fix(language-core): nullable modelvalues (#4648)

packages/language-core/lib/codegen/script/scriptSetup.ts

@@ -413,7 +413,7 @@ function* generateDefinePropType(scriptSetup: NonNullable<Sfc['scriptSetup']>, p
 	}
 	else if ((defineProp.name && defineProp.nameIsString) || !defineProp.nameIsString) {
 		// Infer from actual prop declaration code 
-		yield `NonNullable<typeof ${propName}['value']>`;
+		yield `typeof ${propName}['value']`;
 	}
 	else if (defineProp.defaultValue) {
 		// Infer from defineProp({default: T})

test-workspace/tsc/vue2/tsconfig.json

@@ -21,6 +21,7 @@
 		"../vue3/#4327",
 		"../vue3/#4512",
 		"../vue3/#4540",
+		"../vue3/#4646",
 		"../vue3/components",
 		"../vue3/defineEmits",
 		"../vue3/defineModel",

test-workspace/tsc/vue3/#4646/child.vue

@@ -0,0 +1,13 @@
+<template>{{ msg }}</template>
+
+<script lang="ts" setup>
+import {exactType} from 'tsc/shared'
+import {PropType} from 'vue'
+
+const msg = defineModel('msg', {
+	type: String as PropType<string | null>,
+	required: true,
+})
+
+exactType(msg.value, {} as string | null)
+</script>

test-workspace/tsc/vue3/#4646/child2.vue

@@ -0,0 +1,5 @@
+<template>{{ other }}</template>
+
+<script lang="ts" setup>
+const other = defineModel<string | null>('other')
+</script>

test-workspace/tsc/vue3/#4646/parent.vue

@@ -0,0 +1,15 @@
+<template>
+  <child v-model:msg="msg" />
+  <child :msg="msg" @update:msg="v => exactType(v, {} as string|null)" />
+
+  <child2 v-model:other="other" />
+</template>
+<script lang="ts" setup>
+import { exactType } from 'tsc/shared'
+import { ref } from 'vue'
+import child from './child.vue'
+import child2 from './child2.vue'
+
+const msg = ref<string | null>('test')
+const other = ref<string | null>('test2')
+</script>