keyof T should never print as a union of strings

TypeScript Version: 3.6.2

Search Terms: extends keyof generic

Code

export const bindEvent = <Node extends HTMLElement | HTMLDocument,
	K extends keyof HTMLElementEventMap>(
	node: Node,
	type: K,
	callback: (event: HTMLElementEventMap[K]) => unknown,
) => {
	node.addEventListener(type, callback as EventListener);

	return () => {
		node.removeEventListener(type, callback as EventListener);
	};
};

tsc

Expected behavior:
The generic K to still be extends keyof, instead of spreading the type out.

Actual behavior:
types generated:

export declare const bindEvent: <Node_1 extends HTMLElement | HTMLDocument, K extends "fullscreenchange" | "fullscreenerror" | "abort" | "animationcancel" | "animationend" | "animationiteration" | "animationstart" | "auxclick" | "blur" | "cancel" | "canplay" | "canplaythrough" | "change" | "click" | "close" | "contextmenu" | "cuechange" | "dblclick" | "drag" | "dragend" | "dragenter" | "dragexit" | "dragleave" | "dragover" | "dragstart" | "drop" | "durationchange" | "emptied" | "ended" | "error" | "focus" | "focusin" | "focusout" | "gotpointercapture" | "input" | "invalid" | "keydown" | "keypress" | "keyup" | "load" | "loadeddata" | "loadedmetadata" | "loadend" | "loadstart" | "lostpointercapture" | "mousedown" | "mouseenter" | "mouseleave" | "mousemove" | "mouseout" | "mouseover" | "mouseup" | "pause" | "play" | "playing" | "pointercancel" | "pointerdown" | "pointerenter" | "pointerleave" | "pointermove" | "pointerout" | "pointerover" | "pointerup" | "progress" | "ratechange" | "reset" | "resize" | "scroll" | "securitypolicyviolation" | "seeked" | "seeking" | "select" | "selectionchange" | "selectstart" | "stalled" | "submit" | "suspend" | "timeupdate" | "toggle" | "touchcancel" | "touchend" | "touchmove" | "touchstart" | "transitioncancel" | "transitionend" | "transitionrun" | "transitionstart" | "volumechange" | "waiting" | "wheel" | "copy" | "cut" | "paste">(node: Node_1, type: K, callback: (event: HTMLElementEventMap[K]) => unknown) => () => void;

No repository file or test path is mentioned. Reproduce the issue with the provided snippet and TypeScript 3.6.2, then trace declaration generation and type printing to identify where the generic constraint is expanded. Done means the generated declaration preserves K as extending keyof HTMLElementEventMap rather than printing the union of event names.