RFC: @errorCode to provide context for errors for properties

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
35/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Stale
Tech stack
typescript
Domain
documentation

Research direction

Start by reviewing the existing @link tag behavior and the proposed TypeScript discriminated-union example. Determine how an @errorCode tag should represent property-related diagnostics and what specification changes are needed; done means the syntax and expected error-context behavior are defined clearly enough for implementation.

Written by the indexing model from the issue text.

Description

It would be nice to be able to inform users when they encounter specific errors related to a property.

In this example use case, we would like to inform the user that a property on a discriminated union can only be set when the discriminator matches the type.

interface Base {
  discriminator: boolean;
  foo: string | never;
}

interface UnionTypeA extends Base {
  discriminator: true;
  foo: string;
}

interface UnionTypeB extends Base {
  discriminator: false;

  /**
   *
   * {@errorCode 2322 | This property can only be set when discriminator is equal to `true`}
   *
   */
  foo: never;
}

type DiscriminatedUnion = UnionTypeA | UnionTypeB;

const bar: DiscriminatedUnion = {
  discriminator: false,
  foo: ""
}

The current error is shown as:
Screenshot 2024-08-23 at 11 35 35 AM

I based the syntax around what I have seen as prior art in the @link tag.

Apologies if this has been suggested or discussed before, I could not find anything from an initial search of issues.

Dominant language
TypeScript
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Forks
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Avg merge
17h 24m
Merged PRs (30d)
8

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