Opaque types for WebGL

WebGL types are included in the default `lib.d.ts`. However, most types are defined as empty interfaces, which means that the compiler doesn't catch many WebGL errors. Consider the following code: ``` ts function foo(gl: WebGLRenderingContext, fbo: WebGLFramebuffer) { gl.bindFramebuffer(gl.FRAMEBUFFER, fbo); // Correct call gl.bindFramebuffer(gl.FRAMEBUFFER, "abc"); // This should be a compile error! fbo = gl.createFramebuffer(); // Correct call fbo = new WebGLFramebuffer; // This should be a compile error! } ``` - The second parameter of `gl.bindFramebuffer` should be a `WebGLFramebuffer` object, but passing a `string` does not emit a compile error or warning. - The type `WebGLFramebuffer` can only be constructed via `WebGLRenderingContext.createFramebuffer`, calling new throws an error at runtime Ideally, Typescript would know that `WebGLFramebuffer`, even though it has no public properties, cannot be constructed or converted to any other type. I assume that this is not easy to specify with structural typing, but having such opaque types could be useful for other libraries as well (e.g., for returning handles). If that is not possible, can we find a workaround that at least helps catching the above mentioned bugs? For reference, here's how the above types are currently defined in `lib.d.ts`: ``` ts interface WebGLFramebuffer extends WebGLObject { } declare var WebGLFramebuffer: { prototype: WebGLFramebuffer; new(): WebGLFramebuffer; } interface WebGLRenderingContext { bindFramebuffer(target: number, framebuffer: WebGLFramebuffer): void; // + many other methods } ```