例)synで関数名を取得する
pub struct ItemFn {
pub attrs: Vec,
pub vis: Visibility,
pub sig: Signature,
pub block: Box,
}
pub struct Signature {
pub constness: Option,
pub asyncness: Option,
pub unsafety: Option,
pub abi: Option,
pub fn_token: Token![fn],
pub ident: Ident,
pub generics: Generics,
pub paren_token: token::Paren,
pub inputs: Punctuated,
pub variadic: Option,
pub output: ReturnType,
}
関数名を持つ