Macro error: expected Expr

[colinmarc]

rust-analyzer version: rust-analyzer 1.84.1 (e71f9a9 2025-01-27)

rustc version: rustc 1.84.1 (e71f9a9a9 2025-01-27)

editor or extension: zed or nvim

I'm getting an LSP error on a macro that compiles fine. The issue is reproducible on commit ba3f8bce2749329d2b02922d7637e8546c5eb81b of https://github.com/colinmarc/magic-mirror.

Here is the macro invocation that rust-analyzer doesn't like:

https://github.com/colinmarc/magic-mirror/blob/ba3f8bce2749329d2b02922d7637e8546c5eb81b/mm-server/src/encoder/h264.rs#L22-L28

And here is where the macro lives:

https://github.com/colinmarc/magic-mirror/blob/ba3f8bce2749329d2b02922d7637e8546c5eb81b/mm-server/src/vulkan/chain.rs#L28

Please ignore how insane the macro is 😓 Building the project is also a bit of a hassle, sorry about that. It requires linux and cmake nasm protoc libxkbcommon-dev. Detailed build instructions here: https://colinmarc.github.io/magic-mirror/setup/server/#building-mmserver-from-source

[ChayimFriedman2]

Minimized reproduction:

macro_rules! a {
    ($t:tt) => {};
}

macro_rules! b {
    ($t:ty) => {
        a!($t);
    };
}

b!(&'static str);

None groups strike again...

[colinmarc]

Thanks so much for boiling it down, I could not have gotten there.

Does that mean the issue is in __replace_expr? Do you have a suggested workaround for the time being?

[ChayimFriedman2]

You can wrap it in parentheses:

                    Self::new(__replace_expr!(($HeadStruct) Default::default()), $(__replace_expr!(($Struct) Default::default()),)*)