Trait Eq

1.6.0 (const: unstable) · Source

pub trait Eq: PartialEq { }

Expand description

Trait for comparisons corresponding to equivalence relations.

The primary difference to PartialEq is the additional requirement for reflexivity. A type that implements PartialEq guarantees that for all a, b and c:

symmetric: a == b implies b == a
transitive: a == b and b == c implies a == c
consistent: a != b if and only if !(a == b)

Eq, which builds on top of PartialEq also implies:

reflexive: a == a

This property cannot be checked by the compiler, and therefore Eq is a trait without methods.

Violating this property is a logic error. The behavior resulting from a logic error is not specified, but users of the trait must ensure that such logic errors do not result in undefined behavior. This means that unsafe code must not rely on the correctness of these methods.

Floating point types such as f32 and f64 implement only PartialEq but not Eq because NaN != NaN.

§Derivable

This trait can be used with #[derive]. When derived, because Eq has no extra methods, it is only informing the compiler that this is an equivalence relation rather than a partial equivalence relation. Note that the derive strategy requires all fields are Eq, which isn’t always desired.

§How can I implement `Eq`?

If you cannot use the derive strategy, specify that your type implements Eq, which has no extra methods:

enum BookFormat {
    Paperback,
    Hardback,
    Ebook,
}

struct Book {
    isbn: i32,
    format: BookFormat,
}

impl PartialEq for Book {
    fn eq(&self, other: &Self) -> bool {
        self.isbn == other.isbn
    }
}

impl Eq for Book {}

Dyn Compatibility§

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Eq

Trait Eq Copy item path

§Derivable

§How can I implement Eq?

Dyn Compatibility§

Implementors§

impl Eq for !

impl Eq for ()

impl Eq for ATerm

impl Eq for Aarch64Architecture

impl Eq for Abbreviation

impl Eq for AbbreviationsCacheStrategy

impl Eq for Abi

impl Eq for AbstractHeapType

impl Eq for AbstractHeapType

impl Eq for AbstractResourceIndex

impl Eq for AccessError

impl Eq for Adapter

impl Eq for AdapterId

impl Eq for AdapterModuleId

impl Eq for AdapterOptions

impl Eq for AddrParseError

impl Eq for Address

impl Eq for AddressSize

impl Eq for AliasableResourceId

impl Eq for wasmtime_environ::__core::mem::Alignment

impl Eq for wasmtime_environ::__core::fmt::Alignment

impl Eq for AllocError

impl Eq for AnyTypeId

impl Eq for ArangeEntry

impl Eq for Architecture

impl Eq for Architecture

impl Eq for ArmArchitecture

impl Eq for ArrayType

impl Eq for ArrayType

impl Eq for ArrayType

impl Eq for AsciiChar

impl Eq for Assume

impl Eq for Atom

impl Eq for AtomicOrdering

impl Eq for Attribute

impl Eq for AttributeSpecification

impl Eq for AttributeValue

impl Eq for Augmentation

impl Eq for B0

impl Eq for B1

impl Eq for BacktraceStatus

impl Eq for BacktraceStyle

impl Eq for BareFunctionType

impl Eq for BaseAddresses

impl Eq for BaseUnresolvedName

impl Eq for BigEndian

impl Eq for BigEndian

impl Eq for BinaryFormat

impl Eq for BinaryFormat

impl Eq for BlockType

impl Eq for BrTable<'_>

impl Eq for BuildMetadata

impl Eq for BuiltinFunctionIndex

impl Eq for BuiltinType

impl Eq for ByteStr

impl Eq for ByteString

impl Eq for CDataModel

impl Eq for CStr

impl Eq for CString

impl Eq for CallFrameInstruction

impl Eq for CallOffset

impl Eq for CallbackId

impl Eq for CallingConvention

impl Eq for CanonicalAbiInfo

impl Eq for CanonicalFunction

impl Eq for CanonicalOption

impl Eq for CanonicalOption

impl Eq for CanonicalOptions

impl Eq for CanonicalOptionsDataModel

impl Eq for Catch

impl Eq for CharCase

impl Eq for CharTryFromError

impl Eq for CieId

impl Eq for Class

Trait Eq

§How can I implement `Eq`?