Stream: beginners

Topic: Compiler crashes when assigned *specific* record field.

Ian McLerran (May 16 2024 at 13:41):

So I recently encountered a very strange bug when I introduced a new field to a type aliased record. I have two functions which each build this record in slightly different ways, but are nearly identical. However, one of my functions crashes the compiler when I include assignment of this field in the function. It crashes with the following message:

thread 'main' panicked at crates/compiler/gen_llvm/src/llvm/build.rs:5764:19:
Error in alias analysis: error in module ModName("UserApp"), function definition FuncName("\x0c\x00\x00\x00\x18\x00\x00\x00\xd3m\xe6\x0f\xa9\xd7\x9c\x94"), definition of value binding ValueId(12): could not find func in module ModName("UserApp") with name FuncName("<\x00\x00\x00\x1a\x00\x00\x00\xb8\x89\xb1cv\xbb\x90\x8e")

My function is below. Note that the field which causes the crash is currently commented out. Also note: as it currently stands, with the value is being assigned to a placeholder at the top of the function but not included in the record, I do not get the compiler panic. The compiler simply complains about my record not matching the expected return type. The crash only occurs if I include the value in the record.

## Build the request body to be sent in the Http request using a prompt string
buildPromptRequestBody : Client, Str -> RequestBody
buildPromptRequestBody = \client, prompt ->
    responseFormat = client.responseFormat
    {
        model: client.model,
        messages: Option.none {},
        prompt: Option.some prompt,
        temperature: client.temperature,
        topA: client.topA,
        topP: client.topP,
        topK: client.topK,
        frequencyPenalty: client.frequencyPenalty,
        presencePenalty: client.presencePenalty,
        repetitionPenalty: client.repetitionPenalty,
        minP: client.minP,
        seed: client.seed,
        maxTokens: client.maxTokens,
        provider: { order: client.providerOrder },
        # responseFormat,
        models: client.models,
        route: client.route,
    }

I have a second function which is nearly identical, but instead of prompt, it assigns messages. The second function has no problems with the responseFormat record field, and is assigning it without issue - I can leave that line in, and no crash is encountered.

Ian McLerran (May 16 2024 at 17:33):

Okay, some more detail:

• responseFormat is of the type Option { type: Str}, where Option is the opaque from roc-json.
• After a little testing, and hardcoding the value of responseFormat:
  • Changing the record to have 2 fields instead of 1 would prevent the crash.
  • Changing the record to have 1 field, but a U8 instead of a Str would prevent the crash.
  • Leaving the record the same, but hardcoding to Option.none {} would result in a different crash.
  • Keeping the record to 1 field of type Str, but changing the name of the field still crashed.
• Thus:
  • responseFormat: Option.some { type: "" } crashes as described.
  • responseFormat: Option.some { type: "", extra: "" } does not crash.
  • responseFormat: Option.some { type: 0 } does not crash.
  • responseFormat: Option.none {} crashes with a new panic message.

Ian McLerran (May 16 2024 at 17:36):

Here is the code for Json.Option:

Option val := [Some val, None] implements [ Eq, Decoding { decoder: decoderRes  }, Encoding { toEncoder: toEncoderRes } ]

none = \{} -> @Option (None)

some = \val -> @Option (Some val)

Ian McLerran (May 16 2024 at 17:41):

One more detail: after splitting my two functions described in my original message into separate modules, both produce the same crash.

Ian McLerran (May 16 2024 at 17:41):

TLDR:
There appears to be a bug in the compiler that does not like:
Option { field: Str } as a type.
I need to do more troubleshooting, I have this same type elsewhere in code and working fine (IE, its in my client). Not sure what differentiates, since both are records with a field of this type.

Last updated: Jul 26 2025 at 12:14 UTC