Trait concordium_std::marker::StructuralEq

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 RecvTimeoutError

impl StructuralEq for IpAddr

impl<T> StructuralEq for TrySendError<T>

impl StructuralEq for Ipv6MulticastScope

impl StructuralEq for FromVecWithNulError

impl StructuralEq for AddrParseError

impl StructuralEq for BacktraceStatus

impl<T> StructuralEq for Cursor<T>

impl StructuralEq for Output

impl StructuralEq for FromBytesWithNulError

impl StructuralEq for IntoStringError

impl StructuralEq for TryRecvError

impl StructuralEq for Permissions

impl StructuralEq for AccessError

impl StructuralEq for SocketAddr

impl<T> StructuralEq for SendError<T>

impl StructuralEq for Shutdown

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

impl StructuralEq for SystemTime

impl StructuralEq for CString

impl StructuralEq for RecvError

impl StructuralEq for NulError

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

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

impl StructuralEq for WaitTimeoutResult

impl StructuralEq for VarError

impl StructuralEq for FileType

impl StructuralEq for StripPrefixError

impl StructuralEq for ExitStatus

impl StructuralEq for SeekFrom

impl StructuralEq for ThreadId

impl StructuralEq for ErrorKind

impl StructuralEq for Instant

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

impl StructuralEq for DecodeUtf16Error

impl<Idx> StructuralEq for RangeToInclusive<Idx>

impl<Idx> StructuralEq for RangeFrom<Idx>

impl StructuralEq for Utf8Error

impl StructuralEq for TypeId

impl<T> StructuralEq for Reverse<T>

impl<T> StructuralEq for Poll<T>

impl StructuralEq for NoneError

impl StructuralEq for RangeFull

impl<'a> StructuralEq for Utf8LossyChunk<'a>

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

impl<Idx> StructuralEq for RangeInclusive<Idx>

impl<Idx> StructuralEq for Range<Idx>

impl StructuralEq for Ordering

impl<T> StructuralEq for Option<T>

impl StructuralEq for CharTryFromError

impl StructuralEq for ParseBoolError

impl StructuralEq for ParseCharError

impl StructuralEq for Error

impl StructuralEq for CpuidResult

impl<Idx> StructuralEq for RangeTo<Idx>

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

impl StructuralEq for LayoutError

impl StructuralEq for Layout

impl StructuralEq for SearchStep

impl StructuralEq for Duration

impl StructuralEq for AllocError

impl StructuralEq for FromUtf8Error

impl StructuralEq for Pages

impl StructuralEq for Pages

impl StructuralEq for Words

impl StructuralEq for Bytes

impl StructuralEq for Words

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Implementors

impl StructuralEq for TryReserveError

impl StructuralEq for Address

impl StructuralEq for AmountParseError

impl StructuralEq for LogError

impl StructuralEq for NewContractNameError

impl StructuralEq for NewReceiveNameError

impl StructuralEq for ParseDurationError

impl StructuralEq for FpCategory

impl StructuralEq for IntErrorKind

impl StructuralEq for Fields

impl StructuralEq for SizeLength

impl StructuralEq for Type

impl StructuralEq for ActionsTree

impl StructuralEq for ContractStateError

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 AccountAddress

impl StructuralEq for Amount

impl StructuralEq for AttributeTag

impl StructuralEq for ContractAddress

impl StructuralEq for concordium_std::Duration

impl StructuralEq for OwnedContractName

impl StructuralEq for OwnedReceiveName

impl StructuralEq for ParseError

impl StructuralEq for Reject

impl StructuralEq for String

impl StructuralEq for Timestamp

impl StructuralEq for PhantomPinned

impl<'a> StructuralEq for ContractName<'a>

impl<'a> StructuralEq for ReceiveName<'a>

impl<T> StructuralEq for Bound<T>

impl<T> StructuralEq for BTreeSet<T>

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

impl<T> StructuralEq for Wrapping<T>

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

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