Prevent delete non-optional property

[s97712]

Search Terms

Suggestion

Prevent delete non-optional property

Use Cases

Examples

inferface Test{
  value: number
}

const foo: Test = {
  value:1
}

foo.value = undefined
[ts] Type 'undefined' is not assignable to type 'number'. [2322]
the compiler reported error, everything is normal

delete foo.value;
The complier should be prevent this situation, it behaviors like the foo.value = undefined, but here complier reported not error.

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

[ajafff]

Related to #26549 and probably a duplicate of #13783

There's a lint rule to disallow delete on non-optional properties: https://github.com/fimbullinter/wotan/blob/master/packages/mimir/docs/delete-only-optional-property.md (CLI documentation)