wasmtime_environ::__core::prelude::rust_2015

Trait Eq

1.55.0 (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 and a != b implies !(a == b)
transitive: a == b and b == c implies a == c

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", so this trait is not object safe.

Eq

Trait Eq Copy item path

§Derivable

§How can I implement Eq?

Dyn Compatibility§

Implementors§

impl Eq for DecodeError

impl Eq for cpp_demangle::ast::ArrayType

impl Eq for BaseUnresolvedName

impl Eq for BuiltinType

impl Eq for CallOffset

impl Eq for ClassEnumType

impl Eq for CtorDtorName

impl Eq for Decltype

impl Eq for DestructorName

impl Eq for cpp_demangle::ast::Encoding

impl Eq for ExceptionSpec

impl Eq for ExplicitObjectParameter

impl Eq for ExprPrimary

impl Eq for cpp_demangle::ast::Expression

impl Eq for GlobalCtorDtor

impl Eq for LocalName

impl Eq for MangledName

impl Eq for Name

impl Eq for NestedName

impl Eq for OperatorName

impl Eq for ParametricBuiltinType

impl Eq for cpp_demangle::ast::Prefix

impl Eq for PrefixHandle

impl Eq for RefQualifier

impl Eq for SimpleOperatorName

impl Eq for SpecialName

impl Eq for StandardBuiltinType

impl Eq for Substitution

impl Eq for TemplateArg

impl Eq for TemplateTemplateParamHandle

impl Eq for Type

impl Eq for TypeHandle

impl Eq for UnqualifiedName

impl Eq for UnresolvedName

impl Eq for UnresolvedType

impl Eq for UnresolvedTypeHandle

impl Eq for UnscopedName

impl Eq for UnscopedTemplateNameHandle

impl Eq for VectorType

impl Eq for WellKnownComponent

impl Eq for DemangleNodeType

impl Eq for cpp_demangle::error::Error

impl Eq for hashbrown::TryReserveError

impl Eq for indexmap::GetDisjointMutError

impl Eq for Level

impl Eq for LevelFilter

impl Eq for postcard::error::Error

impl Eq for Op

impl Eq for CDataModel

impl Eq for Size

impl Eq for ParseError

impl Eq for Aarch64Architecture

impl Eq for target_lexicon::targets::Architecture

impl Eq for ArmArchitecture

impl Eq for target_lexicon::targets::BinaryFormat

impl Eq for CleverArchitecture

impl Eq for CustomVendor

impl Eq for Environment

impl Eq for Mips32Architecture

impl Eq for Mips64Architecture

impl Eq for OperatingSystem

impl Eq for Riscv32Architecture

impl Eq for Riscv64Architecture

impl Eq for target_lexicon::targets::Vendor

impl Eq for X86_32Architecture

impl Eq for CallingConvention

impl Eq for target_lexicon::triple::Endianness

impl Eq for PointerWidth

impl Eq for wasmparser::parser::Encoding

impl Eq for ComponentOuterAliasKind

impl Eq for CanonicalFunction

impl Eq for CanonicalOption

impl Eq for ComponentExternalKind

impl Eq for ComponentTypeRef

Trait Eq

§How can I implement `Eq`?