Function rustc_hir_pretty::fn_to_string

pub fn fn_to_string(
    decl: &FnDecl<'_>, 
    header: FnHeader, 
    name: Option<Symbol>, 
    generics: &Generics<'_>, 
    vis: &Visibility<'_>, 
    arg_names: &[Ident], 
    body_id: Option<BodyId>
) -> String