CODEBASE: Fix lint errors 3 (#1758)

This is a really big refactor because it actually *fixes* a lot of the lint errors instead of disabling them.

src/Types/Jsonable.ts

@@ -1,3 +1,4 @@
+import { arrayAssert } from "../utils/helpers/typeAssertion";
 import type { IReviverValue } from "../utils/JSONReviver";
 // Versions of js builtin classes that can be converted to and from JSON for use in save files
 
@@ -6,6 +7,7 @@ export class JSONSet<T> extends Set<T> {
     return { ctor: "JSONSet", data: Array.from(this) };
   }
   static fromJSON(value: IReviverValue): JSONSet<any> {
+    arrayAssert(value.data);
     return new JSONSet(value.data);
   }
 }
@@ -16,6 +18,15 @@ export class JSONMap<K, __V> extends Map<K, __V> {
   }
 
   static fromJSON(value: IReviverValue): JSONMap<any, any> {
-    return new JSONMap(value.data);
+    arrayAssert(value.data);
+    for (const item of value.data) {
+      arrayAssert(item);
+      if (item.length !== 2) {
+        console.error("Invalid data passed to JSONMap.fromJSON(). Value:", value);
+        throw new Error(`An item is not an array with exactly 2 items. Its length is ${item.length}.`);
+      }
+    }
+    // We validated the data above, so it's safe to typecast here.
+    return new JSONMap(value.data as [unknown, unknown][]);
   }
 }