}),
),
);
- // In general, fields in packed structs are copied via a
- // block, e.g. `&{self.0}`. The one exception is `[u8]`
- // fields, which cannot be copied and also never cause
- // unaligned references. This exception is allowed to
- // handle the `FlexZeroSlice` type in the `zerovec` crate
- // within `icu4x-0.9.0`.
- //
- // Once use of `icu4x-0.9.0` has dropped sufficiently, this
- // exception should be removed.
- let is_u8_slice = if let TyKind::Slice(ty) = &struct_field.ty.kind &&
- let TyKind::Path(None, rustc_ast::Path { segments, .. }) = &ty.kind &&
- let [seg] = segments.as_slice() &&
- seg.ident.name == sym::u8 && seg.args.is_none()
- {
- true
- } else {
- false
- };
if is_packed {
- if is_u8_slice {
+ // In general, fields in packed structs are copied via a
+ // block, e.g. `&{self.0}`. The two exceptions are `[u8]`
+ // and `str` fields, which cannot be copied and also never
+ // cause unaligned references. These exceptions are allowed
+ // to handle the `FlexZeroSlice` type in the `zerovec`
+ // crate within `icu4x-0.9.0`.
+ //
+ // Once use of `icu4x-0.9.0` has dropped sufficiently, this
+ // exception should be removed.
+ let is_simple_path = |ty: &P<ast::Ty>, sym| {
+ if let TyKind::Path(None, ast::Path { segments, .. }) = &ty.kind &&
+ let [seg] = segments.as_slice() &&
+ seg.ident.name == sym && seg.args.is_none()
+ {
+ true
+ } else {
+ false
+ }
+ };
+
+ let exception = if let TyKind::Slice(ty) = &struct_field.ty.kind &&
+ is_simple_path(ty, sym::u8)
+ {
+ Some("byte")
+ } else if is_simple_path(&struct_field.ty, sym::str) {
+ Some("string")
+ } else {
+ None
+ };
+
+ if let Some(ty) = exception {
cx.sess.parse_sess.buffer_lint_with_diagnostic(
BYTE_SLICE_IN_PACKED_STRUCT_WITH_DERIVE,
sp,
ast::CRATE_NODE_ID,
- "byte slice in a packed struct that derives a built-in trait",
+ &format!(
+ "{} slice in a packed struct that derives a built-in trait",
+ ty
+ ),
rustc_lint_defs::BuiltinLintDiagnostics::ByteSliceInPackedStructWithDerive
);
} else {
declare_lint! {
/// The `byte_slice_in_packed_struct_with_derive` lint detects cases where a byte slice field
- /// (`[u8]`) is used in a `packed` struct that derives one or more built-in traits.
+ /// (`[u8]`) or string slice field (`str`) is used in a `packed` struct that derives one or
+ /// more built-in traits.
///
/// ### Example
///
/// ### Explanation
///
/// This was previously accepted but is being phased out, because fields in packed structs are
- /// now required to implement `Copy` for `derive` to work. Byte slices are a temporary
- /// exception because certain crates depended on them.
+ /// now required to implement `Copy` for `derive` to work. Byte slices and string slices are a
+ /// temporary exception because certain crates depended on them.
pub BYTE_SLICE_IN_PACKED_STRUCT_WITH_DERIVE,
Warn,
- "`[u8]` slice used in a packed struct with `derive`",
+ "`[u8]` or `str` used in a packed struct with `derive`",
@future_incompatible = FutureIncompatibleInfo {
reference: "issue #107457 <https://github.com/rust-lang/rust/issues/107457>",
reason: FutureIncompatibilityReason::FutureReleaseErrorReportNow,
//~^^ this was previously accepted
}
+// Again, currently allowed, but will be phased out.
+#[derive(Debug)]
+#[repr(packed)]
+struct WithStr {
+ width: u8,
+ data: str,
+ //~^ WARNING string slice in a packed struct that derives a built-in trait
+ //~^^ this was previously accepted
+}
+
fn main() {}
= note: `#[warn(byte_slice_in_packed_struct_with_derive)]` on by default
= note: this warning originates in the derive macro `Debug` (in Nightly builds, run with -Z macro-backtrace for more info)
+warning: string slice in a packed struct that derives a built-in trait
+ --> $DIR/deriving-with-repr-packed.rs:41:5
+ |
+LL | #[derive(Debug)]
+ | ----- in this derive macro expansion
+...
+LL | data: str,
+ | ^^^^^^^^^
+ |
+ = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+ = note: for more information, see issue #107457 <https://github.com/rust-lang/rust/issues/107457>
+ = help: consider implementing the trait by hand, or remove the `packed` attribute
+ = note: this warning originates in the derive macro `Debug` (in Nightly builds, run with -Z macro-backtrace for more info)
+
error[E0507]: cannot move out of `self` which is behind a shared reference
--> $DIR/deriving-with-repr-packed.rs:22:10
|
|
= note: this error originates in the derive macro `Debug` (in Nightly builds, run with -Z macro-backtrace for more info)
-error: aborting due to previous error; 1 warning emitted
+error: aborting due to previous error; 2 warnings emitted
For more information about this error, try `rustc --explain E0507`.
Future incompatibility report: Future breakage diagnostic:
= note: `#[warn(byte_slice_in_packed_struct_with_derive)]` on by default
= note: this warning originates in the derive macro `Debug` (in Nightly builds, run with -Z macro-backtrace for more info)
+Future breakage diagnostic:
+warning: string slice in a packed struct that derives a built-in trait
+ --> $DIR/deriving-with-repr-packed.rs:41:5
+ |
+LL | #[derive(Debug)]
+ | ----- in this derive macro expansion
+...
+LL | data: str,
+ | ^^^^^^^^^
+ |
+ = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+ = note: for more information, see issue #107457 <https://github.com/rust-lang/rust/issues/107457>
+ = help: consider implementing the trait by hand, or remove the `packed` attribute
+ = note: `#[warn(byte_slice_in_packed_struct_with_derive)]` on by default
+ = note: this warning originates in the derive macro `Debug` (in Nightly builds, run with -Z macro-backtrace for more info)
+
projects / rust.git / commitdiff