Macro expansion in for trait items

[josephDunne]

Hi, I see that in ast.rs there is no expectation for macro items inside a trait:

pub enum TraitItemKind {
    Const(P<Ty>, Option<P<Expr>>),
    Method(MethodSig, Option<P<Block>>),
    Type(TyParamBounds, Option<P<Ty>>),
}

Is there a reason for this? I would like to build up Trait definitions via macros the same way I would build a struct or impl items using macros.

[jseyfried]

c.f. #5668
cc @nrc -- do you think we should support this?

[josephDunne]

My use case is generating trait extensions for a builder object for the Rust version of Flatbuffers: google/flatbuffers#3894
Would be nice to get rid of the boilerplate with macros.

[nrc]

I think we probably could, I'm in no great rush, but it seems like a good thing.

[jseyfried]

This was fixed in #34213.