microsoft / microsoft/TypeScript

this is any type in class property assignment to function

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Description

From https://github.com/Microsoft/vscode/issues/30003

TypeScript Version: 2.4.1

Code

 class AppComponent {
    items = [ 'Angular 4', 'React', 'Underscore'];

    foo = function () {
        return this.items
    }
}

Expected behavior:
The type of this in foo should be AppComponent

Actual behavior:
The type of this in foo is any

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the provided AppComponent reproduction and investigate how TypeScript infers this for a function assigned to a class property. Compare the expected AppComponent type with the actual any type, then verify the corrected inference using the same example.

Written by the indexing model from the issue text.

Assessment

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

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