wasmer_types::lib::std::fmt

Trait Debug

1.0.0 · Source

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

Available on crate feature std only.

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,
)");

Debug

Trait Debug Copy item path

§Stability

§Examples

Required Methods§

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

§Errors

§Examples

Implementors§

impl Debug for ExportIndex

impl Debug for ExternType

impl Debug for GlobalInit

impl Debug for ImportIndex

impl Debug for LibCall

impl Debug for MemoryStyle

impl Debug for ModuleHash

impl Debug for Mutability

impl Debug for OnCalledAction

impl Debug for TableStyle

impl Debug for TagKind

impl Debug for TrapCode

impl Debug for wasmer_types::Type

impl Debug for CompileError

impl Debug for DeserializeError

impl Debug for ImportError

impl Debug for MemoryError

impl Debug for ParseCpuFeatureError

impl Debug for PreInstantiationError

impl Debug for SerializeError

impl Debug for WasmError

impl Debug for Aarch64Architecture

impl Debug for Architecture

impl Debug for BinaryFormat

impl Debug for CallingConvention

impl Debug for CpuFeature

impl Debug for Endianness

impl Debug for Environment

impl Debug for OperatingSystem

impl Debug for PointerWidth

impl Debug for Vendor

impl Debug for wasmer_types::lib::std::cmp::Ordering

impl Debug for Infallible

impl Debug for TypeKind

impl Debug for wasmer_types::lib::std::slice::GetDisjointMutError

impl Debug for wasmer_types::lib::std::sync::atomic::Ordering

impl Debug for wasmer_types::lib::std::sync::mpmc::RecvTimeoutError

impl Debug for wasmer_types::lib::std::sync::mpmc::TryRecvError

impl Debug for wasmer_types::lib::std::fmt::Alignment

impl Debug for DebugAsHex

impl Debug for Sign

impl Debug for TryReserveErrorKind

impl Debug for AsciiChar

impl Debug for FromBytesWithNulError

impl Debug for c_void

impl Debug for Locality

impl Debug for AtomicOrdering

impl Debug for SimdAlign

impl Debug for IpAddr

impl Debug for Ipv6MulticastScope

impl Debug for core::net::socket_addr::SocketAddr

impl Debug for FpCategory

impl Debug for IntErrorKind

impl Debug for SearchStep

impl Debug for BacktraceStatus

impl Debug for VarError

impl Debug for std::fs::TryLockError

impl Debug for SeekFrom

impl Debug for ErrorKind

impl Debug for Shutdown

impl Debug for AncillaryError

impl Debug for BacktraceStyle

impl Debug for const_oid::error::Error

impl Debug for TruncSide

impl Debug for hashbrown::TryReserveError

impl Debug for FromHexError

impl Debug for indexmap::GetDisjointMutError

impl Debug for DIR

impl Debug for FILE

impl Debug for timezone

impl Debug for tpacket_versions

Trait Debug

impl Debug for ArchivedDataInitializerLocation
where MemoryIndex: Archive, Option<GlobalIndex>: Archive, usize: Archive,

impl Debug for ArchivedOwnedDataInitializer
where DataInitializerLocation: Archive, Box<[u8]>: Archive,