Crate derive_more

Expand description

`derive_more`

Rust has lots of builtin traits that are implemented for its basic types, such as Add, Not, From or Display. However, when wrapping these types inside your own structs or enums you lose the implementations of these traits and are required to recreate them. This is especially annoying when your own structures are very simple, such as when using the commonly advised newtype pattern (e.g. MyInt(i32)).

This library tries to remove these annoyances and the corresponding boilerplate code. It does this by allowing you to derive lots of commonly used traits for both structs and enums.

Example code

By using this library the following code just works:

use derive_more::{Add, Display, From, Into};

#[derive(PartialEq, From, Add)]
struct MyInt(i32);

#[derive(PartialEq, From, Into)]
struct Point2D {
    x: i32,
    y: i32,
}

#[derive(PartialEq, From, Add, Display)]
enum MyEnum {
    #[display("int: {_0}")]
    Int(i32),
    Uint(u32),
    #[display("nothing")]
    Nothing,
}

assert!(MyInt(11) == MyInt(5) + 6.into());
assert!((5, 6) == Point2D { x: 5, y: 6 }.into());
assert!(MyEnum::Int(15) == (MyEnum::Int(8) + 7.into()).unwrap());
assert!(MyEnum::Int(15).to_string() == "int: 15");
assert!(MyEnum::Uint(42).to_string() == "42");
assert!(MyEnum::Nothing.to_string() == "nothing");

The derivable traits

Below are all the traits that you can derive using this library. Some trait derivations are so similar that the further documentation will only show a single one of them. You can recognize these by the “-like” suffix in their name. The trait name before that will be the only one that is used throughout the further documentation.

It is important to understand what code gets generated when using one of the derives from this crate. That is why the links below explain what code gets generated for a trait for each group from before.

You can use the cargo-expand utility to see the exact code that is generated for your specific type. This will show you your code with all macros and derives expanded.

NOTE: You still have to derive each trait separately. So #[derive(Mul)] doesn’t automatically derive Div as well. To derive both you should do #[derive(Mul, Div)]

Conversion traits

These are traits that are used to convert automatically between types.

Formatting traits

These traits are used for converting a struct to a string in different ways.

Debug
Display-like, contains Display, Binary, Octal, LowerHex, UpperHex, LowerExp, UpperExp, Pointer

Error-handling traits

These traits are used to define error-types.

Error

Operators

These are traits that can be used for operator overloading.

Index
Deref
Not-like, contains Not and Neg
Add-like, contains Add, Sub, BitAnd, BitOr, BitXor
Mul-like, contains Mul, Div, Rem, Shr and Shl
Sum-like, contains Sum and Product
IndexMut
DerefMut
AddAssign-like, contains AddAssign, SubAssign, BitAndAssign, BitOrAssign and BitXorAssign
MulAssign-like, contains MulAssign, DivAssign, RemAssign, ShrAssign and ShlAssign

Static methods

These don’t derive traits, but derive static methods instead.

Constructor, this derives a new method that can be used as a constructor. This is very basic if you need more customization for your constructor, check out the derive-new crate.
IsVariant, for each variant foo of an enum type, derives a is_foo method.
Unwrap, for each variant foo of an enum type, derives an unwrap_foo method.
TryUnwrap, for each variant foo of an enum type, derives an try_unwrap_foo method.

Installation

This library requires Rust 1.72 or higher. To avoid redundant compilation times, by default no derives are supported. You have to enable each type of derive as a feature in Cargo.toml:

[dependencies]
derive_more = "=1.0.0-beta.6"
# You can specify the types of derives that you need for less time spent
# compiling. For the full list of features see this crate its `Cargo.toml`.
features = ["from", "add", "iterator"]

# If you don't care much about compilation times and simply want to have
# support for all the possible derives, you can use the "full" feature.
features = ["full"]

# If you run in a `no_std` environment you should disable the default features,
# because the only default feature is the "std" feature.
# NOTE: You can combine this with "full" feature to get support for all the
#       possible derives in a `no_std` environment.
default-features = false

And this to the top of your Rust file:

// use the derives that you want in the file
use derive_more::{Add, Display, From};

If you’re still using Rust 2015, add this instead:

extern crate core;
#[macro_use]
extern crate derive_more;

Re-exports

This crate also re-exports all of the standard library traits that it adds derives for. So both the Display derive and the Display trait will be in scope when you add the following code:

use derive_more::Display;

Modules

derive
Module containing macro definitions only, without corresponding traits.

Structs

FromStrErrorfrom_str
Error of parsing an enum value its string representation.
TryFromReprErrortry_from and (try_into or try_from)
Error returned by the derived TryFrom implementation on enums to convert from their repr.
TryIntoErrortry_into and (try_into or try_from)
Error returned by the derived TryInto implementation.
TryUnwrapErrortry_unwrap
Error returned by the derived TryUnwrap implementation.
UnitErroradd or not
Error returned by the derived implementations when an arithmetic or logic operation is invoked on a unit-like variant of an enum.
WrongVariantErroradd
Error returned by the derived implementations when an arithmetic or logic operation is invoked on mismatched enum variants.

Enums

BinaryErroradd
Possible errors returned by the derived implementations of binary arithmetic or logic operations.

Derive Macros

Addadd
What #[derive(Add)] generates
AddAssignadd_assign
What #[derive(AddAssign)] generates
AsMutas_ref
What #[derive(AsRef)] generates
AsRefas_ref
What #[derive(AsRef)] generates
Binarydisplay
What #[derive(Display)] generates
BitAndadd
What #[derive(Add)] generates
BitAndAssignadd_assign
What #[derive(AddAssign)] generates
BitOradd
What #[derive(Add)] generates
BitOrAssignadd_assign
What #[derive(AddAssign)] generates
BitXoradd
What #[derive(Add)] generates
BitXorAssignadd_assign
What #[derive(AddAssign)] generates
Constructorconstructor
What #[derive(Constructor)] generates
Debugdebug
What #[derive(Debug)] generates
Derefderef
Using #[derive(Deref)]
DerefMutderef_mut
What #[derive(DerefMut)] generates
Displaydisplay
What #[derive(Display)] generates
Divmul
What #[derive(Mul)] generates
DivAssignmul_assign
What #[derive(MulAssign)] generates
Errorerror
Using #[derive(Error)]
Fromfrom
What #[derive(From)] generates
FromStrfrom_str
What #[derive(FromStr)] generates
Indexindex
What #[derive(Index)] generates
IndexMutindex_mut
What #[derive(IndexMut)] generates
Intointo
What #[derive(Into)] generates
IntoIteratorinto_iterator
Using #[derive(IntoIterator)]
IsVariantis_variant
What #[derive(IsVariant)] generates
LowerExpdisplay
What #[derive(Display)] generates
LowerHexdisplay
What #[derive(Display)] generates
Mulmul
What #[derive(Mul)] generates
MulAssignmul_assign
What #[derive(MulAssign)] generates
Negnot
What #[derive(Not)] generates
Notnot
What #[derive(Not)] generates
Octaldisplay
What #[derive(Display)] generates
Pointerdisplay
What #[derive(Display)] generates
Productsum
Using #[derive(Sum)]
Remmul
What #[derive(Mul)] generates
RemAssignmul_assign
What #[derive(MulAssign)] generates
Shlmul
What #[derive(Mul)] generates
ShlAssignmul_assign
What #[derive(MulAssign)] generates
Shrmul
What #[derive(Mul)] generates
ShrAssignmul_assign
What #[derive(MulAssign)] generates
Subadd
What #[derive(Add)] generates
SubAssignadd_assign
What #[derive(AddAssign)] generates
Sumsum
Using #[derive(Sum)]
TryFromtry_from
What #[derive(TryFrom)] generates
TryIntotry_into
What #[derive(TryInto)] generates
TryUnwraptry_unwrap
What #[derive(TryUnwrap)] generates
Unwrapunwrap
What #[derive(Unwrap)] generates
UpperExpdisplay
What #[derive(Display)] generates
UpperHexdisplay
What #[derive(Display)] generates