Represents a Rust function declaration built with RustQ.Rust.fn/2.
RustQ.Rust.fn/2
@type t() :: %RustQ.Rust.Function{ args: [term()], attrs: [term()], body: iodata(), generics: [term()], name: atom() | String.t(), returns: term(), vis: atom() | String.t() | nil, where: [term()] }