avoid parsing of expression in closure expecting attributes

[ModProg]

These require syn.features = ["full"] but AFAICT it would be possible to just accept any tokens?

Maybe I'm overlooking something thought.

[Kyuuhachi]

It only has full as a dev-dependency; when compiling as a library only parsing and derive are used. If that's not what you're referring to, would you mind clarifying the question?

[ModProg]

Well, syn doesn't support, e.g., #[parse(peek_func = |p| ...)] without the full feature.

[Kyuuhachi]

I still don't know what you're talking about. syn::Expr requires full or derive. Could you explain what the actual issue is here?

[ModProg]

#[derive(syn_derive::Parse)]
enum Test {
    #[parse(peek_func = |ps| ps.peek(syn::Token![for]) && ps.peek2(syn::Token![if]))]
    Test(syn::Ident),
}

Yields this error when compiling:

❯ cargo check
    Checking syn_derive_test v0.1.0
error: unsupported expression; enable syn's features=["full"]
 --> src/main.rs:7:25
  |
7 |     #[parse(peek_func = |ps| ps.peek(syn::Token![for]) && ps.peek2(syn::Token![if]))]
  |                         ^

[ModProg]

(It is also not enought to add syn with full oneself):

[package]
name = "syn_derive_test"
version = "0.1.0"
edition = "2021"

[dependencies]
syn = { version = "2.0.38", features = ["full"] }
syn_derive = "0.1.7"

still yields the same error

[Kyuuhachi]

Huh, seems you're right. Unfortunately it's not as simple as parsing until the next comma, since that could be inside a || or <>. I'd have to either reimplement a sizeable part of the expr parsing, which I'd rather not, or enable full.

As a compromise, I could add a full feature flag to syn_derive to enable it.

[ModProg]

Huh, seems you're right. Unfortunately it's not as simple as parsing until the next comma, since that could be inside a || or <>. I'd have to either reimplement a sizeable part of the expr parsing, which I'd rather not, or enable full.

Right, I only now noticed that you also have attributes where a value can follow a function.

As a compromise, I could add a full feature flag to syn_derive to enable it.

I'm not sure how bad the overhead of full really is, so it might be fine to have it on by default as well.

[Kyuuhachi]

Added an enabled-by-default full feature in v0.1.8. Thanks for reporting.