Optional parameters indicated via JSDoc are not respected

[mihaip]

TypeScript Version: nightly (1.9.0-dev.20160521) (same behavior in 1.8.10).

Given this plain JavaScript file annotated with JSDoc for the Closure Compiler (included via allowJs):

/**
 * @param {number=} input
 * @return {number}
 */
function legacyMethod(input) {
    if (typeof input === "undefined") {
        return 0;
    }
    return input * input;
};

And this TypeScript file:

console.log(legacyMethod(1));
console.log(legacyMethod());

I would expect that the second legacyMethod call to also be fine, due to the = suffix on the type (see https://developers.google.com/closure/compiler/docs/js-for-compiler#types for more details on the Closure Compiler type language). Based on Visual Studio Code's Intellisense the extracted type for legacyMethod is function legacyMethod(input?: number): number which seems correct. However, when running, I get:

main.ts(2,13): error TS2346: Supplied parameters do not match any signature of call target.

Out of curiosity, I tried legacyMethod(undefined) which worked (as did legacyMethod(null), which the Closure Compiler would not have allowed, since optional parameters are undefined, not null).

[sandersn]

Duplicate of #6992 -- that bug also has some interesting discussion about what to do in the case that we still can't find a matching signature.