Allow enums in local scopes

[joshuacc]

Currently the following is allowed:

enum Color { red, green, blue }

function fun(myColor) {
    if (myColor == Color.red) {
        console.log("awesome");
    } else {
        console.log("bummer");
    }
}

This compiles, but gives a warning:

function fun(myColor) {
    enum Color { red, green, blue } // Warning "Statement expected"

    if (myColor == Color.red) {
        console.log("awesome");
    } else {
        console.log("bummer");
    }
}

Especially when refactoring existing JavaScript code, there are cases where an enum would be useful, but wouldn't be used outside of a single function. In those cases, I think it makes sense to allow the enum to be defined inside of the function's scope.

[danquirk]

Presumably this could be considered along with other kinds of types we would allow in a future 'local types' feature. Edited the title appropriately.