RFC: @errorCode to provide context for errors for properties #422

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:

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.