Spread component props immutably during SSR

src/compiler/compile/render_ssr/handlers/InlineComponent.ts

@@ -36,7 +36,7 @@ export default function(node: InlineComponent, renderer: Renderer, options: Rend
 	let props;
 
 	if (uses_spread) {
-		props = x`@_Object.assign(${
+		props = x`@_Object.assign({}, ${
 			node.attributes
 				.map(attribute => {
 					if (attribute.is_spread) {

test/js/samples/ssr-spread-component-props-immutably/_config.js

@@ -0,0 +1,5 @@
+export default {
+	options: {
+		generate: 'ssr'
+	}
+};

test/js/samples/ssr-spread-component-props-immutably/expected.js

@@ -0,0 +1,11 @@
+/* generated by Svelte vX.Y.Z */
+import { create_ssr_component, validate_component } from "svelte/internal";
+
+import Component from './Component.svelte';
+
+const Component_1 = create_ssr_component(($$result, $$props, $$bindings, slots) => {
+	let props = { x: 1, y: 2, z: 3 };
+	return `${validate_component(Component, "Component").$$render($$result, Object.assign({}, props, { x: 2 }), {}, {})}`;
+});
+
+export default Component_1;

test/js/samples/ssr-spread-component-props-immutably/input.svelte

@@ -0,0 +1,11 @@
+<script>
+	import Component from './Component.svelte';
+
+	let props = {
+		x: 1,
+		y: 2,
+		z: 3,
+	};
+</script>
+
+<Component {...props} x={2} />