparent {
#[primary_span]
pub attr_span: Span,
#[label]
pub span: Span,
}

#[derive(Diagnostic)]
#[diag(passes_link_ordinal)]
pub struct LinkOrdinal {
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1 change: 1 addition & 0 deletions compiler/rustc_span/src/symbol.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1674,6 +1674,7 @@ symbols! {
rustc_private,
rustc_proc_macro_decls,
rustc_promotable,
rustc_pub_transparent,
rustc_reallocator,
rustc_regions,
rustc_reservation_impl,
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3 changes: 3 additions & 0 deletions library/core/src/cell.rs
Original file line number Diff line number Diff line change
Expand Up @@ -306,6 +306,7 @@ pub use once::OnceCell;
/// See the [module-level documentation](self) for more.
#[stable(feature = "rust1", since = "1.0.0")]
#[repr(transparent)]
#[cfg_attr(not(bootstrap), rustc_pub_transparent)]
pub struct Cell<T: ?Sized> {
value: UnsafeCell<T>,
}
Expand Down Expand Up @@ -2055,6 +2056,7 @@ impl<T: ?Sized + fmt::Display> fmt::Display for RefMut<'_, T> {
#[lang = "unsafe_cell"]
#[stable(feature = "rust1", since = "1.0.0")]
#[repr(transparent)]
#[cfg_attr(not(bootstrap), rustc_pub_transparent)]
pub struct UnsafeCell<T: ?Sized> {
value: T,
}
Expand Down Expand Up @@ -2297,6 +2299,7 @@ impl<T> UnsafeCell<*mut T> {
/// See [`UnsafeCell`] for details.
#[unstable(feature = "sync_unsafe_cell", issue = "95439")]
#[repr(transparent)]
#[cfg_attr(not(bootstrap), rustc_pub_transparent)]
pub struct SyncUnsafeCell<T: ?Sized> {
value: UnsafeCell<T>,
}
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1 change: 1 addition & 0 deletions library/core/src/mem/manually_drop.rs
Original file line number Diff line number Diff line change
Expand Up @@ -47,6 +47,7 @@ use crate::ptr;
#[lang = "manually_drop"]
#[derive(Copy, Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord, Hash)]
#[repr(transparent)]
#[cfg_attr(not(bootstrap), rustc_pub_transparent)]
pub struct ManuallyDrop<T: ?Sized> {
value: T,
}
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1 change: 1 addition & 0 deletions library/core/src/mem/maybe_uninit.rs
Original file line number Diff line number Diff line change
Expand Up @@ -237,6 +237,7 @@ use crate::{fmt, intrinsics, ptr, slice};
#[lang = "maybe_uninit"]
#[derive(Copy)]
#[repr(transparent)]
#[cfg_attr(not(bootstrap), rustc_pub_transparent)]
pub union MaybeUninit<T> {
uninit: (),
value: ManuallyDrop<T>,
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1 change: 1 addition & 0 deletions library/core/src/pin.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1084,6 +1084,7 @@ use crate::{cmp, fmt};
#[lang = "pin"]
#[fundamental]
#[repr(transparent)]
#[cfg_attr(not(bootstrap), rustc_pub_transparent)]
#[derive(Copy, Clone)]
pub struct Pin<Ptr> {
// FIXME(#93176): this field is made `#[unstable] #[doc(hidden)] pub` to:
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25 changes: 25 additions & 0 deletions tests/ui/attributes/rustc_pub_transparent.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,25 @@
#![feature(rustc_attrs, transparent_unions)]

#[rustc_pub_transparent]
#[repr(transparent)]
union E<T: Copy> {
value: T,
uninit: (),
}

#[repr(transparent)]
#[rustc_pub_transparent]
struct S<T>(T);

#[rustc_pub_transparent] //~ ERROR attribute should be applied to `#[repr(transparent)]` types
#[repr(C)]
struct S1 {
A: u8,
}

#[rustc_pub_transparent] //~ ERROR attribute should be applied to `#[repr(transparent)]` types
struct S2<T> {
value: T,
}

fn main() {}
23 changes: 23 additions & 0 deletions tests/ui/attributes/rustc_pub_transparent.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,23 @@
error: attribute should be applied to `#[repr(transparent)]` types
--> $DIR/rustc_pub_transparent.rs:14:1
|
LL | #[rustc_pub_transparent]
| ^^^^^^^^^^^^^^^^^^^^^^^^
LL | #[repr(C)]
LL | / struct S1 {
LL | | A: u8,
LL | | }
| |_- not a `#[repr(transparent)]` type

error: attribute should be applied to `#[repr(transparent)]` types
--> $DIR/rustc_pub_transparent.rs:20:1
|
LL | #[rustc_pub_transparent]
| ^^^^^^^^^^^^^^^^^^^^^^^^
LL | / struct S2<T> {
LL | | value: T,
LL | | }
| |_- not a `#[repr(transparent)]` type

error: aborting due to 2 previous errors

Original file line number Diff line number Diff line change
@@ -0,0 +1,25 @@
//@ check-pass

#![feature(sync_unsafe_cell)]
#![allow(unused)]
#![deny(repr_transparent_external_private_fields)]

// https://github.com/rust-lang/rust/issues/129470

struct ZST;

#[repr(transparent)]
struct TransparentWithManuallyDropZST {
value: i32,
md: std::mem::ManuallyDrop<ZST>,
mu: std::mem::MaybeUninit<ZST>,
p: std::pin::Pin<ZST>,
pd: std::marker::PhantomData<ZST>,
pp: std::marker::PhantomPinned,
c: std::cell::Cell<ZST>,
uc: std::cell::UnsafeCell<ZST>,
suc: std::cell::SyncUnsafeCell<ZST>,
zst: ZST,
}

fn main() {}

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