add test for #2127

test/runtime/samples/prop-subscribable/_config.js

@@ -0,0 +1,11 @@
+import { writable } from '../../../../store.js';
+
+export default {
+	props: {
+		b: writable(42)
+	},
+
+	html: `
+		42
+	`
+};

test/runtime/samples/prop-subscribable/main.svelte

@@ -0,0 +1,7 @@
+<script>
+	export let a;
+	export let b;
+	export let c;
+</script>
+
+{$b}