fix(type): allow specify ref type to ref()

Author: liximomo

src/component/component.ts

@@ -1,6 +1,7 @@
 import Vue, { VueConstructor, VNode, ComponentOptions as Vue2ComponentOptions } from 'vue';
 import { ComponentPropsOptions, ExtractPropTypes } from './componentProps';
 import { UnwrapRef } from '../reactivity';
+import { HasDefined } from '../types/basic';
 
 export type Data = { [key: string]: unknown };
 
@@ -65,14 +66,6 @@ interface ComponentOptions<
   setup?: SetupFunction<Props, RawBindings>;
 }
 
-// Conditional returns can enforce identical types.
-// See here: https://github.com/Microsoft/TypeScript/issues/27024#issuecomment-421529650
-// prettier-ignore
-type Equal<Left, Right> =
-  (<U>() => U extends Left ? 1 : 0) extends (<U>() => U extends Right ? 1 : 0) ? true : false;
-
-type HasDefined<T> = Equal<T, unknown> extends true ? false : true;
-
 // object format with object props declaration
 // see `ExtractPropTypes` in ./componentProps.ts
 export function createComponent<Props, RawBindings = Data, PropsOptions = ComponentPropsOptions>(

src/reactivity/ref.ts

@@ -1,6 +1,7 @@
 import { Data } from '../component';
 import { RefKey } from '../symbols';
 import { proxy, isPlainObject } from '../utils';
+import { HasDefined } from '../types/basic';
 import { reactive } from './reactive';
 
 type BailTypes = Function | Map<any, any> | Set<any> | WeakMap<any, any> | WeakSet<any>;
@@ -106,12 +107,14 @@ type RefValue<T> = T extends Ref<infer V> ? V : UnwrapRef<T>;
 // without init value, explicit typed: a = ref<{ a: number }>()
 // typeof a will be Ref<{ a: number } | undefined>
 export function ref<T = undefined>(): Ref<T | undefined>;
-// with init value: a = ref({ a: ref(0) })
-// typeof a will be Ref<{ a: number }>
-export function ref<T, R = RefValue<T>>(raw: T): Ref<R>;
 // with null as init value: a = ref<{ a: number }>(null);
 // typeof a will be Ref<{ a: number } | null>
-export function ref<T, R = RefValue<T>>(raw: T | null): Ref<R | null>;
+export function ref<T = null>(raw: null): Ref<T | null>;
+// with init value: a = ref({ a: ref(0) })
+// typeof a will be Ref<{ a: number }>
+export function ref<S, T = unknown, R = HasDefined<S> extends true ? S : RefValue<T>>(
+  raw: T
+): Ref<R>;
 // implementation
 export function ref(raw?: any): any {
   // if (isRef(raw)) {

src/types/basic.ts

@@ -1 +1,9 @@
 export type AnyObject = Record<string | number | symbol, any>;
+
+// Conditional returns can enforce identical types.
+// See here: https://github.com/Microsoft/TypeScript/issues/27024#issuecomment-421529650
+// prettier-ignore
+type Equal<Left, Right> =
+  (<U>() => U extends Left ? 1 : 0) extends (<U>() => U extends Right ? 1 : 0) ? true : false;
+
+export type HasDefined<T> = Equal<T, unknown> extends true ? false : true;