Type information lost when destructuring a function result tuple

[jednano]

TypeScript Version: 3.4.0-dev.20190313

Search Terms: type information lost during/when/upon/if destructuring a function result tuple

Code

function foo<T = number>(): [T] {
	return [42 as any]
}
const [x] = foo()

Expected behavior:

const x: number

Actual behavior:

const x: any

Playground Link

Related Issues: #5416 (an old one)

[RyanCavanaugh]

This was only number in TS2.3 (2.2 defaults did not exist, regressed to any in 2.4)