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,
)");

Dyn Compatibility§

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Debug

Trait Debug Copy item path

§Stability

§Examples

Required Methods§

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

§Errors

§Examples

Dyn Compatibility§

Implementors§

impl Debug for !

impl Debug for ()

impl Debug for ATerm

impl Debug for Aarch64Architecture

impl Debug for Abi

impl Debug for AccessError

impl Debug for AddrParseError

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

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

impl Debug for AllocError

impl Debug for AllocationStats

impl Debug for AncillaryError

impl Debug for Architecture

impl Debug for ArchivedCString

impl Debug for ArchivedDataInitializerLocationwhere MemoryIndex: Archive, InitExpr: Archive,

impl Debug for ArchivedDuration

impl Debug for ArchivedIpAddr

impl Debug for ArchivedIpv4Addr

impl Debug for ArchivedIpv6Addr

impl Debug for ArchivedOptionNonZeroI8

impl Debug for ArchivedOptionNonZeroI16

impl Debug for ArchivedOptionNonZeroI32

impl Debug for ArchivedOptionNonZeroI64

impl Debug for ArchivedOptionNonZeroI128

impl Debug for ArchivedOptionNonZeroU8

impl Debug for ArchivedOptionNonZeroU16

impl Debug for ArchivedOptionNonZeroU32

impl Debug for ArchivedOptionNonZeroU64

impl Debug for ArchivedOptionNonZeroU128

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

impl Debug for ArchivedRangeFull

impl Debug for ArchivedSocketAddr

impl Debug for ArchivedSocketAddrV4

impl Debug for ArchivedSocketAddrV6

impl Debug for ArchivedString

impl Debug for Args

impl Debug for ArgsOs

impl Debug for Arguments<'_>

impl Debug for ArmArchitecture

impl Debug for wasmer_types::lib::std::mem::type_info::Array

impl Debug for AsBox

impl Debug for AsOwned

impl Debug for AsString

impl Debug for AsUnixTime

impl Debug for AsVec

impl Debug for AsciiChar

impl Debug for Assume

impl Debug for Atomic<bool>

impl Debug for Atomic<i8>

impl Debug for Atomic<i16>

impl Debug for Atomic<i32>

impl Debug for Atomic<i64>

impl Debug for Atomic<isize>

impl Debug for Atomic<u8>

impl Debug for Atomic<u16>

impl Debug for Atomic<u32>

impl Debug for Atomic<u64>

impl Debug for Atomic<usize>

impl Debug for AtomicI16_be

impl Debug for AtomicI16_le

impl Debug for AtomicI32_be

impl Debug for AtomicI32_le

impl Debug for AtomicI64_be

impl Debug for AtomicI64_le

impl Debug for AtomicOrdering

impl Debug for AtomicU16_be

impl Debug for AtomicU16_le

impl Debug for AtomicU32_be

impl Debug for AtomicU32_le

impl Debug for AtomicU64_be

Trait Debug

impl Debug for ArchivedDataInitializerLocation
where MemoryIndex: Archive, InitExpr: Archive,

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