Switch to an attribute macro

[est31]

It's a bit weird to wrap entire functions / modules into method style macros.

For this though, we'll need support by rustc to syntactically permit postfix macros.

[yonip23]

Maybe you can replace postfix_macros! with a build.rs that does the same thing?

[est31]

I've sent a PR to rustc to syntactically parse postfix macros: rust-lang/rust#78849

The reactions to this are... mixed. I think it'd be best to next implement the suggestion in rust-lang/rust#78849 (comment)

[akriegman]

Any updates on this?

[est31]

No, nothing has changed since.