[][src]Trait scale_info::prelude::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 StructuralEq for ThreadId[src]

impl<'a> StructuralEq for PrefixComponent<'a>[src]

impl StructuralEq for SocketAddr[src]

impl StructuralEq for ExitStatus[src]

impl StructuralEq for Instant[src]

impl StructuralEq for ErrorKind[src]

impl StructuralEq for FromVecWithNulError[src]

impl StructuralEq for Shutdown[src]

impl StructuralEq for CString[src]

impl StructuralEq for RecvError[src]

impl StructuralEq for IpAddr[src]

impl StructuralEq for AccessError[src]

impl<T> StructuralEq for TrySendError<T>[src]

impl<'a> StructuralEq for Component<'a>[src]

impl StructuralEq for VarError[src]

impl<T> StructuralEq for SendError<T>[src]

impl StructuralEq for AddrParseError[src]

impl StructuralEq for StripPrefixError[src]

impl StructuralEq for RecvTimeoutError[src]

impl<T> StructuralEq for Cursor<T>[src]

impl StructuralEq for IntoStringError[src]

impl StructuralEq for TryRecvError[src]

impl StructuralEq for Permissions[src]

impl StructuralEq for SystemTime[src]

impl StructuralEq for UCred[src]

impl StructuralEq for Ipv6MulticastScope[src]

impl StructuralEq for FromBytesWithNulError[src]

impl StructuralEq for NulError[src]

impl<'a> StructuralEq for Prefix<'a>[src]

impl StructuralEq for SeekFrom[src]

impl StructuralEq for FileType[src]

impl StructuralEq for BacktraceStatus[src]

impl StructuralEq for WaitTimeoutResult[src]

impl StructuralEq for Output[src]

impl<Idx> StructuralEq for RangeToInclusive<Idx>[src]

impl<Idx> StructuralEq for RangeInclusive<Idx>[src]

impl StructuralEq for CharTryFromError[src]

impl<Idx> StructuralEq for RangeFrom<Idx>[src]

impl StructuralEq for Utf8Error[src]

impl<T> StructuralEq for Poll<T>[src]

impl<T, E> StructuralEq for Result<T, E>[src]

impl StructuralEq for DecodeUtf16Error[src]

impl<Idx> StructuralEq for Range<Idx>[src]

impl StructuralEq for ParseCharError[src]

impl<Idx> StructuralEq for RangeTo<Idx>[src]

impl StructuralEq for Ordering[src]

impl StructuralEq for AllocError[src]

impl<Y, R> StructuralEq for GeneratorState<Y, R>[src]

impl StructuralEq for Duration[src]

impl StructuralEq for ParseBoolError[src]

impl StructuralEq for RangeFull[src]

impl StructuralEq for CpuidResult[src]

impl StructuralEq for LayoutError[src]

impl<T> StructuralEq for Option<T>[src]

impl StructuralEq for NoneError[src]

impl StructuralEq for Layout[src]

impl<'a> StructuralEq for Utf8LossyChunk<'a>[src]

impl StructuralEq for SearchStep[src]

impl<'a> StructuralEq for Location<'a>[src]

impl<T> StructuralEq for Compact<T>[src]

impl StructuralEq for OptionBool[src]

impl StructuralEq for Error[src]

impl<T> StructuralEq for CapacityError<T>[src]

impl StructuralEq for Error

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Implementors

impl StructuralEq for PathError[src]

impl StructuralEq for TypeDefPrimitive[src]

impl StructuralEq for MetaForm[src]

impl StructuralEq for TryReserveError[src]

impl StructuralEq for FpCategory1.0.0[src]

impl StructuralEq for IntErrorKind[src]

impl StructuralEq for TypeId1.0.0[src]

impl StructuralEq for scale_info::prelude::fmt::Error1.0.0[src]

impl StructuralEq for PhantomPinned1.33.0[src]

impl StructuralEq for NonZeroI81.34.0[src]

impl StructuralEq for NonZeroI161.34.0[src]

impl StructuralEq for NonZeroI321.34.0[src]

impl StructuralEq for NonZeroI641.34.0[src]

impl StructuralEq for NonZeroI1281.34.0[src]

impl StructuralEq for NonZeroIsize1.34.0[src]

impl StructuralEq for NonZeroU81.28.0[src]

impl StructuralEq for NonZeroU161.28.0[src]

impl StructuralEq for NonZeroU321.28.0[src]

impl StructuralEq for NonZeroU641.28.0[src]

impl StructuralEq for NonZeroU1281.28.0[src]

impl StructuralEq for NonZeroUsize1.28.0[src]

impl StructuralEq for ParseFloatError1.0.0[src]

impl StructuralEq for ParseIntError1.0.0[src]

impl StructuralEq for TryFromIntError1.34.0[src]

impl StructuralEq for FromUtf8Error1.0.0[src]

impl StructuralEq for String1.0.0[src]

impl StructuralEq for Registry[src]

impl<'a, T> StructuralEq for Symbol<'a, T>[src]

impl<S> StructuralEq for PortableForm<S>[src]

impl<S> StructuralEq for PortableRegistry<S> where
    S: FormString
[src]

impl<T> StructuralEq for Bound<T>1.17.0[src]

impl<T> StructuralEq for Interner<T>[src]

impl<T> StructuralEq for UntrackedSymbol<T>[src]

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
[src]

impl<T> StructuralEq for ManuallyDrop<T> where
    T: ?Sized
1.20.0[src]

impl<T> StructuralEq for Wrapping<T>1.0.0[src]

impl<T: Form> StructuralEq for TypeDef<T>[src]

impl<T: Form> StructuralEq for Field<T>[src]

impl<T: Form> StructuralEq for Path<T>[src]

impl<T: Form> StructuralEq for Type<T>[src]

impl<T: Form> StructuralEq for TypeDefArray<T>[src]

impl<T: Form> StructuralEq for TypeDefComposite<T>[src]

impl<T: Form> StructuralEq for TypeDefPhantom<T>[src]

impl<T: Form> StructuralEq for TypeDefSequence<T>[src]

impl<T: Form> StructuralEq for TypeDefTuple<T>[src]

impl<T: Form> StructuralEq for TypeDefVariant<T>[src]

impl<T: Form> StructuralEq for Variant<T>[src]

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