No, instead of complaining about 'x' having the 'any' type, Flow will actually try to infer a static type for 'x'. So in the best case there would be no errors

No, instead of complaining about 'x' having the 'any' type, Flow will actually try to infer a static type for 'x'. So in the best case there would be no errors (and in the worst case there would be actual errors to fix).