destructuring iterable fails to typecheck

[skeggse]

Flow version: v0.124.0

Flow should understand putting an iterable on the RHS of an array-destructuring assignment.

Expected behavior

declare var iterable: Iterable<number>;

// No error.
const [...array] = iterable;
(array: number[]);

Actual behavior

• Link to Try-Flow

Note: for whatever reason, assigning an array to iterable in the interim makes flow happy.

References

Possibly related:

• Array pattern in destructuring assignment do not typecheck correctly when assigned to an object. #733
• support destructuring, spread of all iterables, not just arrays #1059
• Arbitrary number properties are allowed #1512
• Destructuring function expression (without invocation) does not report #2612
• Destructuring non-iterables causes potential unsoundness -- does not raise errors #4990

Terms:

spread, spreading, destructure, destructuring, array, iterable, iterator,