Deriving Traits in Rust with Procedural Macros

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I just wrote a new blog post covering how to derive custom traits using procedural macros: Deriving Traits in Rust with Procedural Macros · naftuli.wtf

I ran into some problems, and this works through that :slight_smile:

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Nice! It's good to see it built up step by step.
If you wanted to remove these:

#[macro_use]
extern crate quote;
#[macro_use]
extern crate syn;

you could do:

use quote::quote;
use syn::{parse_macro_input, DeriveInput};

I like to see where macros come from, though it has the caveat of being ambiguous: "am I importing a macro, or a module, or a function?"

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Nice post (good I learned about the generics.split_for_impl, I was trying to crunch the tokens manually and it is annoying and probably wrong).

Anyway, this feels like a bigger hammer than needed for the job. Did you know you can implement traits „en masse“?

impl<T: Template> WritableTemplate for T {
    fn write(&self, path: &Path) -> io::Result<()> {
        let mut file = io::BufWriter(fs::File::create(path)?);
        file.write(self.render.unwrap().trim().as_bytes())?;

        Ok(())
    }
}
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Yes, my bad for leaving them in. I got some helpful corrections on Reddit also that I'll make into GH issues on my blog repo so I'll try to get those changes shipped today.

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Yes, this was also another thing I received in feedback on Reddit, basically using a where clause to automatically implement the trait for all askama::Template implementations. It's a big hammer, but there's another way to add a marker trait to be able to selectively implement the trait. It would have saved me some time if I remembered that it was possible to do this, but there wouldn't be a blog post so I guess it worked out :slight_smile:

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Thanks everybody for the feedback and corrections, I have updated the post accordingly!