Trait tetsy_scale_info::prelude::marker::StructuralEq [−][src]
structural_match
)Required trait for constants used in pattern matches.
Any type that derives Eq
automatically implements this trait, regardless
of whether its type parameters implement Eq
.
This is a hack to work around a limitation in our type system.
Background
We want to require that types of consts used in pattern matches
have the attribute #[derive(PartialEq, Eq)]
.
In a more ideal world, we could check that requirement by just checking that
the given type implements both the StructuralPartialEq
trait and
the Eq
trait. However, you can have ADTs that do derive(PartialEq, Eq)
,
and be a case that we want the compiler to accept, and yet the constant's
type fails to implement Eq
.
Namely, a case like this:
#[derive(PartialEq, Eq)] struct Wrap<X>(X); fn higher_order(_: &()) { } const CFN: Wrap<fn(&())> = Wrap(higher_order); fn main() { match CFN { CFN => {} _ => {} } }
(The problem in the above code is that Wrap<fn(&())>
does not implement
PartialEq
, nor Eq
, because for<'a> fn(&'a _)
does not implement those
traits.)
Therefore, we cannot rely on naive check for StructuralPartialEq
and
mere Eq
.
As a hack to work around this, we use two separate traits injected by each
of the two derives (#[derive(PartialEq)]
and #[derive(Eq)]
) and check
that both of them are present as part of structural-match checking.
Implementations on Foreign Types
impl StructuralEq for SeekFrom
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impl StructuralEq for ThreadId
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impl<'a> StructuralEq for Component<'a>
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impl StructuralEq for ExitStatus
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impl StructuralEq for RecvTimeoutError
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impl StructuralEq for Shutdown
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impl<'a> StructuralEq for Prefix<'a>
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impl StructuralEq for Ipv6MulticastScope
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impl StructuralEq for SystemTime
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impl StructuralEq for AccessError
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impl StructuralEq for Instant
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impl<T> StructuralEq for SendError<T>
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impl StructuralEq for Output
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impl StructuralEq for Permissions
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impl StructuralEq for ErrorKind
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impl StructuralEq for SocketAddr
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impl StructuralEq for AddrParseError
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impl<T> StructuralEq for Cursor<T>
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impl StructuralEq for UCred
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impl StructuralEq for CString
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impl StructuralEq for FileType
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impl StructuralEq for StripPrefixError
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impl StructuralEq for NulError
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impl StructuralEq for TryRecvError
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impl StructuralEq for FromBytesWithNulError
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impl<'a> StructuralEq for PrefixComponent<'a>
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impl StructuralEq for IpAddr
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impl StructuralEq for VarError
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impl StructuralEq for WaitTimeoutResult
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impl StructuralEq for BacktraceStatus
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impl StructuralEq for FromVecWithNulError
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impl<T> StructuralEq for TrySendError<T>
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impl StructuralEq for IntoStringError
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impl StructuralEq for RecvError
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impl<'a> StructuralEq for Utf8LossyChunk<'a>
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impl<Idx> StructuralEq for RangeFrom<Idx>
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impl StructuralEq for Duration
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impl<Idx> StructuralEq for RangeTo<Idx>
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impl StructuralEq for CpuidResult
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impl<Idx> StructuralEq for RangeInclusive<Idx>
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impl StructuralEq for ParseCharError
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impl<T, E> StructuralEq for Result<T, E>
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impl<T> StructuralEq for Option<T>
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impl<Y, R> StructuralEq for GeneratorState<Y, R>
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impl StructuralEq for DecodeUtf16Error
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impl<Idx> StructuralEq for RangeToInclusive<Idx>
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impl StructuralEq for LayoutError
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impl<'a> StructuralEq for Location<'a>
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impl StructuralEq for SearchStep
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impl StructuralEq for ParseBoolError
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impl StructuralEq for RangeFull
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impl StructuralEq for Ordering
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impl StructuralEq for AllocError
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impl<T> StructuralEq for Poll<T>
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impl StructuralEq for Layout
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impl<Idx> StructuralEq for Range<Idx>
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impl StructuralEq for NoneError
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impl StructuralEq for CharTryFromError
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impl StructuralEq for Utf8Error
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impl<T> StructuralEq for Compact<T>
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impl StructuralEq for OptionBool
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impl StructuralEq for Error
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impl<T> StructuralEq for CapacityError<T>
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impl StructuralEq for Error
Loading content...Implementors
impl StructuralEq for PathError
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impl StructuralEq for TypeDefPrimitive
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impl StructuralEq for MetaForm
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impl StructuralEq for TryReserveError
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impl StructuralEq for FpCategory
1.0.0[src]
impl StructuralEq for IntErrorKind
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impl StructuralEq for TypeId
1.0.0[src]
impl StructuralEq for tetsy_scale_info::prelude::fmt::Error
1.0.0[src]
impl StructuralEq for PhantomPinned
1.33.0[src]
impl StructuralEq for NonZeroI8
1.34.0[src]
impl StructuralEq for NonZeroI16
1.34.0[src]
impl StructuralEq for NonZeroI32
1.34.0[src]
impl StructuralEq for NonZeroI64
1.34.0[src]
impl StructuralEq for NonZeroI128
1.34.0[src]
impl StructuralEq for NonZeroIsize
1.34.0[src]
impl StructuralEq for NonZeroU8
1.28.0[src]
impl StructuralEq for NonZeroU16
1.28.0[src]
impl StructuralEq for NonZeroU32
1.28.0[src]
impl StructuralEq for NonZeroU64
1.28.0[src]
impl StructuralEq for NonZeroU128
1.28.0[src]
impl StructuralEq for NonZeroUsize
1.28.0[src]
impl StructuralEq for ParseFloatError
1.0.0[src]
impl StructuralEq for ParseIntError
1.0.0[src]
impl StructuralEq for TryFromIntError
1.34.0[src]
impl StructuralEq for FromUtf8Error
1.0.0[src]
impl StructuralEq for String
1.0.0[src]
impl StructuralEq for Registry
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impl<'a, T> StructuralEq for Symbol<'a, T>
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impl<S> StructuralEq for PortableForm<S>
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impl<S> StructuralEq for PortableRegistry<S> where
S: FormString,
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S: FormString,
impl<T> StructuralEq for Bound<T>
1.17.0[src]
impl<T> StructuralEq for Interner<T>
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impl<T> StructuralEq for UntrackedSymbol<T>
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impl<T> StructuralEq for Reverse<T>
1.19.0[src]
impl<T> StructuralEq for BTreeSet<T>
1.0.0[src]
impl<T> StructuralEq for PhantomData<T> where
T: ?Sized,
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T: ?Sized,
impl<T> StructuralEq for ManuallyDrop<T> where
T: ?Sized,
1.20.0[src]
T: ?Sized,