Crate mayber 

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.

Copyright (c) 2025 Al Liu.

Re-exports

pub use crate::Maybe::Owned;

pub use crate::Maybe::Ref;

Enums

Maybe

An enum that can hold either a reference or an owned value.

Type Aliases

MaybeMut

A type alias for a Maybe enum that holds either a mutable reference or an owned value.

MaybeRef

A type alias for a Maybe enum that holds either a reference or an owned value.