geez 0.1.0

# geez


**G**lobal **E**rror **E**mbedding **Z**ero-cost.

Typed error enums with attributes that look like `thiserror`, implemented as a plain `macro_rules!` macro. No proc-macros, no dependencies.

## Add it


```toml
[dependencies]
geez = "0.1"
```

## Use it


```rust
use geez::geez;

geez! {
    pub enum AppError {
        #[from]
        Io(std::io::Error),

        #[transparent]
        Other(OtherError),

        #[source]
        Wrapped(std::io::Error),

        #[error("bad status {0}: {1}")]
        Status(u16, String),

        #[error("parse failed: {0}")]
        Parse(String),

        Timeout => "request timed out",

        NotFound,
    }
}

fn load() -> Result<()> {
    std::fs::read_to_string("config.toml")?;
    Ok(())
}
```

That also defines `type Result<T> = std::result::Result<T, AppError>` with the same visibility as the enum.

## Attributes


| Write this | What you get |
|---|---|
| `#[from]` | `From<T>` + `Error::source` (one field) |
| `#[transparent]` | `From<T>`, Display and source forward to the inner error (one field) |
| `#[source]` | `Error::source` only — no `From` (one field) |
| `#[error("…")]` | Custom Display. Use `{0}`, `{1}`, … for fields |
| `=> "…"` | Same as `#[error("…")]`, handy for unit variants |
| unit, no message | Display is the variant name (`NotFound`) |
| one field, no message | Display is `"{}"` of the field |

`#[from]`, `#[transparent]`, and `#[source]` are mutually exclusive. Multi-field variants need an `#[error("…")]` (or `=>`).

Tuple variants support up to 8 fields.

## vs thiserror / anyhow


**thiserror** is a proc-macro with a bigger feature set (struct variants, field-level `#[source]`, more format sugar). Reach for it when you need that, or when you already depend on it.

**anyhow** is one opaque error type plus context helpers. Great for binaries and apps. Not what you want for a library’s public error enum.

**geez** sits in the thiserror lane: typed enums for libraries, familiar attributes, zero deps, declarative macro only. Use it when you want a small error enum without pulling in `syn`.

## License


MIT OR Apache-2.0