A set of rust macros that allows you to specify enums that can be "extended" or inherited from.
This project started because I was using the very nice logos library and I wanted to define 2 lexer with some of the same base tokens but extended. I could not find a proper way to do this that was not simply copy-pasting the parts of the enum that I needed, so I set about bodging it with macro abuse.
Technically this approach could also be used for doing the same with structs, but I haven't looked into that yet.
Simply, define the base enum (A) that you want to use. Then add the #[extendable_enum] attribute to it. This will automatically generate a new macro called extend_from_A (or you can specify a name in the attribute arguments). Now, use this new macro for the extended enum B.
```rust use extendableenums::extendableenum;
enum A {
One,
Two,
Three
}
``
In a crate (we'll useXhere) that hasproc-macro` set to true, then:
```rust use X::extend_a;
enum B { Four, Five, Six }
fn main() { let e: B ...; ... match e { B::One => ..., B::Four => ..., } } ```
Because this package uses proc-macro, I am not allowed to export any functions which are not procedural macros. However, the extendable_enum macro makes use of a helper function to construct the proper TokenStream, which is in itself not a procedural macro. As such, a second package exists which exports this function: extendable-enums-helpers. You are required to include both packages in your dependencies section of Cargo.toml.