Need to be able to create structs via macro_rules

[gilescope]

(Currently only possible using tt escape type which doesn't do any processing.)

There's quite a few places I think we need to update but using pyclass as an example to agree the right way to do things. When you pass the argument via macro_rules unless it's the escape sequence type of tt then the Expr::Path seems to get wrapped in an Expr::Group whatever type I choose for the variable I'm passing in: ident, path, expr.

(btw I notice you can't match on box which might make the code a tad nicer.)

[gilescope]

(The test fails to compile without the patch which is why there's no assertions in it)

[kngwyu]

Thanks 👍

[programmerjake]

Encountered this issue myself.

One suggestion: maybe there should be an unwrap_group function that unwraps a group or returns the input unchanged:

// pseudo-code, probably needs some derefs and other misc. cleanup
fn unwrap_group(expr: &syn::Expr) -> &syn::Expr {
    if let syn::Expr::Group(g) = expr {
        &*g.expr
    }
    expr
}

that way, the match cases can be simplified:

            "name" => match unwrap_group(&**right) {
                syn::Expr::Path(exp) if exp.path.segments.len() == 1 => {
                    self.name = Some(exp.clone().into());
                }
                _ => expected!("type name (e.g., Name)"),
            },

[scalexm]

Btw, I would suggest a while let Group(g) = expr approach rather than unwrapping a single layer. Not sure if that could actually happen but it’s harmless.

[davidhewitt]

👍 also my parsing improvements in #1567 might resolve a lot of the problems here. I plan to retest this once that PR is merged.

[davidhewitt]

As this branch is very old, I just rebased it and will merge it if tests are green 🤞

[scalexm]

More of these problems started to appear with Rust 1.53 (at first I thought it was a compiler regression, but actually it’s just the compiler adding a few more groups and pyo3 not handling them correctly).

I think we should use unwrap_group quite liberally: I have found a few more places where we need it. Once this is merged, I’ll open a follow-up PR.