no missing prop warning for non-writable props

src/compiler/compile/render_dom/index.ts

@@ -153,7 +153,7 @@ export default function dom(
 
 	if (component.compile_options.dev) {
 		// checking that expected ones were passed
-		const expected = props.filter(prop => !prop.initialised);
+		const expected = props.filter(prop => prop.writable && !prop.initialised);
 
 		if (expected.length) {
 			dev_props_check = b`

test/runtime/samples/dev-warning-missing-data-function/_config.js

@@ -0,0 +1,7 @@
+export default {
+	compileOptions: {
+		dev: true
+	},
+
+	warnings: []
+};

test/runtime/samples/dev-warning-missing-data-function/main.svelte

@@ -0,0 +1,7 @@
+<script>
+	export function foo() {}
+</script>
+
+<p>
+	{foo()}
+</p>