Do you have any examples to back up your claims? I don't think Flow's type system is more advanced than TypeScript's (which is not Java-like in any way). What

Do you have any examples to back up your claims? I don't think Flow's type system is more advanced than TypeScript's (which is not Java-like in any way). What do you mean by "abstract types"? TS's type system is based around structural interfaces, so you're almost always working with non-concrete types. It also supports discriminated unions, and you can emulate nominal typing with abstract tag properties. https://www.typescriptlang.org/docs/handbook/advanced-types.html https://www.typescriptlang.org/docs/handbook/advanced-types.... https://basarat.gitbooks.io/typescript/docs/tips/nominalTyping.html https://basarat.gitbooks.io/typescript/docs/tips/nominalTypi...