Trait sgx_tstd::marker::StructuralEq

source ·

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);

#[allow(pointer_structural_match)]
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.

Trait sgx_tstd::marker::StructuralEq

Background

Implementors§

impl StructuralEq for hashbrown_tstd::TryReserveError

impl StructuralEq for OCallError

impl StructuralEq for AddressKind

impl StructuralEq for MapAddr

impl StructuralEq for FutexClockId

impl StructuralEq for FutexOp

impl StructuralEq for PageType

impl StructuralEq for Feature

impl StructuralEq for Version

impl StructuralEq for ExceptionType

impl StructuralEq for ExceptionVector

impl StructuralEq for HandleResult

impl StructuralEq for PceError

impl StructuralEq for QcnlError

impl StructuralEq for Quote3Error

impl StructuralEq for SgxStatus

impl StructuralEq for DirIndex

impl StructuralEq for EcResult

impl StructuralEq for RsaKeyType

impl StructuralEq for RsaResult

impl StructuralEq for PckCertFlag

impl StructuralEq for ProdType

impl StructuralEq for QeType

impl StructuralEq for QlAttestationAlgorithmId

impl StructuralEq for QlCertKeyType

impl StructuralEq for QlConfigVersion

impl StructuralEq for QlLogLevel

impl StructuralEq for QlPathType

impl StructuralEq for QlQvResult

impl StructuralEq for QlRequestPolicy

impl StructuralEq for QvPathType

impl StructuralEq for DhSessionRole

impl StructuralEq for EnclaveMode

impl StructuralEq for KeyName

impl StructuralEq for ProtectPerm

impl StructuralEq for RaKeyType

impl StructuralEq for QuoteSignType

impl StructuralEq for SwitchlessWokerEvent

impl StructuralEq for SwitchlessWokerType

impl StructuralEq for SgxDeviceStatus

impl StructuralEq for AsciiChar

impl StructuralEq for sgx_tstd::cmp::Ordering

impl StructuralEq for TryReserveErrorKind

impl StructuralEq for VarError

impl StructuralEq for sgx_tstd::fmt::Alignment

impl StructuralEq for ErrorKind

impl StructuralEq for SeekFrom

impl StructuralEq for IpAddr

impl StructuralEq for Ipv6MulticastScope

impl StructuralEq for Shutdown

impl StructuralEq for SocketAddr

impl StructuralEq for FpCategory

impl StructuralEq for IntErrorKind

impl StructuralEq for SearchStep

impl StructuralEq for sgx_tstd::sync::atomic::Ordering

impl StructuralEq for TcsPolicy

impl StructuralEq for Which

impl StructuralEq for bool

impl StructuralEq for char

impl StructuralEq for i8

impl StructuralEq for i16

impl StructuralEq for i32

impl StructuralEq for i64

impl StructuralEq for i128

impl StructuralEq for isize

impl StructuralEq for str

impl StructuralEq for u8

impl StructuralEq for u16

impl StructuralEq for u32

impl StructuralEq for u64

impl StructuralEq for u128

impl StructuralEq for ()

impl StructuralEq for usize

impl StructuralEq for AlighAllocErr

impl StructuralEq for AlignLayout

impl StructuralEq for AlignLayoutErr

impl StructuralEq for AlignReq