babel/packages/babel-plugin-transform-block-scoping/test/fixtures/pass/destructuring.js

function foo(
   { x: { y: { z: a = 10 } = {}, w: b = 20 }, a: c = 30 }
) {
  assert.equal(a, 10);
  assert.equal(b, 20);
  assert.equal(c, 30);
}

foo({ x: {} });