Allows type guards with switch statement (need help..)

[bsteephenson]

[Sorry.. screwed up rebasing..]
Hi. This PR resolves issue #2214 allowing the following code to work

function logNumber(v: number) { console.log("number:", v); }
function logString(v: string) { console.log("string:", v); }

function foo1(v: number|string) {
    switch (typeof v) {
        case 'number':
            logNumber(v);
            break;
        case 'string':
            logString(v);
            break;
        default:
            throw new Error("unsupported type");
    }
}

I need some help (I'm kinda new to this..)

1. TypeOfExpression doesn't have a member "text" but the Javascript equivalent does. What can I cast TypeOfExpression to to get access to "text"?
2. I'm not sure where I should be writing tests.. (Or what a .types file is)
3. This might be too permissive. In the previous example, if I were to have a case 'Watermelon' it would still work. Should I check to see that the type is a subset of v's type?

Thank you!

[msftclas]

Hi @bsteephenson, I'm your friendly neighborhood Microsoft Pull Request Bot (You can call me MSBOT). Thanks for your contribution!

This seems like a small (but important) contribution, so no Contribution License Agreement is required at this point. Real humans will now evaluate your PR.

TTYL, MSBOT;