Strange behaviour when auto-pairing Unicode brackets

[Omnikar]

Summary

The Lean programming language uses Unicode braces ⟨⟩, so I tried adding auto-pairing for them in my config and the cursor ended up moving in unexpected ways.

Reproduction Steps

1. Add the following to languages.toml:

[[language]]
name = "lean"
[language.auto-pairs]
"⟨" = "⟩"

2. hx foo.lean
3. Type ⟨

I expected this to happen:

⟩ is added after the cursor, and the cursor remains where it is, between ⟨ and ⟩

Instead, this happened:

⟩ is added after the cursor, and the cursor moves 4 characters forward from where it should be.
For example, with | representing the cursor:

|
----

Type ⟨

⟨⟩
--|--

This behaviour causes Helix to panic if it happens close enough to the end of a file.

Helix log

Nothing of relevance

Platform

MacOS

Terminal Emulator

iTerm2 v3.4.16

Helix Version

helix 22.08.1 (42e30e7)

[dead10ck]

Duplicate of #3946