Predicate functions causing internal typechecking errors about flow

[SamChou19815]

You can workaround this problem for now by rewriting the predicate function as a function declaration instead of an arrow function:

export function usesRecursiveBases(
  rate: ?{+type: string, ...}
): boolean %checks {
  return Boolean(
    rate &&
      (isRecursiveRate(rate) ||
        rate.type === "formula" ||
        // $FlowFixMe[incompatible-type]
        rate.type === "break")
  );
}

We will try to fix this soon, but now our predicate function support in non-function declarations seems to be very buggy.