TS4082 occurs when using `composite: true`

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#54,878 3 comments 2 reactions 0 assignees View on GitHub

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
typescript
Domain
compilers

Research direction

Start by running the linked TypeScript Playground reproduction with composite enabled, then compare the exported and local callbacks and the interface and type-alias cases. Trace the compiler path that reports TS4082 and add a regression test; done means the two equivalent callback forms have consistent behavior without regressing the existing type-alias case.

Written by the indexing model from the issue text.

Description

Needs More Info

Bug Report

🔎 Search Terms

TS4082, composite

🕗 Version & Regression Information
  • I was unable to test this on prior versions because composite is a new feature added to typescript (not actually)
⏯ Playground Link

Playground link with relevant code

💻 Code
// This throws
export default (
	a = () => {
		interface Props {}
		return {} as Props
	},
) => {};

// This works
let a = () => {
	interface Props {}
	return {} as Props
}
🙁 Actual behavior

When composite is enabled, the export default statement throws TS4082. And disabling composite fixes this issue.

🙂 Expected behavior

They should both throw, or both not throw :(

This issue only occurs when using an interface. Using a type alias won't cause this issue.

Dominant language
Go
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Avg merge
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Merged PRs (30d)
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