compio::buf::bumpalo::core_alloc::fmt

Trait Debug

1.36.0 · Source

pub trait Debug {
    // Required method
    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>;
}

Expand description

? formatting.

Debug should format the output in a programmer-facing, debugging context.

Generally speaking, you should just derive a Debug implementation.

When used with the alternate format specifier #?, the output is pretty-printed.

For more information on formatters, see the module-level documentation.

This trait can be used with #[derive] if all fields implement Debug. When derived for structs, it will use the name of the struct, then {, then a comma-separated list of each field’s name and Debug value, then }. For enums, it will use the name of the variant and, if applicable, (, then the Debug values of the fields, then ).

§Stability

Derived Debug formats are not stable, and so may change with future Rust versions. Additionally, Debug implementations of types provided by the standard library (std, core, alloc, etc.) are not stable, and may also change with future Rust versions.

§Examples

Deriving an implementation:

#[derive(Debug)]
struct Point {
    x: i32,
    y: i32,
}

let origin = Point { x: 0, y: 0 };

assert_eq!(
    format!("The origin is: {origin:?}"),
    "The origin is: Point { x: 0, y: 0 }",
);

Manually implementing:

use std::fmt;

struct Point {
    x: i32,
    y: i32,
}

impl fmt::Debug for Point {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Point")
         .field("x", &self.x)
         .field("y", &self.y)
         .finish()
    }
}

let origin = Point { x: 0, y: 0 };

assert_eq!(
    format!("The origin is: {origin:?}"),
    "The origin is: Point { x: 0, y: 0 }",
);

There are a number of helper methods on the Formatter struct to help you with manual implementations, such as debug_struct.

Types that do not wish to use the standard suite of debug representations provided by the Formatter trait (debug_struct, debug_tuple, debug_list, debug_set, debug_map) can do something totally custom by manually writing an arbitrary representation to the Formatter.

impl fmt::Debug for Point {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "Point [{} {}]", self.x, self.y)
    }
}

Debug implementations using either derive or the debug builder API on Formatter support pretty-printing using the alternate flag: {:#?}.

Pretty-printing with #?:

#[derive(Debug)]
struct Point {
    x: i32,
    y: i32,
}

let origin = Point { x: 0, y: 0 };

let expected = "The origin is: Point {
    x: 0,
    y: 0,
}";
assert_eq!(format!("The origin is: {origin:#?}"), expected);

Required Methods§

1.0.0 · Source

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

§Errors

This function should return Err if, and only if, the provided Formatter returns Err. String formatting is considered an infallible operation; this function only returns a Result because writing to the underlying stream might fail and it must provide a way to propagate the fact that an error has occurred back up the stack.

§Examples

use std::fmt;

struct Position {
    longitude: f32,
    latitude: f32,
}

impl fmt::Debug for Position {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_tuple("")
         .field(&self.longitude)
         .field(&self.latitude)
         .finish()
    }
}

let position = Position { longitude: 1.987, latitude: 2.983 };
assert_eq!(format!("{position:?}"), "(1.987, 2.983)");

assert_eq!(format!("{position:#?}"), "(
    1.987,
    2.983,
)");

Implementors§

Debug

Trait Debug Copy item path

§Stability

§Examples

Required Methods§

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

§Errors

§Examples

Implementors§

impl Debug for DriverType

impl Debug for OwnedFd

impl Debug for PipeEnd

impl Debug for PipeMode

impl Debug for SerdeJsonCodecError

impl Debug for ConfigError

impl Debug for ConnectError

impl Debug for compio::quic::ConnectionError

impl Debug for compio::quic::ReadError

impl Debug for ReadExactError

impl Debug for StoppedError

impl Debug for compio::quic::WriteError

impl Debug for compio::quic::h3::error::ConnectionError

impl Debug for LocalError

impl Debug for StreamError

impl Debug for ErrorOrigin

impl Debug for FrameProtocolError

impl Debug for FrameStreamError

impl Debug for compio::quic::h3::proto::frame::Frame<PayloadLen>

impl Debug for FrameError

impl Debug for SettingsError

impl Debug for HeaderError

impl Debug for compio::quic::h3::proto::stream::Side

impl Debug for ConnectionErrorIncoming

impl Debug for StreamErrorIncoming

impl Debug for compio::tls::native_tls::Protocol

impl Debug for EarlyDataError

impl Debug for EchMode

impl Debug for EchStatus

impl Debug for Tls12Resumption

impl Debug for VerifierBuilderError

impl Debug for CompressionCache

impl Debug for CompressionLevel

impl Debug for KeyExchangeAlgorithm

impl Debug for HashAlgorithm

impl Debug for AlertDescription

impl Debug for CertRevocationListError

impl Debug for CertificateCompressionAlgorithm

impl Debug for CertificateError

impl Debug for CipherSuite

impl Debug for compio::tls::rustls::Connection

impl Debug for ContentType

impl Debug for EncryptedClientHelloError

impl Debug for compio::tls::rustls::Error

impl Debug for ExtendedKeyPurpose

impl Debug for HandshakeKind

impl Debug for HandshakeType

impl Debug for InconsistentKeys

impl Debug for InvalidMessage

impl Debug for NamedGroup

impl Debug for PeerIncompatible

impl Debug for PeerMisbehaved

impl Debug for ProtocolVersion

impl Debug for compio::tls::rustls::Side

impl Debug for SignatureAlgorithm

impl Debug for SignatureScheme

impl Debug for SupportedCipherSuite

impl Debug for FipsStatus

impl Debug for compio::tls::rustls::pki_types::IpAddr

impl Debug for ServerName<'_>

impl Debug for compio::tls::rustls::pki_types::pem::Error

impl Debug for SectionKind

impl Debug for compio::tls::rustls::quic::Connection

impl Debug for compio::tls::rustls::quic::Version

impl Debug for CertificateType

impl Debug for EncodeError

impl Debug for EncryptError

impl Debug for compio::ws::tungstenite::Error

impl Debug for Message

impl Debug for compio::ws::tungstenite::error::CapacityError

impl Debug for ProtocolError

Trait Debug