Runtime Exception with List.append. TypeError: undefined is not an object (evaluating 'xs.ctor')

[That-David-Guy]

Version: Elm v0.17

This elm code:

-- [1, 2, 3] doesn't matter, it is the two b's that cause the error
b = [1, 2, 3] |> List.append b
-- OR
b = List.append b [1, 2, 3]
-- OR
b = List.append [1, 2, 3] b

Cause the following runtime exception (i.e. in my Chrome console window, not the elm compile error message)

TypeError: undefined is not an object (evaluating 'xs.ctor')

It seems like the bug is because I shouldn't be using 'b' twice like that. Normally I wouldn't log an issue like this (because it was my fault). But since one of Elms selling points is No Runtime Exceptions, I thought you might want to know.

Cheers

[process-bot]

Thanks for the issue! Make sure it satisfies this checklist. My human colleagues will appreciate it!

Here is what to expect next, and if anyone wants to comment, keep these things in mind.

[process-bot]

Thanks for the issue! Make sure it satisfies this checklist. My human colleagues will appreciate it!

Here is what to expect next, and if anyone wants to comment, keep these things in mind.

[jvoigtlaender]

This issue has been reported many times. In the next release of Elm, this kind of recursive value definition will be rejected by the compiler.

[jvoigtlaender]

This issue has been reported many times. In the next release of Elm, this kind of recursive value definition will be rejected by the compiler.

[evancz]

The issue is elm/compiler#873 and will be detected in 0.18 of Elm.

@jvoigtlaender, I know this issue is annoying, but try not to take it out on people who are just trying to be helpful!

[evancz]

The issue is elm/compiler#873 and will be detected in 0.18 of Elm.

@jvoigtlaender, I know this issue is annoying, but try not to take it out on people who are just trying to be helpful!

[jvoigtlaender]

@evancz, I'm sorry, I honestly don't know what you mean. In what way was I taking something out on somebody? I was just giving the best answer I could. Except for not providing the link to the specific issue in the other repo. And that was simply because I was on mobile, where it's more complicated (for me) to insert links. Oh well, I could have not answered at that time and leave it for later. Other than that, I'm afraid you are seeing ghosts (in seeing unfriendliness in my answering).

[jvoigtlaender]

@evancz, I'm sorry, I honestly don't know what you mean. In what way was I taking something out on somebody? I was just giving the best answer I could. Except for not providing the link to the specific issue in the other repo. And that was simply because I was on mobile, where it's more complicated (for me) to insert links. Oh well, I could have not answered at that time and leave it for later. Other than that, I'm afraid you are seeing ghosts (in seeing unfriendliness in my answering).