Replace paste by with_builtin_macros.

[maximebuyse]

Fixes #1379.

I looked for a solution without introducing a new dependency. concat_idents seems like a good candidate but it doesn't work for function names as discussed in rust-lang/rust#29599. So I replaced paste by with_builtin_macros which builts on top of concat_idents to provide the functionality we need.

[W95Psp]

That looks good to me, let's see how maintained with_builtin_macros is, but for now that seems a great solution! :)

And that works without nightly, so that's nice.

[Nadrieril]

Are you aware of ${concat(x, y)}?

[franziskuskiefer]

with_builtin_macros doesn't look great 😬
Did you try the macro_metavar_expr_concat? If that works, I think it would be the better option.

[maximebuyse]

Are you aware of ${concat(x, y)}?

Looks like it does what we need, thanks! If we are ok to use something experimental, I'll try it.

[karthikbhargavan]

Not that I am expert, but in the same thread that talks about macro_metavar_expr_concat and ${concat}, the last suggestion, especially for stable rust, appears to be with_builtin_macros?

rust-lang/rust#124225 (comment)

[maximebuyse]

Not that I am expert, but in the same thread that talks about macro_metavar_expr_concat and ${concat}, the last suggestion, especially for stable rust, appears to be with_builtin_macros?

rust-lang/rust#124225 (comment)

The suggestion comes from the author of with_builtin_macros though.

[franziskuskiefer]

If we are ok to use something experimental, I'll try it.

If it works, I think something experimental here within the language feels better than a 3rd party crate. We're on nightly anyway.

[maximebuyse]

If we are ok to use something experimental, I'll try it.

If it works, I think something experimental here within the language feels better than a 3rd party crate. We're on nightly anyway.

Yes it works, let's merge then!