properly enforce non-function properties and fix expansion in docs

Author: zefir-git

src/BaseComponent.ts

@@ -18,21 +18,16 @@
 /**
  * Non-readonly non-method keys
  */
-type WritableKeys<T> = Extract<
-    {
+type WritableKeys<T> = {
         [Prop in keyof T]: (
         (<G>() => G extends Pick<T, Prop> ? 1 : 2) extends
             (<G>() => G extends Record<Prop, T[Prop]> ? 1 : 2)
             ? true
             : false
         ) extends false
         ? never
-        : Prop;
-    }[keyof T],
-    {
-        [K in keyof T]: T[K] extends Function ? never : K;
-    }[keyof T]
->;
+        : (T[Prop] extends Function | null ? never : Prop);
+    }[keyof T];
 
 
 /**