When emitting an arrow function, parenthesize the body if it could be interpreted as a block instead of an object literal.

[CyrusNajmabadi]

Fixes #2250

[JsonFreeman]

👍

[DanielRosenwasser]

What about when it's a type assertion in a parenthesized expression?

[CyrusNajmabadi]

I'll add a test for that as well.

[DanielRosenwasser]

Add the following tests

var a = () => <Error>{ name: "foo", message: "bar" };      

var b = () => (<Error>{ name: "foo", message: "bar" });    

var c = () => ({ name: "foo", message: "bar" });           

var d = () => ((<Error>({ name: "foo", message: "bar" })));