Rust analyzer stops responding after adding a bunch of emojis

[A-Walrus]

Summary

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

Adding more of the "👆" emoji to the comment causes the language server to stop responding.

Might be related to #3283 which also has to do with emojis.

I don't think this is an upstream bug in rust-analyzer as trying this in vscode with rust-analyzer works fine

Reproduction Steps

asciinema

I tried this:

1. hx .
2. open the file with

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

3. Wait for language server to respond (by hitting <space> k repeatedly
4. Copy paste the emoji a bunch of times
5. Try viewing the documentation for println! (by hitting <space> k), notice it doesn't respond

I expected this to happen:
I see the documentation for println!, like I did before adding the emojis.

Instead, this happened:
No documentation appeared

Helix log

~/.cache/helix/helix.log

2022-08-01T21:04:07.872 helix_lsp::transport [ERROR] err <- "Panic context:\n"
2022-08-01T21:04:07.872 helix_lsp::transport [ERROR] err <- "> \n"
2022-08-01T21:04:07.873 helix_lsp::transport [ERROR] err <- "version: 0.0.0 (7e2b983fd 2022-07-24)\n"
2022-08-01T21:04:07.873 helix_lsp::transport [ERROR] err <- "notification: textDocument/didChange\n"
2022-08-01T21:04:07.873 helix_lsp::transport [ERROR] err <- "\n"
2022-08-01T21:04:07.873 helix_lsp::transport [ERROR] err <- "thread 'LspServer' panicked at 'assertion failed: self.is_char_boundary(n)', /rustc/1.62.1/library/alloc/src/string.rs:1800:29\n"
2022-08-01T21:04:07.873 helix_lsp::transport [ERROR] err <- "stack backtrace:\n"
2022-08-01T21:04:07.873 helix_lsp::transport [ERROR] err <- "note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.\n"
2022-08-01T21:04:08.061 helix_lsp::transport [ERROR] err: <- StreamClosed
2022-08-01T21:04:08.061 helix_lsp::transport [ERROR] err: <- StreamClosed
2022-08-01T21:04:08.372 helix_lsp::transport [ERROR] err: <- IO(Os { code: 32, kind: BrokenPipe, message: "Broken pipe" })
2022-08-01T21:04:08.403 helix_lsp::transport [ERROR] err: <- IO(Os { code: 32, kind: BrokenPipe, message: "Broken pipe" })
2022-08-01T21:04:08.432 helix_lsp::transport [ERROR] err: <- IO(Os { code: 32, kind: BrokenPipe, message: "Broken pipe" })
2022-08-01T21:04:08.463 helix_lsp::transport [ERROR] err: <- IO(Os { code: 32, kind: BrokenPipe, message: "Broken pipe" })
2022-08-01T21:04:08.494 helix_lsp::transport [ERROR] err: <- IO(Os { code: 32, kind: BrokenPipe, message: "Broken pipe" })
2022-08-01T21:04:08.525 helix_lsp::transport [ERROR] err: <- IO(Os { code: 32, kind: BrokenPipe, message: "Broken pipe" })
2022-08-01T21:04:08.555 helix_lsp::transport [ERROR] err: <- IO(Os { code: 32, kind: BrokenPipe, message: "Broken pipe" })
2022-08-01T21:04:08.586 helix_lsp::transport [ERROR] err: <- IO(Os { code: 32, kind: BrokenPipe, message: "Broken pipe" })
2022-08-01T21:04:08.616 helix_lsp::transport [ERROR] err: <- IO(Os { code: 32, kind: BrokenPipe, message: "Broken pipe" })
2022-08-01T21:04:08.647 helix_lsp::transport [ERROR] err: <- IO(Os { code: 32, kind: BrokenPipe, message: "Broken pipe" })
2022-08-01T21:04:08.677 helix_lsp::transport [ERROR] err: <- IO(Os { code: 32, kind: BrokenPipe, message: "Broken pipe" })
2022-08-01T21:04:08.708 helix_lsp::transport [ERROR] err: <- IO(Os { code: 32, kind: BrokenPipe, message: "Broken pipe" })
2022-08-01T21:04:09.973 helix_lsp::transport [ERROR] err: <- IO(Os { code: 32, kind: BrokenPipe, message: "Broken pipe" })
2022-08-01T21:04:13.802 helix_lsp::transport [ERROR] err: <- IO(Os { code: 32, kind: BrokenPipe, message: "Broken pipe" })
2022-08-01T21:04:14.303 helix_term::application [ERROR] Timed out waiting for language servers to shutdown

Platform

Linux

Terminal Emulator

Kitty

Helix Version

helix 22.05