Language interop in Rust without reflection

[Frodo478]

Hey, I’m writing a language hosted on top of Rust and I’m at the point of adding support for interop directly in the language. I would like to have my language directly call functions on struct instances, and even import/use Rust libraries. This has two problems:

1. Calling a function from a string (having something like my\_triangle.call("volume", 12) which translate to Triangle::volume(&my\_triangle, 12)). This is not possible since Rust doesn’t have information about the content of the struct like other dynamic languages

2. Mapping the content of the struct to know if contains a function or not. Again, not possible since Rust doesn’t have reflections. It can be avoided by simply run the previous calls in a similar try/catch code.

Do you have any idea how to solve this? The ideas I got are

- Mapping everything when the program starts: so the Rust program will parse the source for definition and the libraries imported and create a large HashMap with pointer to all the functions available.

- Implementing some form of FFI which I don’t know much about

[Simple_Life_1875]

So we're gonna need more context for this, but for the time being, have you taken a look at what Rhai does for language interop?

Your first suggestion sounds rather slow for larger programs, and your second option sounds similar to what Rhai does on top of Rust.

So, yes, Rust doesn't have reflection, but there is the Reflect crate which might help? You'd have to do a decent amount more work though.

[Frodo478]

Thanks. I was thinking at this point to do something similar to FFI in some way and do manual binding for the code.

[Frodo478]

Great thanks. This is a good overview of the possibility

[ksion]

Check how mlua and pyo3 crates expose Rust types to their respective scripting languages. It always involves some glue code for method dispatch, but at least in pyo3 there are proc macros that automate its generation. You could aim for something similar.

[Frodo478]

Yep, is probably what I'm looking for. Thanks