::ghost_lite

A lightweight implementation of ::ghost with macro_rules.

Usage

```rust use ghost_lite::ghost;

ghost! { /// ghost macro defines a custom PhantomData, /// which can be used as both a type and a value. pub struct MyPhantomData }

fn main() { let _: MyPhantomData = MyPhantomData; let _ = MyPhantomData::<&str>; } ```

Caveats

1. derive should be in inner attributes (#![derive(...)]). Only the following traits are supported.

   ```rust ghost_lite::ghost! { #![derive(Clone, Copy, Default, Hash, PartialOrd, Ord, PartialEq, Eq, Debug)] pub struct MyPhantom }

   /// String is not copy, but MyPhantom is always Copy, like PhantomData fn test() -> impl Copy { MyPhantom:: }

   fn main() {}

   ```

   derive in outer attributes will be directly prepended to the generated enum, which works like normal derive macros.

   ``rust,compile_fail ghost_lite::ghost! { /// MyPhantom isCloneandCopyonly if T isCloneandCopy` #[derive(Clone, Copy)] pub struct MyPhantom }

   /// String is not copy, so MyPhantom is not Copy fn test() -> impl Copy { MyPhantom:: }

   fn main() {}

   ```

2. The implementation relies on a mod name. To define multiple custom PhantomData types in the same module, you must provide custom mod name with #![mod_value_namespace = my_phantom_data].

   ```rust,compilefail ghostlite::ghost! { struct MyPhantomData1 }

   ghost_lite::ghost! { struct MyPhantomData2 }

   fn main() {}

   ```

   ```rust ghost_lite::ghost! { struct MyPhantomData1 }

   ghostlite::ghost! { #![modvaluenamespace = myphantomdata2] struct MyPhantomData2 }

   fn main() {}

   ```

3. Move type generic bounds to where clause if ghost! reports error.

   Parsing tokens is limited with macro_rules, so complex type bounds are not supported.

   For example:

   ```rust,compilefail ghostlite::ghost! { struct MyPhantomData }

   fn main() {}

   ```

   ```rust ghost_lite::ghost! { struct MyPhantomData where T: Clone + PartialEq }

   fn main() {}

   ```

4. Please don't add a trailing semicolon ;.

   ```rust,compilefail ghostlite::ghost! { struct MyPhantomData; }

   fn main() {}

   ```

   ```rust ghost_lite::ghost! { struct MyPhantomData }

   fn main() {}

   ```