{"id":51514752,"url":"https://github.com/jamesgober/type-lib","last_synced_at":"2026-07-08T10:01:45.879Z","repository":{"id":359485163,"uuid":"1242968722","full_name":"jamesgober/type-lib","owner":"jamesgober","description":"Validation and type constraint library. Declare domain types with invariants enforced at construction (NonEmpty, BoundedInt, EmailAddress, etc.). Parse-don't-validate pattern as a first-class citizen. 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Domain types with invariants enforced at construction. Zero-overhead wrappers.\u003c/p\u003e\n\n\n## What it does\n\n`type-lib` makes invalid states unrepresentable. Instead of validating a value\nevery time it is used, you validate it **once** — at construction — and carry a\ntype that the compiler will only let exist in a valid state. Functions that take\nsuch a type are freed from defensive checks: the type system already did them.\n\nThe foundation is two pieces that compose:\n\n- [`Validator`](docs/API.md#validator) — a reusable, type-level validation rule.\n  It lives on a zero-sized marker type and is selected through the type system,\n  so it carries no state and no storage.\n- [`Refined`](docs/API.md#refined) — a `#[repr(transparent)]` wrapper holding a\n  value proven to satisfy a `Validator`. It has the exact size and layout of the\n  value it wraps, so the guarantee is free at runtime.\n\nA ready-made [`ValidationError`](docs/API.md#validationerror) covers rules that\nneed only a code and a message; rules that need structured failures define their\nown error type through `Validator::Error`.\n\n---\n\n## Features\n\n- **Parse, don't validate** — invariants are enforced at construction and proven\n  by the type thereafter; no re-checking at call sites.\n- **Zero-overhead wrappers** — `Refined\u003cT, V\u003e` is `#[repr(transparent)]` over `T`\n  and stores nothing extra. The validated type is the same size as the raw one.\n- **Built-in rules** — ready-made validators for length\n  ([`NonEmpty`](docs/API.md#length-rules), `MinLen`, `MaxLen`, `LenRange`), numbers\n  (`Positive`, `InRange`, …), and string content (`Ascii`, `Alphanumeric`,\n  `Trimmed`).\n- **Composition** — combine rules at the type level with\n  [`And`](docs/API.md#combinators), `Or`, and `Not`; the result is itself a rule.\n- **Derive macro** — `#[derive(Validated)]` (the `derive` feature) turns a newtype\n  into a named domain type with a checked constructor.\n- **Reusable, type-level rules** — write a `Validator` once and apply it to any\n  value type through the type system.\n- **Tamper-proof by construction** — `Refined` exposes no `\u0026mut` to its inner\n  value and no public field, so a validated value cannot be mutated into an\n  invalid one behind the type's back.\n- **Bring your own error** — use the bundled `ValidationError` or any custom\n  error type via the `Validator::Error` associated type.\n- **`no_std` friendly** — the core API and all borrowed-value rules work without\n  `std`; `alloc` adds owned-type (`String` / `Vec`) length rules and `std` adds\n  the [`std::error::Error`] impl.\n- **Cross-platform** — Linux, macOS, and Windows on stable and MSRV 1.75.\n\n---\n\n## Performance\n\nValidation is the only runtime cost; the wrapper adds none. Local Criterion means\n(Windows x86_64, Rust stable, `cargo bench`):\n\n- `Refined::new` with `Ascii` on a short `\u0026str`: **~0.9 ns**\n- `Refined::new` with `LenRange\u003c3, 16\u003e` on a `\u0026str`: **~2.2 ns**\n- `Refined::new` with `InRange\u003c0, 100\u003e` on an `i32`: **~2.6 ns**\n- `get` / `Deref` accessors: **sub-nanosecond** (compile down to a field read)\n\n---\n\n## API Overview\n\nFor the complete reference with examples, see [docs/API.md](docs/API.md).\n\n- [`Validator`](docs/API.md#validator) — reusable, type-level validation rule\n- [`Refined`](docs/API.md#refined) — zero-cost wrapper around a validated value\n- [`ValidationError`](docs/API.md#validationerror) — ready-made `no_std` error\n- [Built-in rules](docs/API.md#built-in-rules) — length, numeric, and string rules\n- [Combinators](docs/API.md#combinators) — `And`, `Or`, `Not`\n- [`Validated`](docs/API.md#validated-derive) — `#[derive]` for validated newtypes (`derive` feature)\n- [`prelude`](docs/API.md#prelude) — convenient re-exports\n- [`VERSION`](docs/API.md#version) — compile-time crate version\n\nRunnable demos live in [`examples/`](examples): `quick_start`, `built_in_rules`,\n`composing_rules`, `custom_rule`, and `derive_newtype`\n(e.g. `cargo run --example quick_start`).\n\n---\n\n## Installation\n\n```toml\n[dependencies]\ntype-lib = \"1.0.0\"\n\n# with the derive macro\ntype-lib = { version = \"1.0.0\", features = [\"derive\"] }\n\n# no_std build (core API + borrowed-value rules)\ntype-lib = { version = \"1.0.0\", default-features = false }\n\n# no_std + owned-type rules (String / Vec)\ntype-lib = { version = \"1.0.0\", default-features = false, features = [\"alloc\"] }\n```\n\nMSRV: Rust 1.75.\n\n## Quick start\n\n```rust\nuse type_lib::combinator::And;\nuse type_lib::rules::{LenRange, Trimmed};\nuse type_lib::Refined;\n\n// A username: 3–16 characters with no surrounding whitespace.\n// Built once, the type guarantees the invariant everywhere it is used.\ntype Username = Refined\u003cString, And\u003cTrimmed, LenRange\u003c3, 16\u003e\u003e\u003e;\n\nfn main() {\n    let user = Username::new(\"alice\".to_owned());\n    assert!(user.is_ok());\n\n    assert!(Username::new(\"ab\".to_owned()).is_err());        // too short\n    assert!(Username::new(\"  alice  \".to_owned()).is_err()); // whitespace\n}\n```\n\nPrefer a distinct named type with its own constructor? Enable the `derive`\nfeature and annotate a newtype:\n\n```rust\nuse type_lib::combinator::And;\nuse type_lib::rules::{LenRange, Trimmed};\nuse type_lib::Validated;\n\n#[derive(Validated)]\n#[valid(And\u003cTrimmed, LenRange\u003c3, 16\u003e\u003e)]\npub struct Username(String);\n\nlet user = Username::new(\"alice\".to_owned());\nassert!(user.is_ok());\n```\n\nNeed a rule the built-ins don't cover? Implement [`Validator`](docs/API.md#validator)\non a marker type — see the [`custom_rule`](examples/custom_rule.rs) example.\n\nFor the exhaustive API reference, see [docs/API.md](docs/API.md).\n\n---\n\n## Standards\n\n- **REPS** governs every decision. See [REPS.md](REPS.md).\n- **MSRV:** Rust 1.75.\n- **Edition:** 2021.\n- **Cross-platform:** Linux, macOS, Windows.\n\n---\n\n## License\n\nDual-licensed under either of:\n\n- Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE))\n- MIT License ([LICENSE-MIT](LICENSE-MIT))\n\nat your option.\n\n\n\n\u003c!-- FOOT COPYRIGHT\n################################################# --\u003e\n\u003cdiv align=\"center\"\u003e\n  \u003ch2\u003e\u003c/h2\u003e\n  \u003csup\u003eCOPYRIGHT \u003csmall\u003e\u0026copy;\u003c/small\u003e 2026 \u003cstrong\u003eJAMES GOBER.\u003c/strong\u003e\u003c/sup\u003e\n\u003c/div\u003e","project_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fjamesgober%2Ftype-lib","html_url":"https://awesome.ecosyste.ms/projects/github.com%2Fjamesgober%2Ftype-lib","lists_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fjamesgober%2Ftype-lib/lists"}