fix(hex): when overriding a hex prototype method, this is now corre…

…ctly typed

_Polymorphic this_ was the magic word. Thanks to jcalz on stackoverflow:
https://stackoverflow.com/questions/66162731/how-to-set-this-in-extended-interface-method-to-type-variable?noredirect=1#comment116992054_66162731

src/hex/functions/createHexPrototype.ts

@@ -81,15 +81,13 @@ const assertOffset = ({ offset }: HexPrototypeOptions) => {
   return offset
 }
 
-export const createHexPrototype = <T extends DefaultHexPrototype>(
-  customPrototype?: T | Partial<HexPrototypeOptions>,
-) => {
+export const createHexPrototype = <T extends Hex>(customPrototype?: T | Partial<HexPrototypeOptions>) => {
   // pseudo private property
   const s = new WeakMap()
 
   const prototype = {
     ...defaultHexSettings,
-    copy(newProps = {}) {
+    copy(newProps) {
       return copyHex(this, newProps)
     },
     // fixme: make this a getter and name it `asPoint`, or better: add getters for x and y

src/hex/types.ts

@@ -61,8 +61,8 @@ export interface DefaultHexPrototype extends HexSettings {
   s: number
 
   // todo: about 80% sure the newProps type works (it's used in more places, if it works: maybe make it a separate type?)
-  copy<T extends Hex>(this: T, newProps?: Partial<T> | HexCoordinates): T
-  toPoint<T extends Hex>(this: T): Point
+  copy(this: this, newProps?: Partial<this> | HexCoordinates): this
+  toPoint(this: this): Point
 }
 
 export interface Hex extends DefaultHexPrototype, AxialCoordinates {}