Debug Failure. Parameter symbol already has a cached type which differs from newly assigned type.

[albertodvc]

Bug Report

🔎 Search Terms

Error: Debug Failure. Expected [object Object] === [object Object]. Parameter symbol already has a cached type which differs from newly assigned type

🕗 Version & Regression Information

• This is a crash
• This changed between versions 4.6.4 and 4.7.2
• This is still happening with the currently latest 4.8.3

⏯ Playground Link

Can't reproduce in the playgorund. To reproduce, run:

tsc code.js --allowJs --noEmit --target esnext.

💻 Code

code.js

class Model {
  save() {
    return this.createMissingLabels()
      .then(() => this.$store.save(this));
  }

  createMissingLabels() {
    if (this.labels && Array.isArray(this.labels)) {
      return Promise.all(this.labels.map(
        label => this.$store.createLabel(label)
      )).then(labels => (this.labels = labels));
    }
    return Promise.resolve();
  }
}

🙁 Actual behavior

Debug Failure. Expected [object Object] === [object Object]. Parameter symbol already has a cached type which differs from newly assigned type

🙂 Expected behavior

No crash

[jakebailey]

Unsurprisingly, this bisects to #43845, so this appears to be another case where we are accidentally fixing a parameter more than once, but what must be a different code path than #49740.

[smleake]

Seeing this same issue on 4.7.2 (and latest, 4.8.4). Switching to 4.6.4 remedied the problem, but definitely less than ideal.

[TrySpace]

I've been stuck on ts 4.1.5 for a while now, and I can't figure out which type/code is causing the error, when I update to any higher version like from 4.2.0 through 4.9.3 all give the same error...

And since the error only gives a path to typescript internals: node_modules\typescript\lib\typescript.js:79411:26 from assignParameterType, and no stacktrace, it's really hard to debug

Also with --verbose output I can't see which code it is.

Which part of your code causes the error exactly? And which from: #49383?

See also this duplicate (now closed) issue: #49966 it mentions the lack of error message that you would normally expect to be able to debug.

( It seems the error was meant for internal typescript-library development use, not for outside "consumer-devs"? However in practice this error also occurs outside of the internal development)

[jhmaster2000]

I've just ran into this issue on 4.9.3 and while it for some reason fails to reproduce on TSPlayground I did manage to make it reproduce on the TS Bug Workbench. Interestingly, it does not reproduce on the current Nighty (5.0.0-dev.20221130) and instead produces proper TS errors:

• 4.9.3 Bug Workbench
• Nightly Bug Workbench

It seems to be related to implicit inferred types? Given that explicitly setting the same type as it infers causes it to be fixed on 4.9.3...

[danthegoodman]

I ran into this when upgrading TS from 4.2.3 to 4.9.3 on a large internal project. I can't boil it down to a reproducable set of code, but here are the steps I followed to find the offending section of code so I could refactor how the types were specified.

1. Run tsc with --generateTrace traceOutputDir
2. Then run npx @typescript/analyze-trace traceOutputDir

At the top of the output was a path to the file that was last processed. I was then able to comment out all of the code in the file, verify that the compile was successful and then slowly reintroduce code until necessary.

In my case, I was able to add an explicit type to a generic function that was trying to do type inference.

You can read more about that analyze-trace tool here

[marekdedic]

Hi,
I'm running into this issue here: https://github.com/skaut/wordpress-version-checker/actions/runs/6865709436/job/18670310204?pr=1051

I know the file where the issue happens (here), but have no idea how to fix this. And unlike others, I'm on TS 5.2.2

Happy to help investigating this, just don't really know how. On my local machine, it's a heisenbug :(

[andrewbranch]

This was fixed in TypeScript 5.0. @marekdedic if you can still reproduce a bug with the same error message, please file a new issue with some repro steps. The logs from the CI run you linked have expired. Thanks!

[marekdedic]

Hi @andrewbranch

Thanks for the response, unfortunately, I am still getting this with TS 5.3. I filed a new issue (#57435) with a repro. Could you please take a look at it there and let me know if there's anything more you need?