Stream: beginners

Topic: Cryptic error message using basic-cli


view this post on Zulip Noa Vidović (Jun 25 2023 at 19:29):

Hi all, I just found out about Roc and thought I'd try out some features to see how they differ from Elm and Haskell. I could not get my small app to compile, not even after reducing it to a very minimal application. I assumed I must be doing something wrong, but it seems the same as the tutorial as far as I can tell. If it's not a user error, I'll create a Github issue

Here is the code:

app "hello"
    packages { pf: "https://github.com/roc-lang/basic-cli/releases/download/0.3.2/tE4xS_zLdmmxmHwHih9kHWQ7fsXtJr7W7h3425-eZFk.tar.br" }
    imports [pf.Stdout]
    provides main to pf


main =
    Stdout.line "hello"

This panics with the following error message:

thread 'main' panicked at 'not yet implemented: unhandled parse error ListStart(@185)', crates/reporting/src/error/parse.rs:3499:14
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Running it with RUST_BACKTRACE=1 gives the following:

thread 'main' panicked at 'not yet implemented: unhandled parse error ListStart(@185)', crates/reporting/src/error/parse.rs:3499:14
stack backtrace:
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

And running it with RUST_BACKTRACE=full gives:

thread 'main' panicked at 'not yet implemented: unhandled parse error ListStart(@185)', crates/reporting/src/error/parse.rs:3499:14
stack backtrace:
   0:     0x55c779eefe35 - <unknown>
   1:     0x55c7790f3d6e - <unknown>
   2:     0x55c779ee9bf5 - <unknown>
   3:     0x55c779eefc05 - <unknown>
   4:     0x55c779ef157f - <unknown>
   5:     0x55c779ef12ea - <unknown>
   6:     0x55c779ef1bef - <unknown>
   7:     0x55c779ef19a4 - <unknown>
   8:     0x55c779ef033c - <unknown>
   9:     0x55c779ef16f2 - <unknown>
  10:     0x55c778f41c33 - <unknown>
  11:     0x55c779cacf70 - <unknown>
  12:     0x55c779c7f6c9 - <unknown>
  13:     0x55c77996243c - <unknown>
  14:     0x55c779928fa7 - <unknown>
  15:     0x55c77991e905 - <unknown>
  16:     0x55c7798cf206 - <unknown>
  17:     0x55c77942431b - <unknown>
  18:     0x55c7795108ce - <unknown>
  19:     0x55c779353104 - <unknown>
  20:     0x55c77934f1d3 - <unknown>
  21:     0x55c77934f1f1 - <unknown>
  22:     0x55c779ee1bc8 - <unknown>
  23:     0x55c7793560a5 - <unknown>
  24:     0x7ff0ae4c7850 - <unknown>
  25:     0x7ff0ae4c790a - __libc_start_main
  26:     0x55c779056ffe - <unknown>
  27:                0x0 - <unknown>

I am running this code on Manjaro Linux (x86_64), kernel version 5.10.181-2-MANJARO. Please let me know if there is any other relevant system info that I should provide.

view this post on Zulip Folkert de Vries (Jun 25 2023 at 19:35):

simple parse problem. I have a branch that generates this error

── MISSING PROVIDES ──────────────────────────────────── examples/cli/echo.roc ─

I am partway through parsing a header, but I got stuck here:

3│      imports [pf.Stdout]
4│      provides main to pf
                 ^

I am expecting the provides keyword next, like

    provides [main] to pf⏎

so the first argument to provides is a list of things, not just a single name

view this post on Zulip Noa Vidović (Jun 25 2023 at 19:49):

Thank you! Is there a particular reason why I got the cryptic error message instead of the clear one you gave?

view this post on Zulip Folkert de Vries (Jun 25 2023 at 19:58):

yes, it's not implemented on main yet. will make a PR soon

view this post on Zulip Folkert de Vries (Jun 25 2023 at 19:59):

https://github.com/roc-lang/roc/pull/5607

view this post on Zulip Noa Vidović (Jun 25 2023 at 20:01):

Thank you. Also, the tutorial website has the same error that I did (which is where I got it from) in the first example for an app module header. It gets fixed in every subsequent example, though. Is the code for the website public so I could submit a PR to fix the error?

view this post on Zulip Folkert de Vries (Jun 25 2023 at 20:06):

yes. it's just in our normal repository. based on a grep it is in www/generate_tutorial/src/input/tutorial.md

view this post on Zulip Noa Vidović (Jun 25 2023 at 20:12):

Thank you! I have created a pull request #5608


Last updated: Jul 05 2025 at 12:14 UTC