bug: undercurl when using rust on println! commands

[Redoxahmii]

Did you check docs and existing issues?

• I have read all the solarized-osaka.nvim docs
• I have searched the existing issues of solarized-osaka.nvim
• I have searched the existing issues of plugins related to this issue

Neovim version (nvim -v)

v0.9.5

Operating system/version

Arch Linux

Describe the bug

When using this color scheme in a rust file it shows an undercurl on println! like commands and other statements too

You can see here that the same issue does not reproduce if you are using Catppuccin.
The issue is also present in tokyonight.nvim so i'm currently clueless to why this is happening in these 2 themes.

Steps To Reproduce

1. create a .rs file and use println! statements.

Expected Behavior

Should not show the undercurl.

Repro

-- DO NOT change the paths and don't remove the colorscheme
local root = vim.fn.fnamemodify("./.repro", ":p")

-- set stdpaths to use .repro
for _, name in ipairs({ "config", "data", "state", "cache" }) do
  vim.env[("XDG_%s_HOME"):format(name:upper())] = root .. "/" .. name
end

-- bootstrap lazy
local lazypath = root .. "/plugins/lazy.nvim"
if not vim.loop.fs_stat(lazypath) then
  vim.fn.system({ "git", "clone", "--filter=blob:none", "https://github.com/folke/lazy.nvim.git", lazypath, })
end
vim.opt.runtimepath:prepend(lazypath)

-- install plugins
local plugins = {
  "craftzdog/solarized-osaka.nvim",
  "craftzdog/solarized-osaka.nvim",
  -- add any other plugins here
}
require("lazy").setup(plugins, {
  root = root .. "/plugins",
})

vim.cmd.colorscheme("solarized-osaka")
-- add anything else here

[Redoxahmii]

I just noticed in the branches of the project that you have used tokyonight as the base and the issues is also present in that colorscheme in rust so that might be the underlying issue.

[craftzdog]

Can you also report it to tokyonight.nvim? I don't have time to fix it atm but can port the patch into this repo.

[Redoxahmii]

There seems to be a recent issue created for this on tokyonight too after i discussed this on reddit. Let's see how much time it takes for that to resolve.

[Redoxahmii]

SOLUTION: The solution to this was to use rustup and install the stable tool chain but if you are still using the rust package the issue remains.
I am not closing the issue but provided the info if someone else might run into this issue.