Trait wasmer_types::lib::std::marker::StructuralEq[−][src]

pub trait StructuralEq { }

🔬 This is a nightly-only experimental API. (structural_match)

Expand description

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 StructuralEq for CString`[src]

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

`impl StructuralEq for IpAddr`[src]

`impl StructuralEq for Ipv6MulticastScope`[src]

`impl StructuralEq for ExitStatus`[src]

`impl StructuralEq for ErrorKind`[src]

`impl StructuralEq for AddrParseError`[src]

`impl StructuralEq for VarError`[src]

`impl StructuralEq for SocketAddr`[src]

`impl StructuralEq for IntoStringError`[src]

`impl StructuralEq for AccessError`[src]

`impl StructuralEq for Instant`[src]

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

`impl StructuralEq for BacktraceStatus`[src]

`impl StructuralEq for Permissions`[src]

`impl StructuralEq for StripPrefixError`[src]

`impl StructuralEq for UCred`[src]

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

`impl StructuralEq for FromBytesWithNulError`[src]

`impl StructuralEq for FromVecWithNulError`[src]

`impl StructuralEq for SystemTime`[src]

`impl StructuralEq for Output`[src]

`impl StructuralEq for SeekFrom`[src]

`impl StructuralEq for Shutdown`[src]

`impl StructuralEq for NulError`[src]

`impl StructuralEq for ExitStatusError`[src]

`impl StructuralEq for FileType`[src]

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

`impl StructuralEq for NonZeroU64`[src]

`impl StructuralEq for NonZeroI128`[src]

`impl StructuralEq for NonZeroUsize`[src]

`impl StructuralEq for Duration`[src]

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

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

`impl StructuralEq for NonZeroU8`[src]

`impl StructuralEq for DecodeUtf16Error`[src]

`impl StructuralEq for NonZeroI32`[src]

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

`impl StructuralEq for ParseFloatError`[src]

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

`impl StructuralEq for ParseIntError`[src]

`impl StructuralEq for SearchStep`[src]

`impl StructuralEq for AllocError`[src]

`impl StructuralEq for ParseBoolError`[src]

`impl StructuralEq for NonZeroU128`[src]

`impl StructuralEq for CpuidResult`[src]

`impl StructuralEq for TryFromIntError`[src]

`impl StructuralEq for ParseCharError`[src]

`impl StructuralEq for NonZeroI64`[src]

`impl StructuralEq for Layout`[src]

`impl StructuralEq for NonZeroU16`[src]

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

`impl StructuralEq for Utf8Error`[src]

`impl StructuralEq for NonZeroU32`[src]

`impl StructuralEq for CharTryFromError`[src]

`impl StructuralEq for NonZeroIsize`[src]

`impl StructuralEq for IntErrorKind`[src]

`impl StructuralEq for NonZeroI8`[src]

`impl StructuralEq for LayoutError`[src]

`impl StructuralEq for FpCategory`[src]

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

`impl StructuralEq for NonZeroI16`[src]

`impl StructuralEq for TryReserveError`[src]

`impl<T> StructuralEq for BTreeSet<T>`[src]

`impl StructuralEq for TryReserveError`

`impl StructuralEq for ArchivedSocketAddr`[src]

`impl<T> StructuralEq for ArchivedRange<T>`[src]

`impl StructuralEq for ArchivedSocketAddrV4`[src]

`impl StructuralEq for ArchivedDuration`[src]

`impl StructuralEq for ArchivedIpv6Addr`[src]

`impl StructuralEq for ArchivedSocketAddrV6`[src]

`impl<K> StructuralEq for ArchivedHashSet<K> where K: Hash + Eq,` [src]

`impl<T> StructuralEq for ArchivedRangeInclusive<T>`[src]

`impl StructuralEq for ArchivedIpv4Addr`[src]

`impl StructuralEq for ArchivedIpAddr`[src]

Implementors

`impl StructuralEq for ExportIndex`[src]

`impl StructuralEq for ExternType`[src]

`impl StructuralEq for ImportIndex`[src]

`impl StructuralEq for Mutability`[src]

`impl StructuralEq for Type`[src]

`impl StructuralEq for Ordering`1.0.0[src]

`impl StructuralEq for RecvTimeoutError`1.12.0[src]

`impl StructuralEq for TryRecvError`1.0.0[src]

`impl StructuralEq for Bytes`[src]

`impl StructuralEq for CustomSectionIndex`[src]

`impl StructuralEq for DataIndex`[src]

`impl StructuralEq for DataInitializerLocation`[src]

`impl StructuralEq for ElemIndex`[src]

`impl StructuralEq for ExternRef`[src]

`impl StructuralEq for Features`[src]

`impl StructuralEq for FunctionIndex`[src]

`impl StructuralEq for FunctionType`[src]

`impl StructuralEq for GlobalIndex`[src]

`impl StructuralEq for GlobalType`[src]

`impl StructuralEq for LocalFunctionIndex`[src]

`impl StructuralEq for LocalGlobalIndex`[src]

`impl StructuralEq for LocalMemoryIndex`[src]

`impl StructuralEq for LocalTableIndex`[src]

`impl StructuralEq for MemoryIndex`[src]

`impl StructuralEq for MemoryType`[src]

`impl StructuralEq for OwnedDataInitializer`[src]

`impl StructuralEq for Pages`[src]

`impl StructuralEq for SignatureIndex`[src]

`impl StructuralEq for TableIndex`[src]

`impl StructuralEq for TableInitializer`[src]

`impl StructuralEq for TableType`[src]

`impl StructuralEq for V128`[src]

`impl StructuralEq for VMExternRef`[src]

`impl StructuralEq for TypeId`1.0.0[src]

`impl StructuralEq for Error`1.0.0[src]

`impl StructuralEq for RangeFull`1.0.0[src]

`impl StructuralEq for FromUtf8Error`1.0.0[src]

`impl StructuralEq for String`1.0.0[src]

`impl StructuralEq for RecvError`1.0.0[src]

`impl StructuralEq for WaitTimeoutResult`1.5.0[src]

`impl StructuralEq for PhantomPinned`1.33.0[src]

`impl<Idx> StructuralEq for Range<Idx>`1.0.0[src]

`impl<Idx> StructuralEq for RangeFrom<Idx>`1.0.0[src]

`impl<Idx> StructuralEq for RangeInclusive<Idx>`1.26.0[src]

`impl<Idx> StructuralEq for RangeTo<Idx>`1.0.0[src]

`impl<Idx> StructuralEq for RangeToInclusive<Idx>`1.26.0[src]

`impl<K, V> StructuralEq for PrimaryMap<K, V> where K: EntityRef,` [src]

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

`impl<T> StructuralEq for TrySendError<T>`1.0.0[src]

`impl<T> StructuralEq for ExportType<T>`[src]

`impl<T> StructuralEq for ImportType<T>`[src]

`impl<T> StructuralEq for Reverse<T>`1.19.0[src]

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

`impl<T> StructuralEq for SendError<T>`1.0.0[src]

`impl<T> StructuralEq for PhantomData<T> where T: ?Sized,` [src]

`impl<T: ReservedValue> StructuralEq for PackedOption<T>`[src]

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