Trait frame_support::dispatch::Eq

1.0.0 · source ·

pub trait Eq: PartialEq { }

Expand description

Trait for comparisons corresponding to equivalence relations.

This means, that in addition to a == b and a != b being strict inverses, the relation must be (for all a, b and c):

reflexive: a == a;
symmetric: a == b implies b == a (required by PartialEq as well); and
transitive: a == b and b == c implies a == c (required by PartialEq as well).

This property cannot be checked by the compiler, and therefore Eq implies PartialEq, and has no extra 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.

Implement Eq in addition to PartialEq if it’s guaranteed that PartialEq::eq(a, a) always returns true (reflexivity), in addition to the symmetric and transitive properties already required by PartialEq.

§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 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 {}

Object Safety§

This trait is not object safe.

Trait frame_support::dispatch::EqCopy item path

§Derivable

§How can I implement Eq?

Object Safety§

Implementors§

impl Eq for AhoCorasickKind

impl Eq for aho_corasick::packed::api::MatchKind

impl Eq for aho_corasick::util::error::MatchErrorKind

impl Eq for aho_corasick::util::search::Anchored

impl Eq for aho_corasick::util::search::MatchKind

impl Eq for StartKind

impl Eq for arbitrary::error::Error

impl Eq for array_bytes::Error

impl Eq for PrintFmt

impl Eq for ParseAlphabetError

impl Eq for DecodeError

impl Eq for DecodeSliceError

impl Eq for EncodeSliceError

impl Eq for DecodePaddingMode

impl Eq for bs58::alphabet::Error

impl Eq for bs58::decode::Error

impl Eq for bs58::encode::Error

impl Eq for byte_slice_cast::Error

impl Eq for byteorder::BigEndian

impl Eq for byteorder::LittleEndian

impl Eq for const_oid::error::Error

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 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 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 cpp_demangle::ast::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 Reloc

impl Eq for CursorPosition

impl Eq for AtomicRmwOp

impl Eq for FloatCC

impl Eq for IntCC

impl Eq for ValueDef

impl Eq for AnyEntity

impl Eq for ArgumentExtension

impl Eq for ArgumentPurpose

impl Eq for ExternalName

impl Eq for UserFuncName

impl Eq for InstructionData

impl Eq for InstructionFormat

impl Eq for cranelift_codegen::ir::instructions::Opcode

impl Eq for ResolvedConstraint

impl Eq for KnownSymbol

Trait frame_support::dispatch::Eq

§How can I implement `Eq`?