allow regex literals and const regexes/strings to be used when overloading string constants

[kevinbarabash]

Motivation:
I'm working on a small event simulation library. I'd like to overload the simulate function so I'm doing the following:

    function simulate(element: HTMLElement, name: "mousedown", options: MouseOptions);
    function simulate(element: HTMLElement, name: "mousemove", options: MouseOptions);
    function simulate(element: HTMLElement, name: "mouseup", options: MouseOptions);
    function simulate(element: HTMLElement, name: "mouseover", options: MouseOptions);
    function simulate(element: HTMLElement, name: "mouseout", options: MouseOptions);
    function simulate(element: HTMLElement, name: "mouseenter", options: MouseOptions);
    function simulate(element: HTMLElement, name: "mouseleave", options: MouseOptions);
    ...
    function simulate(element: HTMLElement, name: "keydown", options: KeyboardOptions);
    function simulate(element: HTMLElement, name: "keydown", options: KeyboardOptions);
    function simulate(element: HTMLElement, name: "keydown", options: KeyboardOptions);
    ...

Suggestion:
It would be nice if we could allow regex literals or const regexes to be used in the place of string literals when overloading functions as shown below:

const mouseEvents = /mouse(down|move|up|over|out|enter|leave)/;

function simulate(element: HTMLElement, name: mouseEvents, options: MouseOptions);
function simulate(element: HTMLElement, name: /key(up|down|press)/, options: KeyboardOptions);

Since there is no "const" yet maybe we could start with regex literals. The nice thing about allowing constants is that you could then use the same constant in the code in a switch statement or if-else block.

[danquirk]

I'm not sure how well this would play with the resulting signature help for these overloads compared to the explicit version that you have to write today.

I'm not following what you mean with the last sentence about using the same constant in the implementation.

[DanielRosenwasser]

You might also be interested in #1003 instead.

[kevinbarabash]

@DanielRosenwasser If you could define a type as being "click" | "dblclick" | "mousedown" | "mousemove" | ... that would definitely cut down on the number of overloaded definitions.

@danquirk Some code will probably explain things better:

const mouseRegex = /mouse(down|move|up|over|out|enter|leave)/;
const keyboardRegex = /key(up|down|press)/;

function simulate(element: HTMLElement, name: mouseRegex, options: MouseOptions);
function simulate(element: HTMLElement, name: keyboardRegex, options: KeyboardOptions);
function simulate(element: HTMLElement, name: string, options: Options);
function simulate(element: HTMLElement, name: string, options: Options) {
    if (mouseRegex.test(name)) {
        // create a mouse event
    } else if (keyboardRegex.test(name)) {
        // create a keyboard event
    }
}

The thought was that the regex could be by both the type system and also by the code.

[kevinbarabash]

Closing because it's pretty much covered by #1003 and #1007.

[fletchsod-developer]

When ES7 specification come into force, you will find it include the support for overloading.