microsoft / microsoft/TypeScript
Diagnostic code 8030 being incorrectly generated using JSDoc `@type` on a function.
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Description
### 🔎 Search Terms
Diagnostic 8030 is being generated incorrectly when using JSDoc `@type` on a method when the type is being referred to from an interface. This is using the new `tsc` LSP - version 7.0.2.
### 🕗 Version & Regression Information
- This changed between versions 7.0.0-dev.260707.2 and 7.0.2.
- This is the behavior in every version I tried, and I reviewed the FAQ for entries about new native issues being transferred into the main typescript repo.
### ⏯ Playground Link
_No response_
### 💻 Code
```ts
// types.ts
interface Example {
method (): number;
}
export {};
// code.js
const exampleFns = {
/**
* @type {Example['method']} // A JSDoc `@type` tag on a function must have a signature with the correct number of arguments.
*/
method () {
return Math.random();
}
};
```
### 🙁 Actual behavior
in this example, the diagnostic and LSP info does not tell the user that typescript is internally suffixing `| undefined` to the type. As such wrapping the type in `NonNullable` removes the error diagnostic, I do not believe this to be intended behaviour as previous iterations the golang native LSP `tsgo` (7.0.0-dev.260707.2) did not produce this diagnostic, nor did previous versions of typescript.
### 🙂 Expected behavior
The type should be properly referenced with no additional suffixing of types, as it used to.
### Additional information about the issue
_No response_
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by reproducing the diagnostic with types.ts and code.js using the reported TypeScript 7.0.2 and the earlier 7.0.0-dev.260707.2 version. Trace how the JSDoc @type reference to Example['method'] is resolved and why | undefined is added. Done means the valid method type no longer produces diagnostic 8030, with regression coverage for this example.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- javascript, typescript
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Active
- Clarity
- Mostly clear
- Newbie friendliness
- 48/100