Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly
Sign up
Appearance settings
This repository was archived by the owner on May 28, 2025. It is now read-only.

Commit bda31d1

Browse files
committed
built-in derive: remove BYTE_SLICE_IN_PACKED_STRUCT_WITH_DERIVE hack and lint
1 parent 52f3c71 commit bda31d1

File tree

8 files changed

+41
-232
lines changed

8 files changed

+41
-232
lines changed

‎compiler/rustc_builtin_macros/src/deriving/generic/mod.rs‎

Lines changed: 6 additions & 48 deletions
Original file line numberDiff line numberDiff line change
@@ -181,11 +181,10 @@ use crate::{deriving, errors};
181181
use rustc_ast::ptr::P;
182182
use rustc_ast::{
183183
self as ast, BindingMode, ByRef, EnumDef, Expr, GenericArg, GenericParamKind, Generics,
184-
Mutability, PatKind, TyKind,VariantData,
184+
Mutability, PatKind, VariantData,
185185
};
186186
use rustc_attr as attr;
187187
use rustc_expand::base::{Annotatable, ExtCtxt};
188-
use rustc_session::lint::builtin::BYTE_SLICE_IN_PACKED_STRUCT_WITH_DERIVE;
189188
use rustc_span::symbol::{kw, sym, Ident, Symbol};
190189
use rustc_span::{Span, DUMMY_SP};
191190
use std::cell::RefCell;
@@ -1599,52 +1598,11 @@ impl<'a> TraitDef<'a> {
15991598
),
16001599
);
16011600
if is_packed {
1602-
// In general, fields in packed structs are copied via a
1603-
// block, e.g. `&{self.0}`. The two exceptions are `[u8]`
1604-
// and `str` fields, which cannot be copied and also never
1605-
// cause unaligned references. These exceptions are allowed
1606-
// to handle the `FlexZeroSlice` type in the `zerovec`
1607-
// crate within `icu4x-0.9.0`.
1608-
//
1609-
// Once use of `icu4x-0.9.0` has dropped sufficiently, this
1610-
// exception should be removed.
1611-
let is_simple_path = |ty: &P<ast::Ty>, sym| {
1612-
if let TyKind::Path(None, ast::Path { segments, .. }) = &ty.kind
1613-
&& let [seg] = segments.as_slice()
1614-
&& seg.ident.name == sym
1615-
&& seg.args.is_none()
1616-
{
1617-
true
1618-
} else {
1619-
false
1620-
}
1621-
};
1622-
1623-
let exception = if let TyKind::Slice(ty) = &struct_field.ty.kind
1624-
&& is_simple_path(ty, sym::u8)
1625-
{
1626-
Some("byte")
1627-
} else if is_simple_path(&struct_field.ty, sym::str) {
1628-
Some("string")
1629-
} else {
1630-
None
1631-
};
1632-
1633-
if let Some(ty) = exception {
1634-
cx.sess.psess.buffer_lint(
1635-
BYTE_SLICE_IN_PACKED_STRUCT_WITH_DERIVE,
1636-
sp,
1637-
ast::CRATE_NODE_ID,
1638-
rustc_lint_defs::BuiltinLintDiag::ByteSliceInPackedStructWithDerive {
1639-
ty: ty.to_string(),
1640-
},
1641-
);
1642-
} else {
1643-
// Wrap the expression in `{...}`, causing a copy.
1644-
field_expr = cx.expr_block(
1645-
cx.block(struct_field.span, thin_vec![cx.stmt_expr(field_expr)]),
1646-
);
1647-
}
1601+
// Fields in packed structs are wrapped in a block, e.g. `&{self.0}`,
1602+
// causing a copy instead of a (potentially misaligned) reference.
1603+
field_expr = cx.expr_block(
1604+
cx.block(struct_field.span, thin_vec![cx.stmt_expr(field_expr)]),
1605+
);
16481606
}
16491607
cx.expr_addr_of(sp, field_expr)
16501608
})

‎compiler/rustc_lint/src/lib.rs‎

Lines changed: 6 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -537,7 +537,7 @@ fn register_builtins(store: &mut LintStore) {
537537
);
538538
store.register_removed(
539539
"suspicious_auto_trait_impls",
540-
"no longer needed, see #93367 \
540+
"no longer needed, see issue #93367 \
541541
<https://github.com/rust-lang/rust/issues/93367> for more information",
542542
);
543543
store.register_removed(
@@ -559,6 +559,11 @@ fn register_builtins(store: &mut LintStore) {
559559
"box_pointers",
560560
"it does not detect other kinds of allocations, and existed only for historical reasons",
561561
);
562+
store.register_removed(
563+
"byte_slice_in_packed_struct_with_derive",
564+
"converted into hard error, see issue #107457 \
565+
<https://github.com/rust-lang/rust/issues/107457> for more information",
566+
)
562567
}
563568

564569
fn register_internals(store: &mut LintStore) {

‎compiler/rustc_lint_defs/src/builtin.rs‎

Lines changed: 0 additions & 34 deletions
Original file line numberDiff line numberDiff line change
@@ -25,7 +25,6 @@ declare_lint_pass! {
2525
BARE_TRAIT_OBJECTS,
2626
BINDINGS_WITH_VARIANT_NAME,
2727
BREAK_WITH_LABEL_AND_LOOP,
28-
BYTE_SLICE_IN_PACKED_STRUCT_WITH_DERIVE,
2928
CENUM_IMPL_DROP_CAST,
3029
COHERENCE_LEAK_CHECK,
3130
CONFLICTING_REPR_HINTS,
@@ -4246,39 +4245,6 @@ declare_lint! {
42464245
report_in_external_macro
42474246
}
42484247

4249-
declare_lint! {
4250-
/// The `byte_slice_in_packed_struct_with_derive` lint detects cases where a byte slice field
4251-
/// (`[u8]`) or string slice field (`str`) is used in a `packed` struct that derives one or
4252-
/// more built-in traits.
4253-
///
4254-
/// ### Example
4255-
///
4256-
/// ```rust
4257-
/// #[repr(packed)]
4258-
/// #[derive(Hash)]
4259-
/// struct FlexZeroSlice {
4260-
/// width: u8,
4261-
/// data: [u8],
4262-
/// }
4263-
/// ```
4264-
///
4265-
/// {{produces}}
4266-
///
4267-
/// ### Explanation
4268-
///
4269-
/// This was previously accepted but is being phased out, because fields in packed structs are
4270-
/// now required to implement `Copy` for `derive` to work. Byte slices and string slices are a
4271-
/// temporary exception because certain crates depended on them.
4272-
pub BYTE_SLICE_IN_PACKED_STRUCT_WITH_DERIVE,
4273-
Warn,
4274-
"`[u8]` or `str` used in a packed struct with `derive`",
4275-
@future_incompatible = FutureIncompatibleInfo {
4276-
reason: FutureIncompatibilityReason::FutureReleaseErrorReportInDeps,
4277-
reference: "issue #107457 <https://github.com/rust-lang/rust/issues/107457>",
4278-
};
4279-
report_in_external_macro
4280-
}
4281-
42824248
declare_lint! {
42834249
/// The `invalid_macro_export_arguments` lint detects cases where `#[macro_export]` is being used with invalid arguments.
42844250
///

‎tests/ui/derives/deriving-with-repr-packed.rs‎

Lines changed: 4 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -22,25 +22,22 @@ struct Y(usize);
2222
struct X(Y);
2323
//~^ ERROR cannot move out of `self` which is behind a shared reference
2424

25-
// This is currently allowed, but will be phased out at some point. From
26-
// `zerovec` within icu4x-0.9.0.
2725
#[derive(Debug)]
2826
#[repr(packed)]
2927
struct FlexZeroSlice {
3028
width: u8,
3129
data: [u8],
32-
//~^ WARNING byte slice in a packed struct that derives a built-in trait
33-
//~^^ this was previously accepted
30+
//~^ ERROR cannot move
31+
//~| ERROR cannot move
3432
}
3533

36-
// Again, currently allowed, but will be phased out.
3734
#[derive(Debug)]
3835
#[repr(packed)]
3936
struct WithStr {
4037
width: u8,
4138
data: str,
42-
//~^ WARNING string slice in a packed struct that derives a built-in trait
43-
//~^^ this was previously accepted
39+
//~^ ERROR cannot move
40+
//~| ERROR cannot move
4441
}
4542

4643
fn main() {}
Lines changed: 25 additions & 49 deletions
Original file line numberDiff line numberDiff line change
@@ -1,32 +1,3 @@
1-
warning: byte slice in a packed struct that derives a built-in trait
2-
--> $DIR/deriving-with-repr-packed.rs:31:5
3-
|
4-
LL | #[derive(Debug)]
5-
| ----- in this derive macro expansion
6-
...
7-
LL | data: [u8],
8-
| ^^^^^^^^^^
9-
|
10-
= warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
11-
= note: for more information, see issue #107457 <https://github.com/rust-lang/rust/issues/107457>
12-
= help: consider implementing the trait by hand, or remove the `packed` attribute
13-
= note: `#[warn(byte_slice_in_packed_struct_with_derive)]` on by default
14-
= note: this warning originates in the derive macro `Debug` (in Nightly builds, run with -Z macro-backtrace for more info)
15-
16-
warning: string slice in a packed struct that derives a built-in trait
17-
--> $DIR/deriving-with-repr-packed.rs:41:5
18-
|
19-
LL | #[derive(Debug)]
20-
| ----- in this derive macro expansion
21-
...
22-
LL | data: str,
23-
| ^^^^^^^^^
24-
|
25-
= warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
26-
= note: for more information, see issue #107457 <https://github.com/rust-lang/rust/issues/107457>
27-
= help: consider implementing the trait by hand, or remove the `packed` attribute
28-
= note: this warning originates in the derive macro `Debug` (in Nightly builds, run with -Z macro-backtrace for more info)
29-
301
error[E0507]: cannot move out of `self` which is behind a shared reference
312
--> $DIR/deriving-with-repr-packed.rs:22:10
323
|
@@ -47,38 +18,43 @@ LL | struct X(Y);
4718
= note: `#[derive(Debug)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
4819
= note: this error originates in the derive macro `Debug` (in Nightly builds, run with -Z macro-backtrace for more info)
4920

50-
error: aborting due to 1 previous error; 2 warnings emitted
21+
error[E0161]: cannot move a value of type `[u8]`
22+
--> $DIR/deriving-with-repr-packed.rs:29:5
23+
|
24+
LL | data: [u8],
25+
| ^^^^^^^^^^ the size of `[u8]` cannot be statically determined
5126

52-
For more information about this error, try `rustc --explain E0507`.
53-
Future incompatibility report: Future breakage diagnostic:
54-
warning: byte slice in a packed struct that derives a built-in trait
55-
--> $DIR/deriving-with-repr-packed.rs:31:5
27+
error[E0507]: cannot move out of `self.data` which is behind a shared reference
28+
--> $DIR/deriving-with-repr-packed.rs:29:5
5629
|
5730
LL | #[derive(Debug)]
5831
| ----- in this derive macro expansion
5932
...
6033
LL | data: [u8],
61-
| ^^^^^^^^^^
34+
| ^^^^^^^^^^ move occurs because `self.data` has type `[u8]`, which does not implement the `Copy` trait
35+
|
36+
= note: `#[derive(Debug)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
37+
= note: this error originates in the derive macro `Debug` (in Nightly builds, run with -Z macro-backtrace for more info)
38+
39+
error[E0161]: cannot move a value of type `str`
40+
--> $DIR/deriving-with-repr-packed.rs:38:5
6241
|
63-
= warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
64-
= note: for more information, see issue #107457 <https://github.com/rust-lang/rust/issues/107457>
65-
= help: consider implementing the trait by hand, or remove the `packed` attribute
66-
= note: `#[warn(byte_slice_in_packed_struct_with_derive)]` on by default
67-
= note: this warning originates in the derive macro `Debug` (in Nightly builds, run with -Z macro-backtrace for more info)
42+
LL | data: str,
43+
| ^^^^^^^^^ the size of `str` cannot be statically determined
6844

69-
Future breakage diagnostic:
70-
warning: string slice in a packed struct that derives a built-in trait
71-
--> $DIR/deriving-with-repr-packed.rs:41:5
45+
error[E0507]: cannot move out of `self.data` which is behind a shared reference
46+
--> $DIR/deriving-with-repr-packed.rs:38:5
7247
|
7348
LL | #[derive(Debug)]
7449
| ----- in this derive macro expansion
7550
...
7651
LL | data: str,
77-
| ^^^^^^^^^
52+
| ^^^^^^^^^ move occurs because `self.data` has type `str`, which does not implement the `Copy` trait
7853
|
79-
= warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
80-
= note: for more information, see issue #107457 <https://github.com/rust-lang/rust/issues/107457>
81-
= help: consider implementing the trait by hand, or remove the `packed` attribute
82-
= note: `#[warn(byte_slice_in_packed_struct_with_derive)]` on by default
83-
= note: this warning originates in the derive macro `Debug` (in Nightly builds, run with -Z macro-backtrace for more info)
54+
= note: `#[derive(Debug)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
55+
= note: this error originates in the derive macro `Debug` (in Nightly builds, run with -Z macro-backtrace for more info)
56+
57+
error: aborting due to 5 previous errors
8458

59+
Some errors have detailed explanations: E0161, E0507.
60+
For more information about an error, try `rustc --explain E0161`.

‎tests/ui/deriving/deriving-all-codegen.rs‎

Lines changed: 0 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -73,16 +73,6 @@ impl Copy for PackedManualCopy {}
7373
#[derive(Debug, Hash, PartialEq, Eq, PartialOrd, Ord)]
7474
struct Unsized([u32]);
7575

76-
// A packed struct with an unsized `[u8]` field. This is currently allowed, but
77-
// causes a warning and will be phased out at some point.
78-
#[derive(Debug, Hash)]
79-
#[repr(packed)]
80-
struct PackedUnsizedU8([u8]);
81-
//~^ WARNING byte slice in a packed struct that derives a built-in trait
82-
//~^^ WARNING byte slice in a packed struct that derives a built-in trait
83-
//~^^^ this was previously accepted
84-
//~^^^^ this was previously accepted
85-
8676
trait Trait {
8777
type A;
8878
}

‎tests/ui/deriving/deriving-all-codegen.stderr‎

Lines changed: 0 additions & 63 deletions
This file was deleted.

‎tests/ui/deriving/deriving-all-codegen.stdout‎

Lines changed: 0 additions & 20 deletions
Original file line numberDiff line numberDiff line change
@@ -516,26 +516,6 @@ impl ::core::cmp::Ord for Unsized {
516516
}
517517
}
518518

519-
// A packed struct with an unsized `[u8]` field. This is currently allowed, but
520-
// causes a warning and will be phased out at some point.
521-
#[repr(packed)]
522-
struct PackedUnsizedU8([u8]);
523-
#[automatically_derived]
524-
impl ::core::fmt::Debug for PackedUnsizedU8 {
525-
#[inline]
526-
fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
527-
::core::fmt::Formatter::debug_tuple_field1_finish(f,
528-
"PackedUnsizedU8", &&self.0)
529-
}
530-
}
531-
#[automatically_derived]
532-
impl ::core::hash::Hash for PackedUnsizedU8 {
533-
#[inline]
534-
fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
535-
::core::hash::Hash::hash(&self.0, state)
536-
}
537-
}
538-
539519
trait Trait {
540520
type A;
541521
}

0 commit comments

Comments
(0)

AltStyle によって変換されたページ (->オリジナル) /