Template string wrongly infers type from a default value used in destructuring assignment

[LasAtt]

🔎 Search Terms

"template string", "default value", "infer type", "destructuring"

🕗 Version & Regression Information

This changed between versions 5.1.6 and 5.2.2. The bug is also present in 5.3.0-dev.20230928.

⏯ Playground Link

https://www.typescriptlang.org/play?ts=5.3.0-dev.20230928#code/C4TwDgpgBACghgJzgWwM5QLxQN4CgpQBucANgK4QD8AXFKsAgJYB2A5lAD5TNnIBGEBLgC+uXADMyzAMbBGAe2ZQIADxRgSEABRhEKCMEGpa8JGgCUOfFGmL6OIqQqYoAcgCMAJgDMrqMJddMwMjawQDMgQlAAMAEmxicghhaMwMLFdvABYAVlcRXCA

💻 Code

type Params = {
  value?: string | number
}

function example(parameters: Params) {
  const { value = '123' } = parameters
  return `${value}` === '345' // <--- Error: This comparison appears to be unintentional because the types '"123"' and '"345"' have no overlap.(2367)
}

🙁 Actual behavior

The template string expression, ${value}, is assigned type "123", based on a default value assigned to value in a destructing assignment.

🙂 Expected behavior

The expression should instead be assigned a type of string. The field value is correctly assigned a type of string | number, so any template string using value should not be restricted to the default value used in destructuring.

Additional information about the issue

No response

[Andarist]

I'm almost certain that this is a fall out of #53907 and it's definitely a bug. I'll look into this soon.

[LasAtt]

I'm almost certain that this is a fall out of #53907 and it's definitely a bug. I'll look into this soon.

Thank you for looking into it!

[Andarist]

It's actually an old bug but this one is a new manifestation of it. TS playground