Function rustfmt_nightly::closures::rewrite_closure_fn_decl

fn rewrite_closure_fn_decl(
    capture: CaptureBy, 
    asyncness: &Async, 
    movability: Movability, 
    fn_decl: &FnDecl, 
    body: &Expr, 
    span: Span, 
    context: &RewriteContext<'_>, 
    shape: Shape
) -> Option<(String, usize)>