Structural Search and Replace (SSR): replacement referred unknown placeholder

rust-analyzer version: 2022-07-25
rustc version: 1.62.1

Code:

use std::ops::Add;
use typenum::{Sum, consts::*};

// <$l as Add<$r>>::Output ==>> typenum::Sum<$l, $r>

pub type Num = <P1 as Add<P2>>::Output;

fn main() {
    println!("Hello, world!");
}

Steps to reproduce:

1. cargo new sample_text && cd sample_text && cargo add typenum
2. Open text editor with LSP
3. Paste this code snippet to src/main.rs
4. Run code action for commented line with an SSR request

Expected behavior:

Replace

pub type Num = <P1 as Add<P2>>::Output;

with

pub type Num = Sum<P1, P2>;

Observed behavior:

Internal error: replacement referred unknown placeholder $l

Start by reproducing the structural search and replace request on the commented line using the provided sample project. Trace how the replacement referring to $l and $r is interpreted, then verify that the request produces pub type Num = Sum<P1, P2>; instead of the unknown-placeholder error.