Rust 宏规则：？ 如何写一生？

Question

I'm trying to create a lifetime-generic function within a macro. Nothing fancy from the outside, just a hardcoded function-local one:

macro_rules! generate_parse_function {
    ($rule_name:ident, $parse_expr:tt) => {
        fn $rule_name<'a>(code: &'a str) -> (Option<Ast>, &'a str) {
            (Ast::$rule_name, $parse_expr)
        }
    };
}

But no matter what I do it comes out like this:

fn nil< 'a>(code: & 'astr) -> (Option<Ast>, & 'astr){
    (Ast::nil,"NIL")
}

There's a space before 'a (which may or may not be a problem), and the space is removed between a and str (which is definitely a problem). I can't find anything about this on the internet, but it must be a reasonably common scenario. Anybody know what to do here?

Answer 1

Bizarrely, this appears to be a bug in rust-analyzer . It reports the wrong result but when I run cargo-expand manually, I get the correct result (as pointed out by @eggyal).