Refactor to extract existing function to outer scope

TypeScript Version: 3.1.0-dev.20180813

Code

function a(x: number) {
    function b(y: number) {
        return x + y;
    }
    return b(1);
}

Expected behavior:

Refactor on b to convert to:

function a(x: number) {
    return b(1, x);
}
function b(y: number, x: number) {
    return x + y;
}

Actual behavior:

No such refactor.
We already have the ability to refactor code to an outer scope. So a workaround is to highlight the entire body of b and refactor to a function in global scope, then delete b and rename the refactored function to b, then manually update call sites.

The issue names the nested function b and the existing refactor-to-outer-scope capability; start by locating that refactor entry point and its tests. Reproduce the nested-function case, then verify that the refactor moves b, passes captured x as an argument, and updates the call site.