TS 5.8 TypeError: Cannot read properties of undefined (reading 'kind')

[zxbodya]

🔎 Search Terms

TypeError: Cannot read properties of undefined (reading 'kind')

🕗 Version & Regression Information

• This changed between versions 5.7.3 and 5.8.2
• This changed in commit or PR https://github.com/microsoft/TypeScript/pull/60052

⏯ Playground Link

https://www.typescriptlang.org/dev/bug-workbench/?ts=5.8.2#code/KYDwDg9gTgLgBDAnmYcDKMCGNUF44DeAsAFBxyYBccAdgK4C2ARsFANynlPUDOMUASxoBzDiQC+Y0qEiw4AYwA2mHjzgAVYH2Jk4PYDAzZgACj7HqRnAEoC4zgi3x8J4NUw1E1uLgB8hB3IAM2g4E3kIGj44AG0Aa2BEABo4ADdMRTpgAF04CCC4AHkmACtgeRgAOmAafgEtV2tvHXJWhAALAR5K-UMsHBMWttb4xOzqdMzgJMDW8WsxNvtdSVJl0iA

💻 Code

export type State = {
  a: number;
  b: string;
};

export class Test{
  setState(state: State){}
  test = (e: any) => {
    for (const [key, value] of Object.entries(e)) {
      this.setState({
        [key]: value,
      });
    }
  };
}

🙁 Actual behavior

running tsc results in a crash:

TypeError: Cannot read properties of undefined (reading 'kind')

🙂 Expected behavior

No crash is expected, some type errors should be found instead.

Additional information about the issue

No response

[will-path]

I'm also hitting this. Here's the MRE: https://www.typescriptlang.org/play/?#code/C4TwDgpgBAwg9gO2AQwJYIgJwDwGkIgDOUEAHsBAgCbGHCboDmAfFALxQDeAUFFANr4QUdFCGEAugC4oAIzhwANhGQIA3NwC+3bgGNEdKPoR1VwGfCRoMOAEQAzBbagAfKLdnJMt1hx59HOBl6AFcIABpeOS8Ze2RFQgitHXsQhF1gVEQoKhAEZABbVF08AmIyCmpaeiZmAAp7VEw6GXFw6MYZAFlkMFKidvklFQRmAEoLRBR0LH7CVn8oZWAoTAhCEMVzWCnrWfFWNzSqCEaMKnYoY9OZqg0ox0woOuNDfgBrAnaAN3iwiSgcHsHQAdJQaus6mMxlwonxUMC6gBCNYbLYw1GbFZ+ASfEDSKC-RRhKCaDR8PgQBLQTFbD4EAEcIlhcmknR8NbAEKYBCrdZYjTabi5fJFXR1BxOdoYADuUB6YDq-H4krgtnaoQgEnaKs83nacWpEgk0KAA

[lnunno]

Wondering what the status of this one is and if the linked PR can be reviewed / merged?

[RudiVuuren]

It seems the compiler fails to use variables declared by a tuple as index keys. For those of you looking for a workaround in the meantime: redefine your tuples to rather be normal variables (using Object.keys and Object.values for above example) instead.

Workaround

Before

for (const [key, value] of Object.entries(data)) {
    data = { [key]: value };
}

After

for (const key in data) {
    data = { [key]: data[key] };
}

[martinslota]

An alternative, potentially a bit more type-friendly workaround (e.g. when using noUncheckedIndexedAccess ) is to keep using Object.entries() but destructure the entries in a separate statement.

Before

for (const [key, value] of Object.entries(data)) {
    console.log(key, value);
}

After

for (const entry of Object.entries(data)) {
    const [key, value] = entry;
    console.log(key, value);
}