Trait tract_nnef::internal::tract_downcast_rs::__std::marker::StructuralEq

#[lang = "structural_teq"]
pub trait StructuralEq { }

🔬 This is a nightly-only experimental API. (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<'a> StructuralEq for Utf8LossyChunk<'a>

impl StructuralEq for Level

impl<'a> StructuralEq for Metadata<'a>

impl<'a> StructuralEq for MetadataBuilder<'a>

impl StructuralEq for LevelFilter

impl<A> StructuralEq for ExtendedGcd<A>

impl<T> StructuralEq for Complex<T>

impl StructuralEq for ErrorKind

impl StructuralEq for Endianness

impl StructuralEq for Needed

impl<R> StructuralEq for BitPos<R> where
    R: BitRegister, 

impl<R> StructuralEq for BitMask<R> where
    R: BitRegister, 

impl StructuralEq for Msb0

impl StructuralEq for Lsb0

impl<R> StructuralEq for BitIdx<R> where
    R: BitRegister, 

impl<R> StructuralEq for BitTail<R> where
    R: BitRegister, 

impl<R> StructuralEq for BitSel<R> where
    R: BitRegister, 

impl StructuralEq for Error

impl StructuralEq for ErrorCode

impl<T> StructuralEq for CapacityError<T>

impl StructuralEq for BigEndian

impl StructuralEq for LittleEndian

impl StructuralEq for HeaderMode

impl StructuralEq for EntryType

impl StructuralEq for FileTime

impl StructuralEq for Handle

impl StructuralEq for FlushDecompress

impl StructuralEq for Compression

impl StructuralEq for Status

impl StructuralEq for FlushCompress

impl StructuralEq for CompressionStrategy

impl StructuralEq for TDEFLStatus

impl StructuralEq for TDEFLFlush

impl StructuralEq for TINFLStatus

impl StructuralEq for MZError

impl StructuralEq for StreamResult

impl StructuralEq for MZStatus

impl StructuralEq for MZFlush

impl StructuralEq for CompressionLevel

impl StructuralEq for DataFormat

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Implementors

impl StructuralEq for Cost

impl StructuralEq for DatumType

impl StructuralEq for TDim

impl StructuralEq for Validation

impl StructuralEq for SliceInfoElem

impl StructuralEq for TryReserveError

impl StructuralEq for BacktraceStatus

impl StructuralEq for VarError

impl StructuralEq for tract_nnef::internal::tract_downcast_rs::__std::io::ErrorKind

impl StructuralEq for SeekFrom

impl StructuralEq for IpAddr

impl StructuralEq for Ipv6MulticastScope

impl StructuralEq for Shutdown

impl StructuralEq for SocketAddr

impl StructuralEq for FpCategory

impl StructuralEq for IntErrorKind

impl StructuralEq for SearchStep

impl StructuralEq for Ordering

impl StructuralEq for RecvTimeoutError

impl StructuralEq for TryRecvError

impl StructuralEq for AxisInfo

impl StructuralEq for Blob

impl StructuralEq for InletId

impl StructuralEq for OutletId

impl StructuralEq for Symbol

impl StructuralEq for Packer

impl StructuralEq for Axis

impl StructuralEq for IxDynImpl

impl StructuralEq for Slice

impl StructuralEq for AllocError

impl StructuralEq for Layout

impl StructuralEq for LayoutError

impl StructuralEq for String

impl StructuralEq for TypeId

impl StructuralEq for CpuidResult

impl StructuralEq for CharTryFromError

impl StructuralEq for DecodeUtf16Error

impl StructuralEq for ParseCharError

impl StructuralEq for CString

impl StructuralEq for FromBytesWithNulError

impl StructuralEq for FromVecWithNulError

impl StructuralEq for IntoStringError

impl StructuralEq for NulError

impl StructuralEq for tract_nnef::internal::tract_downcast_rs::__std::fmt::Error

impl StructuralEq for FileType

impl StructuralEq for Permissions

impl StructuralEq for AddrParseError

impl StructuralEq for NonZeroI8

impl StructuralEq for NonZeroI16

impl StructuralEq for NonZeroI32

impl StructuralEq for NonZeroI64

impl StructuralEq for NonZeroI128

impl StructuralEq for NonZeroIsize

impl StructuralEq for NonZeroU8

impl StructuralEq for NonZeroU16

impl StructuralEq for NonZeroU32

impl StructuralEq for NonZeroU64

impl StructuralEq for NonZeroU128

impl StructuralEq for NonZeroUsize

impl StructuralEq for ParseFloatError

impl StructuralEq for ParseIntError

impl StructuralEq for TryFromIntError

impl StructuralEq for RangeFull

impl StructuralEq for NoneError

impl StructuralEq for UCred

impl StructuralEq for StripPrefixError

impl StructuralEq for ExitStatus

impl StructuralEq for Output

impl StructuralEq for ParseBoolError

impl StructuralEq for Utf8Error

impl StructuralEq for FromUtf8Error

impl StructuralEq for RecvError

impl StructuralEq for WaitTimeoutResult

impl StructuralEq for AccessError

impl StructuralEq for ThreadId

impl StructuralEq for Duration

impl StructuralEq for Instant

impl StructuralEq for SystemTime

impl StructuralEq for PhantomPinned

impl<'a> StructuralEq for Component<'a>

impl<'a> StructuralEq for Prefix<'a>

impl<'a> StructuralEq for Location<'a>

impl<'a> StructuralEq for PrefixComponent<'a>

impl<A, B> StructuralEq for EitherOrBoth<A, B>

impl<I> StructuralEq for Dim<I> where
    I: ?Sized, 

impl<Idx> StructuralEq for Range<Idx>

impl<Idx> StructuralEq for RangeFrom<Idx>

impl<Idx> StructuralEq for RangeInclusive<Idx>

impl<Idx> StructuralEq for RangeTo<Idx>

impl<Idx> StructuralEq for RangeToInclusive<Idx>

impl<L, R> StructuralEq for Either<L, R>

impl<T> StructuralEq for FoldWhile<T>

impl<T> StructuralEq for Bound<T>

impl<T> StructuralEq for Option<T>

impl<T> StructuralEq for TrySendError<T>

impl<T> StructuralEq for Poll<T>

impl<T> StructuralEq for PhantomData<T> where
    T: ?Sized, 

impl<T> StructuralEq for BTreeSet<T>

impl<T> StructuralEq for Reverse<T>

impl<T> StructuralEq for Cursor<T>

impl<T> StructuralEq for ManuallyDrop<T> where
    T: ?Sized, 

impl<T> StructuralEq for Wrapping<T>

impl<T> StructuralEq for SendError<T>

impl<T, E> StructuralEq for Result<T, E>

impl<Y, R> StructuralEq for GeneratorState<Y, R>

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