allow reactive declarations to only depend on $$props - fixes #2264

src/compile/render-dom/index.ts

@@ -346,6 +346,7 @@ export default function dom(
 		const reactive_declarations = component.reactive_declarations.map(d => {
 			const condition = Array.from(d.dependencies)
 				.filter(n => {
+					if (n === '$$props') return false;
 					const variable = component.var_lookup.get(n);
 					return variable && variable.writable;
 				})
@@ -358,8 +359,11 @@ export default function dom(
 						[✂${d.node.body.start}-${d.node.end}✂]
 					}`;
 
-			return deindent`
-				if (${condition}) ${snippet}`
+			return condition
+				? deindent`
+					if (${condition}) ${snippet}`
+				: deindent`
+					${snippet}`
 		});
 
 		const injected = Array.from(component.injected_reactive_declaration_vars).filter(name => {

test/runtime/samples/props-reactive/Nested.svelte

@@ -0,0 +1,9 @@
+<script>
+	let props;
+	$: {
+		let { foo, bar, baz, ...others } = $$props;
+		props = others;
+	}
+</script>
+
+<p>{props.qux}</p>

test/runtime/samples/props-reactive/_config.js

@@ -0,0 +1,22 @@
+export default {
+	show: 1,
+
+	props: {
+		a: 1,
+		b: 2,
+		c: 3,
+		d: 4
+	},
+
+	html: `
+		<p>4</p>
+	`,
+
+	test({ assert, component, target }) {
+		component.d = 5;
+
+		assert.htmlEqual(target.innerHTML, `
+			<p>5</p>
+		`);
+	}
+};

test/runtime/samples/props-reactive/main.svelte

@@ -0,0 +1,10 @@
+<script>
+	import Nested from './Nested.svelte';
+
+	export let a;
+	export let b;
+	export let c;
+	export let d;
+</script>
+
+<Nested foo={a} bar={b} baz={c} qux={d}/>