Currently, because of the leading | symbol , the following code is invalid TypeScript:

type ReduxAction =
  | { type: "INCREMENT" }
  | { type: "DECREMENT" }
  | { type: "SET_VALUE", value: number };

I suggest we relax the syntax such that a single leading pipe symbol is allowed (but not required) in a union type declaration. Flow and F#, for example, both allow this syntax.

This change is backwards-compatible and gives developers a little more code formatting freedom.