Type Definition syntax_ext::deriving::generic::CombineSubstructureFunc[][src]

type CombineSubstructureFunc<'a> = Box<FnMut(&mut ExtCtxt, Span, &Substructure) -> P<Expr> + 'a>;
🔬 This is a nightly-only experimental API. (rustc_private)

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

Combine the values of all the fields together. The last argument is all the fields of all the structures.