'Canvas#getContext' almost never returns 'null'

TypeScript Version: 2.5.3

Code:

let canvas: HTMLCanvasElement = document.createElement("canvas");
let ctx: CanvasRenderingContext2D = canvas.getContext("2d");
ctx.fillRect(0, 0, canvas.width, canvas.height);

Expected behavior: No errors should occur because the type of canvas is HTMLCanvasElement.

Actual behavior:

test.ts(2,5): error TS2322: Type 'CanvasRenderingContext2D | null' is not assignable to type 'CanvasRenderingContext2D'.
  Type 'null' is not assignable to type 'CanvasRenderingContext2D'.

If I change the type of ctx to CanvasRenderingContext2D | null, then I get

test.ts(3,1): error TS2531: Object is possibly 'null'.

[NaridaL]

This just seems like a perfect use case for !, I don’t think changing the dts is necessary:

let canvas: HTMLCanvasElement = document.createElement("canvas");
let ctx: CanvasRenderingContext2D = canvas.getContext("2d")!; // <--
ctx.fillRect(0, 0, canvas.width, canvas.height);

[weswigham]

For reference,

let canvas: HTMLCanvasElement = document.createElement("canvas");
let ctx: CanvasRenderingContext2D | null;
if (!(ctx = canvas.getContext("2d"))) {
    throw new Error(`2d context not supported or canvas already initialized`);
}
ctx.fillRect(0, 0, canvas.width, canvas.height);

Is a decent way to use it in a typesafe way without really getting in the way; but if you must remove null from the type definition, you should probably only remove it from the overloads for "2d" and "webgl" (and I guess there should be one for "bitmaprenderer"), but not the base signature with string.