1 unstable release

0.1.1	Jan 24, 2026
0.1.0	~~Dec 13, 2025~~

#1283 in Rust patterns

969 downloads per month
Used in tokit

MIT/Apache

44KB
661 lines

mayber

A Rust library for handling either references or owned values with a unified interface.

Overview

mayber provides a flexible Maybe<R, T> type that can hold either a reference (R) or an owned value (T). This is particularly useful when you want to avoid unnecessary allocations or clones while maintaining the flexibility to work with owned data when necessary.

Unlike Cow<T> which is specifically designed for borrowed vs owned variants of the same type, Maybe<R, T> is more generic and works with any reference type and owned type pair.

Installation

Add this to your Cargo.toml:

[dependencies]
mayber = "0.1"

Features

std (default): Standard library support with I/O traits (Read, Write, Seek, BufRead)
alloc: Allocation support for no_std environments
serde: Serialize/Deserialize implementations

# With serde
[dependencies]
mayber = { version = "0.1", features = ["serde"] }

# no_std with alloc
mayber = { version = "0.1", default-features = false, features = ["alloc"] }

When to Use

Accept both references and owned values without cloning
Build flexible APIs that work with borrowed or owned data
Need mutable reference or owned value flexibility (MaybeMut)
Reduce allocations in performance-critical paths

Comparison with `Cow`

Feature	`Cow<'a, T>`	`Maybe<R, T>`
Purpose	Clone-on-write for specific types	Generic reference or owned value
Type flexibility	Limited to `ToOwned` types	Works with any `R` and `T` pair
Common use case	`Cow<'a, str>`, `Cow<'a, [T]>`	`MaybeRef<'a, T>`, `MaybeMut<'a, T>`
Deref behavior	Always derefs to borrowed form	`MaybeRef`/`MaybeMut` implement `Deref`/`DerefMut`

Trait Implementations

MaybeRef<T>: Deref, AsRef, Borrow, PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Hash, Debug, Display
MaybeMut<T>: Deref, DerefMut, AsRef, AsMut, Borrow, BorrowMut, I/O traits (std feature)
Maybe<R, T>: Default, From<T>, From<&T>, Deserialize (serde feature)

Credit

The original idea for this type comes from chumsky's util.rs.

Minimum Supported Rust Version (MSRV)

This crate requires Rust 1.56 or later.

License

mayber is under the terms of both the MIT license and the Apache License (Version 2.0).

See LICENSE-APACHE, LICENSE-MIT for details.

Dependencies

~115KB