Lotoen
FunctionClauseError Elixir LS Crash
Hello, I am currently using Elixir 1.18.4 and OTP 27 with Linux Mint 22.3 - Cinnamon 64-bit as my operating system. I came across this error on Vscode regarding Elixir LS, about how it’s crashed 5 times due to a supposed function clause error.
2026-06-09 19:18:11.366 [error] ** (FunctionClauseError) no function clause matching in IO.chardata_to_string/1
2026-06-09 19:18:11.366 [error]
2026-06-09 19:18:11.366 [error] The following arguments were given to IO.chardata_to_string/1:
2026-06-09 19:18:11.367 [error]
2026-06-09 19:18:11.367 [error] # 1
2026-06-09 19:18:11.367 [error] nil
2026-06-09 19:18:11.367 [error]
2026-06-09 19:18:11.367 [error] Attempted function clauses (showing 2 out of 2):
2026-06-09 19:18:11.367 [error]
2026-06-09 19:18:11.367 [error] def chardata_to_string(+string+) when -is_binary(string)-
2026-06-09 19:18:11.367 [error] def chardata_to_string(+list+) when -is_list(list)-
2026-06-09 19:18:11.367 [error]
2026-06-09 19:18:11.367 [error] (elixir 1.18.4) lib/io.ex:710: IO.chardata_to_string/1
2026-06-09 19:18:11.367 [error] (elixir 1.18.4) lib/file.ex:177: File.regular?/2
2026-06-09 19:18:11.367 [error] (mix 1.18.4) lib/mix/tasks/loadconfig.ex:41: Mix.Tasks.Loadconfig.load_default/0
2026-06-09 19:18:11.368 [error] (mix 1.18.4) lib/mix/task.ex:495: anonymous fn/3 in Mix.Task.run_task/5
2026-06-09 19:18:11.368 [error] /home/lotoen/.vscode/extensions/jakebecker.elixir-ls-0.31.0/elixir-ls-release/installer.exs:373: anonymous fn/7 in ElixirLS.Mix.install/2
2026-06-09 19:18:11.368 [error] (elixir 1.18.4) lib/file.ex:1665: File.cd!/2
2026-06-09 19:18:11.368 [error] /home/lotoen/.vscode/extensions/jakebecker.elixir-ls-0.31.0/elixir-ls-release/installer.exs:370: ElixirLS.Mix.install/2
2026-06-09 19:18:11.368 [error] /home/lotoen/.vscode/extensions/jakebecker.elixir-ls-0.31.0/elixir-ls-release/installer.exs:617: ElixirLS.Installer.install/12026-06-09 19:18:11.366 [error] ** (FunctionClauseError) no function clause matching in IO.chardata_to_string/1
2026-06-09 19:18:11.366 [error]
2026-06-09 19:18:11.366 [error] The following arguments were given to IO.chardata_to_string/1:
2026-06-09 19:18:11.367 [error]
2026-06-09 19:18:11.367 [error] # 1
2026-06-09 19:18:11.367 [error] nil
2026-06-09 19:18:11.367 [error]
2026-06-09 19:18:11.367 [error] Attempted function clauses (showing 2 out of 2):
2026-06-09 19:18:11.367 [error]
2026-06-09 19:18:11.367 [error] def chardata_to_string(+string+) when -is_binary(string)-
2026-06-09 19:18:11.367 [error] def chardata_to_string(+list+) when -is_list(list)-
2026-06-09 19:18:11.367 [error]
2026-06-09 19:18:11.367 [error] (elixir 1.18.4) lib/io.ex:710: IO.chardata_to_string/1
2026-06-09 19:18:11.367 [error] (elixir 1.18.4) lib/file.ex:177: File.regular?/2
2026-06-09 19:18:11.367 [error] (mix 1.18.4) lib/mix/tasks/loadconfig.ex:41: Mix.Tasks.Loadconfig.load_default/0
2026-06-09 19:18:11.368 [error] (mix 1.18.4) lib/mix/task.ex:495: anonymous fn/3 in Mix.Task.run_task/5
2026-06-09 19:18:11.368 [error] /home/lotoen/.vscode/extensions/jakebecker.elixir-ls-0.31.0/elixir-ls-release/installer.exs:373: anonymous fn/7 in ElixirLS.Mix.install/2
2026-06-09 19:18:11.368 [error] (elixir 1.18.4) lib/file.ex:1665: File.cd!/2
2026-06-09 19:18:11.368 [error] /home/lotoen/.vscode/extensions/jakebecker.elixir-ls-0.31.0/elixir-ls-release/installer.exs:370: ElixirLS.Mix.install/2
2026-06-09 19:18:11.368 [error] /home/lotoen/.vscode/extensions/jakebecker.elixir-ls-0.31.0/elixir-ls-release/installer.exs:617: ElixirLS.Installer.install/1
I’ve already tried
-
Restarting & Reinstalling Vscode
-
Disabling and enabling the Elixir LS extension
-
Deleting the _build folder
-
Reinstalling dependencies
-
Restarting the docker containers holding my elixir project
-
Manually running
mix compilein the terminal -
Restarting the elixir language server
So, any help solving this error would be greatly appreciated.
First Post!
christhekeele
Welcome to the forum!
This stacktrace tells me that your mix.exs is setting :config_path to nil, or :config_path is not set. More recent versions of Elixir check for the nil case but 1.18.4 does not. I would check your mix.exs config for issues.
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