unused type parameter message is wrong for jsdoc `@template`

[sandersn]

/**
 * @template {string} K
 * @template V
 */
class MM {
    constructor() {
        /** @type {V} */
        this.t;
    }
}

Expected behavior:
Message: "K is declared but its value is never read"

Actual behavior:
Message: "All type parameters are unused."

Note that the message is the same if K comes second. The code in checkUnusedTypeParameters looks suspicious where it tries to handle template tags, so it's probably just wrong.

[rbrishabh]

Hey! I would like to take this up!

[princeseth]

Hi @sandersn — I've tried to debug this and found that isReferenced property of Symbol object remains undefined for every TypeParameter. Due to this isTypeParameterUnused function always return true for each parameters.
Could you please give some reference where I can initialize isReferenced property of SymbolObject.?
Thanks

[sandersn]

isReferenced is basically only modified in resolveName[Helper]. When the compiler checks /** @type {V} */, it should call resolveName on V, which should then mark it as used.

I'd put a breakpoint in resolveTypeReferenceName and see why resolving V doesn't end up setting isReferenced.