Union types of tuples and never[] incorrectly mutate into array types

[falsandtru]

TypeScript Version: master

Code

const t1 = [0, ''] as [number, string] | undefined || [];
const [a1 = 0] = [0, ''] as [number, string] | undefined || [];
const t2 = [0, ''] as [number, string] | never[];
const [a2 = 0] = [0, ''] as [number, string] | never[];

Both types of t1 and t2 are the same type [number, string] | never[]. But the results of destructuring assignment is different. a1 is number type but a2 is number | string type. a2 should also be number type.

[RyanCavanaugh]

a2 is now number as expected