fix(types): contravariant generic default in ComponentOption (#7369)

Author: HerringtonDarkholme

Diff for: types/options.d.ts

@@ -6,16 +6,17 @@ type Constructor = {
 }
 
 // we don't support infer props in async component
-export type Component<Data=DefaultData<Vue>, Methods=DefaultMethods<Vue>, Computed=DefaultComputed, Props=DefaultProps> =
+// N.B. ComponentOptions<V> is contravariant, the default generic should be bottom type
+export type Component<Data=DefaultData<never>, Methods=DefaultMethods<never>, Computed=DefaultComputed, Props=DefaultProps> =
   | typeof Vue
   | FunctionalComponentOptions<Props>
-  | ComponentOptions<Vue, Data, Methods, Computed, Props>
+  | ComponentOptions<never, Data, Methods, Computed, Props>
 
 interface EsModuleComponent {
   default: Component
 }
 
-export type AsyncComponent<Data=DefaultData<Vue>, Methods=DefaultMethods<Vue>, Computed=DefaultComputed, Props=DefaultProps> = (
+export type AsyncComponent<Data=DefaultData<never>, Methods=DefaultMethods<never>, Computed=DefaultComputed, Props=DefaultProps> = (
   resolve: (component: Component<Data, Methods, Computed, Props>) => void,
   reject: (reason?: any) => void
 ) => Promise<Component | EsModuleComponent> | void;

Diff for: types/test/options-test.ts

@@ -1,11 +1,23 @@
 import Vue, { VNode } from "../index";
-import { AsyncComponent, ComponentOptions, FunctionalComponentOptions } from "../index";
+import { AsyncComponent, ComponentOptions, FunctionalComponentOptions, Component } from "../index";
 import { CreateElement } from "../vue";
 
-interface Component extends Vue {
+interface MyComponent extends Vue {
   a: number;
 }
 
+const option: ComponentOptions<MyComponent> = {
+  data() {
+    return {
+      a: 123
+    }
+  }
+}
+
+// contravariant generic should use never
+const anotherOption: ComponentOptions<never> = option
+const componentType: Component = option
+
 Vue.component('sub-component', {
   components: {
     a: Vue.component(""),
@@ -41,10 +53,10 @@ Vue.component('string-prop', {
 });
 
 class User {
-  private u: number
+  private u = 1
 }
 class Cat {
-  private u: number
+  private u = 1
 }
 
 Vue.component('union-prop', {