rama::crypto::dep::x509_parser::prelude::asn1_rs::nom::lib::std::convert

Trait TryFrom

1.34.0 (const: unstable) · Source

pub trait TryFrom<T>: Sized {
    type Error;

    // Required method
    fn try_from(value: T) -> Result<Self, Self::Error>;
}

Expand description

Simple and safe type conversions that may fail in a controlled way under some circumstances. It is the reciprocal of TryInto.

This is useful when you are doing a type conversion that may trivially succeed but may also need special handling. For example, there is no way to convert an i64 into an i32 using the From trait, because an i64 may contain a value that an i32 cannot represent and so the conversion would lose data. This might be handled by truncating the i64 to an i32 or by simply returning i32::MAX, or by some other method. The From trait is intended for perfect conversions, so the TryFrom trait informs the programmer when a type conversion could go bad and lets them decide how to handle it.

§Generic Implementations

TryFrom<T> for U implies TryInto for T
try_from is reflexive, which means that TryFrom<T> for T is implemented and cannot fail – the associated Error type for calling T::try_from() on a value of type T is Infallible. When the ! type is stabilized Infallible and ! will be equivalent.

Prefer using TryInto over TryFrom when specifying trait bounds on a generic function to ensure that types that only implement TryInto can be used as well.

TryFrom<T> can be implemented as follows:

struct GreaterThanZero(i32);

impl TryFrom<i32> for GreaterThanZero {
    type Error = &'static str;

    fn try_from(value: i32) -> Result<Self, Self::Error> {
        if value <= 0 {
            Err("GreaterThanZero only accepts values greater than zero!")
        } else {
            Ok(GreaterThanZero(value))
        }
    }
}

§Examples

As described, i32 implements TryFrom<i64>:

let big_number = 1_000_000_000_000i64;
// Silently truncates `big_number`, requires detecting
// and handling the truncation after the fact.
let smaller_number = big_number as i32;
assert_eq!(smaller_number, -727379968);

// Returns an error because `big_number` is too big to
// fit in an `i32`.
let try_smaller_number = i32::try_from(big_number);
assert!(try_smaller_number.is_err());

// Returns `Ok(3)`.
let try_successful_smaller_number = i32::try_from(3);
assert!(try_successful_smaller_number.is_ok());

Required Associated Types§

1.34.0 · Source

type Error

The type returned in the event of a conversion error.

Required Methods§

1.34.0 · Source

fn try_from(value: T) -> Result<Self, Self::Error>

Performs the conversion.

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.

Implementors§

§

type Error = Error

Trait TryFromCopy item path

§Generic Implementations

§Examples

Required Associated Types§

type Error

Required Methods§

fn try_from(value: T) -> Result<Self, Self::Error>

Dyn Compatibility§

Implementors§

impl TryFrom<&'static EcdsaSigningAlgorithm> for JWA

type Error = OpaqueError

impl TryFrom<&ApplicationProtocol> for Version

type Error = OpaqueError

impl TryFrom<&PrivateKeyDer<'_>> for KeyPair

type Error = Error

impl TryFrom<&str> for ClientHint

type Error = ClientHintParsingError

impl TryFrom<&str> for DirectoryServeMode

type Error = OpaqueError

impl TryFrom<&str> for Host

type Error = OpaqueError

impl TryFrom<&str> for Interface

type Error = OpaqueError

impl TryFrom<&str> for IpAddr

type Error = AddrParseError

impl TryFrom<&str> for AccessControlAllowOrigin

type Error = Error

impl TryFrom<&str> for DnsResolveMode

type Error = OpaqueError

impl TryFrom<&str> for rama::http::matcher::uri::dep::regex::bytes::Regex

type Error = Error

impl TryFrom<&str> for rama::http::matcher::uri::dep::regex::Regex

type Error = Error

impl TryFrom<&str> for rama::net::address::Authority

type Error = OpaqueError

impl TryFrom<&str> for DomainAddress

type Error = OpaqueError

impl TryFrom<&str> for ProxyAddress

type Error = OpaqueError

impl TryFrom<&str> for SocketAddress

type Error = OpaqueError

impl TryFrom<&str> for Asn

type Error = InvalidAsn

impl TryFrom<&str> for Forwarded

type Error = OpaqueError

impl TryFrom<&str> for ForwardedElement

type Error = OpaqueError

impl TryFrom<&str> for ForwardedProtocol

type Error = InvalidProtocolStr

impl TryFrom<&str> for ForwardedVersion

type Error = InvalidForwardedVersion

impl TryFrom<&str> for NodeId

type Error = OpaqueError

impl TryFrom<&str> for DeviceName

type Error = OpaqueError

impl TryFrom<&str> for Protocol

type Error = InvalidProtocolStr

impl TryFrom<&str> for Basic

type Error = OpaqueError

impl TryFrom<&str> for Bearer

type Error = OpaqueError

impl TryFrom<&str> for NonEmptyString

type Error = EmptyStringErr

impl TryFrom<&str> for Ipv4Addr

type Error = AddrParseError

impl TryFrom<&str> for Ipv6Addr

type Error = AddrParseError

impl TryFrom<&str> for rama::crypto::dep::rcgen::string::BmpString

type Error = Error

impl TryFrom<&str> for rama::crypto::dep::rcgen::string::Ia5String

type Error = Error

impl TryFrom<&str> for rama::crypto::dep::rcgen::string::PrintableString

type Error = Error

impl TryFrom<&str> for rama::crypto::dep::rcgen::string::TeletexString

type Error = Error

impl TryFrom<&str> for rama::crypto::dep::rcgen::string::UniversalString

type Error = Error

impl TryFrom<&str> for Uuid

type Error = Error

impl TryFrom<&str> for Alphabet

Trait TryFrom