Microsoft/TypeScript

【bug】ThisType is invalid when using param on generic object

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#52,969 opened on Feb 25, 2023

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BugDomain: This-TypingHelp Wanted

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Description

Bug Report

🔎 Search Terms

ThisType Object Generic

🕗 Version & Regression Information

I was unable to test this on prior versions because I was not using this feature previously

⏯ Playground Link

Playground link with relevant code

💻 Code

type ILifetime = {
  onShareTimeline: () => string
}

function createObject<D>(obj: D & ILifetime & ThisType<D>) {
  console.warn(obj)
}

// working
createObject({
  title: 'demo',
  onShareTimeline() {
    return ''
  }
})

// not working
createObject({
  title: 'demo',
  onShareTimeline() {
    return this.title
  }
})

🙁 Actual behavior

The generic type is broken

🙂 Expected behavior

The generic type should contain the object properties as those are finally included into the result

Contributor guide

Research direction
Examine how the ThisType utility is handled in the TypeScript checker when used in conjunction with generic constraints. Look at the type inference for generic object literals with intersection types.
Tech stack
typescript
Domain
tooling
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
TypeScript
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70