Fix grammar checks for modifiers on @template type parameters

[Copilot]

Grammar checks for in/out/const modifiers on type parameters in JSDoc @template tags were not resolving the effective parent declaration, causing spurious TS1274 errors like:

/**
 * @template out T
 *            ~~~
 * error TS1274: 'out' modifier can only appear on a type parameter of a class, interface or type alias
 * @typedef {Object} Covariant
 * @property {T} x
 */

Changes

• Resolve JSDoc host for const modifier — when a type parameter is inside a @template tag, look up the effective host declaration (function/class) instead of using the template tag as the parent
• Resolve JSDoc host or @typedef for in/out modifiers — same as above, with fallback to finding a @typedef tag in the same JSDoc block (which acts as a type alias)
• Fix isJSDocTypedefTag — was unconditionally returning false (stubbed with // !!!)
• Use IsTypeOrJSTypeAliasDeclaration — the existing check used IsTypeAliasDeclaration which doesn't match KindJSTypeAliasDeclaration (the reparsed typedef nodes)

[DanielRosenwasser]

(Un)surprisingly, it seems like we have no tests for in/out modifiers when @template parameters are used on classes (maybe we had coverage for function-declared classes a while back).

Since we are now fiddling with logic to find host nodes, we need to make sure we don't regress.

Let's add a compiler test for this

// @checkJs: true
// @Filename: /index.js
/** @template in T */
export class Consumer {
    /** @param {T} value */
    eat(value) {
    }
}

export class Food {
    /** @readonly */ isFood = true;
}

export class Vegetable extends Food {
    /** @readonly */ isVegetables = true;
}

export class Meat extends Food {
    /** @readonly */ isMeat = true;
}

/** @param {Consumer<Food>} omnivore */
export function feed(omnivore) {
    omnivore.eat(new Meat());
}

/** @type {Consumer<Vegetable>} */
let vegetarian = new Consumer();

feed(vegetarian);

Also, this test which validates calculation of in/out

/** @template in T */
export class Producer {
    make(): T {
        throw new Error("Not implemented");
    }
}

/** @template in out T */
export class Consumer {
    /** @param {T} value */
    take = (value) => {}
}

[Copilot]

Copilot encountered an error and was unable to review this pull request. You can try again by re-requesting a review.

[ahejlsberg]

The changes in this PR are overly complicated. With reparsing there's no reason to look for JSDoc hosts and walk around in the AST. All we need is to permit JSTypeAliasDeclaration parents for type parameters when checking in and out modifiers. I will put up a simpler PR.