case-studies VS cargo-expand

Luckily there is a workaround to emulate such a definition, which dtolnay discovered and explained here: https://github.com/dtolnay/case-studies/tree/b9802f6df8dc8e54970b83fb9af6df923b46abf5/unit-type-parameters.

I think they are talking about this one trick which the devs don't want you to know about. Note that while it looks like specialization, it works only in a few very limited cases and is quite fragile, so it's a hack, not a substitute for the real feature.

Also I suggest his case studies repo since you are looking at what is possible: https://github.com/dtolnay/case-studies

/u/dtolnay has a great case studies repository.

Once you have the basics down, read dtolnay's case studies. They show how to do advanced stuff with easy macros.

If you were writing your own println macro, you might be able to get away with this kind of hack: https://github.com/dtolnay/case-studies/blob/master/autoref-specialization/README.md

You can use "Autoref-based stable specialization" or use/mimic the impls crate.

With a subset of specialization likely riding the trains soon and a workaround available, why would you give up?

this works since values and types are in different namespaces (see: Rusts Universes or dtolnay's Case Study about "Unit struct with type parameters")

To do this with traits you would need specialization but since you are using macros you should be able to use "Autoref-based stable specialization". Here is a playground which uses the latter approach to implement the wanted macro without using any nightly features.

It's been superseded by https://github.com/dtolnay/cargo-expand

Try installing cargo expand, it's useful to see how macros eventually get expanded. For example, if you run cargo expand on the following code

You can use cargo expand to see what your code expands to: https://github.com/dtolnay/cargo-expand

Not too familiar with macros but does cargo-expand do what you want or did you mean something else?

Yes. You can use Tools > Expand Macro on the playground or install and run cargo-expand to see what the macro expands to. It just adds a & before the argument.

cargo expand

Along with what others are saying, there is also cargo expand which can show you what code a macro generates

Something that may help you understand code with magic proc macros is this utility. It's basically a wrapper around a Rust compiler flag that allows you to expand macros for a file.

You can use https://github.com/dtolnay/cargo-expand to examine how it works.