Strange behavior decl_macro + try_blocks + type_ascription

[kgv]

First line in main function compiles with error, but second and third compiles without error.

#![allow(unused)]
#![feature(decl_macro)]
#![feature(try_blocks)]
#![feature(type_ascription)]

pub macro test_macro {
    () => {
        try {
            let mut exit_code = 0;
            if exit_code < 0 {
                Err(exit_code)?;
            }
            exit_code
        }: Result<usize, usize>
    }
}

fn main() {
    test_macro!(); // Err
    // test_macro!().unwrap(); // Ok
    // let t = test_macro!(); // Ok
}

(Playground)

Errors:

   Compiling playground v0.0.1 (/playground)
error: expected expression, found `:`
  --> src/main.rs:14:10
   |
14 |         }: Result<usize, usize>
   |          ^ expected expression
...
19 |     test_macro!(); // Err
   |     -------------- in this macro invocation

error: aborting due to previous error

error: Could not compile `playground`.

To learn more, run the command again with --verbose.

[Centril]

cc #31436, #23416, #39412

[lolbinarycat]

triage: type ascription has been removed