Inlay hints not working in macro call

[blaumeise20]

rust-analyzer version: 0add6e9 2021-12-20 stable

rustc version: rustc 1.60.0-nightly (ee5d8d37b 2022-01-17)

When creating macros that accept blocks, if you declare a let, it doesn't show you the type. Doesn't work with function call parameter names either.

fn main() {
    macro_rules! foo {
        (bar $b:block) => {
            $b
        }
    }

    fn baz(val: i32) {
        println!("baz {}", val);
    }

    foo!(bar {
        let x = 123;
        baz(x);
        println!("Hello, world!");
    });

    let x = 123;
    baz(x);
    println!("Hello, world!");
}

[Veykril]

We currently can't(without showing a lot of confusing hints) show inlay hints in macro inputs, this requires #11183 for a proper solution.

[ilyvion]

Just out of curiosity, how is it that rust-analyzer is able to realize what things are within macros when it comes to its tooltips:

whereas presenting that (seemingly) same information in an inlay hint requires a whole new machinery?

Again, I'm just asking out of curiosity, not because I think I've discovered some kind of "gotcha" here, but I really don't understand what the difference comes down to.

[flodiebold]

The hard part is deciding where to place inlay hints in the macro input. I'm not sure I agree that we need macro fragment captures for that, because I think we should also be able to do it for proc macros, but it does need some logic and heuristics specific to each kind of inlay hint to figure out what parts of the macro input should get hints, and no one has implemented that yet.