Possible bug: Complex named function params with defaults and rest causes errors.

[dsifford]

TypeScript Version: 2.1.1 & rc

Sorry if this has already been reported. I searched around and couldn't find exactly this.

This is sort of difficult to describe, so here's an example:

interface Foo {
    bar?: any;
    baz?: any;
}

function foobar({ bar = {}, ...opts }: Foo = {}) {
    console.log(bar);
    console.log(opts.baz);
}

foobar(); // Throws error
foobar({ baz: 'hello' }); // No error
foobar({ bar: { greeting: 'hello' } }); // No error

Playground example

Expected behavior:
I'd expect bar to still be initialized and available in the function call as an empty object when no args are given to the function.

Actual behavior:

The following error gets thrown (reproducible in the playground example above).

Uncaught TypeError: Cannot read property 'bar' of undefined
    at foobar (<anonymous>:11:16)
    at <anonymous>:16:1
    at HTMLButtonElement.excuteButton.onclick (http://www.typescriptlang.org/play/playground.js:242)

[RyanCavanaugh]

We should be emitting the parameter default above the destructuring logic, not below it

[sandersn]

Fix is up at #14090